Emma Gairin
email: emma.gairin@hotmail.fr

Mélanie Dussenne

Manon Mercader

Cécile Berthe

Mathieu Reynaud

Marc Metian

Suzanne C Mills

Philippe Lenfant

Laurence Besseau

Frédéric Bertucci

David Lecchini

Harbours as unique environmental sites of multiple anthropogenic stressors on fish hormonal systems

Keywords: fish, harbours, hormones, anthropogenic stressors, pollution, plastics, ALAN

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Coastlines -the interface between the land and the sea -have been increasingly subjected to anthropogenic pressures such as fishing, boating, pollution, coastal construction, and tourism since the end of the 19 th century (e.g., [START_REF] Crain | Understanding and managing human threats to the coastal marine environment[END_REF][START_REF] Dugan | 8.02 -Estuarine and Coastal Structures: Environmental Effects, A Focus on Shore and Nearshore Structures[END_REF]. Marinas, harbours, and ports are among the most common man-made structures along coastlines worldwide (e.g., [START_REF] Hardaway | Living Shoreline Design Guidelines for Shore Protection in Virginia's Estuarine Environments[END_REF][START_REF] Dafforn | Marine urbanization: an ecological framework for designing multifunctional artificial structures[END_REF]. Harbours are often hotspots of human-mediated environmental pressures which significantly affect the quality of surrounding coastal and marine waters, as well as the native vs. non-native species assemblages [START_REF] Mayer-Pinto | Sydney Harbour: a review of anthropogenic impacts on the biodiversity and ecosystem function of one of the world's largest natural harbours[END_REF]. For example, [START_REF] Harik | Implications of adopting a biodiversity-based vulnerability index versus a shoreline environmental sensitivity index on management and policy planning along coastal areas[END_REF] assessed anthropogenic stressors along the Mediterranean coastline using a multi-criteria index . The study showed that harbours along the Mediterranean coastline are the third largest cause of stress to marine ecosystems, behind landfills and industrial sites [START_REF] Harik | Implications of adopting a biodiversity-based vulnerability index versus a shoreline environmental sensitivity index on management and policy planning along coastal areas[END_REF]. The construction and presence of harbours not only directly destroy natural coastal habitats, but also indirectly damage neighbouring ecosystems through changes in currents and sediment loads which dramatically impact the composition of benthic communities [START_REF] Meinesz | Impact of coastal development on the infralittoral zone along the southeastern Mediterranean shore of continental France[END_REF][START_REF] Martin | Ecological impact of coastal defence structures on sediment and mobile fauna: evaluating and forecasting consequences of unavoidable modifications of native habitats[END_REF][START_REF] Li | Effects of reclamation projects on marine ecological environment in Tianjin Harbor Industrial Zone[END_REF], as well as fish larval dispersal and recruitment [START_REF] Roberts | Connectivity and management of Caribbean coral reefs[END_REF]. Within harbours, direct stressors include pollutants from maritime activities (e.g., diesel spills during vessel refuelling, hydrocarbon pollution from boat traffic - [START_REF] Steen | Monitoring and evaluation of the environmental dissipation of the marine antifoulant 4,5-dichloro-2-n-octyl-4isothiazolin-3-one (DCOIT) in a Danish Harbor[END_REF] in Danish harbours; [START_REF] Bergen | Environmental Monitoring Of Remedial Dredging At The New Bedford Harbor, Ma, Superfund Site[END_REF] in the USA; Ingole et al., 2009 in India;Li et al., 2010 in China;Mayer-Pinto et al., 2015 in Australia;[START_REF] Harik | Implications of adopting a biodiversity-based vulnerability index versus a shoreline environmental sensitivity index on management and policy planning along coastal areas[END_REF] Mediterranean harbours), and pollution generated by neighbouring cities and agricultural activities.

These can lead to high levels of heavy metals and organic pollutants (e.g., high polychlorinated biphenyl levels such as in New Bedford Harbour - [START_REF] Bergen | Environmental Monitoring Of Remedial Dredging At The New Bedford Harbor, Ma, Superfund Site[END_REF][START_REF] Nogales | Anthropogenic perturbations in marine microbial communities[END_REF][START_REF] Mali | Assessment and source identification of pollution risk for touristic ports: Heavy metals and polycyclic aromatic hydrocarbons in sediments of 4 marinas of the Apulia region (Italy)[END_REF], affecting the composition and function of microbial [START_REF] Nogales | Anthropogenic perturbations in marine microbial communities[END_REF] and macro-faunal communities [START_REF] Martínez-Lladó | Distribution of polycyclic aromatic hydrocarbons (PAHs) and tributyltin (TBT) in Barcelona harbour sediments and their impact on benthic communities[END_REF] in the water and sediments in harbours and marinas. Overall, although the legislative framework concerning marine pollution control and prevention has been increasingly enforced in harbours since the early 2000s [START_REF] Aapa | Environmental Management Systems and public seaports[END_REF]ESPO/EcoPorts, 2009;US-EPA, 2009), harbours remain man-made structures in which intense human usage impacts coastline environments.

Nonetheless, harbours and marinas contain marine communities and therefore constitute sites of interest for ecologists and endocrinologists working on fish populations.

In their review of 200 environmental studies on Sydney harbour, [START_REF] Mayer-Pinto | Sydney Harbour: a review of anthropogenic impacts on the biodiversity and ecosystem function of one of the world's largest natural harbours[END_REF] found that 109 focused on contamination, 58 on habitat modification, 11 on invasions by non-indigenous species, and only 8 on fish and fisheries. This relative gap in studies on fisheries from Sydney harbour mirrors the lack in knowledge of the impact of harbours on fish worldwide. Elsewhere, although many studies have been conducted on intertidal sessile organisms living in harbours (e.g., [START_REF] Yung | Some observations on the changes of physico-chemical and biological factors in Victoria Harbour and vicinity, Hong Kong, 1988-1996[END_REF][START_REF] Macfarlane | Assessing effects of petroleum oil on intertidal invertebrate communities in Sydney Harbour: preparedness pays off[END_REF], only a few have monitored mobile species such as fish (e.g., [START_REF] Wooldridge | Environmental management of ports and harbours-implementation of policy through scientific monitoring[END_REF]Mercader et al., 2017a;[START_REF] Meinesz | Impact of coastal development on the infralittoral zone along the southeastern Mediterranean shore of continental France[END_REF]. The low number of studies looking at fish species may be due to practical aspects such as the danger of boat traffic when swimming, as well as fishing restrictions in harbours [START_REF] Ferreira | Presence of microplastics in water, sediments and fish species in an urban coastal environment of Fiji, a Pacific small island developing state[END_REF]. In addition, harbours are seldom considered of interest for fish studies as they are rarely viewed as key habitats in terms of ecological function along coastlines and islands and are often only referred to as polluted and artificial habitats (Mayer-Pinto et al., 2015). These multiple reasons may explain the paucity of scientific papers focusing on the ecology and physiology of fish living in harbours. However, harbours could be considered as unique habitats of key scientific interest. Indeed, they concentrate uncommonly high and varied levels of pollutants. These urbanised centres, previously absent from coastlines, completely differ from the ecosystems they replaced as well as from the surrounding natural areas in terms of abiotic composition (e.g., substrate type, water quality, hydrodynamics). They represent a novel ecosystem [START_REF] Hobbs | Novel ecosystems: intervening in the new ecological world order[END_REF] with their own functional groups of living organisms. These make them unique areas in which to study the synergistic effects of multiple anthropogenic stressors on the ecology, biology, and physiology of fish.

In addition, from an adaptive and evolutionary point of view, they provide a setting for long-term field experiments impossible in mesocosm conditions (e.g., [START_REF] Viard | Anthropogenic hybridization at sea: three evolutionary questions relevant to invasive species management[END_REF][START_REF] Le Moan | An introgression breakthrough left by an anthropogenic contact between two ascidians[END_REF]. The aim of our review is to encourage future research on the biology (with a focus on endocrinology) and ecology of fish affected by multiple stressors encountered in harbours. To do so, we (i) identify the different stressors present in harbours and their potential impacts on marine fauna, (ii) present baseline knowledge on the effect of multiple anthropogenic stressors on two endocrine pathways in marine fish (stress and thyroid hormones), and (iii) propose a framework to conduct integrated research that could provide crucial insights for ecosystem management, as well as a better understanding of hormonal responses in fish under stressful conditions.

Harbours as fish habitats and potential nurseries

Harbours are semi-closed coastal marine areas with limited water mixing with the open sea, in which marine organisms are exposed to multiple stressors (e.g., chemical contamination, elevated nutrients, turbidity, marine debris, microplastics, invasive species, habitat modification, boat traffic and noise and artificial light at night - [START_REF] Li | Effects of reclamation projects on marine ecological environment in Tianjin Harbor Industrial Zone[END_REF][START_REF] Mayer-Pinto | Sydney Harbour: a review of anthropogenic impacts on the biodiversity and ecosystem function of one of the world's largest natural harbours[END_REF]Fig. 1). In this review, we focus on six major anthropogenic stressors that can affect the hormonal system of fish: plastic pollution, chemical contamination, invasive species, boat noise, artificial light at night, temperature variation, as well as their combined effects. Despite the numerous anthropogenic stressors present in harbours, studies have found that harbours can be marine biodiversity hotspots, but these have mostly focused on macro-invertebrates (Johnston et al., 2015;[START_REF] Mayer-Pinto | Sydney Harbour: a review of anthropogenic impacts on the biodiversity and ecosystem function of one of the world's largest natural harbours[END_REF]. The existing quantitative data on fish populations does not paint a similar picture for fish biodiversity [START_REF] Edgar | The production and trophic ecology of shallow-water fish assemblages in southern Australia II. Diets of fishes and trophic relationships between fishes and benthos at Western Port, Victoria[END_REF][START_REF] Clynick | Assemblages of fish associated with coastal marinas in north-western Italy[END_REF][START_REF] Hutchings | Sydney Harbour: its diverse biodiversity[END_REF]. However, recent studies have highlighted that some harbours with artificial habitats (mainly in temperate regions) could be nursery areas for fish [START_REF] Bouchoucha | Potential use of marinas as nursery grounds by rocky fishes: Insights from four Diplodus species in the Mediterranean[END_REF][START_REF] Dufour | Identification of sea bass (Dicentrarchus labrax) nursery areas in the north-western Mediterranean Sea[END_REF]Mercader et al., 2017b;[START_REF] Patranella | Artificial reefs as juvenile fish habitat in a marina[END_REF][START_REF] Meinesz | Impact of coastal development on the infralittoral zone along the southeastern Mediterranean shore of continental France[END_REF]. Breakwaters host high densities of juvenile fish [START_REF] Ruitton | Relationships between algae, benthic herbivorous invertebrates and fishes in rocky sublittoral communities of a temperate sea (Mediterranean)[END_REF][START_REF] Pizzolon | The onset of fish colonization in a coastal defence structure (Chioggia, Northern Adriatic Sea)[END_REF][START_REF] Dufour | Identification of sea bass (Dicentrarchus labrax) nursery areas in the north-western Mediterranean Sea[END_REF] and in some areas (e.g., in Sydney harbour; Clynick 2008) adult fish species richness and abundance inside marinas are close to those found on natural rocky habitats. [START_REF] Meinesz | Impact of coastal development on the infralittoral zone along the southeastern Mediterranean shore of continental France[END_REF] surveyed juvenile fish populations on various artificial infrastructures and natural sites along a 100-km section of the French Mediterranean shoreline.

