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Cephalopods play a key role in many marine trophic networks and constitute alternative fisheries resources, especially given the ongoing decline in finfish stocks. Along the European coast, the eggs of the cuttlefish Sepia officinalis are characterized by an increasing permeability of the eggshell during development, which leads to selective accumulation of essential and non-essential elements in the embryo. Temperature and pH are two critical factors that affect the metabolism of marine organisms in the coastal shallow waters. In this study, we investigated the effects of pH and temperature through a crossed (3 × 2; pH 8.1 (pCO2, 400 ppm), 7.85 (900 ppm) and 7.6 (1400 ppm) at 16 and 19°C, respectively) laboratory experiment. Seawater pH showed a strong effect on the egg weight and non-significant impact on the weight of hatchlings at the end of development implying an egg swelling process and embryo growth disturbances. The lower the seawater pH, the more 110mAg was accumulated in the tissues of hatchlings. The 109Cd concentration factor (CF) decreased with decreasing pH and 65Zn CF reached maximal values pH 7.85, independently of temperature. Our results suggest that pH and temperature affected both the permeability properties of the eggshell and embryonic metabolism. To the best of our knowledge, this is one of the first studies on the consequences of ocean acidification and ocean warming on metal uptake in marine organisms, and our results indicate the need to further evaluate the likely ecotoxicological impact of the global change on the early-life stages of the cuttlefish. [ABSTRACT FROM AUTHOR]

The present study reports the first experimental microplastic-mediated transfer of a key PCB congener into adult specimens of the sea urchin Paracentrotus lividus. Three experiments were conducted to assess whether 14 C-PCB-153 adsorbed onto negatively buoyant microplastics (MPs) (500-600 μm) is bioavailable to the sea urchin: (1) exposure to a low concentration of 14 C-PCB-153 sorbed onto a high number of virgin MPs ("lowPCB highMP" experiment), (2) exposure to a high concentration of 14 C-PCB-153 sorbed onto a relatively low number of virgin MPs ("highPCB lowMP" experiment), and (3) exposure to a low concentration of 14 C-PCB-153 sorbed onto a relatively low number of aged MP ("lowPCB lowMP" experiment). Results showed that the transfer of 14 C-PCB-153 from MPs to sea urchin tissues occurred in each of the three 15-day experiments, suggesting that MPs located on the seafloor may act as vectors of PCB-153 to sea urchins even during short-term exposure events., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The bioaccumulation of mercury (Hg) in marine organisms through various pathways has not yet been fully explored, particularly in cephalopods. This study utilises radiotracer techniques using the isotope 203 Hg to investigate the toxicokinetics and the organotropism of waterborne inorganic Hg (iHg) and dietary inorganic and organic Hg (methylHg, MeHg) in juvenile common cuttlefish Sepia officinalis. The effect of two contrasting CO 2 partial pressures in seawater (400 and 1600 μatm, equivalent to pH 8.08 and 7.54, respectively) and two types of prey (fish and shrimp) were tested as potential driving factors of Hg bioaccumulation. After 14 days of waterborne exposure, juvenile cuttlefish showed a stable concentration factor of 709 ± 54 and 893 ± 117 at pH 8.08 and 7.54, respectively. The accumulated dissolved i 203 Hg was depurated relatively rapidly with a radiotracer biological half-life (Tb 1/2 ) of 44 ± 12 and 55 ± 16 days at pH 8.08 and 7.54, respectively. During the whole exposure period, approximately half of the i 203 Hg was found in the gills, but i 203 Hg also increased in the digestive gland. When fed with 203 Hg-radiolabelled prey, cuttlefish assimilated almost all the Hg provided (>95%) independently of the prey type. Nevertheless, the prey type played a major role on the depuration kinetics with Hg Tb 1/2 approaching infinity in fish fed cuttlefish vs. 25 days in shrimp fed cuttlefish. Such a difference is explained by the different proportion of Hg species in the prey, with fish prey containing more than 80% of MeHg vs. only 30% in shrimp. Four days after ingestion of radiolabelled food, iHg was primarily found in the digestive organs while MeHg was transferred towards the muscular tissues. No significant effect of pH/pCO 2 variation was observed during both the waterborne and dietary exposures on the bioaccumulation kinetics and tissue distribution of i 203 Hg and Me 203 Hg. Dietary exposure is the predominant pathway of Hg bioaccumulation in juvenile cuttlefish., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The fate and toxicity of ingested marine microplastics (MPs) have been of major concern in aquatic ecotoxicology for the last decade. Although their ingestion by a wide range of marine organisms has been proven, the uptake of MPs within organs is not yet fully understood and relies on the ability of ingested microplastics to transfer from the gut to tissues beyond the digestive wall (i.e., translocation). The present study investigates the in vitro transfer of fluorescent high-density polyethylene particles of different sizes classes (1-5 µm; 10-29 µm; 38-45 µm) across the intestinal wall of the sea urchin Paracentrotus lividus using Ussing chambers. Small microplastics (1-5 µm) were proven to be able to cross the intestinal wall of P. lividus and reach the coelomic fluid, while larger microplastics (≥ 10 µm) were not observed to cross the intestinal wall. Results demonstrate a size-dependent passage of polyethylene microparticles across the intestinal walls of P. lividus for the first time, highlighting the suitability of Ussing chamber systems to study the transfer of MPs across the intestinal wall of animals., (Copyright © 2022. Published by Elsevier B.V.)

