Micheline Ghosn

Céline Mahfouz

Rachida Chekri

Baghdad Ouddane

Gaby Khalaf

Thierry Guérin

Rachid Amara

Petru Jitaru
email: petru.jitaru@anses.fr

Assessment of trace element contamination and bioaccumulation in algae (Ulva lactuca), bivalves (Spondylus spinosus) and shrimps (Marsupenaeus japonicus) from the Lebanese coast

Keywords: Bioaccumulation, trace elements, marine organisms, Lebanon, Eastern Mediterranean

In this study, levels of 20 trace elements (Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Sn, Sb, Ba, Hg, Pb and U) and the respective biota-sediment accumulation factors (BSAF) were assessed for three marine species from the Eastern Mediterranean (Lebanese coast) belonging to different trophic levels in the food chain (algae, bivalves and shrimps). Multivariate analyses showed significant differences in trace element accumulation between seasons, sites and species thus highlighting the importance of a multi-species and seasonal approach to monitor trace metals in coastal areas. Biota-sediment accumulation factors (BSAF) showed limited transfer from sediments to marine organisms suggesting that the bioaccumulation of trace elements by marine organisms should be assessed by considering multiple sources of contaminants. Lead (Pb) levels (0.07-4.44 mg.kg -1 ) measured in algae and Cd (0.54-7.74 mg.kg -1 ) and Zn (42.88-972 mg.kg -1 ) levels found in the oyster, were similar and sometimes higher than those found in other polluted areas indicating that the Lebanese coast is subject to environmental pollution.

Introduction

The Mediterranean Sea is known for its high biodiversity; however, significant amounts of chemical contaminants mainly introduced in coastal areas via industrial, agricultural and mining activities, are threatening the marine ecosystem [START_REF] Lafabrie | Metal contamination of Posidonia oceanica meadows along the Corsican coastline (Mediterranean)[END_REF][START_REF] Ourgaud | Trace elements in a Mediterranean scorpaenid fish: Bioaccumulation processes and spatial variations[END_REF][START_REF] Wang | Heavy metal concentrations in water, sediment, and tissues of two fish species (Triplohysa pappenheimi, Gobio hwanghensis) from the Lanzhou section of the Yellow River, China[END_REF]. Toxic trace elements, especially trace metals, which constitute an important part of these discharges, are important pollutants of aquatic environments mainly because of their persistence and tendency to concentrate in marine organisms [START_REF] Afshan | Effect of Different Heavy Metal Pollution on Fish[END_REF][START_REF] Battuello | Zooplankton from a North Western Mediterranean area as a model of metal transfer in a marine environment[END_REF].

Three marine compartments including water column, sediment and biota are usually used to monitor the spatial and temporal trends of marine pollution. Solubility, bioavailability and toxicity of trace elements in seawater are controlled by several physico-chemical parameters, such as pH, temperature, salinity, dissolved oxygen, suspended particles and dissolved organic matter [START_REF] Chakraborty | Benthic macroalgae as biological indicators of heavy metal pollution in the marine environments: A biomonitoring approach for pollution assessment[END_REF][START_REF] Lim | Spatial Variability of Metals in Surface Water and Sediment in the Langat River and Geochemical Factors That Influence Their Water-Sediment Interactions[END_REF]. Moreover, trace element concentrations in water and sediment are affected by a variety of environmental factors such as tides, winds, currents and fresh water input [START_REF] Hatje | Particulate trace metal and major element distributions over consecutive tidal cycles in Port Jackson Estuary, Australia[END_REF][START_REF] Strady | Spatial and temporal variations in trace metal concentrations in surface sediments of the Marennes Oléron Bay. Relation to hydrodynamic forcing[END_REF]. These processes create a stochastic pattern making it difficult to predict the potential adverse health effects on the surrounding organisms caused by accumulation, suspension and mobilization of sediments [START_REF] Meng Chuan | Sediment and Organisms as Marker for Metal Pollution[END_REF]Rajeshkumar et al., 2018;[START_REF] Ribeiro | Distribution and environmental assessment of trace elements contamination of water, sediments and flora from Douro River estuary, Portugal[END_REF]. Sediments do not only act as sinks, but also as sources of chemical contaminants in the marine environment; therefore, they can be used as geomarkers for potential pollution sources and conditions [START_REF] Meng Chuan | Sediment and Organisms as Marker for Metal Pollution[END_REF]. Moreover, unlike water, sediments reflect long term contamination conditions [START_REF] Thomann | Steady-state model of biota sediment accumulation factor for metals in two marine bivalves[END_REF] but they do not necessarily reflect the biota contaminants [START_REF] Meng Chuan | Sediment and Organisms as Marker for Metal Pollution[END_REF][START_REF] Rainbow | Trace metal bioaccumulation: Models, metabolic availability and toxicity[END_REF][START_REF] Wang | Heavy metal concentrations in water, sediment, and tissues of two fish species (Triplohysa pappenheimi, Gobio hwanghensis) from the Lanzhou section of the Yellow River, China[END_REF]. Many marine species have been shown to accumulate trace elements, hence acting as suitable indicators for monitoring local trace elements pollution and their potential ecological and human risks [START_REF] Campanella | Trace metals in seagrass, algae and molluscs from an uncontaminated area in the Mediterranean[END_REF][START_REF] Conti | A biomonitoring study: trace metals in algae and molluscs from Tyrrhenian coastal areas[END_REF]. These species accumulate trace elements reaching levels that are many times higher than those in the water column or sediments [START_REF] Conti | A biomonitoring study: trace metals in algae and molluscs from Tyrrhenian coastal areas[END_REF][START_REF] Diop | Assessment of trace element contamination and bioaccumulation in algae ( Ulva lactuca ), mussels ( Perna perna ), shrimp ( Penaeus kerathurus ), and fish ( Mugil cephalus , Saratherondon melanotheron ) along the Senegalese coast[END_REF].

Accordingly, biomonitoring by using species that belong to different taxonomic groups and trophic levels provides a better assessment of the extent of any contamination in terms of presence and relative magnitude [START_REF] Campanella | Trace metals in seagrass, algae and molluscs from an uncontaminated area in the Mediterranean[END_REF][START_REF] Pérez-Cadahía | Evaluation of PAH bioaccumulation and DNA damage in mussels (Mytilus galloprovincialis) exposed to spilled Prestige crude oil[END_REF]Rainbow, 1995a). A suitable bioindicator should (i) be able to accumulate high levels of pollutants without death; (ii) have a sessile lifestyle to reflect local pollution; (iii) be relevant in the food chain and (iv) be widespread and abundant [START_REF] Zhou | Biomonitoring: An appealing tool for assessment of metal pollution in the aquatic ecosystem[END_REF]. Additionally, ease of sampling and identification are criteria to take into consideration when targeting a bioindicator [START_REF] Rainbow | Cosmopolitan biomonitors of trace metals[END_REF]. So far, mollusks, crustaceans and macrophytes have been shown to be valuable cosmopolitan bioindicators and have been used in several studies [START_REF] Amiard | Metallothioneins in aquatic invertebrates: Their role in metal detoxification and their use as biomarkers[END_REF][START_REF] Bonsignore | Bioaccumulation of heavy metals in fish, crustaceans, molluscs and echinoderms from the Tuscany coast[END_REF][START_REF] Chakraborty | Benthic macroalgae as biological indicators of heavy metal pollution in the marine environments: A biomonitoring approach for pollution assessment[END_REF][START_REF] Chiarelli | Marine Invertebrates as Bioindicators of Heavy Metal Pollution[END_REF][START_REF] Diop | Assessment of trace element contamination and bioaccumulation in algae ( Ulva lactuca ), mussels ( Perna perna ), shrimp ( Penaeus kerathurus ), and fish ( Mugil cephalus , Saratherondon melanotheron ) along the Senegalese coast[END_REF][START_REF] Rouane-Hacene | Seasonal assessment of biological indices, bioaccumulation and bioavailability of heavy metals in mussels Mytilus galloprovincialis from Algerian west coast, applied to environmental monitoring[END_REF][START_REF] Viarengo | Mussels as biological indicators of pollution[END_REF]. Understanding how trace elements are bioaccumulated in food webs is essential for elucidating their environmental behavior, ecotoxicological risks and the potential hazards to human health [START_REF] Chen | Accumulation of heavy metals in food web components across a gradient of lakes[END_REF].