Juvenile fish densities were highly variable between harbours depending on the type of small-scale habitats, with juvenile densities on ripraps or jetties higher or equivalent to those on natural sites. Port and marina jetties might in some cases provide suitable nursery grounds for juvenile fish, at least by comparison with highly urbanized neighbouring sections of the coastline [START_REF] Dufour | Identification of sea bass (Dicentrarchus labrax) nursery areas in the north-western Mediterranean Sea[END_REF][START_REF] Bouchoucha | Potential use of marinas as nursery grounds by rocky fishes: Insights from four Diplodus species in the Mediterranean[END_REF]Mercader et al., 2017b;[START_REF] Patranella | Artificial reefs as juvenile fish habitat in a marina[END_REF][START_REF] Meinesz | Impact of coastal development on the infralittoral zone along the southeastern Mediterranean shore of continental France[END_REF]. Therefore, marinas, harbours, and ports may play a surprisingly vital role in the life cycle of some fish species. This is important when it comes to emblematic protected species, for instance the dusky grouper along the French Mediterranean coastline. This species, which almost disappeared from the French coasts, is almost exclusively found in marine protected areas, and there are very few juveniles. Projects to restore the nursery function in several French and Moroccan Mediterranean ports have led to an increase in observed juveniles (Mercader et al., 2017a;[START_REF] Selfati | Promoting restoration of fish communities using artificial habitats in coastal marinas[END_REF].

Many marine fish species have structured life histories with two distinct stages: first, a pelagic larval stage capable of long-distance dispersal, followed by a relatively sedentary benthic stage (usually juveniles and adults in reefs or along coastlines; [START_REF] Leis | The biology, behavior, and ecology of the pelagic, larval stage of coral reef fishes[END_REF]. After the oceanic dispersal phase, larvae settle in a suitable recruitment site. Recruitment is a critical phase in the life cycle of fish as its success is decisive for population maintenance. Fish must undergo an abrupt transformation from larvae to juvenile during this transition phase [START_REF] Laudet | The Origins and Evolution of Vertebrate Metamorphosis[END_REF]. This transformation, called metamorphosis, is usually quite spectacular and includes changes in behaviour, morphology, and physiology, including biochemical and histological remodelling that affect several tissues at different levels [START_REF] Mccormick | Comparative study of metamorphosis in tropical reef fishes[END_REF][START_REF] Parmentier | Ontogenic and ecological control of metamorphosis onset in a carapid fish, Carapus homei: experimental evidence from vertebra and otolith comparisons[END_REF][START_REF] Frédérich | Mismatch between shape changes and ecological shifts during the post-settlement growth of the surgeonfish, Acanthurus triostegus[END_REF][START_REF] Holzer | Thyroid Hormones: A Triple-Edged Sword for Life History Transitions[END_REF][START_REF] Besson | Anthropogenic stressors impact fish sensory development and survival via thyroid disruption[END_REF]. Metamorphosis is usually triggered by physiological and environmental cues [START_REF] Holzer | Fish larval recruitment to reefs is a thyroid hormone-mediated metamorphosis sensitive to the pesticide chlorpyrifos[END_REF]. Indeed, thyroid hormones (TH, notably thyroxine (T4) and triiodothyronine (T3)); [START_REF] Holzer | Fish larval recruitment to reefs is a thyroid hormone-mediated metamorphosis sensitive to the pesticide chlorpyrifos[END_REF] and cortisol [START_REF] Jesus | Changes in cortisol and thyroid hormone concentrations during early development and metamorphosis in the Japanese flounder, Paralichthys olivaceus[END_REF] act in concert to control and modulate metamorphosis. TH levels increase during post-embryonic development to reach a peak which induces metamorphosis; TH then coordinate ontogenetic transformations from the larval to the juvenile stages [START_REF] Gilbert | Metamorphosis: postembryonic reprogramming of gene expression in amphibian and insect cells[END_REF][START_REF] Wada | Glucocorticoids: mediators of vertebrate ontogenetic transitions[END_REF][START_REF] Isorna | Iodothyronine deiodinases and thyroid hormone receptors regulation during flatfish (Solea senegalensis) metamorphosis[END_REF][START_REF] Mcmenamin | Chapter Five -Metamorphosis in Teleosts[END_REF][START_REF] Campinho | Teleost Metamorphosis: The Role of Thyroid Hormone[END_REF][START_REF] Klann | Variation on a theme: pigmentation variants and mutants of anemonefish[END_REF]. As TH signalling is critical for neurogenesis and the development of sensory organs, it may play a role in determining the "quality" of future juveniles, i.e., their capacity to select suitable habitats, feed efficiently, as well as detect predators and escape from them, which are all crucial for fish to successfully recruit into adult populations [START_REF] Besson | Anthropogenic stressors impact fish sensory development and survival via thyroid disruption[END_REF].

Effects of multiple anthropogenic stressors on the hormonal system of fish living in harbours

In this review, we discuss on the effect of pollutants and stressors on fish endocrinology, with a focus on three major hormonal axes: the hypothalamo-pituitary-interrenal (HPI), hypothalamo-pituitarythyroid (HPT), and hypothalamo-pituitary-gonadal (HPG) axes, as described by Fig. 2. Fig. 2 Modified from Dussenne et al., d2022. Illustration representing the hypothalamo-pituitaryinterrenal (HPI), hypothalamo-pituitary-thyroid (HPT), and hypothalamo-pituitary-gonadal (HPG) axes in non-mammalian species (pink, purple and blue, respectively). Environmental cues are perceived by sensory organs and processed in the brain, where corticotropin-releasing hormone (CRH) and gonadotropin-releasing hormone (GnRH) are secreted. In non-mammalian species, CRH is thought to control both the HPI and HPT axes. CRH acts on the pituitary cells to stimulate the synthesis and release of i) adrenocorticotropic hormone (ACTH) from corticotropic cells (C, pink circles) and ii) thyroidstimulating hormone (TSH) from thyrotropic cells (T, purple circles). HPI axis: ACTH stimulates the secretion of glucocorticoids (GCs) by the interrenal cells. Once secreted, GCs are transported in the blood by corticosteroid binding proteins (BPs). GCs enter target cells where they bind to corticosteroid receptor dimers which then translocate into the nucleus where they bind to specific DNA regions to induce gene expression. HPT axis: TSH stimulates the production of thyroid hormones (THs, T4 and T3) by thyroid follicles. THs are transported to target cells via their specific BPs. Inside target cells, THs are substrates of deiodinase enzymes which can both activate (i.e., forming T3) or inactivate (i.e., rT3 and T2) THs. THs are transported to the cell nucleus where they bind to TR receptors, which activate gene transcription, in fine resulting in metamorphosis. HPG axis: GnRH reaches gonadotropic cells to induce synthesis and release of gonadotropins (LH and FSH). LH and FSH both reach the gonads where they stimulate gonadal maturation and function (i.e., synthesis of sex steroids: E2, T and 11-KT). The balance between these sex steroids, in turn, regulates gametogenesis. RPD: rostral pars distalis, PPD: proximal pars distalis, PI: pars intermedia of the adenohypophysis.

Plastic pollution

Plastic pollution in the marine environment has become a global environmental concern [START_REF] Coyle | Microplastics in the marine environment: A review of their sources, distribution processes, uptake and exchange in ecosystems[END_REF]. Plastics are derived from raw natural substances such as petroleum, coal, and gas [START_REF] Gabbott | Chapter 3 -The geography and geology of plastics: their environmental distribution and fate[END_REF] and can absorb multiple pollutants from the aquatic environment. The mechanical or chemical impacts of plastics on marine organisms are well documented [START_REF] Jacob | Effects of virgin micro-and nanoplastics on fish: trends, meta-analysis, and perspectives[END_REF][START_REF] Welden | The environmental impacts of plastic pollution[END_REF]. Multiple mechanical impacts have been directly or indirectly linked to plastics including entanglement in macro-plastics (impeding mobility, leading to starvation or drowning), and the ingestion or inhalation of smaller plastic debris, such as micro-plastics (MPs) and nano-plastics (NPs; [START_REF] Welden | The environmental impacts of plastic pollution[END_REF]. In fish, most ingested MPs and NPs are eventually excreted, but a small fraction can accumulate in organs and tissues (mainly in the intestine and liver) causing severe tissue damage and inflammation (e.g., [START_REF] Jovanović | Ingestion of microplastics by fish and its potential consequences from a physical perspective[END_REF][START_REF] Wang | Polystyrene microplastics cause tissue damages, sex-specific reproductive disruption and transgenerational effects in marine medaka (Oryzias melastigma)[END_REF][START_REF] Araújo | Effects of triclosan on early development of Solea senegalensis: from biochemical to individual level[END_REF][START_REF] Jacob | A multifaceted assessment of the effects of polyethylene microplastics on juvenile gilthead seabreams (Sparus aurata)[END_REF][START_REF] Marana | Plastic nanoparticles cause mild inflammation, disrupt metabolic pathways, change the gut microbiota and affect reproduction in zebrafish: A full generation multi-omics study[END_REF].

Beyond mechanical risks, marine plastic debris can also act as a reservoir of chemicals that pose potential threats to wildlife. A wide array of contaminants may be contained in plastics: additives such as flame retardants and plasticisers that can leach out from the plastic, or contaminants that get absorbed into plastics from seawater. More than 250 organic compounds have been identified on plastic debris [START_REF] Campanale | A Detailed Review Study on Potential Effects of Microplastics and Additives of Concern on Human Health[END_REF]. Bisphenol A (BPA), used in the manufacturing of plastics, is found in aquatic environments worldwide, notably harbours, and its concentration is positively correlated with the amount of plastic waste generated in the region [START_REF] Wu | Effect of the plastic pollutant bisphenol A on the biology of aquatic organisms: A meta-analysis[END_REF]. BPA is a xenestrogen, i.e., an endocrine disruptor capable of mimicking natural estrogens [START_REF] Matozzo | Vitellogenin as a biomarker of exposure to estrogenic compounds in aquatic invertebrates: a review[END_REF][START_REF] Rubin | Bisphenol A: An endocrine disruptor with widespread exposure and multiple effects[END_REF].

BPA and its congeners can alter testis maturation and decreased sperm quality in fish [START_REF] Chen | Developmental bisphenol A exposure impairs sperm function and reproduction in zebrafish[END_REF][START_REF] Yang | Effects of BPF on steroid hormone homeostasis and gene expression in the hypothalamic-pituitary-gonadal axis of zebrafish[END_REF] and can induce gonad feminisation [START_REF] Drastichová | Effect of exposure to bisphenol A and 17β-estradiol on the sex differentiation in zebrafish (Danio rerio)[END_REF][START_REF] Gonzalez | Impact of bisphenol-A and synthetic estradiol on brain, behavior, gonads and sex hormones in a sexually labile coral reef fish[END_REF].

