Camille Mellin

Christina C Hicks

Damien A Fordham

Christopher D Golden

Marian Kjellevold

M Aaron Macneil

Eva Maire

Sangeeta Mangubhai

David Mouillot

Kirsty L Nash

Camille Mell

Marian Kjellevo

Sangee Mangubh

Johnstone O Omukot

James P W Robin

Rick Stuart-Smith

Jessi Zambora-Mason

Nichola A J Graham

Safeguarding nutrients from coral reefs under climate change

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.

 [START_REF] Burke | Reefs at Risk Revisited[END_REF]The Environment Institute and School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia. [START_REF] Bell | Planning the use of fish for food security in the Pacific[END_REF] Lancaster Environment Centre, Lancaster University, Lancaster, UK. [START_REF] Gillett | Fisheries in the Economies of the Pacific Island Countries and Territories[END_REF] Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, MA, USA. [START_REF]The Regional State of the Coast Report: Western Indian Ocean (UNEP[END_REF] Institute of Marine Research, Bergen, Norway. [START_REF] Wabnitz | Ecotourism, climate change and reef fish consumption in Palau: benefits, trade-offs and adaptation strategies[END_REF] Ocean Frontier Institute, Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada. [START_REF] Cinner | Building adaptive capacity to climate change in tropical coastal communities[END_REF] Talanoa Consulting, Suva, Fiji. [START_REF] Thilsted | Sustaining healthy diets: the role of capture fisheries and aquaculture for improving nutrition in the post-2015 era[END_REF] MARBEC, University of Montpellier, CNRS, IFREMER, IRD, MARBEC, Montpellier, France. [START_REF] Beal | Global trends in dietary micronutrient supplies and estimated prevalence of inadequate intakes[END_REF] Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia. [START_REF] Calder | Marine omega-3 fatty acids and inflammatory processes: effects, mechanisms and clinical relevance[END_REF] Centre for Marine Socioecology, University of Tasmania, Hobart, Tasmania, Australia. [START_REF] Haddad | A new global research agenda for food[END_REF] Kenya Marine and Fisheries Research Institute, Mombasa, Kenya. [START_REF] Golden | Aquatic foods to nourish nations[END_REF] ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia. [START_REF] Macneil | Recovery potential of the world's coral reef fishes[END_REF] College of Science and Engineering, James Cook University, Townsville, Queensland, Australia. ✉ e-mail: camille.mellin@adelaide.edu.au T he world's coral reefs support extraordinary biodiversity and provide essential ecosystem services, including food and income to over 500 million people [START_REF] Burke | Reefs at Risk Revisited[END_REF] and up to 90% of animal protein in some countries across the Pacific and Indian Oceans [START_REF] Bell | Planning the use of fish for food security in the Pacific[END_REF][START_REF] Gillett | Fisheries in the Economies of the Pacific Island Countries and Territories[END_REF][START_REF]The Regional State of the Coast Report: Western Indian Ocean (UNEP[END_REF] . Small-scale reef fisheries are particularly crucial in coastal and rural areas, where they often provide the majority of fish consumed [START_REF] Wabnitz | Ecotourism, climate change and reef fish consumption in Palau: benefits, trade-offs and adaptation strategies[END_REF] , and are socially and culturally important [START_REF] Cinner | Building adaptive capacity to climate change in tropical coastal communities[END_REF] . Aquatic foods are a unique dietary source of iodine, vitamin D and the long-chained n-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid, and are also a valuable source of bioavailable micronutrients, including iron, zinc and vitamins A and B 12 7 . Deficiencies of these micronutrients are linked to a growing triple burden of malnutrition, which refers to the coexistence of overnutrition, undernutrition and micronutrient deficiencies that are responsible for impaired cognitive development and account for 1 million premature deaths per year [START_REF] Beal | Global trends in dietary micronutrient supplies and estimated prevalence of inadequate intakes[END_REF][START_REF] Calder | Marine omega-3 fatty acids and inflammatory processes: effects, mechanisms and clinical relevance[END_REF][START_REF] Haddad | A new global research agenda for food[END_REF] . Fish therefore hold the potential to help address these deficiencies, particularly where nutrient intakes are inadequate [START_REF] Beal | Global trends in dietary micronutrient supplies and estimated prevalence of inadequate intakes[END_REF][START_REF] Golden | Aquatic foods to nourish nations[END_REF] (Fig. 1a). However, coral reefs are highly vulnerable to both overfishing [START_REF] Macneil | Recovery potential of the world's coral reef fishes[END_REF] and climate change [START_REF] Graham | Predicting climate-driven regime shifts versus rebound potential in coral reefs[END_REF] , stressing the need to better understand the current and potential future contributions of coral reef fisheries to human health [START_REF] Golden | Aquatic foods to nourish nations[END_REF] .

Global development has led to complex shifts in food supply and demand through increases in wealth, human population size, urbanization and the globalization of trade and transport. Through the global fish trade, reef fish can now be sold at high prices in European seafood markets and luxury restaurants [START_REF] Crona | Using social-ecological syndromes to understand impacts of international seafood trade on small-scale fisheries[END_REF] (Fig. 1b,c), while the aquarium trade can target species caught by small-scale fishers, some of which would have been consumed locally [START_REF] Okemwa | Catch composition and sustainability of the marine aquarium fishery in Kenya[END_REF] . These globalizing markets erode reef fish biomass, resulting in catch decreases that can force fishers to travel further offshore, increasing inequalities between those who can afford larger and more powerful boats to maintain production and those who cannot [START_REF] Cinner | Responding to change: using scenarios to understand how socioeconomic factors may influence amplifying or dampening exploitation feedbacks among Tanzanian fishers[END_REF] . Global demand for reef fish through trade also drives market prices up, which can make fish unaffordable for local consumers [START_REF] Hicks | Secure local aquatic food systems in the face of declining coral reefs[END_REF] . In parallel, diets in these countries can be influenced by preferences shifting towards a greater demand for meat and a reliance on imported, often processed or high-starch root crop foods characterized by lower nutrient quality [START_REF] Albert | Malnutrition in rural Solomon Islands: an analysis of the problem and its drivers[END_REF][START_REF] Golden | Social-ecological traps link food systems to nutritional outcomes[END_REF] , potentially heightening the risk of metabolic diseases and micronutrient deficiencies [START_REF] Golden | Aquatic foods to nourish nations[END_REF][START_REF] Golden | Social-ecological traps link food systems to nutritional outcomes[END_REF] . Together, the rapidly changing socio-economic context, as is characteristic in tropical regions, simultaneously exacerbates decreases in nutrient-rich foods, particularly where nutrient gaps (for example, East Africa) [START_REF] Beal | Global trends in dietary micronutrient supplies and estimated prevalence of inadequate intakes[END_REF] and increases in diet-related diseases (for example, Pacific islands) 10 are apparent [START_REF] Golden | Aquatic foods to nourish nations[END_REF] .