The substantial development of urban and industrial activities along the coast in Lebanon, as well as, the lack of wastewater treatment strategies, resulted in increased inputs of chemical contaminants to the marine environment [START_REF] Fakhri | The state of the Lebanese coastal waters, in: Review and Perspectives of Environmental Studies in Lebanon[END_REF]. In addition, waste production in Lebanon has increased significantly during the last decade, and the country had experienced a waste crisis in 2015. The regulated dumpsites could no longer manage the tremendous quantity of municipal garbage generated; therefore, numerous illegal and open dumpsites were created throughout the country mainly along the coast [START_REF] Khalil | Municipal leachates health risks: Chemical and cytotoxicity assessment from regulated and unregulated municipal dumpsites in Lebanon[END_REF]. Leachate effluents originating from these coastal landfills are an important source of trace elements contamination in the surrounding aquatic environment [START_REF] Stefanakis | Chapter 7-Treatment of Special Wastewaters in VFCWs[END_REF][START_REF] Youcai | Chapter 1 -Leachate Generation and Characteristics[END_REF], and constitute a serious risk to biota [START_REF] Brand | Potential pollution risks of historic landfills on low-lying coasts and estuaries[END_REF][START_REF] Toufexi | Environmental and human risk assessment of landfill leachate: An integrated approach with the use of cytotoxic and genotoxic stress indices in mussel and human cells[END_REF].

Most environmental studies conducted along the Lebanese coast focused on the contamination of water and sediments [START_REF] Abi-Ghanem | Speciation of three Trace Elements Mercury , Lead , Cadmium in Sediments of the Lebanese Coastal Zones[END_REF][START_REF] Abi-Ghanem | Mercury Distribution and Methylmercury Mobility in the Sediments of Three Sites on the Lebanese Coast, Eastern Mediterranean[END_REF][START_REF] Merhaby | Assessment of trace metals contamination in surficial sediments along Lebanese Coastal Zone[END_REF]. Few studies mostly dating back to the 1980s have focused on marine organisms [START_REF] Kouyoumijian | Levels of mercury, cadmium and copper in fish from Lebanon[END_REF][START_REF] Kouyoumjian | Exposure of the lebanese population to mercury through fishery products and a proposal for a screening standard[END_REF][START_REF] Shiber | Metal concentrations in certain coastal organisms from Beirut[END_REF][START_REF] Shiber | Lead, cadmium, copper, nickel and iron in limpets, mussels and snails from the coast of ras Beirut, Lebanon[END_REF]Nakhlé, 2003) while environmental pressure along the coast has been in continuous increase. To our knowledge, no studies have assessed the bioaccumulation of trace elements along the Lebanese coast, and particularly in organisms belonging to different ecological niches or trophic levels.

The aim of this study was to evaluate the contamination status related to 20 trace elements (Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Sn, Sb, Ba, Hg, Pb and U) of three benthic marine species from different trophic levels, representative of the Lebanese coast (Eastern Mediterranean).

Samples were collected at three sites during dry and wet seasons in 2017. The species selected are the green algae Ulva lactuca that is widely used as a bioindicator of trace elements pollution, the spiny oyster Spondylus spinosus and the kuruma shrimp Marsupenaneus japonicus that are commonly consumed by the Lebanese population and studied for the first time to assess trace elements contamination along the Lebanese coast. Moreover, the results of trace elements in sediments were used to calculate the biota-sediment transfer factor (BSAF) from sediments to biota.

Materials and methods

Study area

Three sites representing the coastline with different levels and types of anthropogenic pressures were selected for this study (Fig. 1). Tripoli (site 1) is mainly known for its artisanal fishing and boat maintenance activities. Several sewage outfalls that discharge wastewater without prior treatment are identified along its coast. A controlled dumpsite north of its port is still receiving waste despite a decision of closure in 2012, thus, leading to increased waste height and uncontrolled leachate [START_REF] El-Hoz | Current Situation and Challenges to Address on the Landfill of Tripoli, Challenges and trends in solid waste management in Mediterranean cities[END_REF]. Beirut, the capital of Lebanon (site 2), is a densely populated (up to 3500 individuals per square meter) and an industrialized area [START_REF] Fakhri | The state of the Lebanese coastal waters, in: Review and Perspectives of Environmental Studies in Lebanon[END_REF]. Several sewage outfalls discharge polluted water in the latter's coastal zone, in addition to the Beirut River that drains industrial effluents into the sea causing water quality degradation. The area comprises textiles, cement and metal fabrication industries, in addition to tanneries, slaughterhouses, as well as, wood and furniture production [START_REF] Fakhri | The state of the Lebanese coastal waters, in: Review and Perspectives of Environmental Studies in Lebanon[END_REF]. Moreover, there are three dumpsites present in this area with the biggest one in the Dora region. The latter dumpsite is responsible for more than half of Lebanon's trace elements discharges in the coastal area [START_REF] Fakhri | The state of the Lebanese coastal waters, in: Review and Perspectives of Environmental Studies in Lebanon[END_REF]. Saida (site 3) is less impacted by anthropogenic pressures compared to Beirut despite being the third densest coastal city in Lebanon. A dumpsite was rehabilitated there in 2014, and a primary wastewater treatment plant has been recently established in its coastal area.

Sample description and collection

Three marine species belonging to different levels of the food chain were selected for this study.

The green macroalgae, Ulva lactuca is a cosmopolitan species that is widely used as a bioindicator [START_REF] Diop | Assessment of trace element contamination and bioaccumulation in algae ( Ulva lactuca ), mussels ( Perna perna ), shrimp ( Penaeus kerathurus ), and fish ( Mugil cephalus , Saratherondon melanotheron ) along the Senegalese coast[END_REF][START_REF] Ho | Ulva lactuca as bioindicator of metal contamination in intertidal waters in Hong Kong[END_REF][START_REF] Kaimoussi | Variations saisonnières des teneurs en métaux (Cd, Cu, Fe, Mn et Zn) chez l'algue Ulva lactuca prélevée au niveau du littoral de la ville d'El Jadida (Maroc)[END_REF][START_REF] Kamala-Kannan | Assessment of heavy metals (Cd, Cr and Pb) in water, sediment and seaweed (Ulva lactuca) in the Pulicat Lake, South East India[END_REF]. The spiny oyster, Spondylus spinosus is a Lessepsian species that is very well-established in the Eastern Mediterranean, has gained commercial importance and is frequently consumed by the Lebanese population. This bivalve species lives attached to rocky substrates and feeds on particles from the water column [START_REF] Aksit | The surface morphology of the ctenidia of Spondylus spinosus (Mollusca: Bivalvia) from Antalya Bay, Turkey[END_REF]. The kuruma shrimp, Marsupenaeus japonicus, is also a Lessepsian species in the Mediterranean. This species inhabits sandy and mud bottoms and feeds on algae, small fish and bivalves [START_REF] Galil | Removal of cadmium from aqueous solution using marine green algae, Ulva lactuca. Egypt[END_REF][START_REF] Quigley | Occurrence of the kuruma prawn Marsupenaeus japonicus (Spence Bate, 1888) in the Celtic Sea, English Channel, and North-West France[END_REF]. These three species were chosen because they live at different depths, and can thus represent the contamination levels at different habitats along the coast.

