The key Dynamic Energy Budget (DEB) energetic parameters were determined for two intensively cultured bivalve species in the Yellow Sea, the Pacific oyster Magallana gigas (Thunberg, 1793) (=Crassostrea gigas) and the Manila clam Ruditapes philippinarum (Adams & Reeve, 1850), through controlled physiological experiment. The parameters obtained include the shape coefficient delta m (0.178 and 0.374, respectively), volume-specific cost for structure [EG] (1675 and 5688 J/cm3), maximum storage density [EM] (2493 and 2159 J/cm3), and volume-specific maintenance rate [pM] (22.49 and 50.87 J/(cm3 & sdot;d)). These parameters were subsequently calibrated using multimodal optimization. Different calibration strategies produced statistically equivalent fits but yielded parameter sets with divergent physiological interpretations, demonstrating that goodness-of-fit alone is insufficient to guarantee biological plausibility. We recommend the integrated calibration approach which first constrains the model with locally measured core parameters, then refines the remaining coefficients via mathematical optimization. This strategy produces parameter sets that are both physiologically interpretable and predictive, thereby improving the reliability of DEB based individual models in aquaculture applications.

Bivalves are increasingly being recognized as sustainable food sources that provide substantial ecosystem services; however, the debate regarding their role as either carbon sources or sinks remains unresolved. This study introduced a novel methodology for the comprehensive assessment of the physiological dynamics of the Manila clam Ruditapes philippinarum, utilizing in situ and continuous-flow experiments. Building upon these empirical findings, we developed a bioenergetic model grounded in Dynamic Energy Budget (DEB) theory. The model incorporates primary food sources, including phytoplankton and detritus, while addressing crucial physiological processes such as ingestion, respiration, calcification and biodeposition. This integrative framework was employed to examine the dynamics of the carbon budgets of clams over a 365-day period, highlighting their role in carbon storage within the ecosystem. Notably, seasonal variations had a significant influence on the clams' physiological performance, including rates of clearance, ingestion and oxygen consumption. According to the model simulation results, each clam stored approximately 973 mg of carbon annually, of which 296 mg was dedicated to shell formation and 677 mg was contributed through biodeposition. This study enhances our understanding of the ecological contributions of bivalves and emphasizes their crucial role in carbon cycling within mariculture environments.

Ocean acidification (OA) is predicted to threaten marine bivalves, casting them as passive victims of changing carbonate chemistry. Contributing to a revised understanding, we identified a conserved mechanism for acid-base regulation that supports intracellular resilience. Using the Manila clam Ruditapes philippinarum as a model, this study demonstrated that intracellular pH (pHi) homeostasis under elevated pCO2 was maintained through cytosolic carbonic anhydrase (CAc)-mediated H+ efflux. A causal link was established by combining in vivo scanning ion-selective electrode technique (SIET) with RNA interference (RNAi), where RpCAc knockdown suppressed H+ efflux and compromised pHi. A coordinated regulatory network involving CAc, soluble adenylyl cyclase (sAC), and Na+/K+-ATPase (NKA) was synergistically upregulated, suggesting an evolved adaptive pathway. Dynamic Energy Budget (DEB) modeling, calibrated with experimental data, revealed that this cellular compensation carries a high energetic cost, leading to a significant reallocation of resources: shell growth was maintained, but somatic growth was severely suppressed. These results elucidate a conserved cytoprotective mechanism that enables short-term tolerance of OA at a substantial somatic cost, redefining resilience to include energetic trade-offs.

Many marine invertebrate larvae are influenced by environmental factors during development, with diatom biofilms playing a crucial role in the settlement and metamorphosis of bivalve larvae. This study found that Navicula sp. biofilms alter the larval microenvironment by increasing dissolved oxygen levels through photosynthesis and decreasing nitrate, ammonium, and phosphate levels in the surrounding water. Exposure to Navicula sp. biofilms induced directional swimming in larvae and significantly shortened the time required for settlement and metamorphosis. Biofilms formed by Navicula sp. contained effective substances and key infochemicals that promoted the settlement and metamorphosis of Mizuhopecten yessoensis larvae. Soluble polysaccharides containing β-1,4-glycosidic bonds secreted by the biofilm were recognized by the larvae, triggering settlement and metamorphosis signaling. Untargeted and targeted metabolomic analyses revealed increased levels of cGMP (Cyclic guanosine monophosphate), and GMP (Guanosine monophosphate), suggesting that larval settlement and metamorphosis may be associated with cGMP regulation. Based on these results, cGMP was selected for subsequent functional analyses. Treatments with the NO donor SNAP, the cGMP analog 8-Br-cGMP, and the sGC activator BAY 41-2272 significantly promoted metamorphosis, whereas the sGC inhibitor ODQ suppressed metamorphosis in a dose-dependent manner. These findings demonstrate that the NO–sGC–cGMP pathway positively regulates the settlement and metamorphosis of M. yessoensis larvae, with cGMP serving as a key effector. This study provides new insights into the mechanisms underlying larval settlement and metamorphosis in bivalves.