Essential ecosystem services under pressure from climate change

The sustainability of coral reef fisheries is jeopardized by complex and interacting socio-ecological stressors that undermine their contribution to food and nutrition security. Climate change has emerged as one of the key stressors threatening coral reefs and their fish-associated services. How fish nutrient concentrations respond to warming oceans remains unclear but these responses are probably affected by both direct (metabolism and trophodynamics) and indirect (habitat and species range shifts) effects. Climatedriven coral habitat loss can cause changes in fish abundance and biomass, revealing potential winners and losers among major fisheries targets that can be predicted using ecological indicators and biological traits. A critical next step is to extend research focused on the quantity of available food (fish biomass) to also consider its nutritional quality, which is relevant to progress in the fields of food security and malnutrition. Biological traits are robust predictors of fish nutrient con-tent and thus potentially indicate how climate-driven changes are expected to impact nutrient availability within future food webs on coral reefs. Here, we outline future research priorities and an anticipatory framework towards sustainable reef fisher-ies contributing to nutrition-sensitive food systems in a warming ocean.

with foundational species such as reef-building corals among the most affected taxa [START_REF] Smale | Marine heatwaves threaten global biodiversity and the provision of ecosystem services[END_REF] . Although algal growth following coral loss can support higher biomass [START_REF] Robinson | Thermal stress induces persistently altered coral reef fish assemblages[END_REF][START_REF] Robinson | Productive instability of coral reef fisheries after climate-driven regime shifts[END_REF][START_REF] Stuart-Smith | Ecosystem restructuring along the Great Barrier Reef following mass coral bleaching[END_REF] and productivity [START_REF] Morais | Severe coral loss shifts energetic dynamics on a coral reef[END_REF] of herbivorous species under moderate fishing pressure, the resulting catch instability that can arise from spatiotemporal variation in reef recovery [START_REF] Robinson | Thermal stress induces persistently altered coral reef fish assemblages[END_REF] has the potential to negatively impact local market supply chains, including fisher incomes and consumer access to seafood, with potential implications for food and nutrient intakes.

Importantly, climate change and human activities interact in many ways, reinforcing pressures on coral reefs that ultimately threaten both ecosystem structure and function (Fig. 2). For example, herbivore depletion through overharvesting can impede post-bleaching coral recovery [START_REF] Graham | Predicting climate-driven regime shifts versus rebound potential in coral reefs[END_REF] , especially on reefs where structural complexity has been degraded [START_REF] Robinson | Habitat and fishing control grazing potential on coral reefs[END_REF] . In turn, the loss of reef structural complexity can reduce the recruitment of juvenile fishes and the replenishment of fish stocks [START_REF] Fontoura | Climate-driven shift in coral morphological structure predicts decline of juvenile reef fishes[END_REF] . The consequences of interactions between climate change and other human-driven processes range from the collapse of reef structure and associated fish stocks [START_REF] Rogers | Fisheries productivity under progressive coral reef degradation[END_REF] to novel benthic communities dominated by stress-tolerant and weedy taxa, where some ecological functions can persist to some extent [START_REF] Bates | Climate resilience in marine protected areas and the 'protection paradox[END_REF][START_REF] Darling | Social-environmental drivers inform strategic management of coral reefs in the Anthropocene[END_REF] , to an increased prevalence of toxic microalgae and ciguatoxins [START_REF] Soliño | Global impact of ciguatoxins and ciguatera fish poisoning on fish, fisheries and consumers[END_REF] .

Future climate projections unanimously predict that without immediate intervention to reduce harmful greenhouse gas emissions, most ecosystem services provided by coral reefs will be severely degraded by the end of the century [START_REF] Rogers | Anticipative management for coral reef ecosystem services in the 21st century[END_REF] . Such detrimental effects of climate change on seafood production in the world's poorest countries will not be counteracted by agricultural production, since 90% of the world's population are projected to experience losses of food production in both sectors simultaneously [START_REF] Thiault | Escaping the perfect storm of simultaneous climate change impacts on agriculture and marine fisheries[END_REF] . Understanding how nutrient availability from coral reef fisheries responds to environmental change will offer potential pathways for maintaining and even boosting access to nutrient-dense seafood under climate change. Managing these fisheries so that they sustain or even increase the nutritional value of harvested stocks in the face of global warming will have many benefits for human health. These potential benefits will probably apply to all coral reef fisheries (that is, not only those targeting coral reef finfish (the focus of this paper), but also those including other reef organisms such as algae and invertebrates, for which data are severely lacking).

Here, we outline the key ecological knowledge gaps and research priorities required to support the future potential contribution of coral reef fisheries to food and nutrition security under climate change. We focus on the impacts of a warming ocean, including both gradual warming and acute marine heatwaves, which have been identified as the primary drivers of coral reef habitat loss [START_REF] Souter | Status of Coral Reefs of the World: 2020[END_REF] . We argue that coral reef management practices currently focusing on fish stocks must be reorientated to sustain and protect nutritional benefits as well. This will require robust projections for the species that are the most likely to provide essential nutrients in warmer oceans, as well as knowledge of the functional traits that characterize them. Achieving this objective will require understanding of the environmental factors and trophic pathways that underpin macro-and micronutrient concentrations in fishes, and how these are likely to change in a warmer ocean with degraded coral reefs. Looking forward, we propose an anticipatory approach for defining safe operating spaces for multiple ecological and social objectives. These much-needed advances are now ready for development and will form the cornerstone of future management interventions to minimize impacts and to improve the adaptive capacity of human societies that rely on coral reef fisheries for food and nutrition.

Unlocking the trophic pathways behind fish nutrient quality in warmer oceans

Environmental determinants of fish nutrient profiles. Recent research has revealed the environmental and biotic correlates of fish nutrient content at the species level (for example, diet, energetic demand and thermal regime) [START_REF] Hicks | Harnessing global fisheries to tackle micronutrient deficiencies[END_REF] , shedding light on the determinants of interspecific variability in nutrient quality. However, the extent to which nutrient profiles differ intra-specifically over space (for example, at biogeographic scales) or time (in response to global warming) is still poorly known. A better understanding is required of the potential mechanisms by which fishes accumulate their nutrients and how these mechanisms respond to thermal stress and habitat loss, both directly (trophodynamics and metabolism) and indirectly (fish microbiome). Trophodynamics determine the flow of energy and nutrients through food webs and thus can predict how fish assimilate bioavailable nutrients or synthesize them from other precursors [START_REF] Bierwagen | Trophodynamics as a tool for understanding coral reef ecosystems[END_REF] . Importantly, fish diet composition and metabolic rates-two major determinants of the nature and strength of trophic pathways-might both be affected by global warming. Fishes primarily derive nutrients from diet, and diet composition is impacted by climate-driven changes in food composition and availability across multiple pathways, including primary and secondary producers. Ocean biogeochemical dynamics, such as changes in light, temperature and nutrient availability, can differentially affect the composition and abundance of phytoplankton communities [START_REF] Flombaum | Present and future global distributions of the marine Cyanobacteria Prochlorococcus and Synechococcus[END_REF] and microphytobenthos, including Gambierdiscus toxicus, the ciguatera-producing dinoflagellate [START_REF] Lehane | Ciguatera: recent advances but the risk remains[END_REF] . Secondary producers may also respond to changing habitats independently from changes in primary producers. For example, dominant epifaunal crustacean taxa vary massively between live coral habitats and dead coral rubble, especially in terms of size structure and productivity [START_REF] Fraser | Production of mobile invertebrate communities on shallow reefs from temperate to tropical seas[END_REF] . Changes in the nutrient profiles of primary and secondary producers can propagate through the food web to higher trophic levels [START_REF] Ullah | Climate change could drive marine food web collapse through altered trophic flows and cyanobacterial proliferation[END_REF] and, in turn, have consequences for the structure and nutrition profile of fish populations and fishery stocks [START_REF] Kang | Omega-3: a link between global climate change and human health[END_REF] . For example, warmer temperatures reduce fatty acid production in phytoplankton [START_REF] Kang | Omega-3: a link between global climate change and human health[END_REF][START_REF] Hixson | Climate warming is predicted to reduce omega-3, long-chain, polyunsaturated fatty acid production in phytoplankton[END_REF][START_REF] Tan | Climate change and n-3 LC-PUFA availability[END_REF] . Because plankton is the main source of omega-3 for fishes, this would ratchet down the omega-3 levels in most species, including apex predators [START_REF] Pethybridge | Spatial patterns and temperature predictions of tuna fatty acids: tracing essential nutrients and changes in primary producers[END_REF] .