Public interest in animal tuberculosis is mainly focused on prevention and eradication of bovine tuberculosis in cattle and wildlife. In cattle, immunodiagnostic tests such as the tuberculin skin test or the interferon gamma (IFN-γ) assay have been established and are commercially available. Feline tuberculosis is rather unknown, and the available diagnostic tools are limited. However, infections with Mycobacterium tuberculosis complex members need to be considered an aetiological differential diagnosis in cats with granulomatous lymphadenopathy or skin nodules and, due to the zoonotic potential, a time-efficient and accurate diagnostic approach is required. The present study describes 11 independent cases of Mycobacterium microti infection in domestic cats in Switzerland. For three cases, clinical presentation, diagnostic imaging, bacteriological results, immunodiagnostic testing, and pathological features are reported. An adapted feline IFN-γ release assay was successfully applied in two cases and appears to be a promising tool for the ante mortem diagnosis of tuberculosis in cats. Direct contact with M. microti reservoir hosts was suspected to be the origin of infection in all three cases. However, there was no evidence of M. microti infection in 346 trapped wild mice from a presumptive endemic region. Therefore, the source and modalities of infection in cats in Switzerland remain to be further elucidated., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2020 Peterhans, Landolt, Friedel, Oberhänsli, Dennler, Willi, Senn, Hinden, Kull, Kipar, Stephan and Ghielmetti.)

The dissolved oxygen concentration of the world's oceans has systematically declined by 2% over the past 50 years, and there has been a notable commensurate expansion of the global oxygen minimum zones (OMZs). Such wide-scale ocean deoxygenation affects the distribution of biological communities, impacts the physiology of organisms that may affect their capacity to absorb and process contaminants. Therefore, the bioaccumulation efficiencies of three contrasting radionuclides, 110m Ag, 134 Cs and 65 Zn were investigated using controlled aquaria in the blue mussel Mytilus edulis under three contrasting dissolved oxygen regimes: normoxic; 7.14 mg L -1 , reduced oxygen; 3.57 mg L -1 and hypoxic 1.78 mg L -1 conditions. Results indicated that hypoxic conditions diminished 110m Ag uptake in the mussel, whereas depuration rates were not affected. Similarly, hypoxia appeared to cause a decrease in the 65 Zn bioaccumulation rate, as evidenced by both weakened uptake and rapid elimination rates. Effects of hypoxia on the metabolome of mussels were also explored by untargeted Nuclear Magnetic Resonance (NMR) spectroscopic methods. The metabolic response was characterised by significantly greater abundance of several amino acids, amino sulfonic acids, dicarboxylic acids, carbohydrates and other metabolites in the lowest oxygen treatment, as compared to the higher oxygen treatments. Clearance rates significantly dropped in hypoxic conditions compared to normoxia. Results suggest that hypoxic conditions, and even partly moderate hypoxia, alter ventilation, an-aerobic, oxidative and osmoregulation metabolism of this mussel, which may further influence the trace element bioaccumulation capacity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Trace elements can be accumulated from coastal environment by aquatic organisms from their food and be transferred throughout the food webs. Studying the effects of salinity on the trophic transfer of trace elements in a euryhaline fish, able to deal with large variations in salinity, is therefore key to understand their dynamics in aquatic environments. In this context, we investigated the potential influence of salinity on the trophic transfer of two essential elements (Mn and Zn) in the euryhaline fish, the turbot Scophthalmus maximus using radiotracer techniques. After acclimation to three salinities (10, 25 and 38), turbots were fed with radiolabelled pellets ( 54 Mn and 65 Zn). Kinetic parameters of depuration were determined after a 21-d period and trophic transfer factors were calculated. Trophic transfer of Mn at the highest salinity was significantly lower than for the other conditions whereas salinity did not significantly influenced Zn trophic transfer. Differences in the processes involved in the regulation (homeostasis) of the two tested trace elements may explain the contrasting influence of seawater salinity for Mn and Zn., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Uptake and depuration kinetics of [ 14 C]C 12 -6-linear alkylbenzene sulfonate (LAS) in the fish Sparus aurata were determined during experimental exposure via seawater or food separately under laboratory conditions. The fish concentrated LAS from seawater (using realistic contaminant concentrations) with a mean BCF value of 20 ± 2 L kg -1 reached within 3 days and