ABSTRACT The Chudao oyster reef in Sanggou Bay, China represents a rare case of reef expansion in the context of global oyster reef degradation. However, its ecosystem structure and functioning remain poorly understood. To fill this knowledge gap, a whole‐biota survey was conducted in May 2024, covering plankton, microorganisms, reef‐dwelling animals, and nekton across different tidal zones. An Ecopath model was subsequently constructed to quantify trophic structure and energy flow. Results revealed a total of 30 reef‐dwelling animal species, with oysters (Magallana gigas) dominant in both density (1335–1605 ind m−2) and biomass (12.87–14.04 kg m−2). Biodiversity indices did not differ significantly among tidal zones (p > 0.05), although relatively higher values were observed in the low‐tide zone. The Ecopath model comprised 17 functional groups with trophic levels ranging from 1.00 to 3.73. Total system throughput (TST) reached 36,752.52 t km−2 year−1, with primary producers contributing 61% of total energy flow. Ecosystem indices indicated a relatively mature and stable ecosystem, while the overall energy transfer efficiency was low (4.21%). As the first ecosystem‐level assessment of the Chudao Oyster Reef Ecosystem (CORE), this study provides valuable quantitative insights into its structural and functional characteristics and establishes a scientific basis for the conservation, management, and sustainable development of this rare expanding oyster reef ecosystem.

Nutrient changes derived from high-resolution sediment records along a typical open coast of the East China Sea were analyzed to assess environmental variations associated with aquaculture practices over recent decades. Biogenic components and stable isotopes significantly fluctuated in the sediment profiles, suggesting substantial environmental changes since the 1930s. Slight increases in total nutrient contents and carbon stable isotopes (S13Corg) were observed from the 1930s to the 1970s, likely due to increasing terrestrial nutrient inputs resulting from population growth within river watersheds. From the 1970s to the 1980s, S15N values slightly decreased, suggesting an influx of anthropogenic nutrients primarily originating from chemical fertilizers. A minor decline was observed in total nitrogen and organic phosphorus, as well as total organic carbon contents during this period, coinciding with the expansion of kelp (Saccharina japonica) cultivation. Since the 1990s, nitrogen and phosphorus have substantially increased by over 31% and 22%, respectively, along with a notable shift toward heavier S15N values attributed to feed inputs. Additionally, fluctuations in S13Corg indicate that feed-based aquaculture has profoundly altered both nutrient structure and composition along the Lianjiang coast. The annual nitrogen and phosphorus loadings absorbed by aquaculture were calculated to be approximately 14,592 f 3812 and 1848 f 762 tin 2020, respectively. Meanwhile, annual nitrogen and phosphorus discharges from feed-based farming amounted to approximately 17,038 f 4465 t and 3343 f 612 t, respectively. Nevertheless, the net N loadings from aquaculture in Lianjiang were one order of magnitude lower than those for discharge or absorption. Kelp accounted for over 86% of nutrient removal in Lianjiang, despite its cultivation period lasting only 4-6 months each year. This suggests that significant net absorption occurs during the kelp cultivation season, which mitigates nutrient loads from adjacent coastal regions. Conversely, during non-cultivation seasons, prominent net discharge of nutrients was expected to affect adjacent coastal areas. Thus, seasonal variations in kelp cultivation practices appear to modify nutrient cycles in the adjacent marine environments.