Most fish species are characterized by mixed diets, suggesting a degree of versatility and opportunism as available food sources change in response to coral bleaching and habitat loss [START_REF] Hempson | Regime shifts shorten food chains for mesopredators with potential sublethal effects[END_REF][START_REF] Bellwood | Sleeping functional group drives coral-reef recovery[END_REF] . Likewise, some tropical species are moving towards temperate areas as oceans warm [START_REF] Sunday | Species traits and climate velocity explain geographic range shifts in an ocean-warming hotspot[END_REF][START_REF] Burrows | Ocean community warming responses explained by thermal affinities and temperature gradients[END_REF][START_REF] Cheung | Signature of ocean warming in global fisheries catch[END_REF] , leading to novel biotic interactions including potential competition between temperate, sub-tropical and tropical species. This implies a degree of adaptability in fish diet for at least some fish species (in particular, ecological generalists [START_REF] Stuart-Smith | Habitat loss and range shifts contribute to ecological generalization amongst reef fishes[END_REF] ), probably driving a shift in their nutrient concentration. This also suggests the existence of dynamic spatial gradients in fish nutrient profiles at biogeographic scales, which have so far remained largely unexplored.

Metabolism is predominantly driven by temperature, which determines the rate at which food is processed and assimilated by biological organisms, and further translates to somatic growth [START_REF] Brown | Toward a metabolic theory of ecology[END_REF] . Warmer temperatures induce faster exothermic biogeochemical reactions and higher metabolic rates, and thus faster and less efficient biomass transfer across the food web, especially in tropical ecosystems [START_REF] Du Pontavice | Climate change undermines the global functioning of marine food webs[END_REF] . This is because, at each trophic level, large energy losses are induced by respiration and metabolic processes that scale with temperature. Yet, whether nutrient assimilation efficiency at each trophic level will similarly be affected by warmer temperatures remains unknown.

Microbiomes can also play an indirect yet probably important role in the way fish assimilate nutrients, but remain a key gap in our understanding of reef trophodynamics. In particular, little is known regarding the environmental drivers of fish hindgut microbiome composition, although a recent study suggested high regional variability in fish gastrointestinal microbial composition and associated nutritional outcomes [START_REF] Jones | The microbiome of the gastrointestinal tract of a range-shifting marine herbivorous fish[END_REF] . For corals, microbial community composition can be affected by thermal stress, leading to a metabolic shift from autotrophy to heterotrophy, and altered metabolism of fatty acids, contributing to a deterioration in coral health [START_REF] Littman | Metagenomic analysis of the coral holobiont during a natural bleaching event on the Great Barrier Reef[END_REF] . Altogether, these examples suggest that microbiomes can be influenced by environmental variation at various stages of trophodynamic pathways that determine fish nutrient profiles, but more research is required to assess the generality of these results and embed them into trophodynamic ecosystem models. As human activities continue to increase greenhouse gas emissions, pollution and overharvesting (blue gradient), safeguarding food and nutrition security traditionally supported by healthy coral reefs (green gradient) will require adaptation to novel coral reef communities and the identification of winners versus losers among fish species, not only in terms of biomass but also nutritional value. Images from Shutterstock.com; used with permission.

Climate impacts on potential nutrient yields from multispecies fisheries. Nutrient changes at the species level scale up to determine community-level nutrient concentrations, with the potential to globally affect the nutritional quality of multispecies fisheries; for instance, through enriched iron and zinc concentrations in fish living on regime-shifted macroalgal reefs [START_REF] Robinson | Climate-induced increases in micronutrient availability for coral reef fisheries[END_REF] (Box 1). This is influenced by compositional shifts in fish communities, with some species decreasing in abundance (losers) in response to marine heatwaves and other climate drivers while others increase (winners) due to more abundant and better-quality food resources [START_REF] Robinson | Thermal stress induces persistently altered coral reef fish assemblages[END_REF][START_REF] Morais | Severe coral loss shifts energetic dynamics on a coral reef[END_REF] , greater stress tolerance, competitiveness or better ability to recolonize habitats after a disturbance [START_REF] Stuart-Smith | Habitat loss and range shifts contribute to ecological generalization amongst reef fishes[END_REF] . The species composition of fisheries catches determines their nutritional quality according to predictable interspecific variation in fish nutrient levels [START_REF] Hicks | Harnessing global fisheries to tackle micronutrient deficiencies[END_REF] , implying that climate-driven compositional shifts are likely to impact the potential of fisheries to supply key nutrients in support of human health. For example, browsing herbivores such as rabbitfishes (family Siganidae) are relatively rich in iron, whereas piscivores have the highest omega-3 concentrations among reef fishes 55,[START_REF] Macneil | NutrientFishbase dataset[END_REF] . Therefore, iron content may increase in fishery catches following climate-driven increases in herbivore biomass, whether through (1) increased algal productivity after coral mortality [START_REF] Robinson | Productive instability of coral reef fisheries after climate-driven regime shifts[END_REF] or (2) an increase in temperature placing herbivorous species closer to their thermal optima (for example, in higher-latitude reefs and sub-tropical regions) and thus optimal fitness [START_REF] Stuart-Smith | Ecosystem restructuring along the Great Barrier Reef following mass coral bleaching[END_REF][START_REF] Waldock | The shape of abundance distributions across temperature gradients in reef fishes[END_REF] . In contrast, size-based food web models predict decreases in piscivore productivity following the collapse of coral habitat structure and subsequent decreases in prey populations [START_REF] Rogers | Fisheries productivity under progressive coral reef degradation[END_REF] , which may reduce omega-3 fatty acids in fishery catches.

The long-term implications of climate change for nutrients supplied by reef fisheries will ultimately depend on how fish populations from different species collectively respond to the combination of warming (gradual and more frequent extreme events) and habitat changes (including reductions in primary production, ocean acidification and deoxygenation [START_REF] Breitburg | Declining oxygen in the global ocean and coastal waters[END_REF] ). By 2050, the combination of poleward species redistributions, decreases in habitat suitability, reduced species richness along the equator (as some species exceed maximum thermal limits) [START_REF] Chaudhary | Global warming is causing a more pronounced dip in marine species richness around the equator[END_REF] and reduced primary productivity is expected to decrease global fisheries catch potential [START_REF] Cheung | Large benefits to marine fisheries of meeting the 1.5°C global warming target[END_REF] , diminishing nutrient yields from coral reefs [START_REF] Golden | Nutrition: fall in fish catch threatens human health[END_REF] . Collectively, gradual warming and more frequent marine heatwaves will modify the rates at which fish assimilate energy and nutrients, influencing the quantity and quality of multispecies catches in warmer oceans and substantially altering the future contribution of reef fisheries to both food and nutrition security.

Indicators of nutrient availability from climate-impacted reefs

Information on inter-and intraspecific shifts in reef fish nutritional quality is fundamental to understanding the effects of environmental change on nutrient production from coral reef fisheries.

