Oyster Culture Research Articles

Intraspecific variation in resilience traits of eelgrass across intertidal stress gradients and oyster aquaculture methods

Intraspecific variation in resilience traits of eelgrass across intertidal stress gradients and oyster aquaculture methods

Oyster grower perspectives on green crab (Carcinus maenas) interactions: using applied social science to inform research and engagement

Research that informs the New Hampshire Aquaculture industry, which has grown significantly over the past few years, and helps the overall associated watershed community to keep Great Bay Estuary healthy is vital. Specific study of green crabs, Carcinus maenas, and their potential effects on oysters, Crassostrea virginica, is important to gain a better understanding of the impact invasive species may have on these ecologically and economically important bivalves. The aim of this study was to document and understand New Hampshire (NH) oyster growers’ perspectives on the issue of green crab predation of oysters. Through a survey, this study documented a preliminary understanding of farmer perspectives and research needs regarding the population of green crabs in NH waters. More specifically, this survey provided a social science perspective and information on areas of potential research - abundance, distribution, and diet of green crabs - that could be beneficial to the oyster industry. This study fills knowledge gaps, helps improve future research (including how to better engage with end users), and facilitates creating and implementing solutions that benefit the NH oyster aquaculture industry.

Design and Experimental Optimization of an Automated Longline-Suspended Oyster Spat Insertion Device

To address the challenges of labor-intensive and costly manual oyster spat insertion in longline-suspended farming, an automated oyster spat insertion device was designed based on negative pressure suction and bundling fixation technologies. Using this device as the experimental platform, a three-factor, three-level Box–Behnken experiment was conducted, with fixation mechanism inclination, negative pressure suction cup span, and horizontal distance between turnover and fixation mechanisms as the experimental factors. The performance of the device was evaluated using the effective fixation rate and damage rate as the experimental indicators. The quadratic polynomial regression models were established to assess the impact of these factors on operational performance, while the response surface method was employed to analyze the interaction effects between factors. Parameter optimization and experimental validation were also performed. The results indicate that the factors affecting the effective fixation rate, in order of significance, are as follows: fixation mechanism inclination, horizontal distance between turnover and fixation mechanisms, and negative pressure suction cup span. For the damage rate, the order of significance is as follows: fixation mechanism inclination > negative pressure suction cup span < horizontal distance between turnover and fixation mechanisms. The optimization results show that when the fixation mechanism inclination is set at 43°, the negative pressure suction cup span at 27 mm, and the horizontal distance between turnover and fixation mechanisms at 179 mm, the effective fixation rate reaches 92.08%, and the damage rate is 4.71%. The relative errors between the measured and model-predicted values are less than 5%, indicating that the regression models are reliable. This research provides valuable insights for advancing the mechanization of the oyster farming industry and replacing manual labor with mechanized equipment.

A highly sensitive and specific real-time quantitative polymerase chain reaction assay for Perkinsus marinus detection in oysters

Oyster aquaculture is one of the fastest-growing food production industries worldwide; however, it faces a significant challenge from the protist Perkinsus marinus, particularly in the USA. Although several quantitative molecular diagnostic methodologies are available for identifying diseases caused by P. marinus, the primer pairs used therein led to non-specific identification of other Perkinsus spp. Hence, a quantitative real-time PCR (Pm-qPCR) assay specific for P. marinus was developed using a TaqMan-based probe with the internal quencher in this study. A primer pair and probe specific to P. marinus were designed from a hypothetical protein of P. marinus collected from the whole-genome shotgun sequence database of the National Center for Biotechnology Information (NCBI). In silico analysis using homologous sequences of P. olseni and P. chesapeaki confirmed the high specificity of primers designed in this study. The Pm-qPCR assay was performed using seven different strains of P. marinus, P. olseni, and P. chesapeaki, revealing high specificity and sensitivity for detecting only P. marinus strains. In conclusion, it was demonstrated that Pm-qPCR can effectively and accurately diagnose P. marinus with high specificity and sensitivity. This assay is promising for monitoring oyster health and disease management in ecosystems and aquaculture.

