Soft Tissues Of Bivalves Research Articles

Trace and Rare Earth Element Fingerprints of Aerobic Oxidation of Methane in Seep‐Dwelling Bivalves

AbstractAerobic methanotrophic bacteria are pivotal in the global carbon cycle by converting methane into biomass and inorganic carbon species. Light rare earth elements (light‐REE; La, Ce) are part of the metalloenzymes mediating the biochemical processes in methanotrophs. However, the partitioning of trace metals and REE in chemosymbiotic megafauna with methanotrophic endosymbionts remains largely unknown. Here we determine stable isotope compositions (δ13C, δ15N) of soft tissues (gill, mantle, foot) as well as trace metal and REE contents of soft tissues and shells of chemosymbiotic bivalves dwelling at methane seeps (Site F and Haima seeps) of the South China Sea. Isotopic compositions of soft tissues are found to reflect the mode of chemosymbiosis (i.e., methanotrophy vs. thiotrophy). Particularly gill tissues of bivalves with methanotrophic endosymbionts display marked light‐REE and trace metal enrichments, which is interpreted to reflect the enzymatic activity of endosymbionts. Additionally, correlations between light‐REE and copper (Cu), zinc (Zn), and molybdenum (Mo) contents in soft tissues of chemosymbiotic mussels are ascribed to the uptake of these elements by the methanotrophic symbionts. An observed higher trace metal content in the tissue of the semi‐infaunal and infaunal bivalves with thiotrophic endosymbionts is believed to reflect the uptake of metals associated with sulfide particles. This study documents diagnostic enrichment of trace metals and light‐REE in the soft tissues of bivalves with chemotrophic endosymbionts and provides new constraints for future identification of chemosymbiosis at ancient seeps.

Microplastics in Mollusks: Research Progress, Current Contamination Status, Analysis Approaches, and Future Perspectives

Plastic fragments < 5 mm, known as microplastics (MPs), are ubiquitously present in the marine environment. Research on MPs pollution has gradually shifted from field investigations to laboratory studies. With the rapid growth of plastic consumption and the prevalence of aquaculture products, studies on marine MPs have focused on key marine species, such as mollusks. This review summarizes the recent knowledge including 77 important relevant literatures (from 2010 to 2021) on MPs contamination in mollusks with the objectives of (1) elucidating the current status of MPs pollution levels in mollusks, (2) highlighting the main methods and techniques for separation, extraction, and identification of MPs in soft tissues of bivalves and (3) presenting the current research progress and future directions. The review visually presents some of the important results in graphic form, which shows that the most common polymer plastics in bivalves are polypropylene, polystyrene, and polyethylene, and the shapes were mainly fiber and threadiness, mollusks are more likely to feed smaller MPs, most of the MPs in bivalves are less than 500 μm, and the abundance of MPs in seawater and the abundance of MPs in mollusks have a positive relationship, etc. This review will provide a comprehensive reference for studies of microplastics in marine organisms and the ecological pollution, and also has scientific guiding significance in the research method.

Laboratory studies on the biodegradation of organisms for estimating carbon storage potential in coastal aquatic ecosystems

ABSTRACT To assess the potential as carbon storages of short-life organisms in shallow coastal areas, refractory carbon fractions were examined using rapid biodegradation experiments. Refractory fractions of primary producers, such as seaweed and phytoplankton represented 31.2%−44.0% of the total carbon content. The seagrass Zostera marina contained a high rate of refractory carbon fraction, with 83.4% of the carbon in the belowground parts of Z. marina remaining as refractory carbon, which suggested that it had a significant function as a carbon storage in the shallow coastal area. The content of refractory carbon in the soft tissues of bivalves and gastropods were approximately 8.5%−31.5%, lower than that in other macrobenthos such as arthropods and echinoderms (29.7%−52.0%). The residual carbon in mollusk shells was mostly particulate inorganic carbon. In addition, 4.0%−19.1% of refractory organic carbon derived from polysaccharides and/or proteins in biominerals, while byssus remained. Considering the amount of shells in the shallow coastal zone, this organic carbon appeared to be a substantial carbon storage. Results suggested that not only primary producers but also macrobenthos and sessile animals have important carbon storage functions in coastal aquatic ecosystems.