The continuous rise in greenhouse gas concentrations in the atmosphere, such as carbon dioxide, has triggered a series of climate change issues on a global scale, including global warming, frequent extreme weather events, and sea-level rise. This threatens natural ecosystem stability and poses severe challenges to food security, water resource allocation, and economic development. Therefore, it has become a core environmental hotspot of concern for governments, scientific research institutions, and the public worldwide. As the largest and most active carbon pool on Earth, the ocean plays an irreplaceable role in regulating the global carbon balance through carbon cycle processes. The ocean can absorb approximately one-third of the carbon dioxide emitted into the atmosphere by human activities annually. This substantially reduces the greenhouse gas accumulation rate in the atmosphere and serves as a "natural buffer" to maintain the global carbon balance and climate system stability. Marine fisheries, one of the pillar industries of the marine economy, provide approximately 30% of animal protein sources for billions of people worldwide, acting as a key link in ensuring food security and building a diversified food supply system. Their ecological value has also been increasing. Previous studies have confirmed that fishery systems are not merely resource utilization activities. Some fishery models also have the function of "carbon sink" — they fix carbon elements through the growth and metabolism of organisms themselves, store them in the form of biomass, or sequester them through sedimentation. They play a unique and positive role in mitigating climate change, and this "production-carbon sequestration" synergistic effect provides important support for the development of the blue carbon economy. In coastal ecosystems, bivalves form a core group in both natural and aquacultural ecosystems. Their physiological activities, such as filtration, metabolism, and biological sedimentation, have profound impacts on the biogeochemical carbon cycle. Numerous studies have demonstrated that bivalves convert carbon from water into their own biomass by filtering organic particles such as phytoplankton. Simultaneously, they promote migration of carbon to sediments through excretion and residue decomposition, thus playing a key role in carbon migration and transformation. Therefore, they have become indispensable biological factors in marine carbon sink research. Physiological energetics studies are the main methods for analyzing the interaction between shellfish and carbon. Extensive studies have been conducted on multiple species, including Crassostrea gigas, Chlamys farreri, Ruditapes philippinarum, Mytilus edulis, Pteria penguin, and Paphia undulata. However, most studies have focused on temperate shellfish, and relatively few studies have been conducted on the physiological energetics and carbon budgets of tropical and subtropical shellfish. However, water sample treatment and analysis are greatly affected by human factors, and the objectivity and reliability of the experimental data urgently need to be improved. Pinctada fucata martensii, also known as the Hepu pearl oyster, belongs to the families Mollusca, Lamellibranchia, Pteriomorphia, Pterioida, and Pteriidae. It is an important mariculture bivalve in China and is the main host oyster for marine pearl cultivation. Currently, research on P. fucata martensii mainly focuses on genetic breeding, molecular genetics, biomineralization mechanisms, and optimization of pearl quality. Relevant studies on physiological energetics have mainly concentrated on the effects of transportation stress, environmental factors, and extreme weather events on physiological energetics, with no research on physiological energetics under in situ flowing water conditions. In this study, P. fucata martensii was selected as the research object. In May 2024, the filtration rate, assimilation efficiency, oxygen consumption rate, and ammonia excretion rate of P. fucata martensii of three size classes (large: shell length 7.27±0.75 cm; medium: shell length 5.20±0.21 cm; small: shell length 4.46±0.30 cm) were measured at Wuzhizhou Island, Sanya, and equations for energy and carbon budgets were established. Prior to treatment, P. fucata martensii were acclimated for 3 days. The experiment was conducted using a standardized measurement method that combined a controllable in situ flowing water experimental system with measurement technologies of a portable particle counter (PAMAS) and a multichannel real-time dissolved oxygen meter (PreSens). The results showed that filtration rates per unit dry weight of the soft body of large, medium, and small-sized P. fucata martensii were (1.75±0.44), (1.30±0.29), and (0.51±0.19) L/(h·g), respectively; filtration rates for large and medium-sized individuals were significantly higher than those of small-sized individuals (P<0.01). Oxygen consumption and ammonia excretion rates of P. fucata martensii of different sizes decreased with decreasing size; however, the differences were not significant (P>0.05). Assimilation efficiency and oxygen-nitrogen ratio ranges were 48%–68% and 2.26–17.68, respectively. Energy allocation of P. fucata martensii of the three sizes showed that fecal energy accounted for the largest proportion (52.00%–64.00%), followed by growth energy (26.28%–39.06%), and excretory energy accounted for the smallest proportion (1.36%–1.60%). The carbon budget equations for large, medium, and small P. fucata martensii were 100Cc=13.94Pc+ 46.97Rc+7.27Uc+31.82Fc, 100Cc=19.80Pc+23.76Rc+3.96Uc+52.48Fc, and 100Cc=3.92Pc+43.14Rc+ 5.88Uc+47.06Fc, respectively. Our findings provide support for further understanding of the energy and carbon allocation patterns of P. fucata martensii in tropical marine areas and for evaluating its carbon sequestration capacity.

The study employs seasonal cruise observations, hydrodynamic modeling, and Lagrangian advection-diffusion models to evaluate the environmental impacts of the fish cages encircling the Nanji islands in a nature reserve region. Results indicate that the local marine environment is predominantly influenced by the seasonal frontal boundaries between the Yangtze River's effluent and the Taiwan Warm Current. Tracer-tracking simulation results reveal that dissolved nutrients from the cages generally contribute to less than 10 % of the observed levels in the water column. Combined observation and particle dispersion modeling results indicate that the overall impact of cage aquaculture on the regional sediment environment remains limited. Particulate waste released from the cages accumulates mainly near the source, with subsequent sedimentary impacts modulated by resuspension processes. The modeling framework presented in this study offers a robust approach for environmental impact assessment of cage aquaculture in regions with comparable hydrodynamic and ecological settings and provides a scientific basis for sustainable aquaculture planning and management.

