Influence of metal exposure on metallothionein synthesis and lipid peroxidation in two bivalve mollusks: the oyster (Crassostrea gigas) and the mussel (Mytilus edulis)

The impact of metals (silver, cadmium, copper, mercury and zinc) on metallothionein (MT) and malondialdehyde (MDA) levels of the oyster (Crassostrea gigas) and the mussel (Mytilus edulis) was studied after 4 or 21 days of metal exposure. Moreover, total protein levels were determined. After 4 days of metal exposure, although C. gigas and M. edulis accumulated cadmium and mercury concentrations in the gills and digestive gland, no significant variation of total protein level was occurred. After 21 days of exposure, metals were bioaccumulated in the gills and the digestive gland of both mollusks. A decrease of total protein concentrations in the gills of oysters and the digestive gland of mussels and an increase on metallothionein concentrations in the gills of both mollusks were observed. An increase of MDA levels was noticed for the gills and the digestive gland of mussels exposed for 21 days to either cadmium, silver or mercury whereas a decrease of MDA levels was observed in the gills of the oysters exposed for the same time to the same metals. The levels of proteins, MDA and MT were metal, species or organ dependent.info:eu-repo/semantics/publishedVersio

Mercury content in commercial pelagic fish and its risk assessment in the Western Indian Ocean,” Sci.

Abstract As top predators of pelagic food webs, large fish naturally bioaccumulate mercury (Hg). Determining Hg burdens in commercialized fish is essential considering the concern about effects of contaminants on human health and the legal thresholds that are therefore set for local consumption and/or exportation. Total Hg levels were measured in the muscular tissue of 183 fish of five commercially important species from the tropical zone of the Western Indian Ocean. All individuals were measured and sexed in order to study the impregnation of Hg with size and sex within each species. Values of Hg found in this part of the Indian Ocean were comparable to Hg in muscular tissue of the same species studied in other areas. The highest Hg levels were noted in Swordfish (Xiphias gladius) caught in waters surrounding Reunion Island (3.97 ± 2.67 μg g − 1 dry weight). Following the Swordfish, in decreasing order of Hg content, were the Yellowfin Tuna (Thunnus albacares) and the Skipjack (Katsuwonus pelamis), then the Common Dolphinfish (Coryphaena hippurus) and the Wahoo (Acanthocybium solandri). In the North of the Mozambique Channel, Swordfish had higher Hg levels than Yellowfin Tunas, and Dolphinfish exhibited intermediate Hg levels. The size of a fish was a determining factor of its Hg burden, as was the species. Differences in size-normalized Hg levels were observed between the two study zones for Swordfish and Common Dolphinfish. Sex, in contrast, did not influence Hg levels suggesting that females and males have similar feeding habits. The muscular Hg levels presented here suggest that consumers of fish originating from theWestern Indian Ocean should limit themselves to one Swordfish based meal per week, or one fish meal a day if they choose to eat tuna or Common Dolphinfish

Spring temperature responses of oaks are synchronous with North Atlantic conditions during the last deglaciation

Paleoclimate proxies based on the measurement of xylem cell anatomy have rarely been developed across the temperature range of a species or applied to wood predating the most recent millennium. Here we describe wood anatomy-based proxies for spring temperatures in central North America from modern bur oaks (Quercus macrocarpa Michx.). The strong coherence of temperature signals across the species range supports the use of these proxies across thousands of years of climatic change. We also used 79 subfossil oak log cross sections from northern Missouri, ¹⁴C-dated to 9.9-13.63 ka (ka is 1000 cal yr BP), to assess the frequency of oak deposition into alluvial sediments and a subset of these oaks for a wood anatomy-based reconstruction of spring paleotemperatures. Temperatures during the Younger Dryas cold period (YD) were up to 3.5 degrees C lower than modern temperatures for that region, equivalent to or lower than those experienced at the northern edge of the modern species range. Compared to extant oaks growing at much higher [CO₂], subfossil oaks had greater vessel frequencies. Besides very low theoretical (or estimated) xylem conductivity near the beginning of the oak record near 13.6 ka, vessel frequencies greater than modern trees compensated for reduced vessel dimensions so that theoretical xylem conductivity was consistently above that of modern trees at the cold northern sites. Significant correlations were found between the frequency of ¹⁴C-dated oaks and either delta δ¹⁸O from the NGRIP (North Greenland Ice Core Project) ice core or from the Cariaco grayscale marine-sediment record from the southern Caribbean sea. Oak deposition into alluvial sediments during the YD was significantly lower than expected given the average sample depth of oaks from 9.9 to 13.6 ka. Reduced oak deposition during the YD suggests that an abrupt shift in climate reduced oak populations across the region and/or changed the rates of channel movement across drainages.Keywords: Pleistocene, Quercus macrocarpa, Holocene, Pre-Boreal, Younger Dryas, Radiocarbon, Wood anatomy, Great Plains\, USA, Phenology, Bolling-Allerod, Xylem, Bur oa

Les métaux (Cd, Cu, Pb et Zn) dans la production des microalgues sur différents milieux de culture (biodisponibilité, bioaccumulation et impact physiologique)