The algae and the spiny oysters were collected by hand picking in the subtidal zone at depth varying between 0.5 and 1.0 m, as well as, 10 and 20 m, respectively. The kuruma shrimps were sampled with trammel nets at an average depth of 40 m. All species were collected at each site and during every season (wet: December-March and dry: June-September). Ulva lactuca was not found at Beirut and Saida during the dry season, and M. japonicus was not found at Beirut during the wet season and Saida during the dry season. The samples were taken immediately to the laboratory on ice. Each individual was measured (nearest 1 mm) and weighed (nearest 0.1 g) in order to standardize individual size between sites. Ten individuals of each species were selected for analysis.

The soft tissues of bivalves and shrimps were removed under a laminar flow hood using a stainlesssteel scalpel. They were then stored in low-density polyethylene vials at -20 °C. Algae were rinsed with distilled water to remove substrate residues. Samples were then lyophilized at -100 ºC until constant weight was achieved and stored at room temperature until analysis. Additionally, surfacial sediment samples were collected (hand picking using a stainless-steel shovel) by diving at each site of the coastal area at depths between 5 and 20 m, during the dry season. They were then placed in plastic bags and taken to the laboratory.

Sample analysis

Bivalves and shrimp soft tissues, as well as, algae were analyzed using an accredited method (French Accreditation Comity-COFRAC) described elsewhere [START_REF] Chevallier | Simultaneous determination of 31 elements in foodstuffs by ICP-MS after closed-vessel microwave digestion: Method validation based on the accuracy profile[END_REF]. Samples were lyophilized and their moisture content was determined. Aliquots of 0.3 g to 0.5 g of each sample were weighed in quartz digestion vessels and then mixed with 3 mL of HNO3 67 % (m/m) (suprapur grade, VWR chemicals, Prolabo, France). Three mL of ultrapure water were added, and the mineralization procedure was carried out using a closed microwave system (Multiwave 3000 from Anton Paar, France). Sample digests were quantitatively transferred to polypropylene tubes and a solution containing a mixture of internal standards, scandium (Sc), indium (In), bismuth (Bi), rhenium (Re) and yttrium (Y) was added at a final concentration of 2 µg.L -1 . The mixtures were then added up with ultrapure water to a final volume of 50 mL. In order to reduce the memory effect of mercury, a solution of gold (Au) was added at a final concentration of 20 µg.L -1 . Samples were analyzed using an ICP-MS 7700 (Agilent Technologies, Courtaboeuf, France).

Sediment analysis procedure

An aliquot of 0.5 g of dried sediment was totally digested in a heating block (HotBlock® SC100 Digestion System), with a mixture of concentrated acids containing HF, HNO3 and HCl in 10:1:3 (v/v/v) ratio, based on the procedure described by Ouddane et al [1999]. The sample was weighed into PTFE digestion cups, when the sediments were totally dissolved at 120 °C, the solution was then diluted with ultrapure Milli-Q+ water (18.2 MΩ cm) and filtered through a 0.45 µm cellulose acetate membrane. Trace element concentrations were determined by inductively coupled plasmaatomic emission spectrometry (ICP-AES, Agilent 5110, dual view) for the major elements (Al and Fe) and by ICP-MS (Varian, 820) for the trace elements (Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, V and Zn). Procedural blanks and certified reference materials (CRMs): ERM-278K (National Research Council of Canada) were prepared using the same analytical procedure and analyzed for quality assurance/quality control. All results were >90% comprised in the confidence intervals.

Quality control

In order to ensure the reliability of the results, several internal quality controls (IQCs) and associated criteria were used. Each run included a standard calibration, three blanks, three CRMs, two different spiked sample solutions, 33 samples including 2 samples analyzed in duplicate and a mid-range standard for every eight samples and at the end of the sequence. The set criteria were as follows: calibration (r² > 0.995), blanks (values < limit of quantification (LOQ)), internal standards (values within 70 and 130% of the target value), mid-range standards (values within 80 and 120% of the target value), spiked standard solutions (spike recovery within 70 and 130% of the theoretical spiked standard value), CRMs (Z-score < ± 2) and duplicates (acceptable if the relative standard deviation (RSD) ≤ 20% when mean value ≥ 5 x LOQ or RSD ≤ 40% when mean value ≥ LOQ and < 5 x LOQ). When acceptance criteria were not achieved, the results were discarded, and the samples were re-analyzed.

Data treatment

Statistics were performed using RStudio Team (2016). The level of significance was set at α=0.05.

As the data was not normally distributed, Kruskal-Wallis non-parametric test and Mann Whitney Utest for pairwise comparison were used to evaluate spatial and inter-specific differences as well as seasonal variations in elemental concentrations. Principal component analysis (PCA) was used after log (x+1) transformation of the data to explore relationships between sites, species and elemental concentrations for the two sampling seasons. Left censored data that are < LOQ and < LOD were excluded from statistical analysis (23 % of the data). All results were reported in mg.kg -1 dry weight (dw).

The biota-sediment accumulation factor (BSAF) is defined as the ratio between the concentration of a given element in a marine organism (Co) and its concentration in sediment (Cs) (both concentrations are expressed in mg.kg -1 dry weight). Bioaccumulation was confirmed when BSAF was > 1 [START_REF] Thomann | Steady-state model of biota sediment accumulation factor for metals in two marine bivalves[END_REF].

Results and discussion

The concentrations of 15 trace elements are presented in Table 1 andTable 5. Trace elements like Ag, Sn, Sb, Ba and U were not detected or showed very low detection frequencies (< 20 %) in the tissues of the selected marine organisms; thus, they were not presented in this study.

Interspecific variability of trace element concentration

For simplicity, the data were processed to reflect the interspecific variability by averaging all data for all sites regardless of the season. Al and Fe showed highest concentrations in algae (378±413 mg.kg -1 dw and 515±473 mg.kg -1 dw, respectively), while Zn (124±162 mg.kg -1 dw) and As (35.2±27.42 mg.kg -1 dw) showed highest concentrations in bivalves, and Cu showed highest concentrations in shrimps (30.91±11.96 mg.kg -1 dw) regardless of the season or site (Table 1). High standard deviations were observed indicating a strong variability among the levels in the same species. Trace element concentrations showed significant differences between all species (p < 0.001). Through multivariate analysis (not shown here), the elemental concentration explained 79% of the interspecific variation. Each species showed affinity to a certain group of trace elements. For instance, U. lactuca showed significantly higher levels of trace elements in the following order: Fe > Al > Ti > Mn > V > Pb > Cr (p < 0.001), while the spiny oyster had the highest levels of Zn > As > Ni > Se > Cd > Co (p < 0.001) and the kuruma shrimp had the highest levels of Cu and Hg (p < 0.001). Similar concentration trends were also recorded in previous studies (Table 2) [START_REF] Akcali | A biomonitoring study: Heavy metals in macroalgae from eastern Aegean coastal areas[END_REF][START_REF] Circuncisão | Minerals from Macroalgae Origin: Health Benefits and Risks for Consumers[END_REF][START_REF] Kaimoussi | Variations saisonnières des teneurs en métaux (Cd, Cu, Fe, Mn et Zn) chez l'algue Ulva lactuca prélevée au niveau du littoral de la ville d'El Jadida (Maroc)[END_REF][START_REF] El-Din | Seaweeds as bioindicators of heavy metals off a hot spot area on the Egyptian Mediterranean Coast during 2008-2010[END_REF][START_REF] Villares | Seasonal variation and background levels of heavy metals in two green seaweeds[END_REF].