Box 1 | Pathways to nutritional gains and losses on climate-impacted coral reefs

Climate-driven loss of coral habitat is expected to change the nutritional value of coral reef fisheries. Coral bleaching and mortality following heat stress can transform reef habitats into low-complexity, algae-dominated states, which reroute nutrient pathways in reef food webs [START_REF] Morillo-Velarde | Habitat degradation alters trophic pathways but not food chain length on shallow Caribbean coral reefs[END_REF] and alter the productivity and composition of fish communities [START_REF] Morais | Severe coral loss shifts energetic dynamics on a coral reef[END_REF] . Nutrient yields on climate-impacted reefs will thus be determined by the effects of these processes on fish nutrient content, both among (changes in species compositions) and within species (changes in the energy sources that determine an individual's nutrient content).

Fish gain micronutrients from their diet, implying that nutrient levels in fish will be influenced by changes to nutrient pathways (within-species effects), while the availability of nutritious target species will depend on the productivity and composition of reef fish communities in post-bleaching reef habitats (among-species effects). Evidence from the Seychelles suggests that disruption of nutrient pathways may have a greater influence on nutrient levels than species compositional changes [START_REF] Robinson | Climate-induced increases in micronutrient availability for coral reef fisheries[END_REF] . In the Seychelles, a mass coral bleaching event in 1998 caused >95% coral mortality, collapsing reef habitat and, on some reefs, provoking macroalgal regime shifts [START_REF] Graham | Predicting climate-driven regime shifts versus rebound potential in coral reefs[END_REF] . Such benthic turnover altered trophic pathways [START_REF] Hempson | Regime shifts shorten food chains for mesopredators with potential sublethal effects[END_REF] , probably because macroalgae replaced plankton as the primary energy nutrient input to the reef food web. Fish on regime-shifted macroalgal reefs had greater iron and zinc concentrations than fish caught on nearby recovering coral reefs, possibly due to greater contributions of mineral-rich tropical seaweeds [START_REF] Kumar | PUFAs and antioxidant properties of some tropical seaweeds from Saurashtra coast of India[END_REF] to primary production.

Reef fish communities also became less diverse after bleaching, forming bottom-heavy trophic pyramids [START_REF] Graham | Predicting climate-driven regime shifts versus rebound potential in coral reefs[END_REF][START_REF] Robinson | Thermal stress induces persistently altered coral reef fish assemblages[END_REF][START_REF] Hempson | Ecosystem regime shifts disrupt trophic structure[END_REF] with enhanced biomass of herbivorous scrapers (Scarinae) and browsers (Siganidae), which are targeted by small-scale trap fisheries [START_REF] Robinson | Productive instability of coral reef fisheries after climate-driven regime shifts[END_REF] . Although browsers were abundant on macroalgal reefs, scraping herbivores dominated fish communities on most reefs both before and after bleaching, suggesting that the average micronutrient concentrations of the target fish community were largely unaffected by changes in reef fish composition. Greater post-bleaching herbivore productivity also increased micronutrient availability to fishers (that is, more fishable biomass).

Scraping herbivores contain higher levels of calcium, iron and zinc than most animal-source foods 55,[START_REF] Macneil | NutrientFishbase dataset[END_REF] and often respond positively to decreases in coral coverage [START_REF] Morais | Severe coral loss shifts energetic dynamics on a coral reef[END_REF] . If fishing pressure is managed sustainably, these species may be nutrition winners, sustaining micronutrient contributions from climate-impacted reefs.

Figure redrawn with permission from Robinson et al. [START_REF] Robinson | Climate-induced increases in micronutrient availability for coral reef fisheries[END_REF] .

Nutrient depletion Nutrient enrichment

Nutrient concentration

Among-species effects

Change in fish assemblage composition after benthic habitat shift

Within-species effects

Change in fish tissue after nutrient pathways are disrupted by benthic habitat shift More low-nutrient species More high-nutrient species Low-nutrient energy source High-nutrient energy source

Post-disturbance benthic regimen

Low coral cover and/or algal overgrowth However, our capacity to effectively monitor shifts in fisheries nutrient production will rely on careful selection of biological traits and ecological indicators that can reveal the vulnerability of coral communities to climate impacts and subsequent responses of fish communities [START_REF] Nash | Ecological indicators for coral reef fisheries management[END_REF] . Biological traits relevant to diet, thermal regime or energetic demand are strong predictors of the nutrient profile of fish species [START_REF] Hicks | Harnessing global fisheries to tackle micronutrient deficiencies[END_REF] . Furthermore, the response of fish communities to changes in coral composition and associated structural complexity probably depends on species traits rather than taxonomic composition per se. Species traits represent a suite of essential biodiversity variables [START_REF] Pereira | Essential biodiversity variables[END_REF] that can reflect trophic ecology, metabolic theory or life history strategy, and thereby provide novel indicators with which to monitor the capacity of reef ecosystems to support essential ecological functions linked to ecosystem services such as food and nutrition security (Box 2). Yet, many of the potential relationships between biological traits, pressures and habitat types, and consequences on the nutritional quality of reef fisheries remain to be explored, particularly from the perspectives of sustainability and resilience of ecosystem processes and services [START_REF] Brandl | Coral reef ecosystem functioning: eight core processes and the role of biodiversity[END_REF] (but see, for example, Maire et al. [START_REF] Maire | Micronutrient supply from global marine fisheries under climate change and overfishing[END_REF] ) (Table 1).

Understanding how changes in reef habitats will impact nutrient supply requires quantification of the degree to which each species (or trait) relies on healthy coral reefs, as well as their ability to cope with alternative reef ecosystem states. Reef health assessments have typically focused on total live hard coral cover-an essential indicator [START_REF] Miloslavich | Essential ocean variables for global sustained observations of biodiversity and ecosystem changes[END_REF] of reef condition that allows for cross-comparisons among regions and ecosystems when measuring the impact of chronic and acute disturbances on coral reefs. However, climate-induced changes in total hard coral cover can obscure changes in coral community composition (for example, from the dominance of fast-growing, branching and tabular species that are important providers of three-dimensional habitat to depauperate communities dominated by taxa with simpler morphologies and slower growth rates [START_REF] Darling | Social-environmental drivers inform strategic management of coral reefs in the Anthropocene[END_REF] ). It follows that fish species that are not particularly reliant on a specific coral habitat tend to have a competitive advantage over habitat specialists as benthic communities shift in composition [START_REF] Stuart-Smith | Habitat loss and range shifts contribute to ecological generalization amongst reef fishes[END_REF] . Therefore, an important remaining question is whether the extent of habitat specialization, potentially inducing diet specialization, can also predict fish nutrient profiles. If so, a community-weighted mean of the species generalization index [START_REF] Stuart-Smith | Habitat loss and range shifts contribute to ecological generalization amongst reef fishes[END_REF] could provide an important tool with which to track nutritional changes at the community level in response to changes in benthic habitats.