La qualité et la production d une culture de microalgues sont dépendantes de différents facteurs physico-chimiques: salinité, pH, concentration en nutriments majeurs et en oligo-éléments dont les métaux traces dans le milieu de culture. Dans ce travail de doctorat, la biodisponibilité de quatre métaux pour des microalgues est étudiée dans les eaux marine côtière et souterraine salée. La biodisponibilité d un métal est dépendante de sa concentration totale et de celle des ligands présents dans le milieu ainsi que de l affinité respective de ces ligands pour le métal. Suite à l étude comparative de la qualité des algues produites, les capacités de complexation des eaux souterraines salées et l eau de mer côtière ont été étudiées afin de mieux comprendre les variations de bioaccumulation des métaux par les microalgues. Une approche expérimentale sur le milieu artificiel DAM élaboré dans ce travail a permis de formuler des hypothèses sur les variations interspécifiques de la bioaccumulation des métaux.The quality and the productivity of microalgal cultures depend on different physico-chemical factors like salinity, pH, nutrient and trace element (including trace metals) concentration in the culture medium. During this doctoral study, the bioavailability of four metals for microalgae was tested in coastal seawater and several salt groundwaters. The bioavailability of a metal depends on its own total concentration as well as that of ligands in the medium, and on the relative affinity of each ligand towards the given metal. After a comparative study of the quality of algae grown in coastal seawater and salt groundwaters, the complexation capacities of these media were studied to allow a better understanding of the observed variations of metal bioaccumualtion in the produced microalgae. An experimental study with a new artificial medium (DAM) developed during our work allowed to put forward some hypotheses regarding the interspecific variations of metal bioaccumulation.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Trace elements in three marine birds breeding on Reunion Island (Western Indian Ocean) Part 1: Factors influencing their bioaccumulation

This work aims to use seabirds as bioindicators of trace element levels in the tropical waters and food webs of the Western Indian ocean. The accumulation patterns of selected toxic (Cd and Hg) and essential (Cu, Fe, Mn, Se and Zn) elements were determined in liver, kidney and pectoral muscles of three species of 162 marine bird

Preliminary results on trace element levels in three species of seabirds from the western Indian Ocean

As top predators of pelagic food webs, marine birds naturally bioaccumulate essential and non-essential elements. Levels of arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), selenium (Se) and zinc (Zn) were determined in the liver, kidneys and muscles of three species of marine birds found on Réunion Island: Barau's Petrel (Pterodroma baraui), Audubon's Shearwater (Puffinus lherminieri bailloni) and the White-tailed Tropicbird (Phaethon lepturus). The study of the 89 birds sampled put forth variations of the elemental levels between organs, age groups (juveniles versus adults) and species. Adult Barau's Petrels showed the highest values of Hg and Cd. This study offers a first glimpse of the levels of impregnation of eight trace elements in top predators of the western Indian Ocean and brings answers to certain questions related to the processes of bioaccumulation in marine top predators of the tropical Indian Ocean.Situés au sommet des réseaux trophiques pélagiques, les oiseaux marins bioaccumulent naturellement des éléments essentiels et non-essentiels tout au long de leur vie. La mesure des teneurs en arsenic (As), cadmium (Cd), cuivre (Cu), fer (Fe), mercure (Hg), manganèse (Mn), sélénium (Se) et zinc (Zn) a été effectuée dans le foie, les reins et les muscles de trois espèces d'oiseaux de l'île de La Réunion, le pétrel de Barau (Pterodroma baraui), le puffin de baillon (Puffinus lherminieri bailloni) et le paille-en-queue à brins blancs (Phaethon lepturus). L'étude des 89 oiseaux échantillonnés fait apparaître des variations des teneurs métalliques entre les organes, les classes d'âge (juvéniles vs adultes), ainsi qu'entre les espèces, les pétrels de Barau adultes ayant les plus fortes teneurs en Hg et Cd. Cette étude offre ainsi, un premier aperçu des niveaux d'imprégnation de 8 éléments traces chez des prédateurs supérieurs de l'Océan Indien occidental tropical et propose des éléments de réponses quant aux processus de bioaccumulation chez ces espèces.Ostrich 2007, 78(2): 435–44

Metal bioaccumulation and storage forms in the shrimp, Rimicaris exoculata, from the Rainbow hydrothermal field (Mid-Atlantic Ridge); preliminary approach to the fluid-organism relationship