Marine organisms acquire trace elements from solution and/or particulate matter. The latter pathway consists of the ingestion of suspended detritus, food prey or even deposited organic matter [START_REF] Amiard | Metallothioneins in aquatic invertebrates: Their role in metal detoxification and their use as biomarkers[END_REF][START_REF] Rainbow | Cosmopolitan biomonitors of trace metals[END_REF]. The bioaccumulation of trace elements in marine organisms is also related to several parameters contributing to inter-and intraspecific variability, namely biotic factors such as the size, age, sex, and metabolism in addition to the position of the organism in the food chain [START_REF] Jakimska | Bioaccumulation of Metals in Tissues of Marine Animals, Part I: the Role and Impact of Heavy Metals on Organisms 10[END_REF]. For example, macrophytic algae essentially respond to dissolved trace element sources and are thus good bioindicators of water quality. They are also known for their exceptional capacity to accumulate essential and trace elements [START_REF] Farias | Macrophytes as bioindicators of heavy metal pollution in estuarine and coastal environments[END_REF]. That capacity is actually related to the cell walls of green macroalgae and particularly the Ulva genus. The cell walls are composed of ulvans which are sulphated heteropolysaccharides with ionic binding properties due to their sulphate groups [START_REF] Alves | A practical perspective on ulvan extracted from green algae[END_REF][START_REF] Cunha | Sulfated Seaweed Polysaccharides as Multifunctional Materials in Drug Delivery Applications[END_REF].

More specifically, U. lactuca is known to have a high capacity to accumulate trace elements with particular affinity to Mn, Fe, Cu, Zn, Pb and Cd [START_REF] Galil | Removal of cadmium from aqueous solution using marine green algae, Ulva lactuca. Egypt[END_REF][START_REF] Ho | Ulva lactuca as bioindicator of metal contamination in intertidal waters in Hong Kong[END_REF]. It has been used in bioremediation for Cd, Pb and Hg removal from aqueous solutions [START_REF] Galil | Removal of cadmium from aqueous solution using marine green algae, Ulva lactuca. Egypt[END_REF][START_REF] Henriques | A macroalgae-based biotechnology for water remediation: Simultaneous removal of Cd, Pb and Hg by living Ulva lactuca[END_REF]. Studies dealing with U. lactuca usually report higher levels of Fe [START_REF] Abdallah | Biomonitoring study of heavy metals in biota and sediments in the South Eastern coast of Mediterranean sea, Egypt[END_REF]) that seems to be dominant in Chlorophyta in general, while Rhodophyta and Phaeophyta (red and brown algae, respectively) tend to accumulate higher levels of Mn [START_REF] Circuncisão | Minerals from Macroalgae Origin: Health Benefits and Risks for Consumers[END_REF]. When comparing to other studies conducted in the Mediterranean area (Table 2), levels of trace elements in the Ulva from our study were generally lower and even closer to values recorded in relatively "uncontaminated" areas; however, Fe was higher [START_REF] Campanella | Trace metals in seagrass, algae and molluscs from an uncontaminated area in the Mediterranean[END_REF][START_REF] Conti | A biomonitoring study: trace metals in algae and molluscs from Tyrrhenian coastal areas[END_REF]. Iron (Fe) is actually known to be an essential element for the normal growth of marine plants [START_REF] Storelli | Heavy Metal Monitoring in Fish, Bivalve Molluscs, Water, and Sediments from Varano Lagoon, Italy[END_REF]. Algal species are able to biomagnify Fe from the surrounding water while industrial effluents continuously increase Fe inputs in the marine environment, which may explain the higher levels observed in our study [START_REF] Akcali | A biomonitoring study: Heavy metals in macroalgae from eastern Aegean coastal areas[END_REF]. A decreasing trend of Pb in the marine environment has been reported, since a regulation limiting the use of leaded gasoline consumption was established in the year 1970 [START_REF] Storelli | Potential human health risks from metals (Hg, Cd, and Pb) and polychlorinated biphenyls (PCBs) via seafood consumption: Estimation of target hazard quotients (THQs) and toxic equivalents (TEQs)[END_REF]. Indeed, levels of Pb in U. lactuca exhibited a decrease when compared to a study done in Beirut in 1977 [START_REF] Shiber | Trace metals with seasoal consideration in coastal algae and moluscs from Beirut[END_REF]. However, the difference between the detection techniques used back then and the recent methods currently should be taken into consideration.

The levels of trace elements in the spiny oyster from the present study were found to be mostly lower than concentrations found in bivalves of other countries around the Mediterranean (Table 2).

For instance, trace elements in the spiny oyster were lower than the ones reported from the Iskenderun Bay, which is considered a polluted area in Turkey [START_REF] Türkmen | Spondylus spinosus, from Coastal Waters of Iskenderun Bay, Northern East Mediterranean Sea, Turkey[END_REF] with few exceptions for Fe, Cu and Zn that are essential elements. Despite the fact that the spiny oyster satisfies all the criteria for a good bioindicator [START_REF] Aksit | The surface morphology of the ctenidia of Spondylus spinosus (Mollusca: Bivalvia) from Antalya Bay, Turkey[END_REF], it has not been commonly used in biomonitoring studies in the Mediterranean. In fact, this species lives attached to rocky substrates in the subtidal zone at a depth of more than 10 m; therefore, its sampling is difficult. Species that are easy to sample and identify such as Patella caerulea and Brachidontes variabilis, have been the subject of several studies around the Mediterranean (Table 2). As a filter feeder, living a little further from the coast compared to other bivalve candidates, S. spinosus would provide information about the contamination status of the surrounding water in the subtidal zone. Levels of Cd found in the spiny oyster were similar to the ones found in P. caerulea and B. variabilis collected previously along the Lebanese coast (Table 2; [START_REF] Nakhlé | Brachidontes variabilis and Patella sp. as quantitative biological indicators for cadmium, lead and mercury in the Lebanese coastal waters[END_REF]. The concentrations of Cu, Cr, Cd and Pb were lower than the ones found in M. galloprovincialis and P. Caerulea from the Tyrrhenian Sea, Italy and concentrations of Fe, Cu, Cd, Zn and Mn were lower compared to concentrations found in Donax trunculus (bivalve) from the Egyptian coast (Table 2). Bivalves are known for their ability to accumulate trace elements in their tissues [START_REF] Zuykov | Bivalve mollusks in metal pollution studies: From bioaccumulation to biomonitoring[END_REF]. They are filter-feeding organisms with low biotransformation capacities that accumulate the bioavailable fraction of contaminants from water at higher levels than those in the ambient environment. Therefore, they can be used as sentinel species to monitor pollution in coastal waters [START_REF] Storelli | Heavy Metal Monitoring in Fish, Bivalve Molluscs, Water, and Sediments from Varano Lagoon, Italy[END_REF][START_REF] Türkmen | Spondylus spinosus, from Coastal Waters of Iskenderun Bay, Northern East Mediterranean Sea, Turkey[END_REF]. High levels of Zn and Cu in mollusks are often attributed to their essentiality.

In general, ranges of trace elements in the spiny oyster of this study fall between the levels observed in contaminated and relatively uncontaminated areas. This suggests a relatively moderate level of trace element contamination in this species when compared to oysters, mussels and limpets collected from other regions around the Mediterranean (Table 2). However, caution must be taken as these species neither share the same habitat of S. spinosus nor the same feeding habits. Patella caerulea also known as the Mediterranean limpet, is a gastropod that inhabits the medio littoral zone and grazes on phytoplankton and macroscopic algae. Brachidontes variabilis, also known as the variable mussel, inhabits shallow waters (at sea level or just below) and lives attached to rocky substrates [START_REF] Nakhlé | Brachidontes variabilis and Patella sp. as quantitative biological indicators for cadmium, lead and mercury in the Lebanese coastal waters[END_REF].

The kuruma shrimp had the highest levels of Cu compared to ulva and spondylus. Crustaceans are known to have hemocyanin, which is an oxygen carrying molecule containing a copper binding site also found in mollusks and arthropods, thus, explaining higher levels of these molecules in crustaceans and bivalves compared to algae [START_REF] Downs | Chapter 9-Insects and Their Connection to Food Allergy[END_REF][START_REF] Rainbow | Metal toxicity, uptake and bioaccumulation in aquatic invertebrates-Modelling zinc in crustaceans[END_REF]. Also known for being deposit feeders, crustaceans are more exposed to sediment related contaminants such as As which is more abundant in sediments than in the water column [START_REF] Kalantzi | Arsenic speciation in fish from Greek coastal areas[END_REF].