The structural complexity of a coral reef-built by the living coral veneer and sustained by the underlying old reef matrix-is a key determinant of reef fish abundance and diversity [START_REF] Graham | The importance of structural complexity in coral reef ecosystems[END_REF] with potentially important implications in terms of nutrition. For example, the scale of complexity in hard reef structure affects where abundance peaks occur in the size spectrum of fish present on the reef [START_REF] Nash | Cross-scale habitat structure drives fish body size distributions on coral reefs[END_REF] . Following coral mortality, reef structure can remain intact in the short term, sustaining fish communities aside from specialist species that require live coral for food or shelter. However, reef structures dominated by dead corals are vulnerable to physical and biological erosion and may begin to collapse within 5 years [START_REF] Pratchett | Oceanography and Marine Biology: An Annual Review[END_REF] . Subsequent loss of structural complexity can drive decreases in fish diversity by 50% [START_REF] Graham | Dynamic fragility of oceanic coral reef ecosystems[END_REF] , homogenize community composition among habitat types [START_REF] Richardson | Mass coral bleaching causes biotic homogenization of reef fish assemblages[END_REF] and change fish size structure by depleting abundances of small-bodied individuals [START_REF] Graham | Lag effects in the impacts of mass coral bleaching on coral reef fish, fisheries, and ecosystems[END_REF] . Size-based food web models predict that such changes to benthic structure could result in a 35% decrease in fisheries productivity [START_REF] Rogers | Fisheries productivity under progressive coral reef degradation[END_REF] . Moreover, turf and macroalgae can proliferate after coral mortality and loss of reef structure, forming alternative benthic regimes that typically support bottom-heavy trophic pyramids [START_REF] Hempson | Ecosystem regime shifts disrupt trophic structure[END_REF] . Nonlinear relationships between algal cover and herbivore biomass [START_REF] Jouffray | Identifying multiple coral reef regimes and their drivers across the Hawaiian archipelago[END_REF] suggest the existence of benthic thresholds triggering shifts in fish community composition, which may help to better predict the biomass, productivity and nutritional quality after coral mortality (Box 1).

Box 2 | Looking ahead: future research priorities towards nutrition security from coral reef fisheries (i) Determine the nutritional vulnerability of fish species under increased temperatures

Combining experimental, observational and modelling approaches would help us to understand the variability in the nutrient content of fish. Warming experiments (for example, ref. [START_REF] Coleman | Climate change does not affect the seafood quality of a commonly targeted fish[END_REF] ) and feeding trials (for example, ref. [START_REF] Sissener | Are we what we eat? Changes to the feed fatty acid composition of farmed salmon and its effects through the food chain[END_REF] ) will provide fundamental knowledge of causal relationships between food availability, temperature and nutritional value. Field-based space-for-time analyses of intraspecific variability in fish nutrient content along temperature gradients will build our understanding of future climate-driven variability in nutritional profiles. The close ties between fish traits and nutrient profiles [START_REF] Hicks | Harnessing global fisheries to tackle micronutrient deficiencies[END_REF] , as well as the extensive literature detailing traits of coral reef fishes [START_REF] Hadj-Hammou | Response and effect traits of coral reef fish[END_REF] , could be leveraged to use trait-based approaches [START_REF] Mouillot | A functional approach reveals community responses to disturbances[END_REF] for predicting spatial and temporal trends in the nutrient content of fishes, notably including when species-specific information is lacking.

(ii) Understand the direct and indirect trophic pathways that affect fish nutritional content Stable isotope analyses provide a powerful method with which to explore the effect of environmental variability on the trophodynamics and ultimately nutrient content of fishes. However, the extreme ecological complexity and range of primary production sources [START_REF] Mcmahon | Tracing carbon flow through coral reef food webs using a compound-specific stable isotope approach[END_REF] on coral reefs present a challenge in the study of trophic pathways.

Compound-specific stable isotope analyses, which target specific essential amino acids rather than the bulk muscle tissue used for traditional isotope analysis [START_REF] Mcmahon | Ocean ecogeochemistry-a review[END_REF] , provide a potential, albeit expensive, solution. Essential amino acids undergo little modification through trophic transfer, so forms synthesized by the primary producer persist as they move up the food chain, permitting researchers to track sources of dietary carbon more accurately 100 and to interpret trophic dynamics, even where basal samples are not available 101 . Lastly, recent developments in next-generation sequencing [START_REF] Jones | The microbiome of the gastrointestinal tract of a range-shifting marine herbivorous fish[END_REF] and metagenomics [START_REF] Littman | Metagenomic analysis of the coral holobiont during a natural bleaching event on the Great Barrier Reef[END_REF] will allow indirect trophic links to be inferred that involve the role of the microbiome associated with fish gastrointestinal tracts as well as fish habitats.

(iii) Establish how nutritional changes propagate from species/populations to reef communities

The use of size-based models to evaluate the impacts of fishing and environmental change is well established 102 and has recently been applied to coral reef systems [START_REF] Rogers | Fisheries productivity under progressive coral reef degradation[END_REF] . Such models, if forced using climate change projections at fisheries-relevant spatial scales, would allow exploration of the effects of fishing and environmental change scenarios on key fish traits and the flow of nutrients through entire reef communities. It is also important for multispecies reef fisheries models to expand and include other aquatic species (for example, algae and invertebrates), which have been generally neglected but can be a major source of nutrition through gleaning (mostly by women) in many coastal communities 103 . Such comprehensive, multispecies reef fisheries models that incorporate nutritional benefits [START_REF] Robinson | Managing fisheries for maximum nutrient yield[END_REF] would provide decision makers with an effective framework with which to anticipate future patterns in nutrient production from reef fisheries, enabling them to be proactive in managing fisheries for nutritional outcomes in a changing world.

While evidence suggests that higher functional redundancy (that is, a higher number of species with similar ecological functions) can initially buffer communities against the detrimental impact of disturbances [START_REF] Mclean | Trait structure and redundancy determine sensitivity to disturbance in marine fish communities[END_REF][START_REF] Nash | Herbivore cross-scale redundancy supports response diversity and promotes coral reef resilience[END_REF] , the general trend over time is a loss of functional redundancy [START_REF] Mclean | Trait structure and redundancy determine sensitivity to disturbance in marine fish communities[END_REF] and biotic homogenization [START_REF] Stuart-Smith | Habitat loss and range shifts contribute to ecological generalization amongst reef fishes[END_REF][START_REF] Richardson | Mass coral bleaching causes biotic homogenization of reef fish assemblages[END_REF] in response to habitat degradation under increasing disturbance regimes. However, the consequences for nutritional quality at the community level remain unknown and future research will need to assess which species traits matter most for predicting winners and losers from a nutrition perspective (Box 2 and Table 1). While nutrient profiles have been predicted from phylogeny [START_REF] Vaitla | Predicting nutrient content of ray-finned fishes using phylogenetic information[END_REF] and traits [START_REF] Hicks | Harnessing global fisheries to tackle micronutrient deficiencies[END_REF] , only one study has related nutrient profiles to traits that reflect species vulnerability to environmental changes [START_REF] Maire | Micronutrient supply from global marine fisheries under climate change and overfishing[END_REF] . This information is necessary to determine how coral and fish traits can be used to derive conservation and resource management policies in the face of a changing climate [START_REF] Kissling | Towards global data products of essential biodiversity variables on species traits[END_REF] , in particular those relevant to future food and nutrition security from coral reef fisheries 34 (Box 2). It will also help to prioritize the indicators that long-term monitoring programmes should focus on in the future and to determine the taxonomic scope and resolution required for making such inferences. For example, collecting data on benthic cover at the species level can be extremely difficult and time consuming, whereas automated image analysis might provide a cost-effective proxy of habitat condition for predicting nutritional outcomes. A key priority for future research should thus focus on using existing, extensive datasets [START_REF] Macneil | NutrientFishbase dataset[END_REF][START_REF] Edgar | Reef Life Survey: establishing the ecological basis for conservation of shallow marine life[END_REF] to identify the most reliable and cost-effective ecological indicators of fish community nutritional responses to climate change (Box 2 and Table 1).