Cadmium concentration in seawater, sediment and soft tissues of bivalves in the harvesting area in Van Don, Quang Ninh province

Cd concentrations were determined in coastal water, sediments and soft tissues of molluscs (hakf-crenate ark (Anadara subcrenata), noble scallop (Mimachlamys nobilis) and undulating venus (Paphia undulata)), which were collected from two stations in the harvesting area in Van Don, Quang Ninh province in 2014. In this study, cadmium concentration in seawater ranged from 0.22 µg.l-1 to 1 µg.l-1 while the concentration in sediment was from 0.59 mg.kg-1 to 1.55 mg.kg-1. Cd accumulated in hakf-crenate ark (Anadara subcrenata), noble scallop (Mimachlamys nobilis) and undulating venus (Paphia undulata) ranged from 0.81 mg.kg-1 to 1.48 mg.kg-1; from 0.35 mg.kg-1 to 2.23 mg.kg-1; from 0.25 mg.kg-1 to 0.81 mg.kg-1, respectively. Research result also showed that cadmium concentration in seawater in rainy season was higher than that in dry season while a contrary trend occurred in sediment. There was a weak correlation between Cd concentration in seawater and concentration of Cd in sediment in this area (r = 0.24). The cadmium fraction in sediment in this area was contributed as follows: residual component (F5) > Mn, Fe oxyhydroxide (F3) > organic matter-bound (F4) > acid soluble (F2) > ion-changeable (F1). Cadmium levels in tissues were in the order of stomach > mantle > gill > foot. Beside, cadmium components in adductor muscle of noble scallop were lowest. Therefore, the risk level for customer when consuming undulating venus (Paphia undulata), hakf-crenate ark (Anadara subcrenata) and adductor muscle was not high.

Corrigendum to “Sources of rare earth elements in shells and soft-tissues of bivalves from Tokyo Bay” [Mar. Chem. 194 (2017) 55–62

Corrigendum to “Sources of rare earth elements in shells and soft-tissues of bivalves from Tokyo Bay” [Mar. Chem. 194 (2017) 55–62

Sources of rare earth elements in shells and soft-tissues of bivalves from Tokyo Bay

Abstract Five species of bivalves (Japanese littleneck, blue mussel, trough shell, Stimpson's quahog, and Japanese dosinia) were collected from three different sites in Tokyo Bay and their shells and soft tissues were analyzed for rare earth element (REE) concentrations. Their REE compositions were compared with those of sediment and seawater at corresponding sites. To estimate the digestive strength of the bivalves, different acids were used to extract the elements in sediment for comparison of REE compositions. The REE concentrations of soft tissues were higher than those of shells. The REE abundance patterns of both shells and soft tissues resembled those of sediments or suspended particles rather than those dissolved in seawater, except for mussels. REE composites calculated by mixing particulate and dissolved REEs at much greater ratios for particulate REEs can explain the REE composition of both shells and soft-tissues. In the case of mussel shells, the contribution of REEs dissolved in seawater is important, but despite this most of mussel REEs similarly originate from suspended particles in seawater. This implies that a simple projection to seawater REEs from the REE composition of shells would be difficult. The apparent partitioning coefficients of REEs over Ca in shells ranged from 0.1 to 10 against REEs/Ca of seawater.