Few studies have measured trace element concentrations in the shrimp M. japonicus, particularly in the Mediterranean Sea [START_REF] Ayas | Determination of seasonal changes on some heavy metal (Cd, Pb, Cr) levels of shrimps and prawn species from North Eastern Mediterranean Sea, Gulf of Mersin, Turkey[END_REF]. More studies were conducted on the caramote prawn, Penaeus kerathurus (Table 2). Levels of trace elements in our study lie in the same range as the ones found in other studies except for Cu and Zn that were around two-fold higher than the ones found in species collected from other sites (Table 2). These two elements are essential as mentioned above however, anthropogenic inputs may increase their levels.

Seasonal and spatial variations

Trace element levels showed seasonal and spatial variation patterns in all species (Table 3 andTable 5). The sites chosen in this study have a different pluviometric pattern during the year. North Lebanon receives more rain than its southern region. During the wet season surface runoff and riverine inputs increase with rainfall and snow melting, all of which affect the physico-chemical properties of water. Parameters such as pH, salinity, water hardness and oxygen concentration revealed significant variation according to seasons (Abboud-Abi [START_REF] Saab | Suivis temporels comparés de la structure thermique d'eaux côtières libanaises (Batroun) et françaises (Marseille) entre juin 1999 et octobre 2002[END_REF][START_REF] Fakhri | Impact of natural and artificial chemical inputs on the marine ecosystem of Batroun region (North Lebanon)[END_REF]. These conditions are known to govern the bioavailability of trace elements in the marine environment and their bioaccumulation by marine organisms (Rainbow, 1995a). Levels of Al, V, Cr, Mn, Fe, Co, Ni, As, Se and Pb were significantly higher in algae during the dry season (p < 0.05) (Table 3). Such a pattern was previously observed in U. lactuca, with increasing trace element concentrations from winter to summer [START_REF] Kaimoussi | Variations saisonnières des teneurs en métaux (Cd, Cu, Fe, Mn et Zn) chez l'algue Ulva lactuca prélevée au niveau du littoral de la ville d'El Jadida (Maroc)[END_REF]. Since the intake of trace elements in algae depends on their concentration in the surrounding water [START_REF] Galil | Removal of cadmium from aqueous solution using marine green algae, Ulva lactuca. Egypt[END_REF][START_REF] Rybak | Freshwater Ulva (Chlorophyta) as a bioaccumulator of selected heavy metals (Cd, Ni and Pb) and alkaline earth metals (Ca and Mg)[END_REF], a higher concentration during summer could be attributed to the increased evaporation and decreased rainfall especially for species living in shallow waters like ulva (Rajeshkumar and Li, 2018;[START_REF] Wang | Remediation of mercury contaminated sites-A review[END_REF]. Higher trace element accumulation during summer can also be explained by the existence of a higher metabolic rate during this season [START_REF] Villares | Seasonal variation and background levels of heavy metals in two green seaweeds[END_REF]. Finally concerning the spatial variation, levels of Al (779±611 mg.kg -1 ), As (7.55±2.15 mg.kg -1 ), Cr (1.09±0.13 mg.kg -1 ) and Pb (1.42±0.23 mg.kg -1 ) were significantly higher in the algae collected from Tripoli compared to Beirut and Saida (p < 0.05) (Table 5). Indeed, the accumulation pattern of trace elements by algae depend on the developmental stage and the physiology of algae [START_REF] Farias | Macrophytes as bioindicators of heavy metal pollution in estuarine and coastal environments[END_REF]. It has been reported that higher trace element levels were found during the growth period of algae [START_REF] Kaimoussi | Variations saisonnières des teneurs en métaux (Cd, Cu, Fe, Mn et Zn) chez l'algue Ulva lactuca prélevée au niveau du littoral de la ville d'El Jadida (Maroc)[END_REF][START_REF] Villares | Seasonal variation and background levels of heavy metals in two green seaweeds[END_REF]. Trace elements showed significant spatial variations in algae (p < 0.05). For most elements, the highest levels were found in Tripoli. More particularly, levels of Al (779±611 mg.kg -1 ), As (7.55±2.15 mg.kg -1 ), Cr (1.09±0.13 mg.kg -1 ) and Pb (1.42±0.23 mg.kg -1 ) were significantly higher at this site. Lead (Pb) levels are close to the ones obtained in relatively polluted areas (Table 2) [START_REF] Akcali | A biomonitoring study: Heavy metals in macroalgae from eastern Aegean coastal areas[END_REF][START_REF] Malea | Trace element seasonality in marine macroalgae of different functional-form groups[END_REF][START_REF] Malea | Trace element patterns in marine macroalgae[END_REF]. These levels can be attributed to the leachate from the dumpsite in Tripoli, as high levels of these elements were detected in the leachate [START_REF] Khalil | Municipal leachates health risks: Chemical and cytotoxicity assessment from regulated and unregulated municipal dumpsites in Lebanon[END_REF].

The kuruma shrimp showed seasonal variation for Ti, Co, As, and Se with higher levels during the wet season. For the rest of the elements, no seasonal changes were recorded, and values were almost the same during both seasons. Penaeus japonicus mainly spawns during the spring and summer months (May-July) at temperatures ranging from 24 to 28 °C in the Eastern Mediterranean [START_REF] Pourang | Tissue Distribution and Redistribution of Trace Elements in Shrimp Species with the Emphasis on the Roles of Metallothionein[END_REF][START_REF] Yilmaz | Influences of sex and seasons on levels of heavy metals in tissues of green tiger shrimp (Penaeus semisulcatus de Hann, 1844)[END_REF]. In addition, the increase in body tissue may contribute to the lower levels of elements observed during the dry season. Significant spatial variation (p < 0.05) was only observed for As, Co, Cd, Cu, Pb, Se and V. The shrimps showed less seasonal and spatial variations compared to the alga and oyster. This could be due to the fact that the shrimp lives further from the coastal zone and may be less subjected to the dynamics of the coastal area [START_REF] Stehr | Toxicopathic liver lesions in English sole and chemical contaminant exposure in Vancouver Harbour, Canada[END_REF]. In fact, the kuruma shrimp was caught at an average depth of 40 m but is known to live down to 90 m depth [START_REF] Quigley | Occurrence of the kuruma prawn Marsupenaeus japonicus (Spence Bate, 1888) in the Celtic Sea, English Channel, and North-West France[END_REF].

The spiny oyster was chosen for the multivariate analysis as it was available at all sites and during all seasons, thus, providing a clearer idea about the spatial variations related to each season. For each season, the oyster showed a different spatial accumulation pattern (Fig. 2). Elemental concentration explained 65% of spatial variability during the wet season (Fig. 2A) and 73 % during the dry season (Fig. 2B). Significant seasonal differences in the spiny oyster were found for Al, Ti, Fe, Zn and As (p < 0.05) with higher levels found during the wet season. Similar findings with higher values during the winter season were found in the blue mussel M. galloprovincialis from the Moroccan coast [START_REF] Azizi | Seasonal variations of heavy metals content in mussels (Mytilus galloprovincialis) from Cala Iris offshore (Northern Morocco)[END_REF]. Higher values recorded during the wet seasons are often associated with increased inputs of trace elements from land-based sources and their accumulation in the water due to increased rain [START_REF] Zuluaga Rodríguez | Content of Hg, Cd, Pb and as in fish species: a review[END_REF]. Moreover, the spiny oyster undergoes sexual maturation and spawns in the period between June and August [START_REF] Shabtay | The Indo-Pacific oyster Spondylus spinosus Schreibers, 1793 in the Eastern Mediterranean Sea: reproductive features[END_REF]. Therefore, an increase in body tissues is probably contributing to the lower levels of elements observed during the dry season [START_REF] Shabtay | The Indo-Pacific oyster Spondylus spinosus Schreibers, 1793 in the Eastern Mediterranean Sea: reproductive features[END_REF].

