Oyster Magallana Gigas Research Articles

A granulocyte highly-expressed α2 adrenergic receptor promotes the expression of IL-17 and TNFs in the immune response of oyster Magallana gigas

A granulocyte highly-expressed α2 adrenergic receptor promotes the expression of IL-17 and TNFs in the immune response of oyster Magallana gigas

Investigating Non-Native Ribbon Worm Cephalothrix simula as a Potential Source of Tetrodotoxin in British Bivalve Shellfish.

Tetrodotoxin (TTX) is a potent marine neurotoxin found in several phylogenetically diverse organisms, some of which are sought as seafood. Since 2015, TTX has been reported in bivalve shellfish from several estuarine locations along the Mediterranean and European Atlantic coasts, posing an emerging food safety concern. Although reports on spatial and temporal distribution have increased in recent years, processes leading to TTX accumulation in European bivalves are yet to be described. Here, we explored the hypothesis that the ribbon worm species Cephalothrix simula, known to contain high levels of TTX, could play a role in the trophic transfer of the toxin into shellfish. During a field study at a single location in southern England, we confirmed C. simula DNA in seawater adjacent to trestle-farmed Pacific oysters Magallana gigas (formerly Crassostrea gigas) with a history of TTX occurrence. C. simula DNA in seawater was significantly higher in June and July during the active phase of toxin accumulation compared to periods of either no or continually decreasing TTX concentrations in M. gigas. In addition, C. simula DNA was detected in oyster digestive glands collected on 15 June 2021, the day with the highest recorded C. simula DNA abundance in seawater. These findings show evidence of a relationship between C. simula and TTX occurrence, providing support for the hypothesis that bivalves may acquire TTX through filter-feeding on microscopic life forms of C. simula present in the water column at particular periods each year. Although further evidence is needed to confirm such feeding activity, this study significantly contributes to discussions about the biological source of TTX in European bivalve shellfish.

Dasysiphonia adriatica sp. nov. (Delesseriaceae, Rhodophyta), a new red algal species from the North Adriatic Sea (Mediterranean Sea)

Dasysiphonia is a genus of the family Delesseriaceae (Rhodophyta) including 9 taxonomically accepted species, among which only the non-indigenous Dasysiphonia japonica has been documented from the Adriatic Sea (Mediterranean). This invasive species is native to Hokkaido Island (Japan) and was introduced to Europe and the Mediterranean Sea through imports of the commercial Pacific oyster Magallana gigas. In this study, we describe a new species belonging to the genus Dasysiphonia, collected in the Mediterranean Sea. This new taxon was sampled in Slovenian coastal waters; its thalli were analysed using both molecular and morphological approaches and it was compared with the other known species. Moreover, samples of the invasive D. japonica were collected from different Venice Lagoon (Italy) sites and used for comparison with the new taxon. The phylogenetic reconstruction, based on the plastid rbcL gene, clearly distinguished the new Slovenian entity from all the known Dasysiphonia species, including the ones recently transferred from the sister genus Dasya. These results indicate that the Slovenian samples represent a new species, hereby named Dasysiphonia adriatica sp. nov.

Dietary regulation of gut bacteria in the Pacific oyster Magallana gigas and Mediterranean mussel Mytilus galloprovincialis

Feed composition affects the gut bacterial community in aquatic species, but little is known about how diet type impacts gut microbiota in molluscan bivalves. This study investigates the impact of feed composition on the gut bacterial community in two commercially important bivalves: Pacific oyster Magallana gigas and Mediterranean mussel Mytilus galloprovincialis. Oysters and mussels were fed with two types of marine algae, live Isochrysis galbana (microalgae) and the dried seaweed powder Ulva sp. (macroalgae) under a laboratory condition for two months. The V1–V2 region of the 16S rDNA was sequenced through an Illumina MiSeq platform to compare the gut bacterial community of oysters and mussels at the start and the end of the feeding trial. Feed composition directly impacted both alpha and beta diversities of gut microbiota, but the degree of the impact differed between bivalve species. The difference in the gut bacterial assemblages of oysters and mussels in the pre- and post-feeding trials indicated that the diet type and host species shape the composition of gut bacteria. Spirochaeta was absent in mussel guts during the pre- and post-feeding trials but was present in oysters, revealing host specificity in colonizing gut bacteria. The results suggest that the diet type and host species can significantly impact the gut bacterial community structure. This study confirms that diet can modulate gut microbial composition in marine filter-feeding organisms, but the extent of dietary modulation depends on feed type and host species.