Males exposed to BPA show increased plasma vitellogenin (VTG) levels or increased vtg gene expression in the liver [START_REF] Sohoni | Reproductive effects of long-term exposure to bisphenol A in the fathead minnow (Pimephales promelas)[END_REF][START_REF] Van Den Belt | Comparison of vitellogenin responses in zebrafish and rainbow trout following exposure to environmental estrogens[END_REF][START_REF] Yang | Effects of BPF on steroid hormone homeostasis and gene expression in the hypothalamic-pituitary-gonadal axis of zebrafish[END_REF][START_REF] Frenzilli | Bisphenol A and Bisphenol S Induce Endocrine and Chromosomal Alterations in Brown Trout[END_REF][START_REF] Gonzalez | Impact of bisphenol-A and synthetic estradiol on brain, behavior, gonads and sex hormones in a sexually labile coral reef fish[END_REF]. VTG is a precursor of the egg-yolk protein; in females, VTG is synthetised in response to estrogens and stored in oocytes. In males, the gene coding for VTG is normally not expressed; its induction is thus used as a marker of estrogen exposure [START_REF] Matozzo | Vitellogenin as a biomarker of exposure to estrogenic compounds in aquatic invertebrates: a review[END_REF]. Together with increased estrogen levels, exposure to BPA is also associated with decreased androgen levels (T and / or 11-KT; [START_REF] Yang | Effects of BPF on steroid hormone homeostasis and gene expression in the hypothalamic-pituitary-gonadal axis of zebrafish[END_REF][START_REF] Gonzalez | Impact of bisphenol-A and synthetic estradiol on brain, behavior, gonads and sex hormones in a sexually labile coral reef fish[END_REF]. Bisphenol also acts on the HPG axis, a hormonal cascade starting with the release of gonadotropin-releasing-hormone (GnRH) from GnRH neurons in the pituitary, stimulating the synthesis of gonadotropins, namely luteinising hormones (LH) and follicle-stimulating hormone (FSH). Both hormones together stimulate gonad maturation and the production of sex steroid hormones (in fish, mainly estradiol (E2), testosterone (T) and 11ketotestosterone (11-KT); [START_REF] Mills | Plasma cortisol and 11-ketotestosterone enzyme immunoassay (EIA) kit validation for three fish species: the orange clownfish Amphiprion percula, the orangefin anemonefish Amphiprion chrysopterus and the blacktip reef shark Carcharhinus melanopterus[END_REF][START_REF] Mills | Natural endocrine profiles of the groupliving skunk anemonefish Amphiprion akallopisos in relation to their size-based dominance hierarchy[END_REF][START_REF] Zohar | Neuroendocrinology of reproduction in teleost fish[END_REF]. Moreover, in fish, kisspeptin (Kiss) neurons are thought to control the synthesis of gonadotropins, acting either directly on the pituitary cells or indirectly on GnRH neurons [START_REF] Somoza | Kisspeptin and GnRH interactions in the reproductive brain of teleosts[END_REF]. Following bisphenol exposure (BPA, bisphenol S, bisphenol F), the expression of Kiss1, Kiss receptor, GnRH2, GnRH3, GnRH receptors, fshβ, lhβ, and aromatase genes increases, whereas the expression of genes involved in steroidogenesis decreases (Ji et al., 2013;[START_REF] Qiu | Actions of bisphenol A and bisphenol S on the reproductive neuroendocrine system during early development in zebrafish[END_REF][START_REF] Yang | Effects of BPF on steroid hormone homeostasis and gene expression in the hypothalamic-pituitary-gonadal axis of zebrafish[END_REF][START_REF] Gonzalez | Impact of bisphenol-A and synthetic estradiol on brain, behavior, gonads and sex hormones in a sexually labile coral reef fish[END_REF].

BPA and their congeners can have profound effects on fish reproductive systems, raising questions about population persistence in the future.

Other studies have evaluated the effects of BPA on the thyroid system and found disruption of the HPT axis [START_REF] Zhang | Waterborne exposure to BPS causes thyroid endocrine disruption in zebrafish larvae[END_REF][START_REF] Wei | Transgenerational thyroid endocrine disruption induced by bisphenol S affects the early development of zebrafish offspring[END_REF][START_REF] Lee | Comparison of thyroid hormone disruption potentials by bisphenols A, S, F, and Z in embryo-larval zebrafish[END_REF] initiated by thyrotropin-releasing hormone (TRH) in mammals and corticotropin-releasing hormone (CRH) in non-mammalian species (see [START_REF] Laudet | The Origins and Evolution of Vertebrate Metamorphosis[END_REF][START_REF] Denver | Endocrinology of complex life cycles: amphibians[END_REF]. In fish, when the HPT axis is stimulated, hypothalamic CRH neurons release CRH in the anterior pituitary, which synthetises and releases thyroid-stimulating hormone (TSH) into the global circulation. In turn, TSH reaches thyroid follicles and stimulates the synthesis of thyroxine (T4), which can be converted into its active form triiodothyronine (T3) in peripheral tissues under the action of deiodinase enzymes [START_REF] Laudet | The Origins and Evolution of Vertebrate Metamorphosis[END_REF][START_REF] Denver | Endocrinology of complex life cycles: amphibians[END_REF]. Several studies have found altered circulating levels of T4 and T3 in individuals exposed to bisphenols compared to control individuals, suggesting a disruption to the HPT axis [START_REF] Zhang | Waterborne exposure to BPS causes thyroid endocrine disruption in zebrafish larvae[END_REF][START_REF] Wei | Transgenerational thyroid endocrine disruption induced by bisphenol S affects the early development of zebrafish offspring[END_REF][START_REF] Lee | Comparison of thyroid hormone disruption potentials by bisphenols A, S, F, and Z in embryo-larval zebrafish[END_REF]. In addition, BPA causes regulatory changes in genes involved in all steps of the HPT axis, for which gene transcription occurs mainly in the brain, pituitary, thyroid, peripheral tissues, and liver [START_REF] Lee | Comparison of thyroid hormone disruption potentials by bisphenols A, S, F, and Z in embryo-larval zebrafish[END_REF]. Interestingly, BPA on one hand and BPS -BPZ on the other hand may have different modes of action on the HPT axis. For example, in vivo (zebrafish embryos) and in vitro experiments have shown that exposure to BPA upregulated the expression of several genes involved in TH synthesis as well as genes involved in thyroid development [START_REF] Gentilcore | Bisphenol A interferes with thyroid specific gene expression[END_REF]. These results were further confirmed in zebrafish embryos exposed to BPA (i.e., upregulation of genes directly implicated in thyroid development and function; [START_REF] Lee | Comparison of thyroid hormone disruption potentials by bisphenols A, S, F, and Z in embryo-larval zebrafish[END_REF]. On the contrary, BPS and BPZ may deregulate gene expression in the brain and pituitary, notably causing the upregulation of crh and tsh gene transcription (at levels above 0.68 mg/L; Lee et al., 2019, higher than those observed in harbours, which are in the few ng/L range; [START_REF] Robinson | Estrogenic compounds in seawater and sediment from Halifax Harbour, Nova Scotia, Canada[END_REF][START_REF] Emnet | Organic Micropollutants in Wastewater Effluents and the Receiving Coastal Waters, Sediments, and Biota of Lyttelton Harbour (Te Whakaraupō), New Zealand[END_REF].

A transgenerational experiment showed that the thyroid hormone disruption -lower T4 and higher T3 circulating levels-seen in F0 zebrafish females exposed to BPS from 2 hours to 120 days post-fertilisation was transferred to eggs, leading to higher T3 circulating levels in F1 embryos, causing adverse effects (delayed hatching, decreased swimming speed and escape behaviour, and reduced pigmentation; [START_REF] Wei | Transgenerational thyroid endocrine disruption induced by bisphenol S affects the early development of zebrafish offspring[END_REF].

Overall, studies have highlighted numerous significant negative consequences of plastics on fish, either mechanically or through chemical impacts on several hormones. BPA is one of many plastic components that cause endocrine disruptions in marine organisms. However, there has been no study on fish living in harbours, although these zones are often exposed to high concentrations of plastics and associated chemicals [START_REF] Claessens | Occurrence and distribution of microplastics in marine sediments along the Belgian coast[END_REF][START_REF] Naidoo | Plastic pollution in five urban estuaries of KwaZulu-Natal, South Africa[END_REF][START_REF] Romeo | Environmental quality assessment of Grand Harbour (Valletta, Maltese Islands): a case study of a busy harbour in the Central Mediterranean Sea[END_REF][START_REF] Chen | Seasonal variation of diversity, weathering, and inventory of microplastics in coast and harbor sediments[END_REF]; characterising the effects of plastics on fish in harbours would be an informative research avenue.

Chemical contamination

In many coastal areas, including marinas, harbours, and ports, the legacy of past industrialisation and the past absence of regulations on emissions is still present. Coastal regions are part of the catchment-coast continuum, where catchment areas are often dominated by intense agriculture, may contain dump sites or landfills, and wastewater discharge is carried across drainage basins into the marine environment. It is therefore unsurprising that chemical contamination is increasing in many harbours and ports across the world (e.g., USA: [START_REF] Dauer | Relationships between Benthic Community Condition, Water Quality, Sediment Quality, Nutrient Loads, and Land Use Patterns in Chesapeake Bay[END_REF]Hong Kong: Nicholson et al., 2011;Brazil: Hatje and Barros 2012;Australia: Mayer-Pinto et al., 2015). Chemical contamination is one of the greatest threats to marine species, leading to impairments in development and reproduction [START_REF] Rochman | Early warning signs of endocrine disruption in adult fish from the ingestion of polyethylene with and without sorbed chemical pollutants from the marine environment[END_REF], the emergence of diseases [START_REF] Kiesecker | Synergism between trematode infection and pesticide exposure: a link to amphibian limb deformities in nature?[END_REF], declines in biodiversity and ecosystem function [START_REF] Johnston | Contaminants reduce the richness and evenness of marine communities: a review and meta-analysis[END_REF]Johnston et al., 2015), and numerous chemical pollutants are thyroid hormone disruptors [START_REF] Jarque | Deiodinases and thyroid metabolism disruption in teleost fish[END_REF].

Persistent organic pollutants

Among the multiple pollutants recorded in harbours, persistent organic pollutants, such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), are the most commonly detected [START_REF] Casado-Martínez | A multivariate assessment of sediment contamination in dredged materials from Spanish ports[END_REF][START_REF] Ghosh | PCB and PAH speciation among particle types in contaminated harbor sediments and effects on PAH bioavailability[END_REF][START_REF] Mali | Identification of hot spots within harbour sediments through a new cumulative hazard index. Case study: Port of Bari, Italy[END_REF]. Persistent organic pollutants are organic compounds that are resistant to environmental degradation through chemical, biological, or photolytic processes [START_REF] Jones | Persistent organic pollutants (POPs): state of the science[END_REF]. These persistent contaminants are usually found only in trace amounts in water but tend to adsorb onto inorganic and organic material settled in sediments [START_REF] Jones | Persistent organic pollutants (POPs): state of the science[END_REF]. Persistent organic pollutants are remobilised by human activities such as dredging, rendering them bioavailable [START_REF] Martins | Impact of remobilized contaminants in Mytilus edulis during dredging operations in a harbour area: Bioaccumulation and biomarker responses[END_REF]. Consequences on aquatic organisms are numerous: they are immunotoxic, genotoxic, mutagenic, and carcinogenic, and have the potential to disrupt hormonal systems [START_REF] Tanabe | Contamination and toxic effects of persistent endocrine disrupters in marine mammals and birds[END_REF][START_REF] Vega-López | Gender related differences in the oxidative stress response to PCB exposure in an endangered goodeid fish (Girardinichthys viviparus)[END_REF][START_REF] Luch | Carcinogenic Polycyclic Aromatic Hydrocarbons[END_REF] Polychlorinated biphenyls (PCBs), along with other organic pollutants (dioxins, and polycyclic aromatic hydrocarbons PAHs, a diverse group of organic molecules produced through the incomplete combustion of fossil fuels, petroleum, or petrochemical materials), have been strictly regulated since

2001, yet remain present in harbour sediments worldwide [START_REF] Connell | Fate and risk evaluation of persistent organic contaminants and related compounds in Victoria Harbour, Hong Kong[END_REF][START_REF] Adami | Detecting and characterising sources of persistent organic pollutants (PAHs and PCBs) in surface sediments of an industrialized area (harbour of Trieste, northern Adriatic Sea)[END_REF][START_REF] Barakat | Organochlorine pesticides and PCB residues in sediments of Alexandria Harbour, Egypt[END_REF][START_REF] Ghosh | PCB and PAH speciation among particle types in contaminated harbor sediments and effects on PAH bioavailability[END_REF]. In Sydney Harbour, 13 of 19 seafood species studied presented tissue concentrations of organic pollutants above standard thresholds for human consumption [START_REF] Manning | Levels of PCDD/Fs and dioxin-like PCBs in seafood from Sydney Harbour, Australia[END_REF]. [START_REF] Leatherland | Lowering of serum thyroxine and triiodothyronine levels in yearling coho salmon, Oncorhynchus kisutch, by dietary mirex and PCBs[END_REF] reported changes in thyroid histological appearance and decreased plasma TH levels in coho salmon (Oncorhynchus kisutch) and chinook salmon (Oncorhynchus tshawytscha) after PCB exposure. Since then, the thyroidal responses of fish to PCBs have shown variable results in different studies, depending on the species and the type of PCB congeners [START_REF] Brown | Contaminant effects on the teleost fish thyroid[END_REF]. A 30-day laboratory exposure to PCB in the diet of juvenile rainbow trout O. mykiss reported several detrimental effects, such as oxidative stress, thyroid system dysfunction -higher T4 levels and more active deiodination [START_REF] Buckman | PCBs can diminish the influence of temperature on thyroid indices in rainbow trout (Oncorhynchus mykiss)[END_REF]. A similar exposure in young-of-the-year Atlantic croaker Micropogonias undulatus decreased both T4 and T3 levels [START_REF] Leroy | Thyroid hormone status of Atlantic croaker exposed to Aroclor 1254 and selected PCB congeners[END_REF]. Altered reproductive physiology has been documented in numerous species (review by [START_REF] Henry | Ecotoxicology of polychlorinated biphenyls in fish-a critical review[END_REF]: for instance, female fish fed with PCB mixtures at environmentally realistic concentrations showed impaired ovarian maturation, delayed reproduction, and produced fewer viable eggs [START_REF] Daouk | Long-term food-exposure of zebrafish to PCB mixtures mimicking some environmental situations induces ovary pathology and impairs reproduction ability[END_REF][START_REF] Horri | Fish life-history traits are affected after chronic dietary exposure to an environmentally realistic marine mixture of PCBs and PBDEs[END_REF].