following a one-compartment exponential model. High differences in BCF were noted among organs, with values ranking in the order gall bladder (1400 ± 600 L kg -1 ) >>  digestive tract (52 ± 9 L kg -1 ) > liver (38 ± 4 L kg -1 ) > gills (16 ± 3 L kg -1 ) > skin (13 ± 2 L kg -1 ) > head (9 ± 1 L kg -1 ) > muscles (4 ± 1 L kg -1 ). After three days of exposure, 14 C activity decreased in gall bladder while it remained constant in other organs. Biotransformation and elimination processes could explain this phenomenon observed in gall bladder. LAS depuration was rapid in all organs (with up to 90% elimination within 2 days) and depuration kinetics was best fitted by a two-compartment exponential-model. When fish were fed with radiolabeled food, ingested LAS was transferred to organs within the first hours following the feeding. Model best describing depuration kinetics of LAS in the whole fish indicated that the contaminant can be considered as not assimilated., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Among the outstanding chemical diversity found in marine sponges, cyclic guanidine alkaloids, present in species of the family Crambeidae, are particularly attractive, not only because of their unique chemical features, but also due to a broad range of biological activities. Despite a growing interest in these natural products as therapeutic agents, their metabolic pathway has not been experimentally investigated. Ex situ feeding experiments using radiolabeled precursors performed on the Mediterranean sponge Crambe crambe suggest arginine and fatty acids as precursors in the metabolic pathway of crambescins. A subsequent bio-inspired approach supported the change of paradigm in the metabolic pathway of cyclic guanidine alkaloids. A large part of the chemical diversity of this family would therefore originate from a tethered Biginelli-like reaction between C-2/C-3 activated fatty acids and a central guanidinylated pyrrolinium., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Plastic pollution is ubiquitous in aquatic environments and its potential impacts to wildlife and humans present a growing global concern. Despite recent efforts in understanding environmental impacts associated with plastic pollution, considerable uncertainties still exist regarding the true risks of nano- and micro-sized plastics (<5 mm). The challenges faced in this field largely relate to the methodological and analytical limitations associated with studying plastic debris at low (environmentally relevant) concentrations. The present paper highlights how radiotracing techniques that are commonly applied to trace the fate and behaviour of chemicals and particles in various systems, can contribute towards addressing several important and outstanding questions in environmental plastic pollution research. Specifically, we discuss the use of radiolabeled microplastics and/or chemicals for 1) determining sorption/desorption kinetics of a range of contaminants to different types of plastics under varying conditions, 2) understanding the influence of microplastics on contaminant and nutrient bioaccumulation in aquatic organisms, and 3) assessing biokinetics, biodistribution, trophic transfer and potential biological impacts of microplastic at realistic concentrations. Radiotracer techniques are uniquely suited for this research because of their sensitivity, accuracy and capacity to measure relevant parameters over time. Obtaining precise and timely information on the fate of plastic particles and co-contaminants in wildlife has widespread applications towards effective monitoring programmes and environmental management strategies., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Ocean acidification have been shown to not affect the capacity of bivalves to bioaccumulation 134 Cs in their tissue; but as this was studied on only one species to date. There is therefore a need to verify if this holds true for other bivalve species or other marine invertebrates. The present short communication confirms that in the scallop Mimachlamys varia and the prawn Penaeus japonicus, two species that supposedly have a record to preferentially concentrates this radionuclide, that bioconcentration of 134 Cs was shown not to be influenced by a decreasing pH (and thereby increasing seawater pCO 2 ). Although the dissolved 134 Cs was taken up in a similar manner under different pH values (8.1, 7.8, and 7.5) in both species, being described by a saturation state equilibrium model, the species displayed different bioconcentration capacities of 134 Cs: CF ss in the prawns was approximately 10-fold higher than in scallops. Such results suggest that the Cs bioconcentration capacity are mainly dependent of the taxa and that uptake processes are independent the physiological ones involved in the biological responses of prawns and scallops to ocean acidification., (Copyright © 2018. Published by Elsevier Ltd.)