Beyond annual metrics: Linking seasonal population dynamics to vertical oyster reef growth.

Oysters are ecosystem engineering species building reef-like biogenic structures in temperate shallow water environments, serving as biodiversity hotspots. Recently, also their ecosystem services such as fish nursery, pollutants sink and self-sustaining coastal protection mechanisms came into a research focus. In light of accelerated sea level rise and increasing environmental dynamics, a determination of vertical growth rates of these biosedimentary structures is paramount in assessing their resilience. This study embarked on a comprehensive survey of seasonal vertical reef growth rates using terrestrial laser scanning and related population dynamics of two intertidal reefs built by the non-native oyster Magallana gigas in the Wadden Sea. We quantified median reef growth at 19.8 mm yr-1 for the Kaiserbalje reef and 17.5 mm yr-1 for the Nordland reef. Additionally, we tested the hypothesis that the seasonal variations in reef growth rates correspond to the local population dynamics, mainly the parameters of shell length and abundance which mirror delayed effects from previous spawning events. Shell growth rates were 0.03-0.06 mm d-1 in winter and 0.10-0.16 mm d-1 in summer, mean oyster abundance from autumn 2019 to spring 2022 was 627 ± 43 ind. m-2 and 338 ± 87 ind. m-2 at the Kaiserbalje and Nordland reefs respectively. Minor reef growth in the topmost reef area reflects an emerging equilibrium of the vertical reef position to actual sea level. Our findings are in accordance with growth of natural Crassostrea virginica reefs on the US East Coast, indicating potential resilience to actual and predicted sea level rise scenarios. Moreover, understanding local hydro-morphodynamic feedback linked to sea level rise will be vital in predicting the three-dimensional stability of these biosedimentary structures and habitats.

Intraspecific variations in oyster (Magallana gigas) ploidy does not affect physiological responses to microplastic pollution

Recent advances in genetic manipulation such as triploid breeding and artificial selection, have rapidly emerged as valuable hatchery methodologies for enhancing seafood stocks. The Pacific oyster Magallana gigas is a leading aquaculture species worldwide and key ecosystem engineer that has received particular attention in this field of science. In light of the growing recognition of the ecological effects of intraspecific variation, oyster polyploids provide a valuable opportunity to assess whether intraspecific diversity affects physiological responses to environmental stressors. While the responses of diploid and triploid oysters to climate change have been extensively investigated, research on their sensitivity to environmental pollution remains scarce. Here, we assess whether genotypic (i.e., ploidy) variation within Magallana gigas affects physiological responses to microplastic pollution. We show that diploid and triploid M. gigas have similar clearance rates and ingest similar amounts of microplastics under laboratory-controlled condition. In addition, they exhibited similar heart rates after prolonged exposure to microplastic leachates. Our findings suggest that intraspecific variations within M. gigas ploidy does not affect oyster responses to microplastic pollution. However, regardless of ploidy, our work highlights significant adverse effects of microplastic leachates on the heart rate of M. gigas and provides evidence of microplastic ingestion in the laboratory.

Genome-wide identification of the HSP70 genes in Pacific oyster Magallana gigas and their response to heat stress.