Life history transitions, such as metamorphosis, are hugely sensitive to endocrine disruption.

Larval and juvenile Japanese flounder (Paralichthys olivaceus) exposed to PCBs show declines in T3 and T4 levels as well as changes in deiodinase gene expression levels, which were associated with slower growth and delay metamorphosis [START_REF] Dong | Disruption of the Thyroid System by the Thyroid-Disrupting Compound Aroclor 1254 in Juvenile Japanese Flounder (Paralichthys olivaceus)[END_REF][START_REF] Dong | Effects of polychlorinated biphenyls on metamorphosis of a marine fish Japanese flounder (Paralichthys olivaceus) in relation to thyroid disruption[END_REF]. The effects of PAHs on the thyroid function in fish remain poorly studied [START_REF] Brown | Contaminant effects on the teleost fish thyroid[END_REF][START_REF] Kim | Thyroid hormone disruption by water-accommodated fractions of crude oil and sediments affected by the Hebei Spirit oil spill in zebrafish and GH3 cells[END_REF][START_REF] Price | The effects of exposure to crude oil or PAHs on fish swim bladder development and function[END_REF].

Nevertheless, a few studies have reported adverse effects on TH. For example, in juvenile common carp (Cyprinus carpio), levels of plasma T3 and T4 were reduced in response to PAHs exposure [START_REF] Shirdel | The response of thyroid hormones, biochemical and enzymological biomarkers to pyrene exposure in common carp (Cyprinus carpio)[END_REF], and similar results were found in zebrafish larvae [START_REF] Kim | Thyroid hormone disruption by water-accommodated fractions of crude oil and sediments affected by the Hebei Spirit oil spill in zebrafish and GH3 cells[END_REF]. In addition, short-term exposures of water-soluble fractions from oil (PAH compounds) to larval and juvenile turbot (Scophthalmus maximus) increased whole-body concentrations of T4, but not T3 [START_REF] Stephens | Stress responses of larval turbot, Scophthalmus maximus L., exposed to sub-lethal concentrations of petroleum hydrocarbons[END_REF].

Overall, the effects of persistent organic pollutants on the thyroid system are varied and depend on the compound and species. Changes in TH levels in both larvae and juveniles may reflect a complex disruption of biological processes, both in terms of TH synthesis and of their biotransformation in peripheral tissues, which may result in developmental deformities of adults.

Metals

Developing fish (embryos, larvae, and juveniles) are particularly sensitive to heavy metal exposure [START_REF] Sfakianakis | Effect of heavy metals on fish larvae deformities: a review[END_REF], and certain metals such as Cadmium (Cd) or Copper (Cu) are often present in harbours and ports [START_REF] Broman | Spatial and seasonal variation of major and trace elements in settling particulate matter in an estuarine-like archipelago area in the Northern Baltic proper[END_REF][START_REF] Jupp | Assessment of heavy metal and petroleum hydrocarbon contamination in the Sultanate of Oman with emphasis on harbours, marinas, terminals and ports[END_REF]. Fish embryos exposed to Cd or Cu have lower hatching rates and survival, while young individuals (larvae and juveniles) notably suffer from severe skeletal deformities, impairments of the lateral line, and cardiac oedema [START_REF] Sfakianakis | Effect of heavy metals on fish larvae deformities: a review[END_REF]. Moreover, Cd exposure negatively impacts the function of both the HPT and the HPI axes (HPI ends with the synthesis and release of corticosteroids, mainly cortisol). Indeed, fish larvae exposed to Cd show complete disturbance of gene expression in the HPT axis and reduced circulating plasma levels of T4 [START_REF] Jancic | Cadmium effects on the thyroid gland[END_REF][START_REF] Li | Effects of waterborne cadmium on thyroid hormone levels and related gene expression in Chinese rare minnow larvae[END_REF]. Cd can also disturb cortisol synthesis by suppressing the expression of genes coding for proteins which are essential for corticosteroid production (i.e. StAR (steroidogenic acute regulatory protein) and MC2R (Melanocortin 2 receptor, which triggers steroid biosynthesis following activation by ACTH); [START_REF] Sandhu | Cadmium-mediated disruption of cortisol biosynthesis involves suppression of corticosteroidogenic genes in rainbow trout[END_REF]. Cadmium could potentially have detrimental effects on the metamorphosis and development of young fish and alter the reproductive system of adults. Persistent organic pollutants, such as PCBs, and metals, such as Cd, are examples of a large number of contaminants with varied and potentially cumulative effects.

Pesticides

A commonly used insecticide, chlorpyrifos (CPF), significantly decreases thyroid hormone levels of exposed fish juveniles, thus altering their metamorphosis, leading to decreased intestine lengthening and impaired grazing behaviour [START_REF] Holzer | Fish larval recruitment to reefs is a thyroid hormone-mediated metamorphosis sensitive to the pesticide chlorpyrifos[END_REF]. [START_REF] Besson | Anthropogenic stressors impact fish sensory development and survival via thyroid disruption[END_REF] also showed that CPF and increased temperature, independently as well as synergistically, affect sensory development and predator avoidance behaviour in a coral reef fish [START_REF] Besson | Anthropogenic stressors impact fish sensory development and survival via thyroid disruption[END_REF]. Their results suggest that TH signalling might be the underlying physiological process impacted by these different stressors, however, each stressor might affect physiological process in unique ways. Increased temperature impacts T4 levels, suggesting an alteration at the neuroendocrine level -before T4 is converted to other compounds such as T3. In contrast, CPF is thought to have a more downstream effect, possibly by acting on T3 metabolism [START_REF] Besson | Anthropogenic stressors impact fish sensory development and survival via thyroid disruption[END_REF][START_REF] Holzer | Fish larval recruitment to reefs is a thyroid hormone-mediated metamorphosis sensitive to the pesticide chlorpyrifos[END_REF]. Fish exposed to these stressors had impaired antipredator behaviour, similar to that of pre-metamorphosed larvae, and experienced higher mortality from predation. The disruption of TH signalling during fish metamorphosis can cause neurological defects, with possible community-level consequences that may even threaten the maintenance of a species [START_REF] Crane | The effects of methimazole on development of the fathead minnow, Pimephales promelas, from embryo to adult[END_REF][START_REF] Noyes | The toxicology of climate change: environmental contaminants in a warming world[END_REF][START_REF] Laudet | The Origins and Evolution of Vertebrate Metamorphosis[END_REF][START_REF] Holzer | Fish larval recruitment to reefs is a thyroid hormone-mediated metamorphosis sensitive to the pesticide chlorpyrifos[END_REF][START_REF] Pinsky | Greater vulnerability to warming of marine versus terrestrial ectotherms[END_REF]. Indeed, changes in survival rates during this transition and post-settlement can have drastic effects on population replenishment. This is of particular concern as nurseries are mainly located in shallow coastal waters and some harbours are even qualified as nurseries [START_REF] Bouchoucha | Potential use of marinas as nursery grounds by rocky fishes: Insights from four Diplodus species in the Mediterranean[END_REF]Mercader et al., 2017b;[START_REF] Patranella | Artificial reefs as juvenile fish habitat in a marina[END_REF][START_REF] Meinesz | Impact of coastal development on the infralittoral zone along the southeastern Mediterranean shore of continental France[END_REF] despite containing multiple stressors that can affect fish metamorphosis and subsequent juvenile quality. As such, harbours are ideal sites to study the impact of multiple stressors on fish endocrine pathways "in situ", in an ecologically relevant context.

Understanding how harbours effect fish hormonal systems during metamorphosis is of great importance from a conservation perspective.

Wastewater discharge

In addition to pesticides, many other contaminants can reach the coast and harbours (endocrine disruptors, pharmaceuticals, etc.) through wastewater discharge [START_REF] Mossa | Field measurements and monitoring of wastewater discharge in sea water[END_REF][START_REF] Hamdhani | Release of treated effluent into streams: A global review of ecological impacts with a consideration of its potential use for environmental flows[END_REF]. Among these, triclosan (TCS) is a synthetic chlorinated bactericide used in a vast number of personal care (soaps, toothpastes, deodorants, etc.) and textile products [START_REF] Adolfsson-Erici | Triclosan, a commonly used bactericide found in human milk and in the aquatic environment in Sweden[END_REF]. TCS has been monitored in US streams [START_REF] Kolpin | Pharmaceuticals, hormones, and other organic wastewater contaminants in US streams, 1999-2000: A national reconnaissance[END_REF] and coastal waters (i.e., in the Narragansett Bay: [START_REF] Katz | Factors regulating the accumulation and spatial distribution of the emerging contaminant triclosan in the sediments of an urbanized estuary: Greenwich Bay, Rhode Island, USA[END_REF]the San Francisco Bay: Jackson and Sutton, 2008;[START_REF] Kerrigan | Quantification of hydroxylated polybrominated diphenyl ethers (OH-BDEs), triclosan, and related compounds in freshwater and coastal systems[END_REF]. TCS has structural similarities with THs, suggesting it could disturb thyroid function [START_REF] Adolfsson-Erici | Triclosan, a commonly used bactericide found in human milk and in the aquatic environment in Sweden[END_REF]. Studies have investigated the toxicity of TCS on various organisms and reported high mortality rates, deformities, perturbations of behaviour, and reproductive failure [START_REF] Orvos | Aquatic toxicity of triclosan[END_REF][START_REF] Oliveira | Effects of triclosan on zebrafish early-life stages and adults[END_REF][START_REF] Nassef | In ovo nanoinjection of triclosan, diclofenac and carbamazepine affects embryonic development of medaka fish (Oryzias latipes)[END_REF]review by Dann and Hontela 2011). However, few studies have investigated the effects of TCS on fish metamorphosis. In the sheepshead minnow Cyprinodon variegatus, the T3 peak observed in control fish (indicative of metamorphosis climax) is absent in fish exposed to TCS, resulting in delayed metamorphosis [START_REF] Schnitzler | Triclosan exposure results in alterations of thyroid hormone status and retarded early development and metamorphosis in Cyprinodon variegatus[END_REF]. Zebrafish larvae exposed to TCS also displayed delayed metamorphosis [START_REF] Stenzel | Larval exposure to environmentally relevant concentrations of triclosan impairs metamorphosis and reproductive fitness in zebrafish[END_REF]. In the sole Solea senegalensis, TCS had the opposite effect and accelerated metamorphosis [START_REF] Araújo | Effects of triclosan on early development of Solea senegalensis: from biochemical to individual level[END_REF]. The mechanisms of action of TCS remain unclear but are thought to modulate the expression of several genes involved in the HPT axis, notably affecting the expression of TH receptors α and β in the North American bullfrog Rana catesbeiana [START_REF] Veldhoen | The bactericidal agent triclosan modulates thyroid hormoneassociated gene expression and disrupts postembryonic anuran development[END_REF], and upregulating of the expression of the tsh gene in adult zebrafish [START_REF] Pinto | Triclosan interferes with the thyroid axis in the zebrafish (Danio rerio)[END_REF]. TCS is detected in the environment worldwide, and has been recorded in various organisms, including humans [START_REF] Dann | Triclosan: environmental exposure, toxicity and mechanisms of action[END_REF]. A better understanding of the risks associated with its use is urgent.