Concerning spatial variation, S. spinosus samples collected in Tripoli were characterized by higher levels for most trace elements during the wet season, while samples from Saida displayed highest concentrations during the dry season. This is mainly due to the differences in rainfall patterns and physico-chemical parameter variation of water between northern and the southern sites as explained above, and also to the sources involved in trace element input at each site.

More precisely, Abou Ali river drains effluents into the coastal area in Tripoli (Fig. 1). A wastewater treatment plant was established in the area but has not been working properly. In addition, a dumpsite in Tripoli is still receiving waste until present. This is leading to increased waste load and a difficulty to control leachate that is drained to the sea without treatment [START_REF] El-Hoz | Current Situation and Challenges to Address on the Landfill of Tripoli, Challenges and trends in solid waste management in Mediterranean cities[END_REF]. A study carried out on the leachate produced by dumpsites in Lebanon showed increased levels of trace elements of Mn, Cr, Ni and Cd due to lack of efficient waste management [START_REF] Khalil | Municipal leachates health risks: Chemical and cytotoxicity assessment from regulated and unregulated municipal dumpsites in Lebanon[END_REF]. For most contaminants, concentrations in dumpsite leachate in Lebanon were higher than the toxicity reference values (TRVs) that are used for ecological risk assessment [START_REF] Khalil | Municipal leachates health risks: Chemical and cytotoxicity assessment from regulated and unregulated municipal dumpsites in Lebanon[END_REF]. They reached 12 times the TRV for Pb and 27 folds for Cd. Spondylus spinosus showed relatively high levels of Cd (p < 0.05) mainly recorded in Tripoli (Table 5) for both seasons (4.21±0.77 and 3.80±0.01 mg.kg -1 for the wet and dry season, respectively), with higher levels (p < 0.05) for the wet season. High levels of Cd were also recorded by [START_REF] Nakhlé | Brachidontes variabilis and Patella sp. as quantitative biological indicators for cadmium, lead and mercury in the Lebanese coastal waters[END_REF] in mussel tissues sampled in Selaata (South of Tripoli), (0.6-8.7 and 1.08-4.03 mg.kg -1 in Patella and Brachidontes, respectively, Table 2) and a decreasing trend was reported southward as the influence of a phosphogypsum plant southern of Tripoli (Fig. 1) decreased, highlighting the influence of the plant on Cd levels in the area. A study on the effects of the plant on the marine coastal zone in that area [START_REF] Fakhri | Impact of natural and artificial chemical inputs on the marine ecosystem of Batroun region (North Lebanon)[END_REF] has shown that wind regime along the Lebanese coast played a substantial role in spreading various contaminants over a wide area. In addition, the impact of that plant is likely to affect the neighboring northern marine environment especially with a dominant northern marine current along the Lebanese coast [START_REF] Fakhri | Impact of wind on the dispersion of contaminants in the Lebanese northern marine area 16[END_REF]. Accumulation of Cu, Cr, Ni, Zn, Ti and Cd are more likely to be influenced by anthropogenic inputs due to the presence of industries such as tanneries and electroplating industries, especially in Beirut, releasing those contaminants in the environment [START_REF] Fakhri | The state of the Lebanese coastal waters, in: Review and Perspectives of Environmental Studies in Lebanon[END_REF][START_REF] Jaishankar | Toxicity, mechanism and health effects of some heavy metals[END_REF][START_REF] Oliveira | Chromium as an Environmental Pollutant: Insights on Induced Plant Toxicity[END_REF] and studies conducted on the leachate are supportive of this hypothesis.

Biota-sediment accumulation factor (BSAF)

The concentrations of different elements in the sediment are presented in Table 1 and the calculated biota-sediment accumulation factors (BSAFs) are provided in Table 4. The BSAFs displayed in Table 4 represent the average of BSAFs calculated per species and site for the dry season.

For U. lactuca all the elements had a BSAF<1 suggesting no bioaccumulation from the sediment.

The same has been observed in a study done along the Senegalese coast. However, they found a higher TF (Transfer Factor) from water to the green algae suggesting higher accumulation from water rather than from sediments [START_REF] Diop | Assessment of trace element contamination and bioaccumulation in algae ( Ulva lactuca ), mussels ( Perna perna ), shrimp ( Penaeus kerathurus ), and fish ( Mugil cephalus , Saratherondon melanotheron ) along the Senegalese coast[END_REF]. Several studies reported significant correlation between the levels of trace elements accumulated by U. lactuca and those in the water and sediments [START_REF] Akcali | A biomonitoring study: Heavy metals in macroalgae from eastern Aegean coastal areas[END_REF][START_REF] Bonanno | The alga Ulva lactuca (Ulvaceae, Chlorophyta) as a bioindicator of trace element contamination along the coast of Sicily, Italy[END_REF][START_REF] Chakraborty | Benthic macroalgae as biological indicators of heavy metal pollution in the marine environments: A biomonitoring approach for pollution assessment[END_REF] while other researchers found no significant correlation between trace element concentrations in algae and those in water and sediment [START_REF] Kamala-Kannan | Assessment of heavy metals (Cd, Cr and Pb) in water, sediment and seaweed (Ulva lactuca) in the Pulicat Lake, South East India[END_REF][START_REF] Malea | Use of the green alga Ulva rigida C. Agardh as an indicator species to reassess metal pollution in the Thermaikos Gulf, Greece, after 13 years 8[END_REF]. Although the uptake by seaweed is mainly from solution, levels of trace elements in sediments reflect the degree of pollution to a certain extent in the water column, as concentrations in water are indirectly related to the sediment through processes of resuspension and interstitial diffusion of trace elements [START_REF] Bonanno | The alga Ulva lactuca (Ulvaceae, Chlorophyta) as a bioindicator of trace element contamination along the coast of Sicily, Italy[END_REF][START_REF] Thomann | Steady-state model of biota sediment accumulation factor for metals in two marine bivalves[END_REF].

The spiny oyster accumulated Cu, Zn and Cd with the highest BSAF recorded for Zn and Cd in Tripoli compared to the shrimp (Table 4). Bivalves are known to accumulate substantial amounts of trace elements from water [START_REF] Zuykov | Bivalve mollusks in metal pollution studies: From bioaccumulation to biomonitoring[END_REF] and are able to accumulate trace elements at higher concentrations than those in water and sediments [START_REF] Swaleh | Heavy Metals Bioaccumulation in Edible Marine Bivalve Mollusks of Tudor Creek Mombasa Kenya[END_REF]. BSAF for Zn was the highest for the oyster compared to the alga and shrimp. Bivalves are high accumulators of Zn as they absorb it readily from water because it is an essential trace element for their metabolism as is Cu for shrimps. In fact, Cu, Zn and Cd induce the metal binding protein, metallothionein; thus, they are metabolically active having a high assimilation efficiency and low depuration rates [START_REF] Thomann | Steady-state model of biota sediment accumulation factor for metals in two marine bivalves[END_REF]. However, the levels of essential trace elements accumulated by marine organisms do not always reflect a metabolic requirement as marine invertebrates may often accumulate trace elements due to their high ambient level [START_REF] Rainbow | Metal toxicity, uptake and bioaccumulation in aquatic invertebrates-Modelling zinc in crustaceans[END_REF].

The kuruma shrimp had BSAFs >1 for Cu and Zn with higher values for Cu (Table 4). Copper (Cu) is an essential element in shrimps as it is associated to hemocyanin. Crustaceans take up trace elements from food and water in proportion to the dissolved concentration of the element (Rainbow, 1995b). In some cases, an increase of uptake is reflected by an elevated concentration, such as, the case of Cd in decapod crustaceans. However even if the uptake rates of trace elements by crustaceans respond to changes in the total dissolved trace element concentration, not all contaminants are in an available form for uptake (Rainbow, 1995b). Concerning Hg, the BSAF was >1 only in Tripoli. Sediments in Tripoli had a higher level of Hg compared to Beirut and Saida (Table 1). The shrimp is known to live close to the bottom and thus may be more exposed to sediment-related pollutants than algae and bivalves [START_REF] Pinedo-Hernández | Speciation and bioavailability of mercury in sediments impacted by gold mining in Colombia 7[END_REF].

