Mya Arenaria Research Articles

Long-term response of coastal macrofauna communities to de-eutrophication and sea level rise mediated habitat changes (1980s versus 2018)

Since the last decades, previous long-term Wadden Sea studies revealed significant changes in the abundance, biomass and spatial distribution of characteristic macrofauna communities in response to environmental changes and anthropogenic stressors. In this study, we performed statistical community analysis for the East-Frisian Wadden Sea (EFWS, southern North Sea) on two reference datasets across a period with severe climatic and environmental changes (1980s-2018). Therefore, historical macrofauna data from the Quantitative Sensitivity Mapping (1980s, SENSI 1) were reanalyzed and compared with data from the Synoptic Intertidal Benthic Survey (SIBES/SENSI 3) collected in 2018. Our results revealed significant quantitative and spatial changes in the characteristic macrofauna communities between the 1980s and 2018, most likely in response to de-eutrophication and sea level rise mediated habitat changes. Since the 1980s, the total number of taxa remained relatively stable (1980s: 90, 2018: 81), but the total abundance decreased by ca. -31% and the total biomass decreased by ca. -45%, particularly in the eastern regions of the study site probably due to de-eutrophication processes. Thereby, the mean abundances/m2 of ≥ -80% (1980s-2018) in the EFWS of several dominant species decreased: e.g. the gastropod Peringia ulvae, the polychaete Lanice conchilega and the bivalve Mya arenaria. In contrast, the mean abundance/m2 of one dominant species increased by ≥ +80% (1980s-2018): the invasive bivalve Ensis leei. The mean biomass [g/m2] of three dominant species decreased by ≥ -80% (1980s-2018): P. ulvae, L. conchilega and the amphipod Corophium volutator. In contrast, the mean biomass [g/m2] of one dominant species increased by ≥ +75% (1980s-2018): the polychaete Arenicola marina. In the western part of the EFWS, not only higher abundances of A. marina, but also of L. conchilega and P. ulvae were found in 2018, caused i.a. by sea level rise mediated decreasing mud contents and sand accretion on tidal flats. At the community level, the Oligochaeta/Heteromastus community increased in spatial distribution in the western EFWS in 2018 in the vicinity of increasing mussel/oyster beds.

Evidence of polystyrene nanoplastic contamination and potential impacts in Mya arenaria clams in the Saint-Lawrence estuary (Canada)

Plastic materials found in the environment are expected to degrade into smaller plastic nanoparticles (NPs) posing a greater toxic risk because they sorb contaminants and pass physiological barriers. Moreover the presence and effects of NPs is difficult to tease out from the contamination background at polluted sites. The purpose of this study was to examine for the presence of polystyrene NPs in feral Mya arenaria clam population near anthropogenic sources of pollution and potential toxic effects. Polystyrene NPs were determined by a newly developed fluorescence-based and size exclusion chromatography methodologies. Clam health status was determined by following changes in air survival time, condition factor, growth, alcohol/aldehyde dehydrogenase (AADH), protein aggregation and lactate dehydrogenase (LDH). In addition, multi-elemental analysis in tissues was also determined. The results revealed that clams collected at 2 polluted sites contained elevated amounts of polystyrene-like NPs between 10 and 110 nm in size based on size exclusion chromatography. Elevated levels of AADH suggest the presence of hydroxylated products and were correlated with plastic NPs in tissues. Moreover, principal component analysis revealed that As, Ca, Cu, Sn and V were closely related to either polystyrene-like NPs in tissues or AADH activity. Although we cannot rule out other pollutants, clams contaminated by polystyrene-like NPs had lower condition, growth rate, air survival time and LDH activity. Increased metal/element contamination reported to sorb onto plastic polymers were also related to NPs in tissues. In conclusion, clams populations close to anthropogenic sources of pollution show evidence of polystyrene-like NPs contamination and could contribute to decreased clam health status.