Large-scale oyster farming accelerates the removal of dissolved inorganic carbon from seawater in Sanggou Bay

While the direct impact of oyster calcification and respiration on the seawater inorganic carbon system is well-acknowledged, their indirect effect through filter feeding activities remains unclear. Here we studied the impact of large-scale oyster farming on the removal of dissolved inorganic carbon (DIC) from seawater. Field investigations showed that the DIC level in the oyster farming area in Sanggou Bay, China were significantly lower than that in the non-farming area. In-lab incubation showed that regardless of whether incubated in high or low-transparent environments, the DIC removal rate of seawater from the oyster farming area was significantly higher than that of the non-farming area. These results indicate that cultivated oyster facilitates the removal of seawater DIC in the farming area. To reveal the indirect effect of filter feeding activities on DIC removal, we used 6-m3 ponds to simulate the oyster-farming environment. Results showed that the average DIC level of the oyster-cultivating groups was 105.83 μmol/kg lower than that of the control groups (without of oyster) after a six-day cultivation. Surprisingly, the average concentration of Chl-a in oyster-cultivating groups was significantly higher than that of the control group at the end of the experiment. Similarly, DIC level declined faster while Chl-a concentration increased faster in seawater that previously experienced 12～20 hours of oyster cultivation than that in the control seawater. It was noticed that the transparence of seawater within 6-m3 ponds increased significantly just after hours of oyster cultivation. This enhanced transparency created a favorable light environment that supported phytoplankton photosynthesis and simultaneously accelerated the DIC removal rate. Overall, oysters not only remove the inorganic carbon in the seawater through calcification but also create a suitable environment for phytoplankton photosynthesis through their filtering activity, and subsequently accelerating the removal of inorganic carbon in the seawater of the oyster farming area.

Long-term responses of intertidal and subtidal seagrasses to anthropogenic disturbances and sea warming in the northwestern pacific coast

Long-term ecological research is imperative for comprehensively understanding how ecosystems respond to environmental changes over time. This study examined the long-term responses of seagrasses (Zostera japonica, Z. marina, and Z caespitosa) in intertidal and subtidal zones to anthropogenic disturbances and sea warming on the southern coast of the Korean peninsula over 15 years (2008–2022). Dramatic declines in the intertidal seagrasses were observed due to human activities such as clam harvesting and oyster cultivation, resulting in the disappearance of almost all Z. japonica in intertidal zones. Subtidal seagrasses, including Z. marina and Z. caespitosa decreased gradually throughout the study period. The biomass and canopy height of the subtidal Z. marina showed an inverse trend against water temperature. In addition, water temperature anomalies such as marine heat waves (MHWs) caused abrupt declines of seagrasses within both the intertidal and subtidal zones. Annually repeated and acute human-induced disturbances were the primary threat to the intertidal seagrass species. Nevertheless, the subtidal seagrasses were primarily affected by unpredictable summer MHWs as well as gradual rising water temperatures, with MHWs causing more dramatic alterations in the coastal seagrass ecosystems compared to gradual SST rising. The continuous decline of seagrasses due to natural and human-induced disturbances will alter the structure of shallow coastal ecosystems, leading to significant changes in the ecosystem services they provide. The results of this study underscore the importance of management actions in coastal seagrass ecosystems and highlight the need to predict future impacts of ongoing climate change.