Finally, trace elements found in marine organisms may be the result of uptake from different sources and not only from sediment. Bioaccumulation is the result of several factors including bioavailability, multiple routes of exposure and metabolism that can widely vary among species [START_REF] Jakimska | Bioaccumulation of Metals in Tissues of Marine Animals, Part I: the Role and Impact of Heavy Metals on Organisms 10[END_REF]. Each species uptakes trace elements differently; hence, it is important to consider different taxa and even tissues in the same organism when establishing monitoring programs and assessing bioaccumulation [START_REF] Yüzereroğlu | Heavy metals in Patella caerulea (Mollusca, Gastropoda) in polluted and non-polluted areas from the Iskenderun Gulf (Mediterranean Turkey)[END_REF].

Conclusion

The present study provided levels for 20 trace elements in three marine species from the Lebanese coast in relation to spatio-temporal variation and biota-sediment transfer. Significant differences were observed in trace element accumulation between species revealing the importance of using multiple bioindicator organisms to monitor coastal pollution by trace elements. Our results generally ranged in value between those previously recorded in relatively uncontaminated areas and those recorded in polluted ones. This suggested an overall moderate level of contamination in the studied sites with highest levels mostly found in Tripoli. This study reported for the first time trace element levels in the spiny oyster from the Lebanese coast. Seasonal and spatial variations were observed and reflected differently for each species, highlighting the importance of seasonality when it comes to monitoring programs. The sediment-biota transfer study showed limited transfer of trace elements between these environmental compartments. Ecological risks from trace elements are not simple to document, as marine organisms accumulate trace elements through different routes and responses may vary widely among species. Thus, understanding toxicity requires more than just total element accumulated in tissues especially when considering the complexity of environmental factors. However, bioindicators remain good integrative markers of chemical exposure to contaminants in a polluted ecosystem, which helps to identify research needs as a first step towards further investigation.

Figure 1 Figure 2

 12 Figure 1 Map showing the sampling sites along the Lebanese coast (WWTP: waste water treatment plant)

Table 1

 1 Mean concentration ± standard deviation (SD) of trace elements (mg.kg -1 dw) in sampled marine organisms and sediments. n: number of samples.

	Species	n	Al	Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn	As	Se	Cd	Hg	Pb
	U. lactuca	40	378±413	19.4±12.7	3.53±2.77	1.08±0.90	29.4±37.8	516±473	0.34±0.38	2.13±0.63	2.30±1.49	5.12±2.29	4.78±2.60	0.34±0.15	0.05±0.03	0.04±0.02	1.04±1.03
	S. spinosus	60	11.1±13.4	1.43±1.54	0.21±0.18	0.54±0.14	4.51±2.98	27.6±24.5	0.86±0.46	6.47±3.27	8.50±6.45	124±162	35.2±27.4	3.00±0.94	3.00±1.33	0.07±0.04	0.89±0.87
	M. japonicus	30	2.75±2.73	0.68±0.69	0.05±0.09	0.06±0.04	0.64±0.38	7.77±7.06	0.05±0.06	0.33±0.40	30.9±12.0	61.2±9.8	28.7±23.6	1.77±0.49	0.02±0.02	0.15±0.15	0.04±0.04
		1 (Tripoli)	3403	-	26.6	29.7	228	13287	5.19	12.0	6.29	21.5	-	-	0.32	0.120	17.3
	Sediments a	1 (Beirut)	4305	-	38.2	22.9	228	22921	7.13	15.1	3.85	24.3	-	-	0.53	0.07	7.25
		1 (Saida)	2592	-	4.75	5.04	175	1550	0.97	3.58	2.02	4.99	-	-	0.13	0.07	3.35
	a SD for sediment analysis is not available (n=1).

Table 2

 2 Comparison of trace element concentrations (mg.kg -1 dw) measured in marine organisms from the Eastern Mediterranean (minimum and maximum levels in each group are marked in bold).

	Species	Location	Al	Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn	As	Se	Cd	Hg	Pb	Reference
		Ras Beirut (Lebanon)	-	-	-	< 7.5-16.3	-	258-595	-	9.4-43.1	24.4-52.5	41.3-206	-	-	< 0.8-2.3	-	< 7.5-37.5	(Shiber, 1980)
	U. lactuca	Tyrrhenian Sea (Central Italy)	-	-	-	1.39-2.06	-	-	-	-	4.9-6.4	-	-	-	0.13-0.21	-	1.67-2.28	(Conti and Cecchetti, 2003)
		Eastern Harbour (Egypt)	-	-	-	-	73.9± 4.8	515± 2	7.08± 1.3	-	14.5± 4.7	63.1± 3.2	-	-	1.84± 0.93	-	-	(Abdallah and
		El Mex Bay (Egypt)	-			-	33.3± 3.9	709± 13	6.58 ±1.4		7.24± 2.30	27.4± 8.3			0.73± 0.24		-	Abdallah, 2008)
		Monastir (Tunisia)	-	-	-	-	13	410	-	-	8	68	-	-	-	-	12.6	(Yaich et al., 2011)
	U. fasciata	Abou Qir Bay (Egypt)	-	-	-	-	16.0	65.2	1.12	3.64	2.96	12.6	-	-	1.27	0.06	2.84	(Shams El-Din et al., 2014)
	Ulva sp.	Gulf of Thessaloniki (Greece)			16.9 ± 0.69	14.4± 3.72	132 ± 48	-	1.7± 0.12	9.25± 2.88	11.3± 1.02	116± 4.3	0.59± 0.41	2.89± 1.21	0.04± 0.01	-	6.27± 1.79	(Malea and 2014)
	U. intestinalis	Gulf of Thessaloniki (Greece)	-	-	15.8± 1.09	13.8± 2.95	37.3 ± 7.08	-	0.84± 0.17	7.41± 0.69	9.15± 1.73	122± 10.3	1.50± 0.47	4.83± 1.09	0.034± 0.004	-	4.62± 1.19	(Malea et al., 2015)
	U. rigida	Gulf of Thessaloniki (Greece)	-	-	16.24± 1.19	9.38± 1.49	37.9 ± 10.0	-	0.56± 0.13	6.44± 0.55	7.39± 0.89	122± 14	1.45± 0.25	2.71± 0.77	0.03± 0.003	-	3.06± 0.67	(Malea et al., 2015)
		Çanakkale/City (Turkey)	-	-	-	0.78± 0.20	-	198± 19	-	-	8.51± 0.86	50.1± 6.0	-	-	54.2± 13.7	53.2± 3.17	5.65± 0.87
	Ulva sp.	Izmir/Foça (Turkey) Izmir/Bostanli (Turkey) Izmir/Narlidere (Turkey)	---	---	---	1.75± 0.42 1.95± 0.51 4.22± 1.53	---	130± 26.9 232± 28.6 308± 74	---	---	13.9± 3.11 8.29± 0.21 8.21± 1.21	67.8 ± 16.0 40.4± 6.1 61.3± 6.5	---	---	14.9± 1.89 18.7± 2.27 22 ± 6.24	48.4± 11.8 59.5± 14.4 199± 62	1.75± 0.42 1.95± 0.51 4.22± 1.53	(Akcali and Kucuksezgin, 2011)
		Izmir/Urla (Turkey)	-	-	-	0.94± 0.12	-	146± 34	-	-	7.78± 0.35	81.0± 0.47	-	-	24.9± 7.88	73.0± 12.9	0.94± 0.12
	U. lactuca	Lebanese Coast	66.5-1535	2.28-43.8	0.25-9.54	0.21-3.74	1.49-128	53.6-1714	0.03-1.31	1.36-3.99	0.24 -5.64	1.20-8.89	1.10-10.9	0.17-0.72	0.01-0.10	0.03-0.06	0.07-4.44	Present study
		Sicilian Coast (Italy)	-	-	-	0.19-0.46	-	-	-	-	1.21-2.35	3.5-14.6	-	-	3.30-6.30	-	0.14-1.52	(Campanella et al., 2001)
	Patella Caerulea	Sicilian Coast (Italy)	-	-	-	0.10-1.01	-	-	-	-	0.47-3.79	2.2-19.1	-	-	1.7-11.8	-	0.06-2.18	(Cubadda et al., 2001)
		Tyrrhenian Sea (Italy)	-	-	-	0.72-0.96	-	-	-	-	10.2-19.2	-	-	-	2.89-4.06	-	0.51-1.50	(Conti and Cecchetti, 2003)
		Lebanese Coast	-