Effects of semidiurnal water column acidification and sediment presence on growth and survival of the bivalve Mya arenaria

In coastal environments, water column pH is affected by a variety of factors that result in lower and more variable pH in comparison to the open ocean. Consequently, it is critical to integrate variability in pH into laboratory experiments to better predict the response of coastal organisms to ocean acidification. For infaunal organisms, sediment can provide refuge from the water column conditions especially in coastal environments. As such, understanding how both water column conditions and the potential buffering abilities of sediment interact can provide insight into how infaunal organisms may respond to future oceanic conditions. Effects of pH variability on juvenile soft-shell clams (Mya arenaria; 2–11 mm in shell length), an ecologically and economically important species in the Bay of Fundy, Canada, were examined in a laboratory experiment. We manipulated pH through the addition of CO2 to seawater and exposed M. arenaria to three water treatments, no CO2 addition (mean ± sd; pH = 7.95 ± 0.06), semidiurnal intermittent CO2 addition (“on” pH =7.70 ± 0.13, “off” pH = 7.90 ± 0.11), and constant CO2 addition (pH = 7.73 ± 0.13). We found that M. arenaria final shell length, three mass metrics, and survival were negatively impacted by the constant CO2 addition treatment. Growth of juvenile M. arenaria only occurred in the presence of sediment, indicating the importance of sediment to M. arenaria, although sediment did not buffer the effects of constant CO2 addition. In the presence of sediment, the semidiurnal intermittent CO2 addition treatment did not negatively impact the growth of M. arenaria, indicating that it provided the clams with a recovery period. The similar growth rates of juvenile M. arenaria burrowed in sediment in the intermittent CO2 addition and control treatments suggests that M. arenaria may not be as negatively affected by future oceanic conditions as anticipated. This study demonstrated that pH variability can alter the response of benthic invertebrates to CO2 addition and thus this type of approach should be used to study other species of invertebrates.

Effects of different oxygen regimes on ecological performance and bioenergetics of a coastal marine bioturbator, the soft shell clam Mya arenaria

Benthic species are exposed to oxygen fluctuations that can affect their performance and survival. Physiological effects and ecological consequences of fluctuating oxygen are not well understood in marine bioturbators such as the soft-shell clam Mya arenaria. We explored the effects of different oxygen regimes (21 days of exposure to constant hypoxia (~4.1 kPa PO2), cyclic hypoxia (~2.1–~10.4 kPa PO2) or normoxia (~21 kPa PO2)) on energy metabolism, oxidative stress and ecological behaviors (bioirrigation and bioturbation) of M. arenaria. Constant hypoxia and post-hypoxic recovery in cyclic hypoxia led to oxidative injury of proteins and lipids, respectively. Clams acclimated to constant hypoxia maintained aerobic capacity similar to the normoxic clams. In contrast, clams acclimated to cyclic hypoxia suppressed aerobic metabolism and activated anaerobiosis during hypoxia, and strongly upregulated aerobic metabolism during recovery. Constant hypoxia led to decreased lipid content, whereas in cyclic hypoxia proteins and glycogen accumulated during recovery and were broken down during the hypoxic phase. Digging of clams was impaired by constant and cyclic hypoxia, and bioirrigation was also suppressed under constant hypoxia. Overall, cyclic hypoxia appears less stressful for M. arenaria due to the metabolic flexibility that ensures recovery during reoxygenation and mitigates the negative effects of hypoxia, whereas constant hypoxia leads to depletion of energy reserves and impairs ecological functions of M. arenaria potentially leading to negative ecological consequences in benthic ecosystems.

Биология двустворчатых моллюсков Mya arenaria (Linnaeus, 1758) губы Хлебная Кольского залива Баренцева моря

For the first time, data about distribution and biology of the bivalve mollusk Mya arenaria Linnaeus, 1758 living in the Kola Bay of the Barents Sea has been obtained. The work was carried out on the Khlebnaya Bay intertidal zone since March to November 2021 as a part of a complex coastal expedition of the MMBI RAS. The quantitative characteristics, size and age composition of the Mya arenaria settlement were investigated. The features of the allometric growth of mollusks are considered.