Considered as the most vulnerable ontogenic stages to environmental stressors, the early-life stages of fish paid a peculiar attention with respect to their vulnerability to metal and radionuclides contamination. Concomitantly, the increasing anthropogenic CO 2 release in the atmosphere will cause major change of the seawater chemistry that could affect the trace elements and radionuclides bioconcentration efficiencies by marine organisms. The aim of this work was to 1) delineate the uptake behaviours of Ag, Am, Cd, Co and Zn in seabream eggs during 65 h of development and retention by newly hatched and 7 h-old larvae maintained in clean seawater, respectively, and 2) investigate the effects of elevated pCO 2 on the bioconcentration efficiencies of these elements in eggs. Besides differing in terms of maximal concentration factors values, the uptake kinetics showed element-specific patterns with Am being linearly bioconcentrated and Co and Zn showing a saturation state equilibrium. The 110m Ag and 109 Cd uptake kinetics shared a two-phases pattern being best described by a saturation equation during the first 24 h of development, and then an exponential loss of accumulated elements although the radiotracer concentrations in the surrounding water remained constant. At hatching time, the radioactivity of 110m Ag was the highest among radiotracers detected in the larvae. After 7 h in depuration conditions, 60% of this metal was still detected whereas 241 Am, 60 Co and 65 Zn were almost totally lost, suggesting an efficient incorporation of Ag in the embryo during the egg development. Finally, this study brought first qualitative data on the effect of pCO 2 /pH on metal bioconcentration in eggs, raising the need to unravel chemical and biological processes to predict a potential shift of the toxicity of environmental contamination of fish early life stages with future ocean change., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The uptake and depuration kinetics of 134 Cs and 241 Am were investigated in the bloody cockle Anadara senilis exposed via seawater and food in controlled conditions, using animals of different weight groups in order to assess how their bioaccumulation is affected by allometry and, hence, the individual's age. This study is one of the few experiments investigating bioaccumulation capacities of radionuclides in a West-African bivalve. Results showed that allometric relationships were mainly dependent on the exposure pathway considered. Significant relationships with body weight of bloody cockles were found during the uptake from dissolved phase for both radionuclides; they followed inverse power functions: smaller cockles concentrated both radionuclides more than larger ones. In contrast, radionuclide absorption and assimilation efficiencies from water and food, respectively, did not show any significant relationship with weight: only slight variation was observed between small and large organisms for the retention of 241 Am accumulated from food. A bioaccumulation model was used to assess the contribution of each pathway of exposure (food vs. water) in organisms grouped in small and large individuals. We found that, regardless of the size, 134 Cs was mainly bioaccumulated through the dietary pathway. In the case of 241 Am, the relative contribution of each pathway is weight-dependent: major contribution of dissolved pathway in smaller organisms and the major dietary contribution in larger organisms., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

To better understand bioaccumulation of radiocaesium in the commercially important Japanese flatfish, Paralichthys olivaceus, the uptake and depuration kinetics of caesium via both seawater and food were assessed simultaneously using controlled aquaria. The pre-conditioned fish were exposed to radionuclides via the two different pathways (aqueous versus dietary) concurrently using two isotopes of caesium, 137 Cs and 134 Cs, respectively. Dissolved caesium uptake was linear and did not reach a steady state over the course of the 8-day exposure period. Consumption of 134 Cs-labelled food led to higher bioaccumulation rates of radioactive Cs than via seawater exposure of 137 Cs during uptake and following depuration, though the model-derived long-lived biological half-lives of both pathways was approximately 66 d. Further development of this method for assessing multiple radiocaesium bioaccumulation pathways simultaneously could lead to a promising new approach for studying Cs contamination in marine organisms., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The marine organisms which inhabit the coastline