Antifouling compounds

Antifouling compounds are used on many submerged structures (e.g., ship hulls, buoys) to prevent the recruitment of marine organisms, but have many unintended impacts. Tributyltin (TBT) used to be a widespread antifouling agent. Its use became regulated in the 1980s and was banned in 2008 [START_REF] Imo | Anti-fouling Systems: International Convention on the Control of Harmful Anti-fouling Systems on Ships, 2001 (AFS 2001) and Guidelines for Survey and Certification of Anti-fouling Systems on Ships (resolution MEPC[END_REF] after it was linked to a global decline in marine molluscs, likely causing reproductive failure [START_REF] Gibbs | Reproductive Failure in the Gastropod Nucella Lapillus Associated with Imposex Caused by Tributyltin Pollution: A Review BT -Organotin: Environmental fate and effects[END_REF][START_REF] Antizar-Ladislao | Environmental levels, toxicity and human exposure to tributyltin (TBT)contaminated marine environment[END_REF]. TBT has been shown to delay tadpole metamorphosis and growth in amphibians [START_REF] Shi | Effects of tributyltin on metamorphosis and gonadal differentiation of Xenopus laevis at environmentally relevant concentrations[END_REF] and studies reported altered T4 and T3 levels and HPT gene expression in the zebrafish Danio rerio, goldfish Carassius auratus as well as in marine rockfish Sebastiscus marmoratus [START_REF] Zhang | Tributyltin exposure causes lipotoxicity responses in the ovaries of rockfish, Sebastiscus marmoratus[END_REF][START_REF] Zhang | Tributyltin disrupts feeding and energy metabolism in the goldfish (Carassius auratus)[END_REF][START_REF] Li | Effects of the tributyltin on the blood parameters, immune responses and thyroid hormone system in zebrafish[END_REF]. Recently, medetomidine, a veterinary anaesthetic, has emerged as a new antifouling agent [START_REF] Dahlström | Surface active adrenoceptor compounds prevent the settlement of cyprid larvae of Balanus improvisus[END_REF]. It is widely used [START_REF] Wendt | The toxicity of the three antifouling biocides DCOIT, TPBP and medetomidine to the marine pelagic copepod Acartia tonsa[END_REF] even though its ecotoxicological effects are poorly understood. Recent studies on amphibians showed that tadpoles exposed to medetomidine experienced delayed metamorphosis [START_REF] Barr | Exposure to the antifouling chemical medetomidine slows development, reduces body mass, and delays metamorphosis in wood frog (Lithobates sylvaticus) tadpoles[END_REF][START_REF] Fong | Differential sensitivity to the antifouling chemical medetomidine between wood frog and American toad tadpoles with evidence for low-dose stimulation and high-dose inhibition of metamorphosis[END_REF]. Medetomidine induces paleness in fish [START_REF] Bellas | Sublethal effects of a new antifouling candidate on lumpfish (Cyclopterus lumpus L.) and Atlantic cod (Gadus morhua L.) larvae[END_REF][START_REF] Hilvarsson | Medetomidine as a candidate antifoulant: Sublethal effects on juvenile turbot (Psetta maxima L.)[END_REF][START_REF] Lennquist | Responses in fish exposed to medetomidine, a new antifouling agent[END_REF], which may be due to altered thyroid function, as TH regulates fish pigmentation [START_REF] Mcmenamin | Thyroid hormone-dependent adult pigment cell lineage and pattern in zebrafish[END_REF][START_REF] Saunders | Thyroid hormone regulates distinct paths to maturation in pigment cell lineages[END_REF][START_REF] Salis | Thyroid hormones regulate the formation and environmental plasticity of white bars in clownfishes[END_REF].

Case study of chemical contaminants: the San Francisco Bay

The San Francisco Bay features on the "303(d)" list of impaired water bodies in the US from the federal Clean Water Act. Chemical contaminants found in the San Francisco Bay include pesticides (diazinon, chlordane, dieldrin, dichlorodiphenyltrichloroethane), polyaromatic hydrocarbons, and chlorinated compounds. Several of the compounds monitored in the bay as well as in marine organisms are sometimes found in concentrations higher than the screening values established by the US EPA [START_REF] Fairey | Organochlorines and other environmental contaminants in muscle tissues of sportfish collected from San Francisco Bay[END_REF][START_REF] Davis | Polychlorinated biphenyls (PCBs) in San Francisco Bay[END_REF][START_REF] Greenfield | Polychlorinated biphenyl spatial patterns in San Francisco Bay forage fish[END_REF]. To our knowledge, only one study investigated fish TH levels in the vicinity of a harbour in the area [START_REF] Brar | Evidence for thyroid endocrine disruption in wild fish in San Francisco Bay, California, USA. Relationships to contaminant exposures[END_REF]. In this work, young individuals of two fish species, the shiner surfperch (Cymatogaster aggregate) and the Pacific staghorn sculpin (Leptocottus armatus), were sampled in several locations across the San Francisco Bay and over two consecutive years. Over the 2-year sampling period, both species had reduced T4 concentrations in locations with concentrated human activities (among which the Oakland inner harbour and the San Leandro Bay) compared to other locations [START_REF] Brar | Evidence for thyroid endocrine disruption in wild fish in San Francisco Bay, California, USA. Relationships to contaminant exposures[END_REF]. Fish liver analyses revealed the presence of over 85% of existing PCB congeners, with concentrations inversely correlated to T4 levels. Fishes also had significant differences in T3 concentrations and T3/T4 ratios across the study locations, which might reveal an alteration of deiodinase activity in peripheral tissues. The sampled sculpins may have been undergoing metamorphosis at the time of sampling (as indicated by their body size ;[START_REF] Goto | Alternative life-history styles of Japanese freshwater sculpins revisited BT -Alternative life-history styles of fishes[END_REF]).

The altered TH levels due to contaminant exposure in the long term and notably during metamorphosis may lead to thyroid dysfunction, alter metamorphosis, and threaten population persistence.

Invasive species

Harbours, in addition to being subjected to anthropogenic stressors, are very susceptible to invasions of aquatic species. [START_REF] Boets | Assessing the importance of alien macro-Crustacea (Malacostraca) within macroinvertebrate assemblages in Belgian coastal harbours[END_REF] showed that one fourth of all crustacean species across four Belgian harbours were non-native. Invasive species in harbours mainly arrive in ballast water or from hull fouling [START_REF] Carlton | Transoceanic and interoceanic dispersal of coastal marine organisms, the biology of ballast water[END_REF][START_REF] Ruiz | Invasion of coastal marine communities in North America: apparent patterns, processes, and biases[END_REF][START_REF] Boets | Assessing the importance of alien macro-Crustacea (Malacostraca) within macroinvertebrate assemblages in Belgian coastal harbours[END_REF]. They can also originate from aquaculture or the aquarium trade [START_REF] Naylor | Aquaculture--A Gateway for Exotic Species[END_REF]. The arrival of new species in a harbour can cause interspecific competition with native species, leading to increased predation and stress. In fish, stress is mediated by glucocorticoids, among which cortisol is often measured as an indicator of stress (e.g., [START_REF] Beldade | Cascading effects of thermally-induced anemone bleaching on associated anemonefish hormonal stress response and reproduction[END_REF]. During a stressful situation, the HPI axis is stimulated, leading to the release of cortisol into the organism [START_REF] Wendelaar Bonga | The stress response in fish[END_REF]. During acute stress, cortisol release is considered adaptive because it stimulates the catabolism of lipids, mobilising energy to cope with the stressful event [START_REF] Van Weerd | The effects of chronic stress on growth in fish: a critical appraisal[END_REF]. However, prolonged stress can have detrimental effects on organisms, including impaired disease resistance, loss of appetite, reduced growth, and altered reproduction [START_REF] Wendelaar Bonga | The stress response in fish[END_REF][START_REF] Van Weerd | The effects of chronic stress on growth in fish: a critical appraisal[END_REF]. The presence of invasive species which could induce stress in native species has never been explored in fish living in harbours or elsewhere. The only insight available is from a mammal, the Eurasian red squirrel (Sciurus vulgaris), faced with the invasion of grey squirrels (S. carolinensis; [START_REF] Santicchia | Stress in biological invasions: Introduced invasive grey squirrels increase physiological stress in native Eurasian red squirrels[END_REF]. The presence of the invader induced high physiological stress in the native species: faecal glucocorticoid levels of native individuals were related to the abundance of invasive individuals. Whether alien species can induce physiological stress in fish has not yet been studied. Given the highly mobile nature of fish, and because cortisol levels fluctuate extremely rapidly (within a few minutes; Pankhurst 2011), it will be particularly challenging to assess stress levels in response to invasive species from blood samples in harbours.

Boat noise

Sound travels faster and further underwater compared with in air, and the frequency and intensity of anthropogenic underwater sounds overlap with the ranges of natural biological sounds [START_REF] Hastings | Effects of sound on fish[END_REF][START_REF] Slabbekoorn | A noisy spring: the impact of globally rising underwater sound levels on fish[END_REF]. Anthropogenic underwater sounds have therefore been defined as pollutants. Within the EU Marine Strategy Framework Directive (MSFD) (2010/477/EU European Commission Decision), two indicators have been proposed to monitor this pollution: impulsive noise and continuous noise. The anthropogenic contribution to the soundscapes of many harbours worldwide, notably in the northern hemisphere, is dominated by continuous noise caused by commercial shipping [START_REF] Hildebrand | Anthropogenic and natural sources of ambient noise in the ocean[END_REF][START_REF] Mckenna | Relationship between container ship underwater noise levels and ship design, operational and oceanographic conditions[END_REF]. In the northeast Pacific, noise from commercial shipping in inshore waters is also the most persistent type of anthropogenic noise, notably in large ports such as Vancouver and Seattle [START_REF] Erbe | Identifying Modeled Ship Noise Hotspots for Marine Mammals of Canada's Pacific Region[END_REF]. In addition, tourism and recreational boating also add a substantial amount of noise to coastal underwater soundscapes (e.g., [START_REF] Mcdonald | Increases in deep ocean ambient noise in the Northeast Pacific west of San Nicolas Island, California[END_REF][START_REF] Hermannsen | Recreational vessels without Automatic Identification System (AIS) dominate anthropogenic noise contributions to a shallow water soundscape[END_REF][START_REF] Mccormick | Effects of boat noise on fish faststart escape response depend on engine type[END_REF]. During a lockdown put in place by governments worldwide to slow the spread of COVID-19 (April-May 2020), the vocal activity of a range of coral reef fish living in the marina of Pointe-à-Pitre (Guadeloupe, French West Indies), located next to a major maritime harbour, was reduced as a response to the lower levels of anthropogenic noise they experienced [START_REF] Bertucci | Changes to an urban marina soundscape associated with COVID-19 lockdown in Guadeloupe[END_REF].

Several studies have highlighted the effect of noise on fish physiology, although none have directly tested this on fish living in harbours. The potential stressors caused by anthropogenic underwater noise include behavioural responses, which are mediated through androgen and glucocorticoid pathways [START_REF] Mills | Hormonal and behavioural effects of motorboat noise on wild coral reef fish[END_REF] and may ultimately lead to hearing impairment or habitat abandonment. Noise can affect physiology as early as the embryonic stage in fish, with heart rates shown to increase in staghorn damselfish embryos (Amblyglyphidodon curacao) exposed to noise from boats with 2-and 4-stroke engines [START_REF] Jain-Schlaepfer | Impact of motorboats on fish embryos depends on engine type[END_REF]. This study also demonstrated that heart rate doubled with playbacks of 2-stroke engines compared to 4-stroke engine playbacks. Similarly, heart rate increased by approximately 10% when sounds of small boats powered by 2-stroke engines were played back to embryos of damselfishes Amphiprion melanopus and Acanthochromis polyacanthus [START_REF] Fakan | Boat noise affects the early life history of two damselfishes[END_REF]. Similar exposures to anthropogenic noise in starved green Chromis (Chromis viridis) and spiny damselfish (A. polyacanthus) caused a heightened corticosteroid stress response (Armstrong-Smith, 2016). Besides the Pomacentridae family, which has received most attention, boat noise playbacks also increased whole body cortisol levels of a Labridae species, the slippery dick (Halichoeres bivittatus; [START_REF] Staaterman | Exposure to boat noise in the field yields minimal stress response in wild reef fish[END_REF]. Should this exposure be prolonged, elevated cortisol levels might ultimately impact immune responses and weaken responses to diseases and parasites [START_REF] Fast | Cortisol response and immune-related effects of Atlantic salmon (Salmo salar Linnaeus) subjected to short-and long-term stress[END_REF]. While elevated cortisol levels drove fish to hide in their shelter during anthropogenic noise, circulating androgens such as testosterone, correlated with aggression in orange-fin anemonefish (Amphiprion chrysopterus) when exposed to both 30 min and 48 hours of boat noise [START_REF] Mills | Hormonal and behavioural effects of motorboat noise on wild coral reef fish[END_REF].