Assessing the size at maturity, spawning, and condition of the truncate soft-shell clam (Mya truncata) of southern Baffin Island, Nunavut, Canada.

The truncate soft-shell clam Mya truncata is an important source of country food for Inuit communities across the territory of Nunavut, Canada. M. truncata also plays an important role in marine ecosystems, yet there is little understanding of their life history and condition in Canadian Arctic waters. To provide a foundation on which aspects of the life history and condition of M. truncata of Baffin Island can be monitored in the future with a changing climate and fishery development, this study estimated size at maturity and provides insights into the spawning cycle and weight-length condition indices of clams from inner Frobisher Bay and the north shore of the Hudson Strait. Male and female M. truncata exhibited similar lengths at 50% attainment of sexual maturity, 31 mm and 32 mm shell length (SL), respectively. Most (77%) of the sexually mature M. truncata collected from inner Frobisher Bay in late August and 35% of clams collected from the Hudson Strait in early September were in the ripe stage of gonadal development. These results lead us to suggest a spring spawning season and that M. truncata invest in gonadal development for the next year’s spawning during the late summer-early autumn ice-free season while phytoplankton concentrations are high. Dry bodyweight-SL relationships were used to show that M. truncata condition can differ significantly over small and large spatial scales based on plotted 95% confidence intervals.

COI amplicon sequence data of environmental DNA collected from the Bronx River Estuary, New York City

In this data paper, we describe environmental DNA (eDNA) cytochrome c oxidase (COI) amplicon sequence data from New York City’s Bronx River Estuary. As urban systems continue to expand, describing and monitoring their biodiversity is increasingly important for sustainability. Once polluted and overexploited, New York City’s Bronx River Estuary is undergoing revitalization and restoration. To investigate and characterize the area’s diversity, we collected and sequenced river sediment and surface water samples from Hunts Point Riverside and Soundview Parks (ntotal = 48; nsediment = 25; nwater = 23). COI analysis using universal primers mlCOIintF and jgHCO2198 detected 27,328 Amplicon Sequence Variants (ASVs) from 7,653,541 sequences, and rarefaction curves reached asymptotes indicating sufficient sampling depth. Of these, eukaryotes represented 9,841ASVs from 3,562,254 sequences. At the study sites over the sampling period, community composition varied by substrate (river sediment versus surface water) and with water temperature, but not pH. The three most common phyla were Bacillariophyta (diatoms), Annelida (segmented worms), and Ochrophyta (e.g. brown and golden algae). Of the eukaryotic ASVs, we identified 614 (6.2%) to species level, including several dinoflagellates linked to Harmful Algal Blooms such as Heterocapsa spp., as well as the invasive amphipod Grandidierella japonica. The analysis detected common bivalves including blue (Mytilus edulis) and ribbed (Geukensia demissa) mussels, as well as soft-shell clams (Mya arenaria), in addition to Eastern oysters (Crassostrea virginica) that are being reintroduced to the area. Fish species undergoing restoration such as river herring (Alosa pseudoharengus, A. aestivalis) failed to be identified, although relatively common fish including Atlantic silversides (Menidia menidia), menhaden (Brevoortia tyrannus), striped bass (Morone saxatilis), and mummichogs (Fundulus heteroclitus) were found. The data highlight the utility of eDNA metabarcoding for analyzing urban estuarine biodiversity and provide a baseline for future work in the area.

Abstract PR017: Progression and regression dynamics of bivalve transmissible neoplasia in the soft-shell clam (Mya arenaria) after both natural and experimental exposure