Balancing food security, ecosystem functioning and other socio-ecological goals

The ecological management of multispecies fisheries on tropical reefs is challenging because fisheries and landing sites are widely dispersed, catches are often unreported [START_REF] Pauly | Accurate catches and the sustainability of coral reef fisheries[END_REF] and formal governance, monitoring and management are often lacking [START_REF] Worm | The future of fish[END_REF] . However, the need for sustainable reef fisheries has motivated the search for solutions through alternative fisheries-independent, biomass-based models, showing that fishing can be compatible with the maintenance of key ecosystem functions [START_REF] Mcclanahan | Critical thresholds and tangible targets for ecosystem-based management of coral reef fisheries[END_REF] . These approaches have typically aggregated fish communities into either total biomass [START_REF] Mcclanahan | Critical thresholds and tangible targets for ecosystem-based management of coral reef fisheries[END_REF] or trophic group biomass [START_REF] Macneil | Recovery potential of the world's coral reef fishes[END_REF] and used space-for-time substitutions of large observational datasets to infer temporal dynamics. Consistently, such work has shown that, out of a total unfished biomass averaging ~1,000 kg ha -1 (ref. [START_REF] Macneil | Recovery potential of the world's coral reef fishes[END_REF] ), fishing down to approximately 50% of total unfished biomass tends to maintain important reef ecosystem structure and function [START_REF] Mcclanahan | Critical thresholds and tangible targets for ecosystem-based management of coral reef fisheries[END_REF] and that there are clear benefits from having some form of reef management in place [START_REF] Macneil | Recovery potential of the world's coral reef fishes[END_REF][START_REF] Cinner | Meeting fisheries, ecosystem function, and biodiversity goals in a human-dominated world[END_REF] .

Maximizing sustainable production while maintaining ecosystem function is a major goal in coral reef fisheries science, but it is not the only one. Maximizing economic yield, incorporating socio-cultural dimensions and addressing nutrient deficiencies [START_REF] Hicks | Harnessing global fisheries to tackle micronutrient deficiencies[END_REF] important goals that also need to be considered where coral reef fisheries operate. This broad range of objectives, and the potential for synergies and trade-offs among them, raise the importance of defining a safe operating space for coral reefs informed by multiple social and ecological dimensions (Fig. 3). Within this framework, boundaries that delineate safe operating spaces need to be jointly defined based on indicators for multiple dimensions. For example, a safe zone is one that allows for sustainable yield while delivering nutritional quality and still preserving functional diversity.

Monitoring of the indicators and targets relevant to each goal, and comparison with safe zone boundaries, will be necessary to assess the overall performance and sustainability of coral reef fisheries and will ultimately support efforts to maximize synergies and minimize trade-offs. The combination of maximum sustainable yield, maximum economic yield and recent developments in modelling maximum nutrient yield for fisheries now provides an interdisciplinary framework for comparing nutritional outcomes with other ecological and socio-economic objectives [START_REF] Robinson | Managing fisheries for maximum nutrient yield[END_REF] .

A key question for reef fisheries management is how models of reef fisheries and biomass-based targets should be adapted to incorporate potential nutritional benefits while handling uncertainty surrounding the future composition and abundance of reef fish communities impacted by ongoing environmental changes [START_REF] Graham | Extinction vulnerability of coral reef fishes[END_REF] . These multispecies models will need to account for future changes in fish nutritional content as well as food safety parameters that, while beyond the scope of this paper, are likely to change with, for example, increasing levels of methylmercury in warmer oceans [START_REF] Schartup | Climate change and overfishing increase neurotoxicant in marine predators[END_REF] .

A critical first step will be to collate comprehensive food composition and safety databases from small-scale domestic fisheries, along with country-specific statistics on catches, local consumption and consumer preferences (Table 1), which are still crucially lacking in many countries with coral reefs.

Temperature-dependent models 87 that also account for species range shifts [START_REF] Pinsky Malin | Preparing ocean governance for species on the move[END_REF] and life history traits [START_REF] Thorson | Predicting recruitment density dependence and intrinsic growth rate for all fishes worldwide using a data-integrated life-history model[END_REF] will then be needed to project future changes in fisheries contributions to food and nutrition security, accounting for associated uncertainty (Box 2). For example, work from temperate ecosystems has shown that the direction and magnitude of the expected maximum sustainable yield are sensitive to factors such as taxonomy, ecoregion and life history 87 , providing promising insights for coral reef fisheries. Together, a combination of these approaches and their spatially explicit extensions will help to identify which target species are most susceptible (losers) to negative impacts and which will thrive (winners) under future environmental changes (Box 1). This knowledge will contribute to a better understanding of how future environmental changes will alter the ecological capacity of coral reef fisheries, their associated nutrient supply and the flows of these nutrients to consumers. These data will allow fisheries management to be governed not only by ecological and economic priorities but also through the lens of human nutritional vulnerability and needs, to harness the species that will thrive to their fullest nutritional potential (Table 1). Enhancement of the contribution coral reefs can make to future food and nutrition security will ultimately require a holistic approach that incorporates improved local The colours of the different dimensions of coral reef fisheries correspond to their status in relation to the boundaries. For example, reef habitats are shaded red as in this example they have crossed the ecological ceiling (the level at which ecological goals are unlikely to be met and irreversible change may have occurred; red boundary) and are now in such a depauperate state that irreversible changes have occurred. Safe zones (the level at which both social and ecological goals may be met; green) and boundaries (where there is uncertainty around the capacity to meet ecological goals; orange) need to be jointly defined for multiple interacting dimensions, as illustrated in b. The social foundation (blue) represents the level below which social goals are unlikely to be met. b, Examples of interactions between the indicators of three dimensions include trade-offs (for example, decreases in functional richness with increasing catch biomass), synergies (for example, increases in the mean calcium concentration of the catch with increasing functional richness) and scale-dependent interactions (for example, higher mean calcium concentrations of catches at intermediate levels of catch biomass). The status of each dimension (a) and relationships between indicators and green safe zones (b) are illustrative only.

management of small-scale domestic fisheries [START_REF] Cinner | Meeting fisheries, ecosystem function, and biodiversity goals in a human-dominated world[END_REF] and agriculture with integrated and targeted programmes that provide vulnerable societies with healthy and sustainable diets [START_REF] Albert | Malnutrition in rural Solomon Islands: an analysis of the problem and its drivers[END_REF] , such as socio-economic incentives, nutrition-sensitive policies and integration into education [START_REF] Albert | Malnutrition in rural Solomon Islands: an analysis of the problem and its drivers[END_REF] , as well as public nutrition programmes (for example, in schools) [START_REF] Ahern | Locally-procured fish is essential in school feeding programmes in sub-Saharan Africa[END_REF] . At larger scales, inclusion of food and nutrition security experts in the development of international trade agreements will be essential to ensure that nutrient-rich catches are retained for vulnerable populations [START_REF] Hicks | Secure local aquatic food systems in the face of declining coral reefs[END_REF] and to provide a key resource in addressing nutrient deficiencies (Table 1).

Conclusion

Coral reef fisheries represent an important resource for addressing micronutrient deficiencies, particularly in countries where reef dependency is high and these deficiencies are most acute. Yet, the complex interplay between climate change and other socio-ecological stressors is increasingly impacting reef ecosystem structure and function, with major consequences for ecosystem services that support food provision and nutrition. Our capacity to adapt to novel fish communities based on fewer or different coral reefs will rely on a better understanding of the modified trophic pathways that will affect the nutrient profiles of fished species, as well as how these changes will propagate from individual fish to entire communities throughout food webs. Transdisciplinary approaches (from the collection of baseline data on catches and the domestic consumption of reef-based seafoods to the identification of safe operating spaces for future coral reef fisheries) are required to fill knowledge gaps and inform fisheries management policies, and to ensure their uptake in the management of local fisheries and the regulation of trade and export markets. Addressing such key priorities will provide important opportunities towards much-needed nutrition-sensitive approaches to fisheries management and conservation.