are exposed to a number of anthropogenic pressures that may interact. For instance, the accumulation of toxic metals present in coastal waters is expected to be modified by ocean acidification through e.g. changes in physiological performance and/or elements availability. Changes in bioaccumulation due to lowering pH are likely to be differently affected depending on the nature (essential vs. non-essential) and speciation of each element. The Mediterranean is of high concern for possible cumulative effects due to strong human influences on the coastline. The aim of this study was to determine the effect of ocean acidification (from pH 8.1 down to -1.0 pH units) on the incorporation kinetics of six trace metals (Mn, Co, Zn, Se, Ag, Cd, Cs) and one radionuclide ( 241 Am) in the larvae of an economically- and ecologically-relevant sea urchin of the Mediterranean coastline: Paracentrotus lividus. The radiolabelled metals and radionuclides added in trace concentrations allowed precise tracing of their incorporation in larvae during the first 74 h of their development. Independently of the expected indirect effect of pH on larval size/developmental rates, Paracentrotus lividus larvae exposed to decreasing pHs incorporated significantly more Mn and Ag and slightly less Cd. The incorporation of Co, Cs and 241 Am was unchanged, and Zn and Se exhibited complex incorporation behaviors. Studies such as this are necessary prerequisites to the implementation of metal toxicity mitigation policies for the future ocean. We discuss possible reasons and mechanisms for the specific effect of pH on each metals., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In order to better understand the influence of changing salinity conditions on the trophic transfer of 137 Cs in marine fish that live in dynamic coastal environments, its depuration kinetics was investigated in controlled aquaria. The juvenile turbot Scophthalmus maximus was acclimated to three distinct salinity conditions (10, 25 and 38) and then single-fed with compounded pellets that were radiolabelled with 137 Cs. At the end of a 21-d depuration period, assimilation efficiencies (i.e. AEs = proportion of 137 Cs ingested that is actually assimilated by turbots) were determined from observational data acquired over the three weeks. Our results showed that AEs of 137 Cs in the turbots acclimated to the highest salinity condition were significantly lower than for the other conditions (p < 0.05). Osmoregulation likely explains the decreasing AE observed at the highest salinity condition. Indeed, observations indicate that fish depurate ingested 137 Cs at a higher rate when they increase ion excretion, needed to counterbalance the elevated salinity. Such data confirm that ambient salinity plays an important role in trophic transfer of 137 Cs in some fish species. Implications for such findings extend to seafood safety and climate change impact studies, where the salinity of coastal waters may shift in future years in response to changing weather patterns., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Studying dietary metal transfer kinetics is essential to gain a better understanding in global metal accumulation rates and its impacts in marine fish. While there exists a solid understanding on the influence of various biotic factors on this transfer, metal assimilation in fish might be also affected by abiotic factors, as has been observed in marine invertebrates. The present study therefore aims to understand the potential effects of two climate-related master variables, temperature and pH, on the assimilation efficiency (AE) of essential (Co and Zn) and non-essential (Ag) metals in the turbot Scophthalmus maximus using radiotracer tools. Juvenile turbots were acclimated for 8 weeks at two temperatures (17 and 20 °C) and pH (7.5 and 8.0) regimes, under controlled laboratory conditions, and then fed with radiolabelled shrimp ( 57 Co, 65 Zn and 110m Ag). Assimilation efficiencies of Co and Ag in juvenile turbot, determined after a 21-day depuration period, were not affected by pre-exposition to the different environmental conditions. In contrast, temperature did significantly influence Zn AE (p < 0.05), while pH variations did not affect the assimilation of any of the metals studied. In fact, temperature is known to affect gut physiology, specifically the membrane properties of anterior intestine cells where Zn is adsorbed and assimilated from the ingested food. These results are relevant to accurately assess the influence of abiotic factors in AEs of metals in fish as they are highly element-dependent and also modulated by metabolic processes.