Abstract In nature, cancer is not typically contagious – cancer lives and dies within a host. However, there are three known forms of clonal cancer lineages, in which the cancer cells themselves spread throughout populations by “jumping” from one animal to another. In mammals, there are two species known to be affected by these transmissible cancers – Tasmanian devils (Tasmanian Devil Facial Tumor Disease) and dogs (Canine Transmissible Venereal Tumor). In bivalves, transmissible cancers are found in at least six different species around the world, in which there are at least seven independently derived clonal neoplastic lineages. Mya arenaria (the soft-shell clam) is the first of these bivalve species confirmed to be affected by a Bivalve Transmissible Neoplasia (BTN). BTN was originally described as disseminated neoplasia when first documented in the 1970s. This disease is characterized by high numbers of rounded, polyploid, non-adherent neoplastic cells in the circulatory fluid (hemolymph) of animals that later disseminate into tissues during the final stages of disease, often proving fatal. In this emerging field, there is still much that is unknown regarding the dynamics of disease progression in vivo. I sought to define these dynamics for the first time. I analyzed hemolymph samples from both naturally infected and experimentally infected soft-shell clams, collected from Maine, USA, over the course of disease progression. Every two weeks, hemolymph was drawn from each animal, and the DNA was analyzed using a cancer-specific qPCR assay, which quantifies the copy number of a cancer-specific target (Steamer) and a control target (N1N2). I used the two values to determine the fraction of neoplastic cells found in the hemolymph of each animal at every two-week timepoint. I have observed three main disease outcomes for both naturally and experimentally infected animals - 1) progression to death; 2) regression; and 3) long-term non-progression. My observation of significant regression and non-progression in clams exposed to BTN contrasts earlier reports suggesting near complete lethality of the disease. This finding may suggest that clam populations have evolved resistance to this cancer. Interestingly, I additionally observed a consistent long latent period after injection in the experimentally infected animals where neoplastic cells were undetectable in the hemolymph for a period of 16-20 weeks before progression. Based on my findings of this latent period, where no cancer is detectable in the hemolymph of infected animals, I hypothesize that the cells may be engrafting into a solid tissue rather than solely dividing and circulating in the hemolymph itself as originally hypothesized. These findings are a significant starting point in understanding how BTN can transmit both within individuals and throughout populations, potentially providing remarkable insight into cancer evolution and host resistance. Citation Format: Rachael M. Giersch, Marisa A. Yonemitsu, Samuel F.M. Hart, Michael J. Metzger. Progression and regression dynamics of bivalve transmissible neoplasia in the soft-shell clam (Mya arenaria) after both natural and experimental exposure [abstract]. In: Proceedings of the AACR Special Conference on the Evolutionary Dynamics in Carcinogenesis and Response to Therapy; 2022 Mar 14-17. Philadelphia (PA): AACR; Cancer Res 2022;82(10 Suppl):Abstract nr PR017.

Abstract A003: Genome evolution of a transmissible cancer in the soft-shell clam (Mya arenaria)

Abstract A small number of transmissible cancer lineages exist in which cancer cells metastasize repeatedly to new hosts and live past the death of their original hosts. Transmissible cancers have been observed in the dog, Tasmanian devil, and most recently in numerous bivalves species, including one lineage that has spread through the soft-shell clam (Mya arenaria) population along the east coast of North America. We assembled a highly contiguous 1.2 Gb soft-shell clam reference genome and characterized the genome evolution of this transmissible cancer lineage. Our analyses confirm that all cancer samples descended from a single founder clam, but cluster in two geographically separated sub-lineages. In both sub-lineages, we observe high somatic mutation density, widespread copy number gain, structural rearrangement and transposable element activity, all indicative an unstable cancer genome. We also discovered a novel mutational signature generating mutations at a stable rate, predicting the cancer to be 344 to 877 years old and indicating it spread undetected long before it was first observed in the 1970s. Citation Format: Samuel F.M. Hart, Rachael M. Giersch, Marisa A. Yonemitsu, Brian Beal, Stephen P. Goff, Michael J. Metzger. Genome evolution of a transmissible cancer in the soft-shell clam (Mya arenaria) [abstract]. In: Proceedings of the AACR Special Conference on the Evolutionary Dynamics in Carcinogenesis and Response to Therapy; 2022 Mar 14-17. Philadelphia (PA): AACR; Cancer Res 2022;82(10 Suppl):Abstract nr A003.