Massive Outbreak of Aurelia coerulea in Geoje Bay, Korea

This study was carried out to elucidate the causes of massive outbreaks of Aurelia coerulea in Geoje Bay, Korea, from November 2022 to October 2023. Adult medusae consistently spawn with planulae, and the populations of A. coerulea in Geoje Bay could be categorized into current-year and overwintering populations. The current-year population began with the emergence of ephyrae in February and grew until October, while the overwintering population comprised a mixture of surviving current-year population and additional individuals that joined during the warm season. The size of the planulae are significantly larger than the annual average during the cold season. These results appear to be the energy accumulation of planulae for polyp formation under low water temperatures. Planulae form polyps within a temperature range of 5–25 °C, suggesting the possibility of year-round polyp recruitment. In Geoje Bay, the highest appearance rate of A. coerulea was in April (8.71 ± 12.5 ind. m−3), with ephyrae experiencing higher growth rates up to the young medusa stage. However, from April, a decline in zooplankton biomass resulted in reduced growth rates in adults, indicating that jellyfish growth was primarily regulated by food availability. Additionally, submersed oyster shells in oyster farms served as the main habitat for jellyfish polyps. A. coerulea populations were also characterized by the continuous spawning of planulae throughout the year. In conclusion, this study suggests that stable polyp habitats, abundant food supply during the initial developmental period of the population, and suitable ranges of water temperature were significant factors inducing the massive outbreak of A. coerulea in Geoje Bay, Korea.

Assessing the spatial variability of cage movement and velocity attenuation of an off-bottom oyster farm and its influence on eastern oyster (Crassostrea virginica) growth performance

The global shellfish aquaculture industry has expanded over the last seven decades. Similarly, the size of individual shellfish farming operations has grown in some states. Circulation processes in natural water bodies are dynamic and vary across multiple temporal and spatial scales. How gear installation affects the circulation of currents and waves, and subsequent phytoplankton delivery to crops within farms, is largely unknown. Documenting and understanding variability in wave and current energy within an individual farm could help optimize production. Our study sought to understand the variability in oyster growth attributable to hydrodynamic and atmospheric forcing across an active commercial shellfish aquaculture lease in the Patuxent River, Maryland. We observed a 17 % reduction in water flow downstream of the farm (rho = −0.673, p = 0.002, Spearman rank test), suggesting the bottom cages attenuated downstream current velocity during flood tides. Differences in flow speed and the movement of cages and oysters throughout the farm correlated with variances in oyster shell morphology and oyster survival while in bottom cages. Our results demonstrate the occurrence of variability in production within an individual farm location. Further, our findings suggest that insight into the spatial growth patterns across a lease can be practical for forecasting growth and quality of cultured oysters and may enable growers to strategically place oysters within their farm to improve yield and product consistency.

Comparative Transcriptomic Analyses Reveal Differences in the Responses of Diploid and Triploid Eastern Oysters to Environmental Stress.

Triploid oysters are commonly used as the basis for production in the aquaculture of eastern oysters along the USA East and Gulf of Mexico coasts. While they are valued for their rapid growth, incidents of triploid mortality during summer months have been well documented in eastern oysters, especially at low salinity sites. We compared global transcriptomic responses of diploid and triploid oysters bred from the same three maternal source populations at two different hatcheries and outplanted to a high (annual mean salinity = 19.4 ± 6.7) and low (annual mean salinity = 9.3 ± 5.0) salinity site. Oysters were sampled for gene expression at the onset of a mortality event in the summer of 2021 to identify triploid-specific gene expression patterns associated with low salinity sites, which ultimately experienced greater triploid mortality. We also examined chromosome-specific gene expression to test for instances of aneuploidy in experimental triploid oyster lines, another possible contributor to elevated mortality in triploids. We observed a strong effect of hatchery conditions (cohort) on triploid-specific mortality (field data) and a strong interactive effect of hatchery, ploidy, and outplant site on gene expression. At the low salinity site where triploid oysters experienced high mortality, we observed downregulation of transcripts related to calcium signaling, ciliary activity, and cell cycle checkpoints in triploids relative to diploids. These transcripts suggest dampening of the salinity stress response and problems during cell division as key cellular processes associated with elevated mortality risk in triploid oysters. No instances of aneuploidy were detected in our triploid oyster lines. Our results suggest that triploid oysters may be fundamentally less tolerant of rapid decreases in salinity, indicating that oyster farmers may need to limit the use of triploid oysters to sites with more stable salinity conditions.