Heat shock protein 70 (HSP70), the most prominent and well-characterized stress protein in animals, plays an important role in assisting animals in responding to various adverse conditions. In the present study, a total of 113 HSP70 gene family members were identified in the updated genome of Magallana gigas (designated MgHSP70) (previously known as Crassostrea gigas). There were 75, 12, 11, and 8 HSP70s located in the cytoplasm, nucleus, mitochondria, and endoplasmic reticulum, respectively, and 7 HSP70s were located in both the nucleus and cytoplasm. Among 113 MgHSP70 genes, 107 were unevenly distributed in 8chromosomes of M. gigas with the greatest number in chromosome 07 (61 genes, 57.01%). The MgHSP70 gene family members were mainly assigned intofive clusters, among which the HSPa12 subfamily underwent lineage-specific expansion, consisting of 89 members. A total of 68 MgHSP70 genes (60.18%) were tandemly duplicated and formed 30 gene pairs, among which 14 gene pairs were under strong positive selection. In general, the expression of MgHSP70s was tissue-specific, with the highest expression in labial palp and gilland the lowest expression in adductor muscle and hemocytes. There were 35, 31, and 47 significantly upregulated genes at 6, 12, and 24h after heat shock treatment (28°C), respectively. The expression patterns of different tandemly duplicated genes exhibited distinct characteristics aftershock treatment, indicating that these genes may have different functions. Nevertheless, genes within the same tandemly duplicated group exhibit similar expression patterns. Most of the tandemly duplicated HSP70 gene pairs showed the highest expression levels at 24h. This study provides a comprehensive description of the MgHSP70 gene family in M. gigas and offers valuable insights into the functions of HSP70 in the mollusc adaptation of oysters to environmental stress.

Comparison of the effects of reef and anthropogenic soundscapes on oyster larvae settlement

Settlement is a critical period in the life cycle of marine invertebrates with a planktonic larval stage. For reef-building invertebrates such as oysters and corals, settlement rates are predictive for long-term reef survival. Increasing evidence suggests that marine invertebrates use information from ocean soundscapes to inform settlement decisions. Sessile marine invertebrates with a planktonic stage are particularly reliant on environmental cues to direct them to ideal habitats. As gregarious settlers, oysters prefer to settle amongst members of the same species. It has been hypothesized that oyster larvae from species Crassostrea virginica and Ostrea angasi use distinct conspecific oyster reef sounds to navigate to ideal habitats. In controlled laboratory experiments we exposed Pacific Oyster Magallana gigas larvae to anthropogenic sounds from conspecific oyster reefs, vessels, combined reef-vessel sounds as well as off-reef and no speaker controls. Our findings show that sounds recorded at conspecific reefs induced higher percentages of settlement by about 1.44 and 1.64 times compared to off-reef and no speaker controls, respectively. In contrast, the settlement increase compared to the no speaker control was non-significant for vessel sounds (1.21 fold), combined reef-vessel sounds (1.30 fold), and off-reef sounds (1.18 fold). This study serves as a foundational stepping stone for exploring larval sound feature preferences within this species.

In-situ verification of a deep-learning-based larval identification system for the Pacific oyster Magallana gigas

Natural seedlings are collected for use at Pacific oyster (Magallana gigas) aquaculture sites in Japan. For seedling collection to be successful, aquaculture farmers identify target larvae through microscopic observation, using morphological features such as the shell height/shell length ratio, lateral asymmetry of the shell, and umbo development. To reduce the time and labor associated with larval identification, we developed a deep-learning-based Pacific oyster larvae identification system, which consisted of a tablet connecting a new photographic device to capture images for identification. The final accuracies of the trained identification system for the learning datasets for measuring accuracy were 82.5% and 80.5% for precision (P) and recall (R), respectively, for all sizes of larvae (shell height ≥100 µm). We verified our identification system at an oyster aquaculture site. The obtained accuracy in the verification was low for some samples (63.6%–100.0% and 41.9%–100.0% for P and R, respectively, for pre-attachment stage larvae), indicating a decrease in identification accuracy for the in-situ samples. The decrease likely occurred owing to the natural variability of larvae. We modified the learning dataset with high variation in oyster larval images and retrained the identification system. The accuracy of the retrained identification system was increased to 83.9%–100.0% for P and R and thus satisfied the requirements for practical application for pre-attachment stage larvae. For small-sized larvae, P was improved but R was relatively low, indicating that although the detection level of our identification model for oyster larvae is low, the accuracy of the detected oyster larvae is high.