Abstract A023: Progression and regression dynamics of bivalve transmissible neoplasia in the soft-shell clam (Mya arenaria) after both natural and experimental exposure

Abstract This abstract is being presented as a short talk in the scientific program. A full abstract is available in the Proffered Abstracts section (PR017) of the Conference Proceedings. Citation Format: Rachael M. Giersch, Marisa A. Yonemitsu, Samuel F.M. Hart, Michael J. Metzger. Progression and regression dynamics of bivalve transmissible neoplasia in the soft-shell clam (Mya arenaria) after both natural and experimental exposure [abstract]. In: Proceedings of the AACR Special Conference on the Evolutionary Dynamics in Carcinogenesis and Response to Therapy; 2022 Mar 14-17. Philadelphia (PA): AACR; Cancer Res 2022;82(10 Suppl):Abstract nr A023.

Global Crystallographic Texture of Freshwater Bivalve Mollusks of the Unionidae Family from Eastern Europe Studied by Neutron Diffraction.

The crystallographic texture of the whole valves of bivalve mollusks from the family Unionidae Unio pictorum Linnaeus, 1758 and Anodonta cygnea Linnaeus, 1758 is studied using pole figures measured using neutron diffraction. The use of neutron diffraction, in contrast to X-rays, makes it possible to study the valves without destroying them. Thus, we can discuss the study of the global texture of the entire valve. It was revealed that the pole figures of aragonite in the valves repeat their shape. The pole density maxima for U. pictorum from the Danube Delta and the Gulf of Finland in the Baltic Sea, living at different salinities and temperatures, differs by 0.41 mrd. The maximum value of the crystallographic texture for A. cygnea from the Danube Delta was also measured (5.07 mrd). In terms of texture sharpness, it surpasses the shell of marine bivalve mollusks, which are partially or completely composed of aragonite. Although U. pictorum and Mya arenaria Linnaeus, 1758 have different microstructures, their pole figures are very similar in isolines pattern, but differ in pole density maxima. No relationship was found between the crystallographic texture and the microstructure in U. pictorum. In addition, we report good qualitative agreement between aragonite X-ray pole figures of Sinanodonta woodiana Lea, 1834 from the Czech river Luznice, and neutron pole figures of U. pictorum from the Danube Delta.

Ultra-conserved elements provide insights to the biogeographic patterns of three benthic macroinvertebrate species in the Baltic Sea

The Baltic Sea, with its steep salinity gradient, high water retention time, and relatively young age, represents a marginal ecosystem between marine and freshwater extremes. Due to differing invasion history and dispersal capabilities of Baltic species, there are large differences in species distributions, species-specific genetic structure and variation, and edge populations that may represent both a subset of the original population, as well as unique genetic lineages. We used a phylogenomic approach to investigate relationships between populations of three benthic macroinvertebrate species: Pygospio elegans, Corophium volutator, and Mya arenaria, providing new insight into evolutionary dynamics among populations in the Baltic Sea and the adjacent North Sea. We found little relation among the populations of P. elegans and C. volutator, in contrast to M. arenaria, which exhibits a higher degree of resemblance between populations. We also found low relation within sites sampled at different times of the year for all species. Each species exhibited unique phylogenetic patterns, suggesting the North Sea populations of P. elegans and M. arenaria are closely related to populations within the Baltic Sea, and with only C. volutator showing trends resembling isolation by distance. These differences could be explained by both their different invasion histories and dispersal capabilities of the individual species.