At the Rainbow hydrothermal site the concentrations of metals in the fluid are the highest observed in the Mid-Atlantic Ridge hydrothermal areas, and the shrimps Rimicaris exoculata were observed forming dense swarms in small depressions on the chimney walls. In order to understand the fluid-organism relationship, we investigated the relative abundance of metals in the water surrounding R. exoculata and their bioaccumulation by the shrimps. This first approach stresses a net metal enrichment around R. exoculata. Precipitation, scavenging and oxidative redissolution processes in the mixing zone are controlling the concentrations of metals. Their bioaccumulation varies according to their bioavailability in the surrounding water. Metals are abundant as insoluble forms in the tissues but the hypothesis of external deposits on the gills and the cuticle of the abdomen cannot be rejected. The regular lysosomal breakdown of metallothioneins may participate to the relative abundance of these insoluble forms. Improvements concerning the preparation of the biological material and the use of a complementary histological technique are needed to answer the questions emerging from our work. The study of the distribution of metals between dissolved and particulate fractions in the water surrounding the shrimps has to be performed, in order to provide data on the bioavailability of metals.Sur la ride Médio-Atlantique, les plus fortes concentrations en métaux dans le fluide hydrothermal ont été enregistrées sur le site Rainbow où d’abondants nuages de la crevette Rimicaris exoculata sont observés dans les dépressions des parois des cheminées. L’étude des relations entre le fluide et les organismes a été abordée à travers la quantification des métaux dans l’environnement immédiat des crevettes et dans leurs tissus, et en étudiant leur forme de stockage dans ces tissus. Notre travail met en évidence un fort enrichissement en métaux de l’environnement des crevettes. L’abondance relative de ces métaux est sous la dépendance de phénomènes de précipitations, d’adsorption et de redissolution oxydative. Leur bioaccumulation fluctue en accord avec leur biodisponibilité. Des dépôts externes sur les branchies et la cuticule de l’abdomen, qui s’ajouteraient au phénomène naturel de dégradation des métallothionéines dans les lysosomes, pourraient contribuer à leur forte accumulation sous forme de composés insolubles. Certaines questions soulevées par cette étude trouveront une réponse grâce à un meilleur conditionnement des échantillons biologiques, à des observations histologiques complémentaires, ainsi qu’à des dosages chimiques ou biochimiques. A l’avenir, la prise en compte de la distribution des métaux entre phases dissoute et particulaire dans l’eau environnant les organismes apparaît comme une nécessité pour évaluer la biodisponibilité des métaux

Bioaccumulation of trace elements in pelagic fish from the Western Indian Ocean

Trace elements were analyzed in fish of commercial interest to determine their importance in marine systems of the Western Indian Ocean and their bioaccumulation patterns. The results are equivalent or lower than levels reported in ichthyofauna worldwide. Certain values of muscular Cd, Hg, Pb and Zn were however above thresholds for human consumption. Levels varied among tissues, species and with fish length, but were seldom influenced by the nutritional condition of the fish, its gender and its reproductive status. Correlations between hepatic Hg and Se levels in Swordfish (r 2 = 0.747) and Yellowfin Tunas (r 2 = 0.226), and among metallothionein linking metals imply the existence of detoxification processes in these species. Differences in levels between fish from the Mozambique Channel and Reunion Island probably reflect differences of diets rather than differences of elemental availability in both environments. Capsule: Metal bioaccumulation was quantified in four species of pelagic fish

STUDIES OF INTERACTION BETWEEN DISSOLVED METALS AND THEIR SPECIATION AND PHYTOPLANKTON IN A CONTINUOUS FLOW PHOTOBIOREACTOR

particiapantHalf of the world primary productivity is due to marine phytoplankton. Factors that affect the physiology of these organisms are therefore very important to understand plankton dynamics in the global ocean coastal and pelagic settings. Depending on local conditions, metallic micronutrients can be limiting (e.g., Fe in HNLC areas) and affect plankton population structure. While iron is a pivotal micronutrient that impacts global primary productivity, interactions of other metals with phytoplankton have also gained attention. Among these interactions are the potential effects of increased trace metals on plankton dynamics and vice versa. In order to examine the impact of other trace metals upon selected phytoplankton species, we furthered the development of an already existing continuous flow photobioreactor to make it compatible with trace-metal-clean conditions and neutral with respect reduced sulfur gases which were examined. The effect on reduced sulfur dynamics has global relevance because a fraction of this pool (dimethylsulfide) is gaseous and after fluxing into the atmosphere, it is active in Earth's solar radiation balance. Experimenting with mono-specific continuous cultures, we examined the effects of environmentally relevant, dissolved Ag and Cd concentration and speciation on the growth of Isochrysis isogalbana and Phaeodactylum tricornutum. Results acquired so far suggest that while increased Ag and Cd levels have little effect on the growth of these phytoplankton species, they have one reduced sulfur release. Effects of pCO2 on culture growth and metal speciation were also investigated. Preliminary results of the photobioreactor and this suite of experiments will be presented

Responses of wild small mammals to a pollution gradient: Host factors influence metal and metallothionein levels.

International audienceWe investigated how host factors (species, age, gender) modulated Cd, Pb, Zn, and Cu concentrations, metallothionein levels (MTs) and their relationships in 7 sympatric small mammal species along a pollution gradient. Cd concentrations in liver and kidneys increased with age in all species. Age effect on other metals and MTs differs among species. Gender did not influence metal and MT levels except in the bank vole. Three patterns linking internal metal concentrations and MTs were observed along the gradient: a low metal accumulation with a (i) high (wood mouse) or (ii) low (bank vole) level of MTs accompanied by a slight or no increase of MTs with Cd accumulation; (iii) an elevated metal accumulation with a sharp increase of MTs (common and pygmy shrews). In risk assessment and biomonitoring perspectives, we conclude that measurements of MTs and metals might be associated because they cannot be interpreted properly when considered separately