Short communication: The boring sponge (Pione vastifica, Hancock, 1849) induces oxidative stress in the Pacific oyster (Magallana gigas, Thunberg, 1793)

Boring sponge infection affects growth, development and reduces the soft tissue weight of oysters. In this study, we investigated the effects of boring sponge on the activity of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GP)) in the mantle, and the production of reactive oxygen species (ROS) and potential genotoxicity in hemocytes of the Pacific oyster Magallana gigas. Our results showed a significant increase in ROS production and DNA damage in hemocytes. Notably, the activity of SOD, CAT, and GP in the mantle was not significantly affected by boring sponge infection. Collectively, these results suggest that sponge invasion may cause oxidative stress in Pacific oyster hemocytes through ROS overproduction.

Biochemical responses in Pacific oysters Magallana gigas (Thunberg, 1793): Tools to evaluate the environmental quality of aquaculture areas

The discharge of sanitary sewage into the bays of the Florianópolis Metropolitan Area (Southern Brazil), has led to the contamination of oyster farms. Consequently, linear alkylbenzenes (LABs) were quantified in the sediment, and the biochemical responses in gills and digestive gland of oysters from six farms were assessed. Our findings revealed elevated levels of LABs in the sediment of the Imaruim and Serraria farms. Additionally, alterations were observed in the antioxidant enzymes: catalase, glutathione peroxidase and superoxide dismutase in both oyster tissue from the Serraria, Santo Antonio de Lisboa and Sambaqui farms. Furthermore, correlation analyses indicated strong and moderate associations between biochemical responses, organic contaminants, and certain physicochemical parameters. Consequently, our results demonstrated the activation of the antioxidant system in oysters, representing a protective response to the presence of sanitary sewage and other contaminants. Therefore, we propose the utilization of biochemical biomarkers for monitoring the environmental quality of farms.

Antimicrobial Resistance Profile of Planctomycetota Isolated from Oyster Shell Biofilm: Ecological Relevance within the One Health Concept

Background: Planctomycetota isolation in pure culture is still challenging with most of the reported data coming from molecular-based methods. Here, we intended to isolate Planctomycetota from the filter-feeder Pacific oyster Magallana gigas, extending the search to a not yet explored natural reservoir and to characterize their antimicrobial resistance phenotype. Methods: Oyster samples from different supermarkets and from a farm producer were subject to isolation in selective medium. Inoculation was performed from the shell biofilm and after an enrichment of the edible content. Results: Planctomycetota isolates (n = 65) were only obtained from the shell biofilm with four different species identified: Rhodopirellula baltica (n = 62), Rhodopirellula rubra (n = 1), Rhodopirellula heiligendammensis (n = 1) and Gimesia chilikensis (n = 1). This study reports the first association of Planctomycetota members with oysters and the first description of R. heiligendammensis in Portugal. Moreover, R. rubra, originally identified in Portugal, was isolated from oysters of French origin. Antibiotic susceptibility testing, conducted in strains belonging to two species never assayed before revealed multidrug resistance phenotypes with bacteria showing resistance to several classes of clinically relevant antibiotics (e.g., β-lactams and aminoglycosides). Conclusion: The ecological role and impact of Planctomycetota on oyster holobiont and, ultimately, in public health, under the One Health concept, is discussed.