Effect of Predator Exclusion on Softshell Clam (Mya arenaria L.) Recruitment

Despite estimates of very high (>99.9%) pre-settlement mortality, the extremely large numbers of eggs released into the plankton means that there are abundant post-larval softshell clams (Mya arenaria) available to settle and populate intertidal flats. Many seemingly suitable flats remain devoid of clams, presumably due to post-settlement predation. Predator exclusion/clam recruitment boxes (wooden frames covered top and bottom with a fine plastic screening) were set on a mudflat in Salem Harbor, Salem, MA from April to November 2019. Clam larvae were able to settle through the screen into the boxes but large (>1.9 mm) predators such as European green crabs (Carcinus maenas) and milky ribbon worms (Cerebratulus lacteus) were excluded. At the end of the study, four of five boxes contained between 121 and 290 juvenile softshell clams ranging in size from 7 mm to 32 mm shell length. A bimodal frequency distribution of sizes likely illustrates an early summer (June) set represented by a larger size grouping followed by a second late-summer set represented by a smaller size grouping. Small green crabs (9–46 mm carapace width) found in all five boxes must have grown from extremely small stage 1 crabs that were able to settle or crawl through the screening as recently settled individuals. Resulting empty clam shells could be paired to yield the equivalent of additional clams, making the total number per box between 147 and 417 individuals. No clams were found in samples outside of the boxes, indicating that the absence of a clam population on the mudflat is due to post-settlement predation and not pre-settlement mortality.

Seasonal Changes in Shell Microstructure of Some Common Bivalve Molluscs in the Mid-Atlantic Region

Bivalve molluscs record histories of individual growth as alternating periods of activity (shell deposition) and inactivity (growth cessation marks) within their multilayered shells, and in some species, as alternating sublayers with different morphology. Shell growth patterns reflect tidal, daily, and seasonal cycles of key environmental parameters, such as submergence and temperature, which influence physiology (e.g., feeding, respiration, metabolic rates, and reproductive cycles). Knowledge of the periodicity of formation of various structures within the shell enables researchers to place a calendar across the growth history of an animal knowing only the date of collection. In turn, this enables both the determination of age (essential in studies of population dynamics) and the assessment of how bivalve populations responded to known environmental events, be they anthropogenic or natural, after the event has occurred. Seasonal microstructural shell growth patterns of six common bivalve species living in fresh (Corbicula fluminea O. F. Müller, 1774), brackish (Rangia cuneata G. B. Sowerby I, 1832), lower estuarine (Geukensia demissa Dillwyn, 1817), coastal (Mytilus edulis Linnaeus, 1758 and Mya arenaria Linnaeus, 1758), and continental shelf (Spisula solidissima Dillwyn, 1817) habitats in the mid-Atlantic region of the United States are documented using optical and scanning electron microscopy based on collections in the late 1980s. Some of the works have been published previously, but the results for each of the six species are combined and summarized in one volume as a guide to the seasonal shell microstructure for some common bivalves in New Jersey waters. The utility of shell growth pattern analysis in environmental impact assessments and population dynamics studies is evaluated within each habitat and example applications are provided. Although the results reported here were from studies conducted over 30 y ago, they represent collectively a contribution to our knowledge of molluscan shell microstructure that remain relevant today and are published as a coherent monograph before they are lost as so many other important unpublished works have been as time ran out on aging authors before they could relay the precious secrets they uncovered over the years.

The commonly applied Brey model to estimate benthic secondary production cannot be used for communities dominated by large bivalves

The Brey model to calculate secondary production from data on biomass and mean individual weight is widely used, but so far it has not been tested for communities in which one or a few species dominate. On the base of a long-term (tens of years) data series on estimates of densities, biomass, mean individual weights and annual production of the most important bivalve species (together accounting for about 60% of the zoobenthic biomass) in a vast tidal-flat area, we compared production values obtained by two methods: the weight-increment summation method and the Brey model. In 4 out of the 5 studied bivalve species, the Brey estimates were on average substantially lower than the direct estimates. As a consequence, the Brey method seriously underestimated the production of the entire bivalve community in about half of the years. In 10 out of the 28 years, the Brey estimates were even less than half of the actual bivalve production. The one species (Limecola balthica) with a satisfactory match between the two methods was (as contrasted to the 4 other species: Cerastoderma edule, Mytilus edulis, Mya arenaria, Ensis leei) characterized by low annual weight increments and the simultaneous presence of many year classes, none of them strongly dominating. As secondary production of the studied ecosystem is dominated by the group of large bivalves, Brey estimates for such bivalve-dominated systems are inadequate for a study of their functioning.