Costs of induced defenses dissipate by maturity for diploid and triploid oysters

Oyster reef restoration efforts and on-bottom aquaculture are frequently plagued with high predation rates. Oysters are phenotypically plastic, and rearing juvenile oysters, Crassostrea virginica, with predator cues causes them to grow stronger shells that increases survivorship in the field. However, induced defenses (e.g., shell hardening in oysters) are often associated with cost-benefit trade-offs, and the extent the increased shell strength persists into adulthood and alters the growth of somatic and reproductive tissues remains unknown. We raised diploid oysters (used in reef restoration) and triploid oysters (used in aquaculture) with and without predator cues for one month before placing individuals on an oyster farm to grow to market size. Oyster shell characteristics, soft tissue mass, and reproductive investment were measured periodically over one year of culture and compared across treatments. Both diploid and triploid oysters had significantly stronger and smaller shells than controls at the end of their nursery period. However, while diploid shells became 15 % stronger and 17 % smaller than controls, triploid shells became 28 % stronger and 23 % smaller. Additionally, triploid oysters exposed to predator cues returned to the size of controls faster and maintained their shell strength differences longer than diploids. Differences in soft tissue mass between treatments mirrored the patterns exhibited in shell size and weight with greater initial physiological costs and faster recovery for triploid individuals. There was no significant difference in somatic or reproductive tissue mass between induced and control oysters of the same ploidy after seven months in the field. Triploid oysters were 15–110 % larger than diploids depending on the characteristic measured at maturity. Additionally, there was a significant interaction between treatment and ploidy because induced triploids had marginally greater growth than their control counterparts while induced diploids had marginally less growth than controls. These findings demonstrate that physiological costs of oysters reacting to predators in early life stages are minimal by the time individuals reach maturity. Early exposure to predator cues is a promising tool for improving oyster survivorship in restoration and aquaculture operations, especially in regions with high predation pressure.

Triploid eastern oysters (Crassostrea virginica) display high susceptibility to microbial infections but only during early ontogenetic stages

Over the last two decades, oyster aquaculture has largely shifted from the use of diploids to the near-exclusive use of triploids in many regions, with some hatcheries now producing >90 % triploid oyster spat. The increased demand for triploids is primarily driven by substantial growth advantages and more consistent meat quality associated with sterile triploid animals, with most data suggesting triploids and diploids display comparable adult survivorship. Although adult performance appears similar, anecdotal reports from farmers have suggested that triploids may exhibit greater frailty during earlier age classes, particularly in response to bacterial infections. Due to the extent of triploid production now taking place, the possibility of early ontogenetic frailty in triploids could pose a significant risk to oyster aquaculture production. To evaluate these claims, two cohorts of half-sibling diploid and triploid eastern oyster lines were generated in 2020 and 2021. A subset of larvae and juveniles from these lines were then exposed to a cocktail of bacterial (Vibrio) pathogens and monitored for viability. The remaining oysters were then allowed to grow for another 2 months before being deployed in either Peconic Bay, New York (2020), or Patuxent River, Maryland (2021), where their survivorship was followed for another year. Results showed that triploids were at significantly greater risk of mortality during the larvae and juvenile stages, though differential mortality decreased with age. These trends were consistent across the two spawning events, and the extent of early ontogenetic triploid frailty was observed to vary between the lines tested. This work provides valuable data for hatchery managers and farmers alike and suggests areas where specific attention and further work are required.