Trophic transfer of Zn in fish is affected by the type of food and environmental variables such as temperature. However, there is still a lack of knowledge regarding the effects of such factors on Zn organotropism. For this reason, a series of experimental studies have investigated how the distribution and the concentration of Zn is affected by some environmentally-relevant factors (food quality, food availability, water pH, and temperature) in turbot Scophthalmus maximus using radiotracer techniques. In three different experiments, Zn distribution in seven body compartments of juvenile turbot and the calculation of Zn concentration index (I C ) for each compartment were compared. Its distribution as well as its concentration in the body compartments of juvenile turbots were not affected by the experimental conditions tested. This apparent consistency in the Zn organotropism can be explained by the ability of the fish to maintain Zn homeostasis at non-toxic Zn concentrations in their diet. These results are important to better understand the trophic transfer of Zn in fish under realistic environmental conditions., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Diet is an important pathway for metal uptake in marine organisms, and assimilation efficiency is one of the most relevant parameters to quantify trophic transfer of metals along aquatic food webs. The most commonly used method to estimate this parameter is pulse-chase feeding using radiolabeled food. This approach is, however, based on several assumptions that are not always tested in an experimental context. The present study aimed to validate the approach by assessing single-feeding and multiple-feeding approaches, using a model species (the turbot Scophthalmus maximus). Using the kinetic data obtained from the single-feeding experiment, the reconstruction of a multi-feeding experiment was tested for consistency with data provided by an actual multi-feeding performed under the same experimental conditions. The results validated the single-feeding approach. Environ Toxicol Chem 2017;36:1227-1234. © 2016 SETAC., (© 2016 SETAC.)

Little information exists on the effects of ocean acidification (OA) on the digestive and post-digestive processes in marine fish. Here, we investigated OA impacts (Δ pH = 0.5) on the trophic transfer of select trace elements in the clownfish Amphiprion ocellaris using radiotracer techniques. Assimilation efficiencies of three essential elements (Co, Mn and Zn) as well as their other short-term and long-term kinetic parameters in juvenile clownfish were not affected by this experimental pH change. In complement, their stomach pH during digestion were not affected by the variation in seawater pH. Such observations suggest that OA impacts do not affect element assimilation in these fish. This apparent pCO2 tolerance may imply that clownfish have the ability to self-regulate pH shifts in their digestive tract, or that they can metabolically accommodate such shifts. Such results are important to accurately assess future OA impacts on diverse marine biota, as such impacts are highly species specific, complex, and may be modulated by species-specific metabolic processes.

Bioaccumulation kinetics of five dissolved metals were determined in the mangrove oyster Crassostrea gasar, using corresponding radiotracers ((54)Mn, (57)Co, (65)Zn, (109)Cd and (110m)Ag). Additionally, their bioaccessibility to human consumers was estimated. Results indicated that over a 14-day exposure (54)Mn and (57)Co were linearly concentrated in oysters whereas (109)Cd, (65)Zn and (110m)Ag were starting to saturate (steady-state not reached). Whole-body concentration factors at 14 days (CF14d in toto) ranged from 187 ± 65 to 629 ± 179 with the lowest bioconcentration capacity for Co and the highest for Ag. Depuration kinetics were best described by a double-exponential model with associated biological half-lives ranging from 26 days (Ag) to almost 8 months (Zn and Cd). Bioaccessible fraction of the studied elements was estimated using in vitro digestions, which suggested that oysters consumed seasoned with lemon enhanced the accessibility of Cd, Mn and Zn to human consumers, but not Ag and Co.