Stable isotopes reveal minimal spatial and temporal variation in diet of the wrymouth (Cryptacanthodes maculatus)

AbstractPredation by infaunal and epibenthic predators is often an important determinant of marine soft‐bottom community structure. The role of the predatory, benthic‐dwelling fish, the wrymouth (Cryptacanthodes maculatus), in the soft‐bottom food web has received little attention. The purpose of our study was to examine spatial and temporal variability in diet and trophic position of wrymouth at two lower intertidal sites in eastern Maine, USA. Wrymouth, their potential prey, and primary producers were collected in the spring and summer of 2013 in Machiasport and Beals, Maine. Stable isotope analysis was used to determine trophic position of the fish and its potential diet. Wrymouth δ13C signatures were influenced by location and ranged from −12.6‰ to −11.5‰, whereas δ15N signatures varied little (12.3‰–12.7‰) between locations or seasons. Wrymouth trophic position ranged from 3.02 to 3.48, indicating that they are tertiary consumers. The intertidal zone consisted of two distinct clusters of taxa, characterized by the presence of either macroalgae (mostly fucoids) or eelgrass (Zostera marina). Wrymouth diet consisted primarily of predatory polychaetes. Stable carbon and nitrogen isotope signatures varied across seasons and locations for multiple species, including our base species, Mya arenaria. Results suggest wrymouth are generalist feeders with limited seasonal and spatial variation in diet. Bottom‐up processes, however, are fundamentally different between the two study sites and influence their trophic structure. This result highlights the importance of collecting baseline data and evaluating trophic interactions at multiple spatial scales within small regional areas in coastal systems.

Long-term investigation of heavy metal variations in mollusks along the Chinese Bohai Sea

Biomonitoring is an effective way to assess the effects of pollutants on marine ecosystems. As an important fishing region in China, the Chinese Bohai Sea has been contaminated with heavy metals, posing great risks to seafood safety and human health. Herein, the spatiotemporal variations in the concentrations of seven heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) in 11 species of mollusks (658 samples) collected from the Chinese Bohai Sea were studied during 2006–2016. The concentrations of Cr, As, Cd, and Pb in approximately 41%, 100%, 71%, and 18% of the sampled mollusks exceeded the maximum permissible levels in aquatic products set by China, indicating that the mollusks were contaminated with varied concentrations of heavy metals. Except for slight fluctuations, no significant temporal variations were observed during the sampling period, suggesting a relatively stable status of these metals. Cluster analysis showed that oyster had higher bioaccumulation potential for Zn and Cu, whereas Mactra veneriformis, Rapana venosa, Meretrix meretrix, Chlamys farreri, and Mya arenaria had higher bioaccumulation potentials for Cr, As, Ni, Cd, and Pb, respectively. These findings are useful for biomonitoring and developing guidelines for seafood consumption in coastal regions. Significant relationships were observed between heavy metal concentrations in mollusks and socioeconomic indices (gross domestic product, per capita gross domestic product, and population amount), suggesting the effects of anthropogenic activities on heavy metal contamination. Our study established a good model to evaluate the risks of heavy metals and provided a sound scientific basis for controlling seafood safety in coastal regions.

Мікроскопічні водорості водойм Кінбурнської піщаної коси (НПП «Білобережжя Святослава», Україна)

Taxonomical composition of microscopic algae of different reservoirs (Dnieper estuary, Kefalny, Guryansky and Cherepashy lakes, Yagorlytsky Bay) of the Kinburn sand spit of north-western part of the Black Sea (National Nature Park “Biloberezhzha of Svyatoslav”) is studied. Material tests that is collected on sandy and silty soils served as for researches, and also in becoming overgrown with of mussels Mytilus galloprovincialis Lamarck, Mya arenaria L., Cerastoderma lamarcki Reeve and Balanus improvisus Darwin, macroscopic algae (Ceramium virgatum Roth, Cladophora vagabunda (L.) Hoek, C. siwaschensis C.Meyer, Ulva intestinalis L., Polysiphonia elongata (Huds.) Harv.) of Kіnburnska braid from September in 2019 for October in 2021. On the whole it was collected and analysed 90 standards. 116 species of microscopic algae are educed, that to 74 genera, 52 families, 31 orders, 9 classes, 6 divisions, belong, 3 kingdoms and 2 empires. After systematic composition Bacillariophyta (76 species) prevailed above Cyanophyta (26), Chlorophyta (7), Dinophyta (3), Chrysophyta (3) and by Haptophyta (1). 86 species of algae were found in the microphytobenthos of Yagorlyk Bay, 56 in Dnieper estuary, 33 in Cherepashy, 22 in Guryansky and 17 in Kefalny lakes. As a result of researches it was educed 2 new and 4 rare species of microscopic algae for the aquatorium of the Black Sea.