Table 3

 3 Mean concentration ± standard deviation (mg.kg -1 dw) of trace elements measured in marine organisms sampled during the wet (S1) and dry (S2) seasons. the symbol *indicates significant differences between seasons p < 0.05

	Species	Season	Al	Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn	As	Se	Cd	Hg	Pb
		S1	245 ± 214*	18.4 ± 14.1	3.05 ± 2.98*	0.63 ± 0.36*	8.66 ± 4.92*	359 ± 274*	0.14 ± 0.07*	2.35 ± 0.65*	2.47 ± 1.72	5.18 ± 2.65	3.86 ± 2.09*	0.27 ± 0.11*	0.06 ± 0.03	N.D	0.65 ± 0.60*
	U. lactuca	S2	779 ± 610	22.3 ± 8.16	4.98 ± 1.51	2.43 ± 0.71	91.7 ± 23.2	2443 ± 1216	0.95 ± 0.24	1.72 ± 0.36	1.82 ± 0.25	4.92 ± 0.80	7.55 ± 2.15	0.52 ± 0.09	0.04 ± 0.01	0.04 ± 0.02	6.87 ± 12.2
	S. spinosus	S1 S2	14.9 ± 16.4* 7.94 ± 8.27	2.00 ± 1.82* 1.00 ± 1.06	0.23 ± 0.18 0.21 ± 0.18	0.54 ± 0.17 0.55 ± 0.11	4.72 ± 2.86 4.51 ± 3.14	6.98 ± 5.44* 19.73 ± 10.37	0.95 ± 0.48 0.77 ± 0.44	5.59 ± 3.16 7.31 ± 3.19	7.56 ± 6.75 9.45 ± 6.1	186.80 ± 212* 62.98 ± 20.9	40.98 ± 32.55* 31.00 ± 20.0	3.19 ± 1.03 2.75 ± 0.80	3.2 ± 1.51 2.74 ± 1.10	0.14 ± 0.02 0.06 ± 0.03	0.83 ± 0.72 1.02 ± 1.00
	M.	S1	2.93 ± 2.85	1.27 ± 1.14*	0.08 ± 0.12	0.15 ± 0.03	0.68 ± 0.49	6.98 ± 5.44	0.08 ± 0.08*	N.D	32.72 ± 14.6	63.4 ± 12.73	36.0 ± 25.0*	1.92 ± 0.54*	0.03 ± 0.03	0.12 ± 0.05	0.03 ± 0.01
	japonicus	S2	2.59 ± 9.31	0.48 ± 0.76	0.02 ± 0.03	0.05 ± 0.02	0.60 ± 0.41	8.55 ± 10.03	0.03 ± 0.02	0.17 ± 0.04	29.1 ± 9.39	58.9 ± 6.02	21.43 ± 17.84	1.61 ± 0.35	0.01 ± 0.09	0.17 ± 1.20	0.05 ± 0.15

a

Table 5

 5 Mean concentration ± SD of trace elements (mg.kg -1 dw) measured in marine organisms collected during the wet (S1) and dry (S2) seasons. Letters indicate statistically significant differences between sites per row ( abc S1, def S2). Absence of letters indicates no significant differences between sites.

	Analyte	Species	Tripoli		Beirut		Saida
			S1	S2	S1	S2	S1	S2
		U.lactuca	444±271 a	779±611	140±43 b	-	149±71 b	-
	Al	S. spinosus	7.38±5.34 a	4.27±2.83 d	28.1±24.2 b	2.49±1.50 d	10.8±6.1 ab	15.5±10.0
		M. japonicus	2.46±2.17	2.35±3.08	-	2.83±1.50	3.36±3.43	-
		U. Lactuca	36.7±5.3 a	22.3± 8.2	6.28±3.15 b	-	12.1±4.6 b	-
	Ti	S. spinosus	1.09±0.36 a	0.64±0.32 d	3.36±2.53 b	0.45±0.09 d	1.35±0.42 ab	1.77±1.57 e
		M. japonicus	2.00±2.17	0.55±0.32	-	0.40±0.22	0.97±0.62	-
								-
		U. Lactuca	1.72±0.12 a	4.98±1.51	0.39 ± 0.12 b	-	7.03±1.11 c
	V	S. spinosus	0.13±0.03 a	0.09±0.02 d	0.45±0.14 b	0.07±0.02 d	0.11±0.03 a	0.43±0.14 e
		M. japonicus	0.13±0.16 a	0.02±0.01	-	0.02±0.01	0.02±0.02 b	-
		U. Lactuca	1.09±0.13 a	2.43±0.71	0.34±0.11 b	-	0.46±0.18 b	-
	Cr	S. spinosus	0.54±0.11	0.50±0.09	0.58±0.24	0.55±0.09	0.49±0.11	0.59±0.14
		M. japonicus	N.D.	0.04±0.01	-	0.06±0.03	0.15±0.03	-
		U. Lactuca	13.6±1.29 a	91.7± 23.2	2.58±0.82 b	-	9.82±2.47 a	-
	Mn	S. spinosus	6.74±3.75 ab	2.76±1.09 d	3.20±1.16 a	2.54±1.35 d	4.22±1.88 b	7.62±3.24 e
		M. japonicus	0.68± 0.67	0.46±0.09 d	-	0.74±0.24 e	0.67±0.24	-
		U. Lactuca	701±132 a	2443±1217	123 ± 67 b	-	254±126 b	-
	Fe	S. spinosus	16.4±4.74 a	15.61±2.92 d	69.6±33.8 b	11.1±2.56 d	22.2±7.3 ab	30.5±9.8 e
		M. japonicus	5.50±2.49	5.42±5.92	-	11.7±10.9	8.47±7.17	-
		U. Lactuca	0.19±0.02 a	0.95±0.24	0.37±0.02 b	-	0.22±0.04 a	-
	Co	S. spinosus	1.45±0.35 a	0.95±0.51 d	0.76±0.37 b	0.39±0.18 e	0.64±0.22 b	0.97±0.30 d
		M. japonicus	0.11±0.10 a	0.04±0.02	-	0.02±0.01	0.05±0.02 b	-
		U. Lactuca	1.87±0.14 a	1.72±0.36	N.D.	-	2.78±0.63 b	-
	Ni	S. spinosus	6.81±1.41 a	8.36±2.17 d	1.64±0.79 b	3.96±1.63 e	8.32±1.56 a	9.75±2.46 d
		M. japonicus	N.D.	0.15±0.04	-	0.18±0.06	N.D.
		U. Lactuca	2.71±0.35 a	1.82±0.25	0.42±0.13 b	-	4.28±0.99 a	-
	Cu	S. spinosus	15.3±5.5 a	9.18±5.37 de	1.63±0.57 b	6.13±4.39 d	5.77±2.72 a	13.0±6.9 e
		M. japonicus	24.6±6.2 a	35.2±7.8 d	-	23.0±3.5 e	40.9±16.3 b	-

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Acknowledgement

MG thanks the Lebanese National Council for Scientific Research (CNRS-L) for the Ph.D. financial support and the Laboratory for Food Safety (Anses) for the opportunity to carry out the project in the unit Trace Metals and Minerals/Department of Chemical Contaminants in Food.