Through biodeposition, oysters increase the flux of organic carbon (OC) that deposits and stabilizes on the seafloor and is potentially recorded in the sediment core. However, the linkage between oyster farming and OC burial has not received much attention. This study selected a typical oyster farm with approximately half a century of farming history in Sanggou Bay, China. The OC burial efficiency during the vicissitude of the farm was reconstructed by estimating OC biodeposition flux and OC burial flux. Additionally, microbial necromass was determined to indicate microbial activities. The results showed an increase in OC burial flux when farming became intensive, reaching an average of 91.60 ± 10.98 g m−2 yr−1 with a mean microbial necromass contribution of 30.51 ± 8.56% to the sediment OC. However, the burial efficiency was negatively correlated with OC biodeposition flux with an average of 30.17 ± 12.19%. The outcomes suggest that oyster farming has a strong OC burial capacity. Nevertheless, biodeposition flux from excessive farming triggers stronger microbial degradation of OC, reducing the ratio of OC from biodeposit to burial.

In shellfish farms,to guide selection,it is important to rapidly determine the gonadal condition of the parents based on the appearance and morphology of the shells.For the intuitive shell size traits of shellfish,without the intuitive weight traits of the soft body and gonadal wet weights,the shellfish must be dissected and weighed pre-data collection in the laborious shellfish death after dissection is a significant loss to the breeding plant.It is crucial to determine weight trait growth(gonadal wet,soft body wet,and total wet weights)by measuring visual data(shell length,width,and height).Pathway analysis,which was developed by the quantitative geneticist Wright in the 1920s,identifies the correlations between parameters and categorizes their correlation coefficients into direct and indirect influences through other parameters to create the optimal regression equations.Pathway analysis to guide selective breeding of aquatic organisms was achieved for many species using the morphological traits of body mass and soft weight;however,pathway analysis of soft body and gonad wet weights,which are not readily available,was not reported.Mya japonica has a flavor comparable to that of a Crassostrea gigas whose soft body wet weight is heavier than that of an oyster of the same size,with a high meat yield and economic value.The relationship between shell size and weight traits of M.japonica during the breeding period was explored to guide seed shell selection during breeding.In this study,the shell size traits(shell length X1,width X2,and height X3)and weight traits(total wet weight Y1,soft wet weight Y2,and gonad wet weight Y3)of 185 M.japonica from Jiaozhou Bay,Qingdao,were measured,and a path analysis of shell size traits on weight traits was conducted.The results demonstrated that the correlation coefficients of six traits of the six breeding M.japonica traits reached a highly significant level(0.01),with correlation coefficients ranging from 0.891 to 0.966.The direct effects of shell width on the total,soft,and gonad wet weights were 0.462,0.519,and 0.537,respectively.The influence of the shell width on the total,soft,and gonadal wet weights was the greatest,with values of 21.34％,26.94％,and 28.84％,respectively.Shell width and height had the greatest degree of co-determination for total,soft,and gonadal wet weights,with values of 32.88％,24.93％,and 21.34％,respectively.Using the multiple regression analysis method,the optimal regression equation of shell size trait to weight trait was established as Y1=0.295X1+1.73X2+1.128X3-72.554,R2=0.954;Y2=0.117X1+0.56X2+0.219X3-19.240,R2=0.927;Y3=0.055X1+0.362X2+0.082X3-9.402,R2=0.891.The results demonstrated that when weight were the primary breeding targets,indirect selection could be performed using shell width,and the synergistic effect of shell height could be considered.Our findings provide a theoretical basis for brood selection for breeding M.japonica.