Comparative Metal Analysis of the Soft Tissues of Three Species of Anodonta (Class: Bivalvia) From Kubanni Lake in Zaria Nigeria

A comparative metal analysis was carried to determine the deposition and composition of metals in the soft tissues of freshwater bivalves; Anodonta anatina, A. marginata and A. implicata, and to establish their role as the possible routes to which metallic elements may get into the food chain. Collections of molluscs were made from four different sites along the bank and substratum of the lake, every two months from July 2011 to June 2012. Prepared soft tissues of the bivalves were digested by wet chemical method and subjected to multi-element analysis using Instrumental Neutron Activation Analysis. Nineteen metallic elements were analysed in the soft tissues of the bivalves, with some of the metals occurring below detectable limits. There was significantly variation (P 0.05) from the other two species. Chemically, the transition metals were higher in number of elements and concentrations with the metalloids having the least concentrations. Six of the metals from the bivalves (Mn, As, Cr, Fe, Co and Zn) are heavy metals. The concentrations of Mn, K, As, Fe, and Ba varied in the bivalves. High concentrations of Mn, K and Zn have been observed in this study. Highly significant positive and negative interactions were observed among the heavy metals. The significant variation in the concentrations of the metals shows that the different metals accumulate differently in the soft tissues of the bivalves. The high tolerance of metal load shown by these molluscs could be indicative of an adaptation to metal pollution. Such high concentrations of the heavy metals could be physiologically detrimental and impair their ecological roles in the Lake ecosystem. This study has shown that the bivalves showed similarity in the type of metals they accumulate and therefore could be used as reliable bio-indicators of metal pollution in the Lake and could serve as routes by which these metals could get to higher trophic levels of the food chain.

Similarities and differences of metal distributions in the tissues of molluscs by using multivariate analyses

Multivariate analysis including correlation, multiple stepwise linear regression, and cluster analyses were applied to investigate the heavy metal concentrations (Cd, Cu, Fe, Ni, Pb, and Zn) in the different parts of bivalves and gastropods. It was also aimed to distinguish statistically the differences between the marine bivalves and the gastropods with regards to the accumulation of heavy metals in the different tissues. The different parts of four species of bivalves and four species of gastropods were obtained and analyzed for heavy metals. The multivariate analyses were then applied on the data. From the multivariate analyses conducted, there were correlations found between the soft tissues of bivalves and gastropods, but none was found between the shells and the soft tissues of most of the molluscs (except for Cerithidea obtusa and Puglina cochlidium). The significant correlations (P < 0.05) found between the soft tissues were further complemented by the multiple stepwise linear regressions where heavy metals in the total soft tissues were influenced by the accumulation in the different types of soft tissues. The present study found that the distributions of heavy metals in the different parts of molluscs were related to their feeding habits and living habitats. The statistical approaches proposed in this study are recommended for use in biomonitoring studies, since multivariate analyses can reduce the cost and time involved in identifying an effective tissue to monitor the heavy metal(s) bioavailability and contamination in tropical coastal waters.

Determination of Cadmium Partitioning in Microalgae and Oysters: Contribution to the Assessment of Trophic Transfer

Alternative methodologies have been applied to the study of cadmium transfer in a food chain: water, microalgae (Skeletonema costatum and Tetraselmis suecica), oysters (Crassostrea gigas). The potential bioavailability of Cd in organisms was assessed through partitioning at the cell or tissue levels, and the predictive value of this method was evaluated by determining directly the metal transfer in an experimental food chain model. Cd concentrations were lower in S. costatum than T. suecica, in controls as well as in contaminated algae. In both algal species, Cd was firmly bound to the cell wall or had entered the cell. Cytosolic Cd was bound to intracellular ligands, the biochemical characteristics of which were not consistent with the hypothesis of detoxification via phytochelatins. In both algal species, Cd was predominantly present in the insoluble fraction, but at pHs such as those existing in the digestive tract of bivalves, it was easily extracted from the cells. Thus, exposure to Cd through phytoplanktonic food induced a significant uptake of this metal in soft tissues of bivalves. Due to the difference in Cd accumulation in algae, Cd doses associated with S. costatum were lower than those bound to T. suecica. Moreover, oysters retained a lower percentage of the metal associated with S. costatum compared to T. suecica (9 and 20%, respectively, after 21 days of exposure). Cd doses potentially available to oysters exposed directly in sea water were considerably higher, and direct uptake induced the highest levels of Cd incorporation but only 2% of dissolved Cd was actually retained by oysters over 21 days of exposure. In the soft tissues of oysters, Cd was distributed equally between soluble and insoluble fractions. Cytosolic Cd was present predominantly in the heat-stable fraction and mainly bound to compounds of molecular weight equal to 13.5 kDa. Moreover, a positive correlation was observed between metallothionein-like protein (MTLP) levels and gross concentrations of Cd in the soft tissues of oysters. These data are consistent with the hypothesis of an important role of metallothioneins in Cd metabolism in oysters and suggest a potential availability of MT-bound fraction of Cd to the consumers. These data are in agreement with the response of oysters exposed to Cd in the field.