Using valve gape analysis to compare sensitivity of native Mytilus edulis to invasive Magallana gigas when exposed to heavy metal contamination

Coastal ecosystems are ecologically and economically important but are under increasing pressure from numerous anthropogenic sources of stress. Both heavy metal pollution and invasive species pose major environmental concerns that can have significant impacts on marine organisms. It is likely that many stresses will occur simultaneously, resulting in potential cumulative ecological effects. The aim of this study was to compare the relative resilience of an invasive oyster Magallana gigas and a native mussel Mytilus edulis to heavy metal pollution, utilising their valve gape response as an indicator. The gape activity of bivalves has been utilised to monitor a range of potential impacts, including for example oil spills, increased turbidity, eutrophication, heavy metal contamination etc. In this study, Hall effect sensors were used on both the native blue mussel (M. edulis) and the pacific oyster (M. gigas), invasive to Ireland. Mussels were shown to be more responsive to pollution events than oysters, where all heavy metals tested (copper, cadmium, zinc, lead) had an effect on transition frequency though significant differences were only observed for lead and cadmium (Control; > Copper, p = 0.0003; >lead, p = 0.0002; >Cadmium, p = 0.0001). Cadmium had an apparent effect on mussels with specimens from this treatment remaining closed for an average of 45.3% of the time. Similarly, significant effects on the duration of time mussels spent fully open was observed when treated with lead and cadmium (Control; > lead, p = 0.03, > cadmium, p = 0.02). In contrast, oysters displayed no significant difference for any treatment for number of gapes, or duration spent open or closed. Though there was an effect of both zinc and copper on the amount of time spent closed, with averages of 63.2 and 68.7% respectively. This indicates oysters may be potentially more resilient to such pollution events; further boosting their competitive advantage. Future mesocosm or field studies are required to quantify this relative resilience.

Immediate and delayed effects of a heatwave and Prorocentrum lima ((Ehrenberg) Stein 1878) bloom on the toxin accumulation, physiology, and survival of the oyster Magallana gigas (Thunberg, 1793)

Warming could facilitate the intensification of toxic algal blooms, two important stressors for marine organisms that are predicted to co-occur more frequently in the future. We investigated the immediate and delayed effects of a heatwave and a simulated bloom (3 × 106 cells L-1) of the diarrhetic shellfish toxin (DST)-producing benthic dinoflagellate Prorocentrum lima on the survival, physiology (oxygen consumption rate, condition index, immune parameters), and toxin accumulation in the Pacific rock oyster Magallana (Crassostrea) gigas. Oysters exposed to both stressors contained higher mean DST concentrations (mean ± 1 SE: 173.3 ± 19.78 μg kg−1 soft tissue) than those exposed to P. lima bloom alone (120.4 ± 20.90 μg kg−1) and exceeded the maximum permitted levels for human consumption. Exposure to individual stressors and their combination modified the physiology of M. gigas. Oysters exposed to heatwave alone had significantly higher oxygen consumption rates (0.7 ± 0.06 mg O2 h−1 g−1) than the control (0.3 ± 0.06 mg O2 h−1 g−1). However, this was not observed in oysters exposed to both heatwave and P. lima (0.5 ± 0.06 mg O2 h−1 g−1). This alteration of the metabolic response to warming in the presence of P. lima may affect the ability of rock oysters to adapt to environmental stressors (i.e., a heatwave) to ensure survival. Immunomodulation, through changes in total hemocyte count, was observed in oysters exposed to P. lima alone and in combination with warming. Individual stressors and their combination did not influence the condition index, but one mortality was recorded in oysters exposed to both stressors. The findings of this study highlight the vulnerability of rock oysters to the predicted increased frequency of heatwaves and toxic algal blooms, and the increased likelihood of shellfish containing higher than regulatory levels of DST in warming coasts.

A Cartilage Matrix Protein Regulates Collagen Synthesis in Mantle of Magallana gigas (Crassostrea gigas) under Ocean Acidification