Impacts of oyster farms on sediment-associated mercury and methylmercury concentrations and health risks in an estuarine, mangrove forest, Zhanjiang Bay, China

Estuarine sediments serve as significant reservoirs for mercury (Hg) and methylmercury(MeHg), which can also interconvert in the external environment. The release of Hg in response to human activities raises concerns about its potential ecological and human health effects. Sediment samples were collected in December 2021 from four locations (sites), and Hg cycling by measuring the concentrations of, and controls on, the spatial distribution of total Hg (THg) and methylmercury (MeHg) in high-tidal zone (HTZ) and mid-tidal zone (MTZ) sediments of a mangrove forest (MF) and oyster farm (OF) was examined in northwestern Zhanjiang Bay, including simultaneous determination of sediment particle size, oxidation-reduction potential (Eh), pH, total organic carbon (TOC), sulfide concentration (S2-), and sulfate reducing bacteria (SRB). The research results indicated that concentrations of both THg and MeHg ranged between 20.0–104.0 ng/g and 0.011–0.277 ng/g in the sediments, respectively. The highest methylation potentials within the MF and OF were in sediments located approximately 10–15 cm below the surface. MeHg in the HTZ of the OF was likely derived from exogenous inputs as Hg methylation appears limited, and the formation of MeHg depended not only on the amount of inorganic mercury available for methylation in SRB, but also on the TOC, pH, Eh and S2- content in the sediment. A risk assessment of MeHg during the anthropogenic disturbance of this estuaries conducted on individuals eating oysters demonstrated that health risks are low.

Effect of diet on larval settlement, growth, and spat survival of the oyster Crassostrea gigas (Thunberg, 1793)

This study aimed to assess the impact of microalgal concentrations in diets on the settlement and metamorphosis stages of pediveliger larvae and spat of Crassostrea gigas oysters. Diets containing microalgal concentrations of 8, 12, and 16×104 cells mL-1 were administered for seven days during the larval settlement phase of pediveliger larvae. In the metamorphosis and postlarval cultivation phases, diets with microalgal concentrations of 8, 16, 24, and 32×104 cells mL-1 and a control group without food were tested for 14 and 21 days, respectively. Growth, yield, and survival were assessed every seven days. The diet comprised 30% Isochrysis galbana and 70% Chaetoceros muelleri microalgae. In the metamorphosis phase, the results revealed no significant differences in larval metamorphosis rate and survival across the tested diets. The concentrations exhibited similar survival in the spat with an initial average shell height of 0.657 ± 0.05 mm, with a significant difference only in growth. In the spat with an initial average shell height of 0.830 ± 0.12 mm, no differences in survival were observed among the tested concentrations. We concluded that diets of 12 and 16×104 cells mL-1 provide high rates of larval metamorphosis and spat yield during the larval settlement and metamorphosis phases. During the spat cultivation phases, diets of 32 and 24×104 cells mL-1 could optimize the cultivation time and yield of C. gigas spat in the laboratory. However, when considering survival alone, no advantage was found in providing a diet with a microalgal concentration above 8×104 cells mL-1 across all C. gigas oyster cultivation phases.

Dual benefits of biofouling reduction in non-fed aquaculture: On-site heat treatment enhances oyster production and mitigates local environmental impacts

We experimentally evaluated the biofouling reduction by on-site heat treatment in enhancing oyster aquaculture production and mitigating its environmental impacts. Specifically, we compared oyster growth, settling flux of particulate organic matter (POM), and its oxygen consumption rate (OCR) between heat-treated (HT) and non-treated (N) sections within suspension oyster farms in a temperate bay. HT demonstrated a substantial reduction of 81–99% in fouling mussel biomass and approximately 20–30% increases in cultivated oysters’ growth and condition index. The settling flux of POM was 10–57% smaller in HT mainly due to the reduction in biodeposition from fouling mussels. However, OCR of settling POM at a unit mass was 6–62% higher in HT than in N; overall, the short-term oxygen consumption by settling POM did not significantly differ between HT and N. The increase in OCR of settling POM in HT may be attributable to the decrease in biodeposits from fouling organisms and increase in the relative contribution of fresh POM entering from unfarmed areas. Meanwhile, from the longer-term perspective, the substantial reduction in settling POM by the heat treatment lower the potential for oxygen consumption in the bottom layers over the half-year farming operation by 31%. In conclusion, on-site heat treatment is a simple tactic for controlling nutrient and POM flows at production sites, simultaneously enhancing oyster production and mitigating the local environmental impact of non-fed oyster aquaculture. Furthermore, this approach exemplifies an effective tactic to enhance the sustainability of primary food production processes.