Development of nickel mining activities along the New Caledonia coasts threatens the biodiversity of coral reefs. Although the validation of tropical marine organisms as bioindicators of metal mining contamination has received much attention in the literature over the last decade, few studies have examined the potential of corals, the fundamental organisms of coral reefs, to monitor nickel (Ni) contamination in tropical marine ecosystems. In an effort to bridge this gap, the present work investigated the bioaccumulation of (63)Ni in the scleractinian coral Stylophora pistillata and in its isolated zooxanthellae Symbiodinium, using radiotracer techniques. Results highlight the high capacities of coral tissues (zooxanthellae and host tissues) to efficiently bioconcentrate (63)Ni compared to skeleton (Concentration Factors CF at 14 days of exposure are 3 orders of magnitude higher in tissues than in skeleton). When non-contaminated conditions were restored, (63)Ni was more efficiently retained in skeleton than in coral tissues, with biological half-lives (Tb½) of 44.3 and 6.5 days, respectively. In addition, our work showed that Symbiodinium bioconcentrated (63)Ni exponentially, with a vol/vol concentration factor at steady state (VCFSS) reaching 14,056. However, compilation of our results highlighted that despite efficient bioconcentration of (63)Ni in Symbiodinium, their contribution to the whole (63)Ni accumulation in coral nubbins represents less than 7%, suggesting that other biologically controlled processes occur in coral host allowing such efficient bioconcentration in coral tissues., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Bioaccumulation of (134)Cs was determined in 5 tropical marine species: three bivalves (the oysters Isognomon isognomum and Malleus regula, and the clam Gafrarium pectinatum), one decapod (shrimp Penaeus stylirostris) and one alga (Lobophora variegata). Marine organisms were exposed to the radionuclides via different pathways: seawater (all of them), food (shrimp and bivalves) and sediment (bivalves). Our results indicate that the studied tropical species accumulate Cs similarly than species from temperate regions whereas retention capacities seems to be greater in the tropical species. Bioaccumulation capacities of the two oysters were similar for all the exposure pathways. The alga, and to a lesser extent the shrimp, concentrated dissolved Cs more efficiently than the bivalves (approx. 14 and 7 times higher, respectively). Assimilation efficiencies of Cs in bivalves and shrimp after a single feeding with radiolabelled food were comprised between 7.0 ± 0.4 and 40.7 ± 4.3%, with a variable retention time (half-life -Tb1/2- ranging from 16 ± 3 to 89 ± 55 d). Although the clam lives buried in the sediment, this exposure pathway resulted in low bioaccumulation efficiency for sediment-bound Cs (mean transfer factor: 0.020 ± 0.001) that was lower than the two oyster species, which are not used to live in this media (0.084 ± 0.003 and 0.080 ± 0.005). Nonetheless, Cs accumulated from sediment was similarly absorbed (61.6 ± 9.7 to 79.2 ± 2.3%) and retained (Tb1/2: 37 ± 2 to 58 ± 25 d) for the three bivalves species. Despite the poor transfer efficiency of Cs from food, the use of a global bioaccumulation model indicated that the trophic pathways was the main uptake route of Cs in the bivalves and shrimp. In shelled organisms, shells played a non-negligible role in Cs uptake, and their composition and structure might play a major role in this process. Indeed, most of the Cs taken up from seawater and sediment was principally located on the hard parts of the bivalves and shrimp, with the exception of G. pectinatum, where Cs was mainly distributed in the soft-parts., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Industrial incidents can result in radionuclide release in the environment, among which (110m)Ag. Indeed, under particular circumstances, non-negligible amounts of (110m)Ag have been measured in the marine environment (as observed in Fukushima Dai-ichi incident). This element can therefore be accumulated by aquatic organisms through different pathways including the trophic transfer. The present study aimed at examining the variation of (110m)Ag assimilation efficiency (AE) by turbots, Scophthalmus maximus, when exposed through different feeds. Pulse-chase feeding experiments were carried out in mesocosms, using radiolabelled feeds (natural prey and commercial pellets). Depuration kinetics of (110m)Ag over 21 days were generally fitted by a two-component exponential model; the ingested radioelement was poorly assimilated by turbots regardless of the food item that was used (AE always <3%). Concentration and subcellular distribution of (110m)Ag in prey did not seem to influence its assimilation by turbot. These results suggest that physiological mechanisms could occur in fish that would prevent the transfer of (110m)Ag from gut lumen to internal organs (e.g. (110m)Ag neutralization in the lumen of the stomach, detoxification mechanisms occurring in the gut)., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Among bivalves, scallops have been shown to be good bioindicator species for radionuclide monitoring. The present paper looked at the Cs bioaccumulation capacities of the variegated scallop Mimachlamys varia exposed separately via seawater and food under laboratory conditions. Results were compared with data previously obtained for the king scallop Pecten maximus, the only Pectinid species for which Cs accumulation has been studied in laboratory. Results indicated that M. varia has higher uptake capacity (CF: 1.86 ± 0.08) but lower absorption efficiency (A0l: 