The shell biosynthesis of oysters plays a critical role in protection against environmental stress, in which cartilage matrix proteins (CMPs) determine the mineralogical and crystallographic properties of the shell. In the present study, a cartilage matrix protein (designated as MgCMP1) was identified from the Pacific oyster Magallana gigas (Crassostrea gigas) with the objective of understanding its possible role in shell formation. The open reading frame (ORF) of MgCMP1 was 1815 bp, encoding a polypeptide of 605 amino acids with two von Willebrand factor (VWA) domains. The mRNA transcript of MgCMP1 was expressed constitutively in all examined tissues with a higher level in the mantle, especially highest in the middle fold (MF) of the three folds of the mantle. In addition, the interaction between recombinant protein MgCMP1 (rMgCMP1) and recombinant protein bone morphogenesis protein 7 (rMgBMP7) was identified in vitro. After injection of dsRNA to inhibit the expression of MgCMP1, the mRNA expression level of Mgcollagen I and Mgcollagen X in the MF of the mantle significantly decreased. After pre-puncturing and acidification treatment (pH 7.8), the thickness and length of the new formation shells were lower than those in control group (pH 8.1), and the positive hybridization signals of the MgCMP1 mRNA transcript in the three mantle folds were obviously weakened, especially in the MF, whereas the mRNA expression level of MgCMP1, Mgcollagen I and Mgcollagen X in the MF of mantle decreased significantly. These results suggested that MgCMP1 was involved in regulating the expression of Mgcollagen I and Mgcollagen X in the MF of the mantle in response to ocean acidification (OA).

Searching for a Home Port in a Polyvectic World: Molecular Analysis and Global Biogeography of the Marine Worm Polydora hoplura (Annelida: Spionidae).

The spionid polychaete Polydora hoplura Claparède, 1868 is a shell borer widely occurring across the world and considered introduced in many areas. It was originally described in the Gulf of Naples, Italy. Adult diagnostic features are the palps with black bands, prostomium weakly incised anteriorly, caruncle extending to the end of chaetiger 3, short occipital antenna, and heavy sickle-shaped spines in the posterior notopodia. The Bayesian inference analysis of sequence data of four gene fragments (2369 bp in total) of the mitochondrial 16S rDNA, nuclear 18S, 28S rDNA and Histone 3 has shown that worms with these morphological features from the Mediterranean, northern Europe, Brazil, South Africa, Australia, Republic of Korea, Japan and California are genetically identical, form a well-supported clade, and can be considered conspecific. The genetic analysis of a 16S dataset detected 15 haplotypes of this species, 10 of which occur only in South Africa. Despite the high genetic diversity of P. hoplura in South Africa, we tentatively propose the Northwest Pacific, or at the most the Indo-West Pacific, as its home region, not the Atlantic Ocean or the Eastern Pacific Ocean. The history of the discovery of P. hoplura around the world appears to be intimately linked to global shipping commencing in the mid-19th century, followed by the advent of the global movement of commercial shellfish (especially the Pacific oyster Magallana gigas) in the 20th century, interlaced with continued, complex dispersal by vessels and aquaculture. Given that P. hoplura has been detected in only a few of the 17 countries where Pacific oysters have been established, we predict that it may already be present in many more regions. As global connectivity through world trade continues to increase, it is likely that novel populations of P. hoplura will continue to emerge.

Long-Term Monitoring of Pollution of the Coastal Water Area of Ussuri Bay with Metals: A Case Study of “Green” Oysters Magallana gigas (= Crassostrea gigas) (Thunberg, 1793)

Long-Term Monitoring of Pollution of the Coastal Water Area of Ussuri Bay with Metals: A Case Study of “Green” Oysters Magallana gigas (= Crassostrea gigas) (Thunberg, 1793)

Long-term Monitoring of Pollution of the Coastal Water Area of Ussuriysk Bay with Metals: Case Study of “Green” Oysters <i>Magallana gigas</i> (<i>= Crassostrea gigas</i>) (Thunberg, 1793)

In September 2021, the content of heavy metals Pb, Cu, Cd, Zn, Ni, Fe, and Mn was estimated in the tissues of the oyster Magallana gigas (= Crassostrea gigas) (Thunberg, 1793) and in the silty fraction of bottom sediments from mollusk habitats in coastal waters around the Muravyov-Amursky Peninsula, including the most polluted area off the western coast of Ussuri Bay of the Sea of Japan. It has been shown that, despite the reclamation of the landfill located here in 2010, being the main source of metal pollution, copper is present in high concentrations in bottom sediments and tissues of oysters, giving them a green color. The mollusks living in this area also retain a high concentration of zinc. The concentrations of Pb, Cd, and Ni in oyster tissues over the past 20 years have decreased by 2–5 times in accordance with the decrease in the number of mobile forms of these metals in bottom sediments; however, they are still 3–6 times higher than regional estimates for polluted water areas. With abnormal accumulation of copper, manganese, on the contrary, demonstrates a decrease in the concentration in the tissues of oysters from the most polluted stations, reflecting the deterioration of the physiological state of mollusks. The results obtained indicate the need to continue the remediation of the western coast of Ussuri Bay and monitor the pollution of coastal waters with metals.