Territorial and occupancy behavior of black sea bass on oyster aquaculture gear and boulder habitat

Territorial and occupancy behavior of black sea bass on oyster aquaculture gear and boulder habitat

Unforeseen green tide of floating tubular Ulva meridionalis, a lethal threat to oyster farming, along the west coast of Taiwan: tracking its origin and ecophysiological insights

Abstract Ulva green tides have adversely affected coastal ecosystems. In June 2023 in Changhua County, Taiwan, an unprecedented floating tubular Ulva bloom spanning about 30 km of coastline caused about 30 % reduction in oyster yield as reported by local farmers. Understanding its taxonomic and ecological basis is crucial for preemptive and remedial measures. Based on molecular (rbcL and tufA) and morphological evidence, U lva meridionalis was the cause of this green tide. Haplotype network analysis (based on ITS) suggests that this green tide originated from northern China via the China Coastal Current. Historical survey data indicate that U. meridionalis arrived in Taoyuan Algal Reef (about 150 km north of the bloom area) as far back as 2018. Our ecophysiological experiments revealed that U. meridionalis exhibited a rapid daily growth rate with biomass increment up to 13–21 % when subjected to local nutrient-rich waters under lower salinity and spring-like conditions. Although historical ecological and poultry/livestock data analyses showed no noticeable change in sea surface temperature and rainfall over the past decade, a gradual rise in agricultural nitrogen and phosphorus output was observed. This taxonomic and ecological background lays the groundwork for long-term ecological monitoring. Moreover, this study exemplifies the detrimental impact of an unforeseen Ulva bloom on oyster farming.

Effects of boring sponge Pione vastifica (Hancock, 1849) infestation on redox status and histological structure in Pacific oyster Magallana gigas (Thunberg, 1793) gills

The Pacific oyster, Magallana gigas (Thunberg, 1793), is the most widely cultivated bivalve species in the world. Despite the oyster's resistance to most pathogens, oyster farms are increasingly suffering losses due to infestation by various boring agents, particularly boring sponges. Boring sponges Pione vastifica (Hancock, 1849) penetrate and destroy the shell of the oysters, creating a network of channels and chambers in the shell. This ultimately results in a reduction in the marketability and barrier protection of oysters, as well as an impairment of their functional status. The objective of this study was to identify the mechanisms of oyster response to exposure to the boring sponge and to assess the health status of the species in the context of its ecological and economic importance. This paper examines the effect of the boring sponge on the organism of Pacific oysters M. gigas, namely on the level of lipid peroxidation and the activity of the main antioxidant enzymes (superoxide dismutase - SOD, catalase - CAT, glutathione peroxidase - GPx), as well as histopathological changes in the gills of oysters with different degrees of boring sponge infestation. In contrast to the SOD activity, the CAT and GPx activities were found to be dependent on the extent of damage inflicted upon the shell by the boring sponge. In the initial phase of shell damage (1 and 25%), the CAT activity exhibited no notable deviation from the control level. However, the GPx level demonstrated a pronounced decline. In the second stage (26-50% of damage), there was an increase in CAT activity, and the levels of GPx returned to control levels. Despite a low level of antioxidant defense activity, an increase in lipid peroxidation was observed. In the fourth stage (76-100% damage), the highest level of lipid peroxidation was observed. This was accompanied by an increase in CAT production and a decrease in GPx activity. However, no significant disturbances in the structure of gill tissues were found with an increasing degree of damage caused by the spread of boring sponges. In our study, only local histological abnormalities were observed in stages 2, 3, and 4 of infection. The results of the present work demonstrate the influence of the boring sponge infestation process on the redox balance of oyster gill.