Fig. 1 |

 1 Fig. 1 | Addressing inadequate micronutrient intake in countries with coral reefs requires policies that integrate the global fish trade dynamics with food and nutrition security policy. a, The risk of inadequate micronutrient intake (averaged across seven nutrients; reproduced with permission from ref. 11 , Springer Nature Limited) in coastal countries is often high for countries with coral reefs (data from UNEP-WCMC 91 ; light blue). Countries with no maritime exclusive economic zone (EEZ) are shown in light grey and countries smaller than 25,000 km 2 are shown as dots. b,c, Blue-barred parrotfish (Scarus ghobban) sold in France (b) and red snapper (Lutjanus species) sold in London (c), both more than 3,500 km from their closest potential point of capture (based on the shortest great-circle distance to the Red Sea). Photo in b is provided by E.M.; photo in c is provided by J.P.W.R.

Fig. 2 |

 2 Fig. 2 | Impacts of climate change and other human stressors on access to reef-based food and nutrition. Amplification of socio-ecological stressors linked to global change (blue) disrupts the provision of ecosystem services provided by coral reefs (green) in support of food and nutrition security.As human activities continue to increase greenhouse gas emissions, pollution and overharvesting (blue gradient), safeguarding food and nutrition security traditionally supported by healthy coral reefs (green gradient) will require adaptation to novel coral reef communities and the identification of winners versus losers among fish species, not only in terms of biomass but also nutritional value. Images from Shutterstock.com; used with permission.

Fig. 3 |

 3 Fig.3| Safe operating spaces for coral reef fisheries and interactions between multiple indicators. a, Safe operating spaces for multiple dimensions of coral reef fisheries, including ecosystem structure and function, ecosystem services and social goals. The colours of the different dimensions of coral reef fisheries correspond to their status in relation to the boundaries. For example, reef habitats are shaded red as in this example they have crossed the ecological ceiling (the level at which ecological goals are unlikely to be met and irreversible change may have occurred; red boundary) and are now in such a depauperate state that irreversible changes have occurred. Safe zones (the level at which both social and ecological goals may be met; green) and boundaries (where there is uncertainty around the capacity to meet ecological goals; orange) need to be jointly defined for multiple interacting dimensions, as illustrated in b. The social foundation (blue) represents the level below which social goals are unlikely to be met. b, Examples of interactions between the indicators of three dimensions include trade-offs (for example, decreases in functional richness with increasing catch biomass), synergies (for example, increases in the mean calcium concentration of the catch with increasing functional richness) and scale-dependent interactions (for example, higher mean calcium concentrations of catches at intermediate levels of catch biomass). The status of each dimension (a) and relationships between indicators and green safe zones (b) are illustrative only.

Table 1 | Key knowledge gaps and potential solutions towards food and nutrition security from coral reef fisheries under climate change

 1 are

	ID	Category	Key knowledge gap	Potential solution	Prerequisite a
	a	Data deficiency Baseline data on nutrient composition and food	Collate relevant, up-to-date nutrient data on reef
			safety parameters for target species	fishes to be integrated in local food composition
				databases
	b		Reliable and disaggregated (for example, sex	Integrate fish catch and consumption into market and
			or ethnicity) statistics of reported catches,	national surveys (for example, household income and
			including from small-scale fisheries, and domestic	expenditure)
			consumption of reef-based seafood
	c		Proportion of total nutrient yield that is exported	Couple nutrient databases with data on fish	a
			through the global and regional fish trade versus	production, export and local consumption (especially
			retained for domestic consumption in different	from small-scale fisheries), accounting for differences
			countries with coral reefs	in reporting format
	d	Analytical need Sensitivity of fish nutritional composition (species	Combine experimental biology and nutritional	a
			level) to environmental variation	analysis on fish sampled along environmental
				gradients (Box 2)
	e		Relative impact of overfishing and climate change	Assess the nutritional and catch contribution of	a and d
			on the potential nutrient supply from coral reef	species and functional groups under varying levels of
			fisheries	exploitation and climate stress
	f		Ecological indicators of nutritional vulnerability in	Identify species and community traits that	a, d and e
			response to environmental change	characterize, among fishery targets, nutritional
				winners in response to environmental change (Box 2)
	g	Policy need	Appropriate incentives and mechanisms for	Incorporate reef fish as a micronutrient source in	a
			managing reef fisheries for nutrition security, and	national dietary guidelines and public nutrition
			the identification of relevant spatial scales	programmes (for example, in schools)
	h		Ecologically and socially sustainable thresholds	Develop socio-ecological models to identify critical	a-f
			for future reef fisheries that enhance nutritional	thresholds and tipping points to inform management
			outcomes while preserving ecosystem function
	i		Key trade-offs and alternative solutions to	Intersect policy frameworks typically used to govern	a-h
			simultaneously maximize fishery production,	and set goals for fishery production, nutrition and
			nutritional content and functional diversity	biodiversity
	j		How changes in the nutrient supply from coral reef	Include food and security experts in trade negotiations	a-i
			fisheries should be integrated with larger-scale	and implement economic incentives and/or subsidies
			policy decisions on fish trade and export markets	for retaining local fish production

a Other elements listed in the table and identified by the ID column.

Acknowledgements C.M. (FT200100870), K.L.N. (DE210100606) and R.D.S.-S. (FT190100599) were by Australian Research Council funding. M.A.M. was supported by the Natural Sciences and Engineering Research Council Canada Research Chairs Program. J.P.W.R. received funding from a Leverhulme Trust Early Career Fellowship. N.A.J.G. received funding from the Royal Society (URF\R\201029) and from the European Union's Horizon 2020 research and innovation programme under grant agreement number 820989 (project COMFORT). C.C.H. receives funding from a European Research Council Starting Grant (759457) and a Philip Leverhulme Prize. C.D.G. and J.Z.-M. receive funding from the National Science Foundation CNH-L 1826668 and the John and Katie Hansen Family Foundation. D.M. is supported by the 2017-2018 Belmont Forum and BiodivERsA REEF-FUTURES project under the BiodivScen ERA-NET COFUND programme and with the funding organization ANR. The work reflects only our view; the European Commission and their executive agency are not responsible for any use that may be made of the information the work contains.

Author contributions

C.M. conceptualized the structure and content of the manuscript after discussion with C.C.H. and N.A.J.G. C.M. wrote the initial draft. D.A.F., C.D.G., M.K., M.A.M., E.M., S.M., D.M., K.L.N., J.O.O., J.P.W.R., R.D.S.-S., J.Z.-M. and G.J.E. expanded on the ideas and engaged in discussion and editing of the final manuscript. All authors contributed to writing, editing, and approving the final manuscript.

Competing interests

The authors declare no competing interests.


A Cousin
email: acousin@irap.omp.eu

O Beyssac

O Forni

P Y Mes- Lin

N Martin

B Chide

E M Hausrath

R Sullivan

F Poulet

E Dehouck

J Lasue

S Schröder

O Gasnault

P Pilleri

R Wiens

S Maurice

Soil diversity on Mars: comparison between Gale and Jezero craters

Introduction: Soils are loose, unconsolidated materials resulting from the physical and chemical alteration of rocks by several processes [eg., [1][2][3]. The study of soils can allow us to estimate the global composition of the crust by examining their primary constituents [2], as well as to better understand the past and present environmental conditions on Mars. Orbital data have shown that dust and soils are hydrated (4 ±1 wt%) and relatively homogeneous across the planet [4]. Soil analyses performed by the Viking, Pathfinder and MER rovers have confirmed this [5]. The Mars Science Laboratory (MSL) mission with the Curiosity rover showed that fine-grained soils in Gale Crater contain up to 3 wt% H2O [1,6,7], and that this hydration is primarily carried by the X-ray amorphous component [8]. ChemCam observations have shown that fine-grained soils are more hydrated than coarser soils [1,9], likely due to the amorphous component [10,11], which appears to contain hydrated Mg sulfates [11]. The Perseverance rover explored the crater floor of Jezero for 414 sols, as well as the delta front for another 235 sols. The soils analyzed during this period allow us to investigate the relationship between the grain size and soil mineralogy, evaluate local vs more global contributions [12], and make comparisons with other in situ data elsewhere on Mars.