33 ± 5%) than P. maximus when exposed to waterborne Cs (CF of P. maximus: 0.94 ± 0.05 and A0l: 45 ± 3%). When scallops were fed radiolabeled phytoplankton, the assimilation efficiency of Cs was similar for the two species (AE: 24 ± 3% for M. varia and 28 ± 4% for P. maximus). Interspecific differences in terms of accumulation and retention, can be explained by physiological factors (including size of individuals) and/or difference in storage mechanisms. Indeed, organotropism differed between the two scallop species, suggesting the occurrence of specific redistribution mechanisms towards the tissues involved in Cs storage, excretion and detoxification. Finally, the present study examined the relative contribution of the different exposure pathways (seawater and food) to global (134)Cs bioaccumulation for M. varia. Results showed that food constitutes the main accumulation pathway, contributing for 77% of the global (134)Cs bioaccumulation., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Uptake and depuration kinetics of dissolved [(14)C]C₁₂-6-linear alkylbenzene sulfonate (LAS) were determined in the shrimp Palaemonetes varians using environmentally relevant exposure concentration. The shrimp concentrated LAS from seawater with a mean BCF value of 120 L kg(-1) after a 7-day exposure. Uptake biokinetics were best described by a saturation model, with an estimated BCFss, of 159 ± 34 L kg(-1), reached after 11.5 days. Shrimp weight influenced significantly BCF value with smaller individuals presenting higher affinity to LAS. To the light of a whole body autoradiography, major accumulation of LAS occurred in the cephalothorax circulatory system (gills, heart, hepatopancreas) and ocular peduncle, but not in the flesh, limiting potential transfer to human consumers. LAS depuration rate constant value of the shrimp was 1.18 ± 0.08 d(-1) leading to less than 1% of remaining LAS in its tissues after 8 days of depuration., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The toxic dinoflagellate Karenia brevis, responsible for early harmful algal blooms in the Gulf of Mexico, produces many secondary metabolites, including potent neurotoxins called brevetoxins (PbTx). These compounds have been identified as toxic agents for humans, and they are also responsible for the deaths of several marine organisms. The overall biosynthesis of these highly complex metabolites has not been fully ascertained, even if there is little doubt on a polyketide origin. In addition to gaining some insights into the metabolic events involved in the biosynthesis of these compounds, feeding studies with labeled precursors helps to discriminate between the de novo biosynthesis of toxins and conversion of stored intermediates into final toxic products in the response to environmental stresses. In this context, the use of radiolabeled precursors is well suited as it allows working with the highest sensitive techniques and consequently with a minor amount of cultured dinoflagellates. We were then able to incorporate [U-¹⁴C]-acetate, the renowned precursor of the polyketide pathway, in several PbTx produced by K. brevis. The specific activities of PbTx-1, -2, -3, and -7, identified by High-Resolution Electrospray Ionization Mass Spectrometer (HRESIMS), were assessed by HPLC-UV and highly sensitive Radio-TLC counting. We demonstrated that working at close to natural concentrations of acetate is a requirement for biosynthetic studies, highlighting the importance of highly sensitive radiolabeling feeding experiments. Quantification of the specific activity of the four, targeted toxins led us to propose that PbTx-1 and PbTx-2 aldehydes originate from oxidation of the primary alcohols of PbTx-7 and PbTx-3, respectively. This approach will open the way for a better comprehension of the metabolic pathways leading to PbTx but also to a better understanding of their regulation by environmental factors.

While marine organisms such as bivalves, seagrasses and macroalgae are commonly used as biomonitors for the environment pollution assessment, widely distributed sponges received little attention as potential helpful species for monitoring programmes. In this study, the trace element and radionuclide bioaccumulation and retention capacities of some marine sponges were estimated in a species-comparative study using radiotracers technique. Six Mediterranean species were exposed to background dissolved concentrations of (110m)Ag, (241)Am, (109)Cd, (60)Co, (134)Cs, (54)Mn, (75)Se and (65)Zn allowing the assessment of the uptake and depuration kinetics for selected elements. Globally, massive demosponges Agelas oroides, Chondrosia reniformis and Ircinia variabilis displayed higher concentration factor (CF) than the erectile ones (Acanthella acuta, Cymbaxinella damicornis, Cymbaxinella verrucosa) at the end of exposure, suggesting that the morphology is a key factor in the metal bioaccumulation efficiency. Considering this observation, two exceptions were noted: (1) A. acuta reached the highest CF for (110m)Ag and strongly retained the accumulated metal without significant Ag loss when placed in depuration conditions and (2) C. reniformis did not accumulate Se as much as A. oroides and I. variabilis. These results suggest that peculiar metal uptake properties in sponges could be driven by specific metabolites or contrasting biosilification processes between species, respectively. This study demonstrated that sponges could be considered as valuable candidate for biomonitoring metal contamination but also that there is a need to experimentally highlight metal-dependant characteristic among species., (Copyright © 2012 Elsevier Ltd. All rights reserved.)