Variations inter-spécifiques de la bioaccumulation et de la toxicité de l'argent á l'égard de trois mollusques bivalves marins

Previous data about silver in marine molluscs have shown a high variability of both accumulation and toxicity of this metal. A potential relationship between these factors has been examined. In a preliminary experiment, three species of bivalves ( Crassostrea gigas, Mytilus galloprovincialis, Chlamys varia) were exposed to silver concentrations varying from 1 to 1000 μg Agl −1 in order to determine parameters of lethal toxicity. Then, specimens of the same species were exposed to sub-lethal levels of silver through food (groups 2), water (groups 3) or both food and water (groups 4). In this main experiment, the level of silver was identical (20 μg Ag1 −1 in the culture medium of algae used as food and in the rearing medium of bivalves. Since the nominal levels of silver in water decreased during the experiment (Tables 1 and 2), seawater and contaminant were renewed every day. The species-related variations of mean lethal time (Table 3) revealed that the most resistant species was the oyster and the lesser one was the scallop. The resistance of oysters was mentioned previously by Martoja et al. (1988) who did not observe any cytological lesion in individuals exposed to silver in experimental conditions similar to those applied in the present study. The susceptibility of scallops has been confirmed since a moderate level of silver of 20 μg Ag l −1 was sufficient to disturb their attachment to the substratum (Table 4) as a consequence of a heavy accumulation of silver sulphide in glandular cells which secrete byssus threads (Martoja et al., 1990). The patterns of bioaccumulation in soft tissues were different in oysters—in which the maximal concentration was reached within 2 weeks (Fig. 1)—and in mussels—which this maximum was not reached after 4 weeks (Fig. 2). Exposure to silver via food induced a significant uptake of this metal in soft tissues of bivalves but it was low compared to uptake from seawater and to the contamination due to the double way of exposure (Table 5). However, the biomass of molluses per unit volume of culture medium varied from species to species. In order to compare strictly the specific ability to concentrate silver, we have determined the quantity of metal available (from food and/or water) per unit weight of filter-feeding organism over a definite period. Then we calculated the percentage of available silver retained by each species (Table 6). These results, as well as the literature data (Brooks and Rumsby, 1965; Folsom and Young, 1965; Preston et al., 1968; Bryan, 1973; Pouvreau and Amiard, 1974), show that Pectinidae and Ostreidae are able to retain very high levels of silver compared to Mytilidae. The species-related behaviour of silver may be interpreted from the point of view of ecotoxicological consequences: • -Species such as the oyster, with a low susceptibility and high ability to concentrate silver, could have an important role as the vector of contamination in food webs. • -Species such as the scallop, able to concentrate high levels of silver and very susceptible, could be eliminated from polluted ecosystens but, in these conditions, their role in trophic transfer will be limited. • -Species such as the mussel, which accumulate only low quantities of silver, will not have any role in food chain contamination and their intermediate susceptibility could have consequences only in highly polluted environments.