Objectives: The SuperCam instrument [13,14] on Perseverance uses the LIBS technique, as does ChemCam on MSL. This technique uses a laser with a spot size of only 150-500 microns [13], allowing analysis of pure phases when the grains are larger than the spot size, or of a mixture finer grains. In general, between 30 and 50 shots are performed on each analysis point (and at least 5 points per target). The shock wave generated by the laser for each shot causes some excavation, so allows new grains to be analyzed with each shot. Thanks to this technique we can analyze the soils in detail, at the sub-millimeter scale. Similarity of techniques between MSL and Mars2020 allows comparisons between Gale and Jezero craters.

The objectives of this study are: (1) classify analyzed soils by grain size; (2) analyze relationships between grain size and composition; (3) evaluate potential local vs. global components present; and (4) compare the compositions of finer grains between Gale and Jezero, to investigate homogeneity of fine-grained soils across Mars, as suggested by previous work [5,6,15,16].

Methodology: This study uses all SuperCam analysis points of regolith material, whatever the type: indurated soil, ripple, disturbed (by the rover wheel for example) and undisturbed soil. Soils on top of a flat rock have been included, but only if the soil was thick enough to avoid sampling the rock below. As the laser beam is small, the grain size analysis was done on each LIBS point and not on the whole image as the objective here is about the size and composition of the grains that were analyzed by LIBS and therefore the methodology used is different from [12]. Only the RMI images were used, except where WATSON images were also available (a few targets only). We use the Wentworth scale for the grain size classification [17]. The ChemCam soil targets come from [18], where targets were classified up to sol 3007, using the same methodology. For chemical compositions, the major element oxide data are used from for both instruments [19,20], using the shot-toshot data, as each laser shot acquires data on a new set of grains due to excavation caused by the shock wave. The first 5 shots are however removed as they can contain more dust [21]. The identified buried coarser grains by [22] have also been removed in the SuperCam dataset. To compare ChemCam and SuperCam data, we have used an Independent Component Analysis (ICA) technique, using a JADE algorithm [START_REF] Comon | High Order Statistics[END_REF][START_REF] Forni | [END_REF][25].

Results: Classification As of sol 645, 48 different Super-Cam targets were soil, with a total of 362 points analyzed. Most of the LIBS points have sampled a fine-grained regolith or a very-coarse grained one (59% and 20%, respectively). The other categories (medium sand, coarse sand and granules or bigger) are less represented with only 7, 6 and 9 % of the population, respectively. Therefore, this study will focus mainly on the fine and very-coarse grained types of regolith. Most of the regolith targets analyzed with Super-Cam are either in the Máaz formation, or along the delta front (specifically at Observation Mountain, the regolith sampling site). The number of observations performed is biased by the time spent in each area, and what was the main mission objective. We did not spend so much time at Observation Mountain (23 sols) but the objective being the regolith sampling, more analyses were performed to help the decision of sampling.

Chemistry/mineralogy vs grain size Very coarse regolith shows more dispersion compared to the fine-grained soils. Both types of soil show a bimodal distribution for the MgO content, but there are more coarser grains enriched in MgO. From the ternary diagram (Fig. 1) the finest grains globally occur in the triangle composed by plagioclase and the two pyroxenes, with a large majority of them located in the middle of it. This is consistent with VISIR data showing homogeneous spectral properties along with a pyroxene signatures in these fine-grained regolith [26]. The coarsest grains (left plot) plot in the olivine-pyroxene-feldspar domain; however, the majority of them are located near the olivine composition. This can also be observed in a Al/Si vs (Fe+Mg)/Si diagram (Fig. 2), where coarsest regolith is overall more enriched in MgO and depleted in Al2O3 compared to Máaz rocks, and finest regolith being mainly in the middle of the mafic-felsic trend, as seen in Gale. Coarse-grained regolith shows more variability in Mg#, and this is discussed more in detail in [27]. Chemistry/mineralogy along the traverse The same type of ternary diagram, shows that fine-grained soils are homogeneous all along the traverse, whereas coarser grains show some variability. Coarse grains analyzed in the Máaz formation show the highest dispersion, with at least 1 point sampling a feldspar-like grain -even though the vast majority correspond to olivines or olivine-low Ca pyroxenes mixtures. At Seítah there is very little dispersion, most of the coarse grains correspond to olivines with a few other points that are more similar to fine-grained soils (e.g. more felsic). At Observation Mountain, only a single very coarse grain was sampled and showed a diverse composition, more altered.

Comparison to Gale crater ICA technique is useful for comparing Gale and Jezero spectral datasets. ICA showed that Jezero fine-grained soils are overall more enriched in MgO compared to those analyzed at Gale crater, whereas the latter are more enriched in K2O. CaO does not seem to differ between the two locations. Data from Jezero seem to show less S whereas the Cl signal seems to be slightly more elevated. This will be investigated more in detail.

Discussion: Fine-grained soils of Jezero have a general composition matching well that of pyroxene. However, the laser beam samples several grains for each shot, and this composition reflects a mixture of several phases. A few shots have sampled some buried coarser grains and this is reflected by the bimodality of the MgO content. Finest grains are more enriched in Cl, H, and S which are related to secondary phases. At Gale crater, this was attributed to the amorphous component [1,7], which contained some hydrated Mg sulfates [11]. Fine-grained regolith seems to contain some local inputs, as S seems to be lower at Jezero, probably due to less sulfate veins in that region, whereas Cl is more present, probably related to the presence of perchlorates [28]. In contrast to Gale crater, very coarse regolith corresponds mainly to olivine. The likely source (Seítah formation) and transport of these grains is discussed in [27]. The only very coarse grains analyzed at Observation Mountain shows a different composition, and might correspond to a more local input, such as from the delta top, or from altered rocks containing some carbonates as seen in the vicinity. These very coarse grains are directly related to local rocks. At Gale crater an important fraction of very coarse grains were felsic, reflecting the dominance of felsic igneous rocks [29,[START_REF] Sauter | pdf 54th Lunar and Planetary Science Conference 2023[END_REF].

Conclusion: Mainly fine-grained and very coarse-grained regolith has been analyzed by SuperCam during the first 634 sols of the Mars2020 mission. Very coarse grains show more dispersion in their compositions due to their size, and they are more locally sourced compared to fine-grained soils, as seen in previous studies. Comparison of the regolith observed at Gale and Jezero showed that even grains <150 microns contain some local component.

Figure 1 :

 1 Figure 1: Ternary diagram representing the very coarse grains (left, in blue) and the fine-grained regolith (right, in orange) observed by SuperCam, shot-to-shot. Individual points correspond to the Calib. Targets.

Figure 2 :

 2 Figure 2: Al/Si vs (Fe+Mg)/Si for fine and coarse-grained soil compared to the Seítah, delta and Máaz rocks.

1349.pdf 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806)

Acknowledgments: The engineers and scientists of the Perseverance rover are thanked for their generous contributions to this work. This work was supported by CNES in France and by the Mars Exploration Program in the US.