Many aquaculture environments suffer from significant silicon deficiencies and severe heavy metal contamination, posing substantial risks to both production and safety in aquaculture. This study aimed to assess the release of silicate from rice husk ash (RHA) and its impact on phytoplankton abundance and community composition, which are key factors affecting shellfish growth and survival. Additionally, the capacity of RHA to adsorb mercury (Hg2+) 2+ ) was examined using different modification methods. The results demonstrated that the concentration of dissolved silicate in seawater increased with higher RHA doses, reaching a maximum of 189.77 +/- 45.61 mu mol L- 1 in the high RHA treatment (HR) with 1.0 g L- 1 of RHA. Notably, the HR treatment group exhibited a significant increase in chlorophyll-a concentration for nano-phytoplankton (2-20 mu m), with an up to eightfold rise in abundance compared to the control group. Moreover, the HR treatment resulted in a maximum diatom abundance of 4217 +/- 741.98 cells L- 1 , benefiting diatom species such as Coscinodiscus sp., Nitzschia sp., and Cyclotella sp. These findings underscore the potential of RHA as a catalyst for diatom growth, which in turn supports the growth of shellfish. Furthermore, no concentrations of mercury (Hg), lead (Pb), cadmium (Cd), arsenic (As), copper (Cu), zinc (Zn), and chromium (Cr) were detected in any of the silicate enrichment treatments, confirming the safety of the RHA. The treatment of RHA with NaOH achieved an impressive removal efficiency of Hg2+, 2+ , reaching up to 97.41 +/- 0.33 %. This study highlights the promising application of agricultural waste RHA as a catalyst for diatom growth and an adsorbent for heavy metals in water systems relevant to aquaculture practices.

Low-salinity conditions are generally used in land-based cultivation to promote the germination and growth of Zostera marina L. and to improve the restoration effect of seagrass beds. Different salinity conditions lead to morphological and physiological differences. To investigate the impacts of salinity and osmotic pressure on the germination and early development of Zostera marina seeds, this study utilized seawater with different salinity conditions and PEG-6000 solutions to simulate various non-ionic osmotic pressures and examine the germination, cotyledon growth, and leaf differentiation over 28 days, as well as determine the biochemical traits on days 1, 3, 5, and 7. The results show that the cumulative germination rate in LS-0 was 91.6%, but it was not significantly affected by the PEG solutions. The different salinities (5, 10, and 15) had no significant effect on the germination rate, which ranged from 76.4% to 78.8%: low salinity and low osmotic pressure stimulated the germination by accelerating the water uptake through increased osmotic pressure differences. The leaf differentiation was regulated by the osmotic pressure and salinity. In LS-10, the most used condition, the leaf differentiation rate was 35.2%, while PEG-10 displayed 6.4%. The total soluble sugar and soluble protein in the seeds decreased. Antioxidant enzyme activities were activated under low-salinity conditions, which supported germination within a tolerable oxidative stress range.

Eelgrass(Zostera marina),a perennial marine seed plant of Magnoliaceae,is commonly found in offshore shallows and river inlets and lives in submerged water.Eelgrass has important ecological services,such as water purification,protection of biodiversity,dike protection,disaster mitigation,and carbon sequestration.In recent years,with the increasing intensity of marine development and utilization and the impact of global climate change,seagrass bed resources have shown signs of increasing decline.The degradation rate of,China's seagrass beds also accelerates annually.Thus,the protection and restoration of seagrass bed resources cannot be delayed.In addition to taking effective management measures,scientific restoration of seagrass beds through human intervention is another important approach to protect existing seagrass beds.Transplanting artificially cultivated seagrass seedlings for seagrass bed restoration is also a way to utilize the seeds efficiently,and the evaluation of seed vigor status is the key to determine the germination rate and seedling establishment rate.Seed vigor is an important index for screening high germination rate,high seedling emergence rate,and other high-quality varieties.It is also the main index reflecting the rapid and neat emergence of seeds and the normal growth of seedlings.At present,methods commonly used to test eelgrass seed vigor are low-temperature germination assay,conductivity assay,enzyme vigor assay,and 2,3,5-tripheyl tetrazolium chloride(TTC)staining assay.However,low-temperature germination test cannot reflect the real vigor level of seeds well,especially in eelgrass seeds,because the germination time needs more than 2 weeks.Seedling growth determination,germination rate determination,and other traditional methods for detecting seed vigor need to be verified by a large number of repetitive experiments,which require large amounts of manpower,material resources,and time,as well as a large amount of investment in the development and development of eelgrass seeds.Similarly,conductivity measurement,enzyme activity measurement,and seedling growth rate measurement need to be validated by a large number of repetitive tests,which require a large investment of labor,material,and time,and may also damage seed samples.With the rapid development of technology,various non-contact,non-destructive,rapid seed viability testing methods have emerged.These methods include non-invasive micro-measurement,near-infrared spectroscopy,hyperspectral imaging,electronic nose detection.Among them,non-invasive micro-measurement determines seed viability by means of the sample.It also determines seed vigor by measuring the ion or molecular flow rate of drops on the seed surface.Given its advantages of non-damage,multi-electrode,multi-angle,high sensitivity,and high resolution,this technique has been applied in different plant research fields,such as plant salt resistance,plant pathology,and plant heavy metal resistance.In this study,we determined the Ca2+flow rate and direction in eelgrass seeds with different activities obtained from drying treatment by a non-invasive microbolometer system to investigate the relationship between Ca2+flow rate and eelgrass seed vigor,and provide a new method for the rapid,non-invasive,and in vivo identification of eelgrass seed vigor.Prior knowledge of seed viability status is a crucial aspect of artificial seedling cultivation,including eelgrass.In this study,eelgrass seeds were subjected to different degrees of drought stress for their special recalcitrant properties,and the same batch of eelgrass seeds was artificially treated to create differences in vigor.While different indicators were used to describe the physiological state of the seeds after the drying treatment,non-invasive micrometry was used to determine the Ca2+flow rate of the seeds and investigate the relationship between eelgrass seed vigor and Ca2+flow rate.In this study,drying treatments were used to artificially create viability differences in eelgrass seeds from the same batch,totaling five drying times(0,1,2,4,and 8 h)and 20 groups of samples.Germination rate,relative conductivity,water content,catalase activity,and malondialdehyde content were determined.Non-invasive micro-measurement was applied to the detection research of eelgrass seed vigor.Its primary objectives were to verify the feasibility of seed vigor grading through preliminary experiments,formulate a demonstration scheme,and further lay a solid foundation for the subsequent establishment of a standardized system for eelgrass seed vigor grading.Results showed that the germination rate gradually decreased and the relative conductivity increased with treatment time,the germination rate of the seeds after 4 h of treatment was 12％lower than that of the untreated seeds,and the germination rate after 8 h of treatment significantly reduced and was 68.7％lower than that of the untreated seeds.Catalase activity also significantly changed with treatment time.The Ca2+was effluxed,and the efflux rate increased with treatment time.The germination rate and Ca2+efflux flow rate were significantly negatively correlated,and the fitted linear equation was y=-0.192 2x+94.09,with an R2 of 0.860 6.This study proved that the Ca2+flow rate could serve as an eelgrass seed vigor detection index,providing a basis for the rapid and non-destructive identification of eelgrass seed vigor.