Survival and Detection of Bivalve Transmissible Neoplasia from the Soft-Shell Clam Mya arenaria (MarBTN) in Seawater.

Many pathogens can cause cancer, but cancer itself does not normally act as an infectious agent. However, transmissible cancers have been found in a few cases in nature: in Tasmanian devils, dogs, and several bivalve species. The transmissible cancers in dogs and devils are known to spread through direct physical contact, but the exact route of transmission of bivalve transmissible neoplasia (BTN) has not yet been confirmed. It has been hypothesized that cancer cells from bivalves could be released by diseased animals and spread through the water column to infect/engraft into other animals. To test the feasibility of this proposed mechanism of transmission, we tested the ability of BTN cells from the soft-shell clam (Mya arenaria BTN, or MarBTN) to survive in artificial seawater. We found that MarBTN cells are highly sensitive to salinity, with acute toxicity at salinity levels lower than those found in the native marine environment. BTN cells also survive longer at lower temperatures, with 50% of cells surviving greater than 12 days in seawater at 10 °C, and more than 19 days at 4 °C. With one clam donor, living cells were observed for more than eight weeks at 4 °C. We also used qPCR of environmental DNA (eDNA) to detect the presence of MarBTN-specific DNA in the environment. We observed release of MarBTN-specific DNA into the water of laboratory aquaria containing highly MarBTN-diseased clams, and we detected MarBTN-specific DNA in seawater samples collected from MarBTN-endemic areas in Maine, although the copy numbers detected in environmental samples were much lower than those found in aquaria. Overall, these data show that MarBTN cells can survive well in seawater, and they are released into the water by diseased animals. These findings support the hypothesis that BTN is spread from animal-to-animal by free cells through seawater.

Spatio-Temporal Variation of Elemental Contamination and Health of Mya arenaria Clam in the Saguenay–St. Lawrence Marine Park

The impacts of pollution and long-term effects of local clam populations are misunderstood in estuaries. The purpose of this study was to follow inorganic contamination in tissues, changes of physiological health indicators, such as condition factor (CF), growth index (GI), resistance in air emersion and dehydration rate, for 5 years in Mya arenaria clams. The sampling scheme comprised one reference site, two sites impacted by human activity (thereafter polluted) and one site recognized as a Saint-Lawrence Estuary (SLE) beluga whale feeding area without known pollution source (Baie Sainte-Marguerite (BSM)). This study revealed that the elemental contamination profiles in clams were increased but differed between the polluted and BSM compared to the reference site. At polluted sites, clams were contaminated by Ag (2.4-fold of reference site), Mn (2.5-fold) and V (6.3-fold). With respect to BSM, clams were mainly contaminated by Ce (2.5-fold), Co (2-fold), Ga (2-fold), La (2.8-fold), Hg (2.5-fold), Ni (2.2-fold), Sm (2-fold) and V (20-fold). This contamination profile suggests sources of pollution from particulate combustion products of gasoline/diesel, crude oil and urban inputs of pollution. The CF, GI and air survival time were all reduced in clams at the polluted sites, while only the CF and dehydration rates were decreased and increased, respectively, at BSM. Long-term analysis revealed that CF and GI tended to decrease over time with episodes of strong amplitude changes and became more resilient to air survival time. In conclusion, the long-term contamination of clams towards metals and elements could compromise the health status of local clam populations. The increased contamination of clams at BSM could represent a risk to the endangered SLE beluga whale population.