In freshwater environments, playbacks of underwater boat noise recorded from the Danube River and in two Austrian lakes led to increased cortisol secretion in the common carp (Cyprinus carpio), the gudgeon (Gobio gobio), and the European perch (Perca fluviatilis; [START_REF] Wysocki | Ship noise and cortisol secretion in European freshwater fishes[END_REF]. However, no increase was observed when fish were exposed to continuous random noise. This indicated that irregular noises such as those caused by ship engines, with fluctuations in amplitude and frequency, constitute important stressors. This study also did not find differences in response between species possessing excellent (common carp and gudgeon) or poor (perch) hearing abilities. Nevertheless, species-specific sensitivities and ranges of hearing capacities may alter the extent to which anthropogenic noise impacts them. Motorboat noise also affects interspecies interactions. Bluestreak cleaner wrasses (Labroides dimidiatus) inspected their fish clients for longer and were significantly less cooperative during exposure to boat noise [START_REF] Nedelec | Motorboat noise disrupts co-operative interspecific interactions[END_REF]. Furthermore, clients did not retaliate as expected (i.e., by chasing) in response to increased cheating by cleaners, suggestive of cognitive impairments due to distraction by both parties. The effects of noise may also depend on multiple acoustic factors, such as sound frequency, intensity, and duration [START_REF] Slabbekoorn | A noisy spring: the impact of globally rising underwater sound levels on fish[END_REF][START_REF] Hawkins | Developing sound exposure criteria for fishes[END_REF].

While some fish species appear to somewhat acclimate to noise in terms of behaviour -with behaviours returning to control levels after continuous noise exposure [START_REF] Nedelec | Repeated exposure to noise increases tolerance in a coral reef fish[END_REF][START_REF] Holmes | Juvenile damselfish are affected but desensitize to small motor boat noise[END_REF][START_REF] Staaterman | Exposure to boat noise in the field yields minimal stress response in wild reef fish[END_REF] -, hormonal effects could be long-lived. This has been documented through the increase in aggressiveness and hiding behaviour of A. chrysopterus, linked to heightened levels of testosterone and cortisol respectively, after short thirty-minute boat noise playbacks, but also over longer two-day playbacks, throughout which A. chrysopterus did not show any habituation or reduction in response [START_REF] Mills | Hormonal and behavioural effects of motorboat noise on wild coral reef fish[END_REF]. It illustrates that changes in the physiological state in response to noise could result in prolonged behavioural effects in reef fish species, which might ultimately lead to alterations in individual fitness and behavioural changes at the population level [START_REF] Radford | Repeated exposure reduces the response to impulsive noise in European seabass[END_REF][START_REF] Popper | An overview of fish bioacoustics and the impacts of anthropogenic sounds on fishes[END_REF].

Artificial light pollution at night

Harbours are one of the largest sources of permanent light on coastlines with light emitted from homes, resorts, and streetlights [START_REF] Davies | The nature, extent, and ecological implications of marine light pollution[END_REF]. Shallow waters in harbours experience light intensities up to 150-200 lux [START_REF] Bolton | Coastal urban lighting has ecological consequences for multiple trophic levels under the sea[END_REF], compared to intensities of 0.03 to 2.5 lux due to skyglow in other zones (when scattered light from streetlights is reflected by clouds; [START_REF] Perkin | Artificial light as a disturbance to lightnaïve streams[END_REF], 0.1-0.3 lux during full moonlight on a clear night, and only 0.00003-0.0001 lux on a cloudy night [START_REF] Rich | Ecological consequences of artificial night lighting[END_REF]. The consequences on living organisms are multiple as artificial-light-at-night (ALAN) could affect functions related to orientation in space (phototropism, phototaxis) and in time (circadian rhythms; Falcón et al., 2020).

Circadian clocks are systems that translate environmental information, mainly the alternation of light and darkness (or photoperiod), into the hormonal signal melatonin to orchestrate a myriad of downstream biochemical, physiological, and behavioural events so that the right process occurs at the right time [START_REF] Falcón | Structural and functional evolution of the pineal melatonin system in vertebrates[END_REF]Falcón et al 2020). In fish, the main source of information on photoperiod and light is from the photosensitive pineal organ, situated at the surface of the brain underneath a translucent window in the skull. The pineal photoreceptors are responsible for the nocturnal production of the time-keeping hormone melatonin, the duration of this nocturnal signal reflecting the duration of the night, while the amplitude varies with temperature in a species-specific manner. Consequently, daily and annual variations in melatonin production provide internal information of daily and annual time, for the orchestration and synchronization of numerous physiological and behavioural processes [START_REF] Falcón | The photosensory function of the pineal organ of the pike (Esox lucius L.) Correlation between structure and function[END_REF][START_REF] Underwood | The pineal and melatonin: Regulators of circadian function in lower vertebrates[END_REF][START_REF] Falcón | Regulation of the Rhythmic Melatonin Secretion by Fish Pineal Photoreceptor Cells BT -Rhythms in Fishes[END_REF][START_REF] Falcón | Structural and functional evolution of the pineal melatonin system in vertebrates[END_REF][START_REF] Grubisic | Light pollution, circadian photoreception, and melatonin in vertebrates[END_REF]. Other tissues that produce hormonal signals include deep brain photoreceptors, the saccus vasculosus, or photoreceptors in the retina [START_REF] Kojima | Vertebrate ancient-long opsin: a green-sensitive photoreceptive molecule present in zebrafish deep brain and retinal horizontal cells[END_REF][START_REF] Philp | Vertebrate ancient (VA) opsin and extraretinal photoreception in the Atlantic salmon (Salmo salar)[END_REF][START_REF] Peirson | The evolution of irradiance detection: melanopsin and the non-visual opsins[END_REF][START_REF] Falcón | Current knowledge on the melatonin system in teleost fish[END_REF][START_REF] Nakane | The saccus vasculosus of fish is a sensor of seasonal changes in day length[END_REF]. The main hormone controlling circadian activities, pineal melatonin, is produced during the night and released in the cerebrospinal fluid and blood to control locomotor activity, food intake, shoaling, and diel vertical migration (Ekstrzm andMeissl, 1997, 2004;[START_REF] Ryer | Effect of light on juvenile walleye pollock shoaling and their interaction with predators[END_REF][START_REF] Mehner | Diel vertical migration of freshwater fishes -proximate triggers, ultimate causes and research perspectives[END_REF][START_REF] Vowles | Effects of avoidance behaviour on downstream fish passage through areas of accelerating flow when light and dark[END_REF]. Pineal melatonin also regulates seasonal rhythms including reproduction, growth and development, sleep rhythms, rhythmicity of locomotor activity, and immune responsiveness [START_REF] Duston | Photoperiodic mechanisms and rhythms of reproduction in the female rainbow trout[END_REF][START_REF] Fairey | Organochlorines and other environmental contaminants in muscle tissues of sportfish collected from San Francisco Bay[END_REF][START_REF] Boeuf | Does light have an influence on fish growth?[END_REF][START_REF] Downing | Effects of light intensity, spectral composition and photoperiod on development and hatching of haddock (Melanogrammus aeglefinus) embryos[END_REF][START_REF] Wiechmann | Role of melatonin and its receptors in the vertebrate retina[END_REF]. However, more and more studies warn about the potentially disruptive effects of ALAN on the synchronization of biological functions and life cycle of species, questioning their sustainability on impacted areas, such as harbours. Almost all studies in fish have shown that broad-spectrum white light, even as little as 1, 0.1 and 0.01 lux, reduces the nocturnal production of plasma melatonin across fish species. ALAN reduced melatonin in temperate freshwater fish such as goldfish (C. auratus; [START_REF] Kezuka | Daily cycles in plasma melatonin levels under long or short photoperiod in the common carp, Cuprinus carpio[END_REF]Iigo et al., 1997), pike (Esox lucius;[START_REF] Falcón | Rhythmic melatonin biosynthesis in a photoreceptive pineal organ: a study in the pike[END_REF][START_REF] Falcón | Regulation of melatonin secretion in a photoreceptive pineal organ: an in vitro study in the pike[END_REF], zebrafish [START_REF] Khan | Artificial Light at Night (ALAN), an alarm to ovarian physiology: a study of possible chronodisruption on zebrafish (Danio rerio)[END_REF] and other freshwater species [START_REF] Porter | Temperature, light intensity and plasma melatonin levels in juvenile Atlantic salmon[END_REF][START_REF] Vera | Influence of light intensity on plasma melatonin and locomotor activity rhythms in tench[END_REF][START_REF] Brüning | Spotlight on fish: light pollution affects circadian rhythms of European perch but does not cause stress[END_REF]Brüning et al., , 2018b)), as well as in marine species such as the Atlantic salmon (Salmo salar), European sea bass (Dicentrarchus labrax) and Arctic charr (Salvelinus alpinus; [START_REF] Porter | Temperature, light intensity and plasma melatonin levels in juvenile Atlantic salmon[END_REF][START_REF] Bayarri | Influence of light intensity, spectrum and orientation on sea bass plasma and ocular melatonin[END_REF][START_REF] Rahman | Effects of moonlight exposure on plasma melatonin rhythms in the seagrass rabbitfish, Siganus canaliculatus[END_REF][START_REF] Vera | Influence of light intensity on plasma melatonin and locomotor activity rhythms in tench[END_REF][START_REF] Nikaido | Photic and circadian regulation of melatonin production in the Mozambique tilapia Oreochromis mossambicus[END_REF][START_REF] Park | Influence of moonlight on mRNA expression patterns of melatonin receptor subtypes in the pineal organ of a tropical fish[END_REF][START_REF] Choi | Changes in circadian parameters of humbug damselfish, Dascyllus aruanus according to lunar phase shifts in Micronesia[END_REF][START_REF] Liu | Light intensity and suppression of nocturnal plasma melatonin in Arctic charr (Salvelinus alpinus)[END_REF]. Tropical marine species have shown some of the strongest responses to light at night of 1 lux (e.g., [START_REF] Rahman | Effects of moonlight exposure on plasma melatonin rhythms in the seagrass rabbitfish, Siganus canaliculatus[END_REF][START_REF] Nikaido | Photic and circadian regulation of melatonin production in the Mozambique tilapia Oreochromis mossambicus[END_REF][START_REF] Carazo | The effect of night illumination, red and infrared light, on locomotor activity, behaviour and melatonin of Senegalese sole (Solea senegalensis) broodstock[END_REF][START_REF] Park | Influence of moonlight on mRNA expression patterns of melatonin receptor subtypes in the pineal organ of a tropical fish[END_REF]. Increasing light intensity had little to no effect suggesting that there is likely a threshold level of ALAN near 1 lux that alters the circadian rhythm in fish [START_REF] Brüning | Spotlight on fish: light pollution affects circadian rhythms of European perch but does not cause stress[END_REF][START_REF] Brüning | Impact of different colours of artificial light at night on melatonin rhythm and gene expression of gonadotropins in European perch[END_REF](Brüning et al., , 2018a)). Even lower light levels, such as skyglow (0.01-0.1 lux), suppress nocturnal melatonin levels [START_REF] Kupprat | Can skyglow reduce nocturnal melatonin concentrations in Eurasian perch?[END_REF]: the strong light pollution observed in harbours can be expected to suppress melatonin secretion at night in fish.