Crassostrea gigas,also known as Pacific oysters,are economic shellfish with the widest range of cultivation,the highest yield in the world,and the most important type of mariculture shellfish in China.However,many C.gigas have died during summer in coastal areas worldwide in recent decades.In 2008,the mortality rate of C.gigas cultured in France reached 40%-100%.In 2009,the mortality rate of C.gigas in some area of Sanggou Bay reached 51%.In 2019,the mortality rate of the Rushan area reached 50%-90%,with the death peak occurring in middle and late August.There were many reasons for the large-scale death of C.gigas,such as temperature,dissolved oxygen,salinity,disease,food availability,and reproduction levels,among which high temperature was the most important abiotic stress factor.The high temperature in summer disturbed the enzyme metabolism of C.gigas,resulting in slow or impeded growth.Furthermore,the reproduction and spawning of C.gigas caused a large amount of protein consumption,and physical weakness combined with high-temperature stress induced many deaths.Therefore,considering the problems faced by C.gigas culture during high summer temperatures,the introduction of new varieties will increase the economic benefits to the industry. Due to its high sterility,triploid C.gigas has attributes such as a fast growth rate,resilience excellent economic characteristics,and high energy conversion efficiency.In recent years,a certain farmed scale has formed in China,especially in northern coastal areas.There have been many studies on the biological and physiological differences between triploid and diploid C.gigas worldwide,mainly focusing on the differences in growth characteristics,soft tissue components,gonadal development,disease resistance,and gill structure.However,comparisons between triploid and diploid C.gigas feeding,metabolic physiology,energy budget,and carbon budget have not been reported.Focusing on the specific period of high temperatures in summer,this study investigated the feeding and metabolic physiological characteristics of triploid and diploid C.gigas using the field flow method,and compared and analyzed their energy allocation strategies in response to a high-temperature environment.The study provide data support for revealing the physiological differences caused by the ploidy effect of C.gigas in order to assist with evaluating the culture capacity. Triploid and diploid C.gigas were selected as research objects in August 2022 to analyze the differences in feeding and metabolic physiology and energy/carbon allocation strategies during high temperatures in summer.Physiological parameters related to intake and metabolism,such as water filtration rate,absorption efficiency,oxygen consumption rate,and ammonia discharge rate,were determined based on the field flow method in Sanggou Bay,Rongcheng,Shandong Province,and energy allocation and carbon allocation were estimated based on the principle of the energy budget.The results revealed that the water filtration rate and assimilation efficiency of triploid C.gigas were higher than those of diploid C.gigas,but there were no significant differences(P＞0.05).There were significant differences in the oxygen consumption rate and ammonia discharge rate between triploid and diploid C.gigas(P＜0.05).The oxygen consumption rate of triploid C.gigas was significantly lower than that of diploid C.gigas(P＜0.05),but ammonia discharge rate was significantly higher than that of diploid C.gigas(P＜0.01).The results of the energy and carbon budget analyses showed that the feeding energy/carbon and assimilation energy/carbon values of triploid C.gigas were higher than those of diploid C.gigas,but there was no significant difference(P＞0.05).There were significant differences in respiratory energy/carbon,excretion energy/carbon,and growth power between triploid and diploid C.gigas(P＜0.05).Respiratory energy/carbon values of triploid C.gigas were significantly lower than those of diploid C.gigas(P＜0.05),but excretion energy/carbon and growth power values were significantly higher than those of diploid C.gigas(P＜0.05).The oxygen/nitrogen ratio of triploid and diploid C.gigas fluctuated in the range of 7.91-14.11 and 59.81-94.19,respectively.Moreover,the main energy supply substances of triploid C.gigas were proteins,while the main energy supply substances of diploid C.gigas were carbohydrates and fats.These results revealed the differences in energy allocation patterns associated with the ploidy effect of C.gigas during high temperatures in summer. From the perspective of individual physiology and ecology,this study found that,compared with diploid C.gigas,triploid C.gigas showed certain advantages in energy allocation strategies by adjusting feeding and metabolic physiological behaviors during the high-temperature summer.However,the internal molecular mechanism of response strategies adopted by triploid C.gigas to cope with an adverse environment is still unclear.Further interpretation at the molecular level needs to be combined with omics and other systems biology techniques.