Considerations for kelp aquaculture on South Africa’s west coast: geospatial analysis and research implications

Abstract The commercial use of kelp continues to gain interest worldwide. While in some East Asian countries kelp farming has a long history, the kelp industry in South Africa is based on harvesting of kelp from natural kelp forests or by beach-cast collection. This study examined the potential for kelp aquaculture on South Africa’s west coast, focusing on the three indigenous species of kelp, Ecklonia maxima, Laminaria pallida and Macrocystis pyrifera. Geospatial analysis was used to identify and assess nine potentially suitable areas for kelp farming, based on natural habitat conditions, and examination of potential conflicts with other users and enabling land-use factors. An assessment of the market, technical and financial aspects of a kelp farming opportunity indicated that a 4 ha kelp farm, with longlines producing 750 to 1,000 t of fresh kelp per annum, could be viable as an integrated aquaculture activity adjacent to an existing mussel or oyster farm. We recommend a detailed feasibility study for kelp aquaculture in South Africa, with market and technical research, and financial modelling. Current seaweed industry legislation is mostly concerned with the wild resource, and there is a need for specific policies relating to seaweed aquaculture to facilitate growth of the industry.

Pertumbuhan tiram mutiara (Pinctada maxima) menggunakan metode karambah apung dan longline

Pearl oyster cultivation is a growing industry in various countries. The growth and quality of pearls produced by oysters is greatly influenced by the cultivation method used. This research aims to compare the growth of pearl oysters (Pinctada maxima) cultivated using the floating cage and longline methods. Different cultivation methods can influence the growth of pearl oysters and the surrounding environmental conditions. Statistical analysis was conducted on sample size, mean values, standard deviation, and standard error of the mean for both cultivation methods. The results indicate no significant difference in the growth of pearl oysters between the floating cage and longline methods. However, biofouling and other disrupting organisms can affect the growth of pearl oysters in the floating cage method. The study also highlights the importance of environmental factors such as water quality, temperature, and food availability in influencing the growth of pearl oysters. Thus, this research provides valuable insights for the pearl oyster cultivation industry in selecting the optimal cultivation method to enhance productivity and the quality of the pearls produced.

The increasing influence of oyster farming on sedimentary organic matter in a semi-closed subtropical bay

Oyster farming activities play a pivotal role in the biogeochemical cycles of coastal marine ecosystems, particularly in terms of sedimentary carbon cycling. To gain deep insights into the influence of expanding oyster culture on the sedimentary carbon cycle, surface sediments were collected from the Maowei Sea, which is the largest oyster farming bay in south China, based on six filed surveys between July 2010 and December 2022. The sediment samples were analyzed for total organic carbon (TOC), total nitrogen (TN), stable carbon and nitrogen isotopes (δ13C and δ15N) to evaluate the inter-annual variations in the source contribution to sedimentary organic matter (SOM). The results revealed that the average contents of sedimentary TOC and TN were 0.67 ± 0.41 % and 0.06 ± 0.03 %, respectively. Fluctuations in the C/N molar ratios ranged from 5.8 to 23.6, with an average of 12.6 ± 2.9, indicating a significant terrestrial input contribution to SOM in the study area. Furthermore, the integration of stable isotope analysis and Bayesian mixing model demonstrated a gradual increase in the mean proportion of shellfish biodeposition to SOM, from 12.0 ± 5.6 % in July 2010 to 21.1 ± 7.3 % in December 2022, consistent with the progressive expansion of oyster aquaculture along this coastal area, thereby emphasizing the substantial influence of oyster farming on SOM composition. With the anticipated expansion of oyster farming scale and production in the future, shellfish biodeposition is expected to assume a more important role in shaping SOM dynamics and sedimentary organic carbon cycling in coastal waters. Overall, this study provided an important perspective for better assessing the impact of expanding mariculture scale on coastal biogeochemical cycles, thereby making valuable contributions to future policy formulation concerning mariculture and ecological conservation.