The pineal gland develops early and detects light even during early embryonic stages [START_REF] Ekström | Ontogenetic development of the pineal organ, parapineal organ, and retina of the three-spined stickleback, Gasterosteus aculeatus L. (Teleostei). Development of photoreceptors[END_REF][START_REF] Östholm | The pineal organ is the first differentiated light receptor in the embryonic salmon, Salmo salar[END_REF][START_REF] Ekstrzm | The pineal organ of teleost fishes[END_REF]. Egg hatching, which normally takes place under the cover of darkness, is impacted by the disturbance of the circadian rhythm by ALAN. Egg hatching was delayed in the European perch Perca fluviatilis, roach Rutilus rutilus, and bleak Alburnus alburnus [START_REF] Brüning | Artificial light at night: implications for early life stages development in four temperate freshwater fish species[END_REF] and completely prevented in laboratory studies of tropical fish species [START_REF] Fobert | Artificial light at night causes reproductive failure in clownfish[END_REF]. One explanation may be that the modified ratio of prolactin (a pituitary hormone) and melatonin resulted in a change in the egg hatching enzyme [START_REF] Brüning | Artificial light at night: implications for early life stages development in four temperate freshwater fish species[END_REF].

Melatonin also regulates the secretion of several components of the HPG axis, such as gonadotropins, sex steroids or gonadal maturation [START_REF] Khan | Melatonin influences gonadotropin II secretion in the Atlantic croaker (Micropogonias undulatus)[END_REF][START_REF] Amano | Roles of melatonin in gonadal maturation of underyearling precocious male masu salmon[END_REF][START_REF] Chattoraj | Melatonin accelerates maturation inducing hormone (MIH): induced oocyte maturation in carps[END_REF][START_REF] Bhattacharya | Melatonin in the regulation of annual testicular events in carp Catla catla: evidence from the studies on the effects of exogenous melatonin, continuous light, and continuous darkness[END_REF][START_REF] Sébert | Melatonin activates brain dopaminergic systems in the eel with an inhibitory impact on reproductive function[END_REF][START_REF] Carnevali | Melatonin Induces Follicle Maturation in Danio rerio[END_REF]. Experimental white light levels as low as 1 lux (but not other wavelengths of light such as blue, green, red) as well as street-lighting in a natural setting (13.3-16.5 lux) suppress mRNA expression of LH and FSH in male and female European perch and roach [START_REF] Brüning | Impact of different colours of artificial light at night on melatonin rhythm and gene expression of gonadotropins in European perch[END_REF](Brüning et al., , 2018b)). ALAN also reduces circulating sex hormones, 17β-estradiol in female European perch and roach (Brüning et al., 2018b), Senegalese sole (Solea senegalensis, [START_REF] García-López | Disruption of gonadal maturation in cultured Senegalese sole Solea senegalensis Kaup by continuous light and/or constant temperature regimes[END_REF], and in male and female perch [START_REF] Migaud | Influence of photoperiod on the onset of gonadogenesis in Eurasian perch Perca fluviatilis[END_REF], as well as 11-ketotestosterone in male European perch and roach (Brüning et al., 2018b), sea bass [START_REF] Rodríguez | Long-term exposure to continuous light inhibits precocity in European male sea bass (Dicentrarchus labrax, L.): hormonal aspects[END_REF][START_REF] Felip | Reduction of sexual maturation in male Dicentrarchus labrax by continuous light both before and during gametogenesis[END_REF] and Senegalese sole [START_REF] García-López | Disruption of gonadal maturation in cultured Senegalese sole Solea senegalensis Kaup by continuous light and/or constant temperature regimes[END_REF]. The cascading impacts of ALAN on sex hormones cause a subsequent failure in gonad maturation for several fish species, including sea bass [START_REF] Rodríguez | Long-term exposure to continuous light inhibits precocity in European male sea bass (Dicentrarchus labrax, L.): hormonal aspects[END_REF], Atlantic cod (Gadus morhua, L.; [START_REF] Taranger | Continuous light delays sexual maturation and increases growth of Atlantic cod (Gadus morhua L.) in sea cages[END_REF], turbot (Scophthalmus maximus; [START_REF] Imsland | Exposure to continuous light inhibits maturation in turbot (Scophthalmus maximus)[END_REF] and Nile tilapia (Oreochromis niloticus; [START_REF] Rad | Effects of different long-day photoperiods on somatic growth and gonadal development in Nile tilapia (Oreochromis niloticus L.)[END_REF].

The impact of ALAN on fish cortisol levels, a commonly measured indicator of stress [START_REF] Mommsen | Cortisol in teleosts: dynamics, mechanisms of action, and metabolic regulation[END_REF], has been mixed. ALAN increased plasma cortisol and glucose in farmed Atlantic salmon [START_REF] Migaud | The effect of spectral composition and light intensity on melatonin, stress and retinal damage in post-smolt Atlantic salmon, Salmo salar[END_REF] but did not affect cortisol levels in dispersing Atlantic salmon fry [START_REF] Newman | Using novel methodologies to examine the impact of artificial light at night on the cortisol stress response in dispersing Atlantic salmon ( Salmo salar L.) fry[END_REF]. There was also no effect of ALAN on the cortisol response of European perch [START_REF] Brüning | Spotlight on fish: light pollution affects circadian rhythms of European perch but does not cause stress[END_REF], red sea bream (Pagrus major) and striped knifejaw (Oplegnathus fasciatus;

(Albula vulpes, [START_REF] Szekeres | Does coastal light pollution alter the nocturnal behavior and blood physiology of juvenile bonefish (Albula vulpes)?[END_REF]. To date, the evidence shows that the hormonal impacts of ALAN in fish are driven by the changes of melatonin levels rather than cortisol levels.

In most cases, all the above experiments on ALAN were completed in laboratory settings lacking many environmental and ecological factors, such as species interactions between predators and prey, as well as refuges linked to habitat complexity [START_REF] Brüning | Spotlight on fish: light pollution affects circadian rhythms of European perch but does not cause stress[END_REF][START_REF] Schligler | Long-term exposure to artificial light at night in the wild decreases survival and growth of a coral reef fish[END_REF]. It is therefore unclear whether ALAN in more natural settings, and over longer periods of time, will lead to similar alterations to hormone levels. However, one recent study in a natural setting showed that longterm exposure to light pollution over 18-23 months negatively impacts the survival and growth of a wild coral reef fish [START_REF] Schligler | Long-term exposure to artificial light at night in the wild decreases survival and growth of a coral reef fish[END_REF]. The higher mortality of orange-fin anemonefish, A. chrysopterus, in the wild [START_REF] Schligler | Long-term exposure to artificial light at night in the wild decreases survival and growth of a coral reef fish[END_REF] agrees with a laboratory study showing increased predation under ALAN of coral reef fish larvae, the convict tang, Acanthurus riostegus [START_REF] O'connor | Live fast, die young: Behavioural and physiological impacts of light pollution on a marine fish during larval recruitment[END_REF]. Despite no studies to date on the impact of ALAN specifically in harbours, the disruption to hormonal rhythms, including those associated with gonadogenesis, as well as the impacts of growth and survival, strongly suggests that the high levels of light pollution in harbours will have downstream consequences for fitness and population dynamics (Brüning et al., 2018b).

Temperature variations in water exchange-limited harbours

The often-enclosed topography of harbours can prevent efficient water cycling with the open ocean. This can cause higher variation in temperature than in "open" coastal areas (i.e., the water tends to be colder in the winter and warmer in the summer). Harbours can hence potentially provide a natural setting in which to study of the effects of temperature variation on hormones and hormone-dependent physiological processes. Multiple studies have highlighted the effect of temperature on a range of processes -e.g., metabolic rates in zebrafish, ATP production in mosquitofish Gambusia affiniscontrolled by thyroid hormone action in organisms (cf. review by Little 2021). In addition, temperature variation in harbours will only be heightened by climate change. Fish are most commonly ectotherms [START_REF] Little | Thyroid hormone regulation of thermal acclimation in ectotherms: Physiological mechanisms and ecoevolutionary implications[END_REF], and thus do not regulate their internal temperatures, but rather adapt their metabolic processes to environmental conditions. This fine-tuning is strongly reliant upon the thyroid axis for numerous taxa: it can be based on the regulation of T3 and T2 levels (in zebrafish; [START_REF] Little | Thyroid hormone actions are temperaturespecific and regulate thermal acclimation in zebrafish (Danio rerio)[END_REF] but it also depends on other parts of the signalling cascade, such as the temperature-sensitive differential expression of nuclear thyroid receptors (in tadpoles; [START_REF] Nakajima | Modulation of plasma protein expression in bullfrog (Rana catesbeiana) tadpoles during seasonal acclimatization and thermal acclimation[END_REF]. Variations in temperature thus have direct effects on the thyroid hormone signalling cascade and can be expected to modify the physiological responses controlled by thyroid hormones (higher T2 and T3 levels in warm conditions, higher metabolic rate, and transcription of ATPase in cold conditions; [START_REF] Little | Thyroid hormone actions are temperaturespecific and regulate thermal acclimation in zebrafish (Danio rerio)[END_REF]. Furthermore, the combination of other stressors impairing thyroid hormone pathways and heightened temperature variability can have negative impacts on fish. For instance, hypothyroid zebrafish have been found to have impaired swimming performances under cold conditions [START_REF] Little | Thyroid hormone actions are temperaturespecific and regulate thermal acclimation in zebrafish (Danio rerio)[END_REF]. Harbours can thus be key sites to study the cumulative consequences of numerous stressors and stronger temperature variability than in natural coastlines with more efficient water renewal.

Combined effects of anthropogenic stressors

Anthropogenic stressors (e.g., chemicals, plastics, boat noise, ALAN, and invasive species) thus occur in harbours and some of their effects on fish endocrine systems are already documented, mostly based on laboratory studies (non-exhaustive list in Table 1). Laboratory studies are particularly suited to isolate causal relationships between a type of contaminant and physiological issues (e.g., [START_REF] Grinwis | Toxicology of environmental chemicals in the flounder (Platichthys flesus) with emphasis on the immune system: field, semifield (mesocosm) and laboratory studies[END_REF], and these relationships are extrapolated to predict field conditions [START_REF] Ankley | The fathead minnow in aquatic toxicology: Past, present and future[END_REF]. However, laboratory studies have numerous limitations when compared to field studies, which is an issue raised by ecotoxicologists over the past decades (Kimball andLevin, 1985, Chapman 2002): they consist of artificial set-ups, with exposure routes differing between the laboratory and field-exposed fish, chemical contaminants often at higher concentrations than those found in harbours, restrained times of exposure to one or multiple contaminants, low number of successive generations, and limited experimental set-up and space. Crucially, they do not replicate all conditions experienced by wild organisms, in particular combinations of numerous stressors [START_REF] Crain | Interactive and cumulative effects of multiple human stressors in marine systems[END_REF] at various levels of acuteness through time (e.g., varying bioavailability of chemical pollutants depending on water parameters [START_REF] Ankley | The fathead minnow in aquatic toxicology: Past, present and future[END_REF]. Wider-scale laboratory studies with microcosms or mesocosms have been suggested (Kimball and Levin, 1985) but involve complex protocols and are again limited in scope. Experimental manipulations of whole ecosystems require numerous impact assessments (e.g., recent experiment with wastewater release into a confined stream, with beforeafter/control-impact; Pereda et al., 2020) and would be difficult to put in place in open water or coastal settings where target fish species grow. However, harbours can be considered as large-scale and longterm ecosystem manipulations and thus provide an ideal study ground to assess the effects of combined anthropogenic stressors on fish.