China is the largest aquaculture country in the world,with mariculture production accounting for more than 50％of the total production in the world.In 2021,the production of shellfish in China increased to 1.546 × 107 tons,accounting for approximately 70％of the mariculture production.Filter-feeding bivalves such as oysters and clams are the main species of mariculture in China.In addition to the important economic values,filter-feeding bivalves influence ecosystem nutrient cycling through feeding,metabolism,and biodeposition and play roles in increasing the water transparency,preventing harmful algal blooms,controlling eutrophication,and promoting carbon storage.The physiological activities of filter-feeding bivalves,especially ingestion and metabolism,form the link between planktonic and benthic ecosystems,and their physiological indicators are the basic parameters for evaluating the energy budget and carrying capacity.However,although researchers have conducted a series of studies on the physiological activities of filter-feeding bivalves,some limitations in monitoring and the subsequent data processing remain.Therefore,it is urgent to improve the measurement of the physiological activities of filter-feeding bivalves,including the accuracy of data collection and the rigorousness of data processing,to ensure the accuracy of the experimental results. Mudflats are located in the interaction zone between the land and sea and are important areas for the habitat,growth,and reproduction of several macrobenthic organisms.As the dominant species of macrobenthic communities,mudflat-buried shellfish play a crucial role in the material and energy flows of a mudflat ecosystem.However,recently,with the expansion of shellfish aquaculture,the mudflat environment has been deteriorating accompanied by a series of ecological problems,such as high mortality and slow growth rates and alteration in the structure of phytoplankton community,which has led to significant losses to the shellfish aquaculture industry.Therefore,the ability of the ecosystem to support shellfish production must be evaluated,and its carrying capacity must be estimated.Generally,numerical methods for estimating the carrying capacity of shellfish based on food limiting indicators include physical-biological ecosystem modelling,trophodynamic modeling,and energy balance modeling.Current methodologies for estimating shellfish carrying capacity are divided into two main categories:dynamic and static modellings.Compared with the dynamic estimation model,static estimation methods are based on the environment of the target area and the key physiological parameters of shellfish and have been widely applied in some aquaculture areas such as Sanggou Bay,Jiaozhou Bay,and Zhangzidao in China. Here,to explore the energy budget and carrying capacity of the surf clam,Mactra veneriformis,and the estuarine clam,Potamocorbula laevis,in Geligang,Liaodong Bay,a portable particle counter and a continuous oxygen monitoring system were used in combination with flow-through chambers to detect the feeding and metabolic parameters of M.veneriformis and P.laevis.Furthermore,the carrying capacity of two mudflat-buried bivalves in Liaodong Bay was estimated based on the organic carbon supply-demand balance model.The results indicated that 1)the clearance rates of M.veneriformis and P.laevis were(4.87±0.85)L/(h·g)and(6.46±2.25)L/(h·g),respectively,and the oxygen consumption rates were(0.94±0.45)mg/(h·g)and(0.22±0.14)mg/(h·g),respectively.The energy absorption of M.veneriformis and P.laevis ranged from 748.97 to 1 333.52 J/(h g),and 931.55 to 1 647.08 J/(h·g),respectively.2)Using organic carbon supply-demand balance model combined with the primary productivity and shellfish clearance rate,we found that the carrying capacity of M.veneriformis in Geligang,Liaodong Bay,was 57,47,and 34 ind./m2 for age-1(total wet weight 6.7 g),age-2(total wet weight 9.3 g)and age-3(total wet weight 14.6 g),respectively;and the carrying capacity of P.laevis was 346,143,and 99 ind./m2 for age-1(total wet weight 0.14 g),age-2(total wet weight 0.69 g),and age-3(total wet weight 1.25 g),respectively.These results provide basic data for the rational exploitation and utilization of shellfish resources and the conservation of biodiversity in a mudflat ecosystem.