Estimating and scaling-up biomass and abundance of epi- and infaunal bivalves in a Swedish archipelago region: Implications for ecological functions and ecosystem services

IntroductionAs suspension-feeders, bivalves play a key role in maintaining regulatory functions of coastal ecosystems, which are linked to important ecosystem services. The functions attributed to bivalves depend on the life habits of a species (epi- or infauna) and their abundance and biomass. To properly quantify and assess these functions, detailed information the distribution, abundance and biomass at the ecosystem scale is critical. Amongst others, this requires an understanding on how environmental conditions shape special patterns in distribution. In this study we investigate this fundamental information on the Swedish west coast, an area where this information is lacking.MethodsA survey which was designed to representatively sample both epi- and infaunal bivalves from randomized locations in various habitat types was conducted. Specifically, abundance and biomass of all species were recorded in the intertidal (0-0.5 m) and the shallow subtidal zone (0.5-2 m). The sites were distributed over an offshore gradient and at two exposure levels. This sampling structure allowed to extrapolate the results to an ecosystem level though information on the areal extent of these habitats using GIS layers.ResultsIt was found that even though there exist a great variability among sites, in general epifaunal bivalves outweigh infaunal bivalves approximately 3 to 1. In terms of abundance, the ratio is more or less reversed and infaunal species occur in greater numbers. Most bivalves were found at an intermediate level of exposure, but due to the areal extend of the sheltered inner-archipelago this was the most important habitat for bivalve abundance and biomass. It was also found that invasive epifaunal oyster Magallana gigas and the invasive infaunal clam Ensis leei both dominated their respective groups in terms of biomass.DiscussionThough the survey was relatively small, these results serve as a valuable insight of the relative importance of epi- and infaunal bivalves in this region. This gives understanding on which species and habitats are particularly important for ecosystem functions and services related to bivalves. This also provide a starting baseline for attempts to quantify ecosystem services provided by certain species or groups of bivalves in the future.

Evaluation of the Spatial Heterogeneity of the Pacific Oyster <i>Magallana gigas</i> (Thunberg, 1793) Cultivation Conditions Using the FARM Marifarm Management Model in Voevoda Bay

In the present study, using the Farm Aquaculture Resource Management (FARM), farm aquaculture resource management model, we calculated the potential productivity of plantations of the oyster Magallana gigas (Thunberg, 1793) (Bivalvia: Ostreidae) in Voevoda Bay (Sea of Japan, Peter the Great Bay, Russkiy Island). When calculating the productivity of cage and bottom plantations of M. gigas, we used the previously obtained results of numerical modeling of bay’s dynamics of hydrological parameters using the open software Delft3D-Flow, taking into account the inflow of fresh water into the bay in 1990–2019. To demonstrate the heterogeneity of growing conditions for M. gigas, three sites 100 × 100 m in size were selected, located in Kruglaya and Melkovodnaya Bays, as well as in the central part of Voevoda Bay. For each plot, modeling of 28 growing periods, lasting 22 months each was performed. The maximum values of oyster yield for the se-cond year of cultivation, expressed in tons of total wet weight, were selected, and distribution histograms for each area were presented. It was shown that, according to hydrological and biological indicators, the growing conditions even in small Voevoda bay are heterogeneous. It has been established that the variability in the productivity of M. gigas is associated mainly with the extreme uneven redistribution of primary production in Voevoda bay under the influence of hydrodynamic factors.