Indeed, combinations of stressors may have cumulative effects on resident organisms. In the laboratory, synergistic effects of chemical pollutants on TH homeostasis have been identified in rats exposed to a range of endocrine disruptors (dioxins, PCBs, polybrominated diphenyl ethers), with combined impacts higher than in a simple dose additive manner [START_REF] Crofton | Thyroid-hormone-disrupting chemicals: evidence for dose-dependent additivity or synergism[END_REF]. The combination of invasive species and heavy metal pollution in harbours has unexpected outcomes: copper and tin contamination result in the recruitment and growth of various invasive species above 'natural' levels in high traffic areas of Sydney harbour, while the recruitment of native species decreases [START_REF] Piola | Pollution reduces native diversity and increases invader dominance in marine hard-substrate communities[END_REF][START_REF] Dafforn | Links between estuarine condition and spatial distributions of marine invaders[END_REF]. Increased larval recruitment of invasive species and increased metal contamination may therefore act in combination to diminish the abundance of native species [START_REF] Dafforn | Links between estuarine condition and spatial distributions of marine invaders[END_REF]. The additional impact of climate change and/or ocean acidification onto these local anthropogenic stressors is also predicted to be largely additive. Increased temperature and decreased pH may induce a higher toxicity of many common contaminants in harbours (Crain et al., 21 2008). Due to the complexity and importance of understanding how global change and multiple local anthropogenic stressors interact, determining the combined impacts of stressors on fish hormonal systems should be a priority to inform managers and stakeholders and improve conservation practices in harbours.

Recommendations for future studies

Harbours are often considered as secondary sources of coastal pollution, notably when compared with direct wastewater inputs. This review emphasises the lack of studies on the endocrine systems of fish in harbours, despite harbours being potential in situ laboratories where multiple stressors occur simultaneously. Characterising the interactions between the hormonal systems of fish and a wide range of stressors in harbours can shed light on numerous issues: how are different endocrine pathways affected by multiple stressors? What consequences do stressors have on the biology and fitness of fish and on their distribution and abundance (i.e., consequences from the molecular and organism level to the population and ecosystem level)? Such integrative studies would provide insights for the development of effective policies to manage and preserve marine biodiversity and would guide solutions to enhance water quality in harbours. Recommendations for future studies are detailed below.

Choice of target fish species

To assess the need for harbour management plans, indicator species can be used. [START_REF] Ford | Use of ecotoxicological tools to evaluate the health of New Bedford Harbor sediments: a microbial biomarker approach[END_REF] focused on changes in the structure and function of the microbial community in New Bedford Harbour (USA) in response to toxic contaminant exposure, with the goal of using microbes as ecotoxicological tools. Sessile invertebrates are often used to monitor harbour environments as harbours serve as sinks for pollutants that bind to sediments and contaminants, such as heavy metals and hydrocarbons, accumulate in the tissues of benthic marine species (e.g., marine mussels; [START_REF] Wade | NOAA's 'Mussel Watch'project: Current use organic compounds in bivalves[END_REF][START_REF] Corsi | Monitoring a Marine Coastal Area: Use of Mytilus galloprovincialis and Mullus barbatus as Bioindicators[END_REF]. Corals have also been identified as environmental indicators of heavy metal contamination and have been used to identify pollution hotspots in Safaga harbour (Egypt; [START_REF] Shabib | Assessment of Heavy Metals and Rare Earth Elements of Coral Reefs in the Safaga Harbor by Neutron Activation Analysis[END_REF]. Mobile fish species can also be used as key species to reflect the water quality of harbours, as organic contaminants and trace metals can also accumulate in fish tissue [START_REF] Bolton | Organic and trace metal contaminants in sediments and English sole tissues from Vancouver Harbour, Canada[END_REF]. Studies conducted in Vancouver Harbour and in the neighbouring Puget Sound estuary reported toxicopathic liver lesions in the English sole Pleuronectes vetulus, a benthic species, which were associated with sediment contaminant levels [START_REF] Goyette | Prevalence of idiopathic liver lesions in English sole and epidermal abnormalities in flatfish from Vancouver Harbour[END_REF][START_REF] Myers | Overview of studies on liver carcinogenesis in English sole from Puget Sound; evidence for a xenobiotic chemical etiology I: Pathology and epizootiology[END_REF][START_REF] Myers | Toxicopathic hepatic lesions as biomarkers of chemical contaminant exposure and effects in marine bottomfish species from the Northeast and Pacific Coasts, USA[END_REF]. [START_REF] Velusamy | Bioaccumulation of heavy metals in commercially important marine fishes from Mumbai Harbor, India[END_REF] confirmed that benthic species are well-suited to assess the impacts of sediment-associated pollution as trace metals highly accumulated in demersal fishes, followed by neritic and pelagic fishes in Mumbai harbour. Thus, benthic fish species (as opposed to pelagic and demersal fish species) could be used in harbours not only as a bioindicator of marine ecosystem health, but also to study the relationship between sediment contaminant concentrations and the prevalence of diseases. Benthic fish species, due to their ecological niche, cannot avoid environmental stressors, and can be sensitive indicators of natural and anthropogenic disturbances in harbours. Conversely, in the event of restoration action in ports, the species to be favoured will be demersal species, which are independent of the substrate (e.g., most coastal fish typical of rocky substrate in the case of the Mediterranean Sea).

Increasing larval recruitment in harbours

harbour areas. However, the relevance of such solutions can be questioned as harbours are generally unfavourable habitats for fish growth and quality. Larval fish recruiting in harbours are exposed to multiple stressors that may impact their ability to grow properly (deformity), to metamorphose, to reproduce (sterility), or to protect themselves from predation. Why should fish recruitment be promoted in harbours if fish survival and metamorphosis are uncertain, and hence if the renewal capacity of fish stocks is not guaranteed? The first ecological restoration actions in ports to rehabilitate the nursery function are encouraging as they show greater species diversity, greater abundance, and better survival [START_REF] Bouchoucha | Potential use of marinas as nursery grounds by rocky fishes: Insights from four Diplodus species in the Mediterranean[END_REF][START_REF] Mercader | Observation of juvenile dusky groupers (Epinephelus marginatus) in artificial habitats of North-Western Mediterranean harbors[END_REF]. This is linked to the fact that the artificial habitats only target demersal species which have food sources independent from polluted harbour substrates. [START_REF] Bouchoucha | Growth, condition and metal concentration in juveniles of two Diplodus species in ports[END_REF] found little to no significant differences between the concentrations of some heavy metals in the muscle tissues of seabream juveniles in a harbour and a natural area. Studies testing the synergistic effects of the multiple stresses present in harbours on the hormonal systems of fish are yet to be performed. Research must focus on these questions to clarify whether the restoration of juvenile nursery areas in harbours is efficient in the long term to mitigate the impacts of coastal modifications.

Answering this question is crucial to implement relevant and efficient conservation actions. Indeed, even if harbours attempt to limit their impacts, for instance by obtaining ecological labels (which should be the direction to follow; [START_REF] Satir | The protection of marine aquatic life: Green Port (EcoPort) model inspired by Green Port concept in selected ports from Turkey, Europe and the USA[END_REF], the creation of a marine protected area in their vicinity could be a better option. However, not all areas are suitable for the implementation of protection measures and restoring degraded habitats in harbours should be considered as a complementary step. Conservation and restoration actions must be adapted to local characteristics and specificities. In any case, the priority remains preventing the degradation of ecosystems and associated ecosystem services.

Recommendations to harbour authorities and researchers

Environmental protection perspectives in harbours should focus around four themes: 1) an analysis of the nursery function of the harbour, through a dynamic and quantitative description of the recruitment of juvenile and of adult fish populations on a long-term basis (as practiced in French

Mediterranean harbours which benefit from ecological restoration action) ; 2) a definition of the physiological "quality" of juvenile fish (eco-physiological status of the recruits, established by measuring the levels of thyroid hormones and baseline cortisol levels); 3) compensation solutions to protect or restore the nursery function of harbours (e.g., [START_REF] Bouchoucha | Potential use of marinas as nursery grounds by rocky fishes: Insights from four Diplodus species in the Mediterranean[END_REF]Mercader et al., 2017b;[START_REF] Meinesz | Impact of coastal development on the infralittoral zone along the southeastern Mediterranean shore of continental France[END_REF]); and 4) proposals for good practices and communication with the general public about possible ecological restoration solutions in and near harbours. The interactive and cumulative effects of anthropogenic stressors on marine fishes in harbours remain largely unknown. These knowledge gaps must be addressed and used along with precautionary principles to develop coherent environmental protection plans. However, based on precautionary principles, the following guidelines can already be formulated (Fig. 3): put in place structures to provide shelters for marine species; clean up and reduce the inputs of plastics and chemical pollution (notably with nature-based methods, such as putting in place wetlands that can filter water in addition to providing habitats; Wood 1995); avoid the discharge of ballast water; reduce the speed of boats to lessen sound pollution; reduce light pollution at night.

Fig. 1 :

 1 Fig. 1: Illustration of the different anthropogenic stressors present in the port of Papeete, Tahiti, French Polynesia (illustration by C. Berthe).

Fig. 3 :

 3 Fig. 3: Illustration of different precautionary measures to improve survival and health in marine organisms that could be adopted in the port of Papeete, Tahiti, French Polynesia

Table 1 :

 1 Examples of the impacts on endocrine systems of fish of different sources of stress that can be found in harbours (non-exhaustive list).

	Category	Source of stress	Impact on	Consequences	Species	Developmental	Reference
				endocrine			stage
				systems
	Plastic pollution Plastic	Bisphenol A	HPT axis	Altered circulating T4 and T3 levels,	Zebrafish Danio rerio	Embryonic, larval,	Gentilcore et al. (2012)
		chemical	and		expression of HPT-related genes,		metamorphosis,	Zhang et al. (2017)
		compounds	congeners		hormonal disruption transferred to		adult	Wei et al. (2018)
					offspring			Lee et al. (2019)
	Plastic pollution Plastic-	Bisphenol A	Reproductive	Altered testis maturation, gonad	Fathead minnow	Adult	Sohoni et al. (2001)
		sorbed		system	feminisation, decreased sperm quality,	Pimephales promelas
		chemical			increased plasma vitellogenin levels,
		compounds			altered expression of genes related to the	Zebrafish D. rerio	Adult	Van den Belt et al. (2003)
					reproductive system			Chen et al. (2017)
								Yang et al. (2017)
						Rainbow trout	Juvenile, adult	Van den Belt et al. (2003)
						Oncorhynchus mykiss
						Brown trout Salmo trutta	Juvenile	Frenzili et al. (2021)
						Anemonefish Amphiprion	Adult	Gonzalez et al. (2021)
						ocellaris
	Chemical	Persistent	Polychlorinat	HPT axis	Altered HPT function, decreased TH	Coho salmon O. kisutch	Juvenile	Leatherland et al. (1978)
	pollution	organic	ed Biphenyl		circulating levels, change in thyroid
		pollutants			gland structure	Flounder Paralichthys	Metamorphosis,	Dong et al. (2014)
					In young individuals: Decreased	olivaceus	juvenile	Dong et al. (2017)
					circulating TH levels, slower growth,
					and delayed metamorphosis
	Chemical	Persistent	Polychlorinat	Reproductive	Impaired ovarian maturation, delayed	Zebrafish D. rerio	Embryonic, larval,	Daouk et al. (2011)
	pollution	organic	ed Biphenyl	system	reproduction, fewer viable eggs		metamorphosis,	Horri et al. (2018)
		pollutants					juvenile, adult
	Chemical	Persistent	Bactericide -	HPT axis	Disruption of thyroid function,	Zebrafish D. rerio	Embryonic,	Oliveira et al. (2009)
	pollution	organic	Triclosan		deformities, modified metamorphosis		metamorphosis,	Stenzel et al. (2019)
		pollutants			timing		adult
						Medaka Oryzias latipes	Embryonic	Nassef et al. (2010)
						Sheepshead minnow	Metamorphosis	Schnitzler et al. (2016)
						Cyprinodon variegatus
						Sole Solea senegalensis	Metamorphosis	Araújo et al. (2019)

Acknowledgments

This work has received several grants: Fondation de France (2019-08602), ANR-19-CE34-0006-Manini, ANR-19-CE14-0010-SENSO. The IAEA is grateful for the support provided to its Marine Laboratories by the Government of the Principality of Monaco.

159

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.