Coastal bays link terrestrial and oceanic carbon reservoirs and play important roles in marine carbon cycles. Particulate organic carbon (POC) produced by phytoplankton is a major autochthonous carbon source in coastal bays. Previous studies on the fate of POC produced by phytoplankton mainly focused on the relationship between phytoplankton and zooplankton in classic food webs, while our knowledge on the roles of bacterioplankton is still limited, particularly in bays under highly intensive aquaculture activities. Here, we investigated bacterial community structure, and the influence of environmental factors and phytoplankton biomass and community structure based on samples collected in August 2022 from Sanggou Bay, a typical aquaculture bay in northern China. Environmental conditions, phytoplankton and bacterial community structure differed significantly between different aquaculture areas, showing higher relative abundance of Synechococcus sp. in the mixing area of shellfish and kelp culture (Area II) than the shellfish culture area (Area I). In contrast, Marivita cryptomonadis was more abundant in Area I, associated with elevated dissolved inorganic nitrogen (DIN), POC, POC/PN (the molar ratio of POC to particulate nitrogen) and sterol-derived total phytoplankton biomass. The strong correlation between total phytoplankton biomass and particle-associated bacteria indicated the important role of this bacterial fraction in processing organic compounds produced by phytoplankton. Significant correlations between bacterial community composition and POC/PN suggested more organic carbon potentially entering detrital biomass pools in Area I compared to Area II. Our results suggest that spatial distribution patterns of bacterial community structure were regulated by multiple abiotic and biotic factors and had a profound impact on the fate of organic carbon under highly intensive aquaculture activities in Sanggou Bay.

Farmed aquaculture species play an important role in regulating nutrient cycles in farming systems. Compared with nitrogen and phosphorus, the role of farmed species in the silicon (Si) cycle remains poorly understood. To help reduce this uncertainty, we clarified the sources and sinks of silicate and quantified the Si pools in an aquaculture system in Sanggou Bay (SGB). The results showed that dissolved inorganic nutrient levels were significantly lower during the dry season than during the wet. Dissolved silicate (DSi) is a potential limiting factor for phytoplankton growth during spring, and phosphorus limitation occurs during summer. The budget results indicated that large amounts of nitrogen, phosphate (DIP), and DSi were buried in the sediment or transformed into other forms during both the wet and dry seasons. The nitrogen and DIP cycles were strongly influenced by bivalve excretion and farmed species harvesting; however, these processes had little impact on the Si cycle. Si availability depends on both external inputs and internal recycling. DSi was primarily supplied from the Yellow Sea, with a minor contribution from the river due to river discharge during spring. However, during summer, riverine inflow (accounting for 83% of the total influx) was the major DSi source followed by benthic flux (12%). Biogenic silica (BSi) burial efficiency in the sediment was estimated to be 78% during spring and 23% during summer. The BSi preservation efficiency in bivalves during spring was high (53%), leading to a higher Si retention than in river discharge. Bivalves biodeposition plays an important role in the Si burial process. We suggest that this high retention is essentially controlled by the biodeposition mechanism, which is directly controlled by the exotic suspension feeders. Bivalves have the potential to alter Si retention in the bay by producing large amounts of biodeposits and accelerating the silica cycle, which may lead to more carbon dioxide being absorbed by diatoms.

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 oysters facilitate 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 h of oyster cultivation than that in the control seawater. It was noticed that the transparency 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.

In the context of global climate change, one central interest is an improved understanding of the global carbon cycle. A large number of studies have investigated carbon cycling and associated elements, mainly nitrogen and phosphorus. However, as an essential element for diatom growth, Si has been largely ignored. Si is the second most abundant element and is widely distributed on Earth. The chemical weathering of silicates on land and photosynthesis of diatoms in the ocean play an important role in atmospheric CO2 levels at various timescales. Diatoms are the primary producers in the ocean and account for as much as 40% of the annual ocean carbon fixation, which have an absolute requirement for Si to form siliceous cells. The main mechanism underlying ocean carbon sinks is a "biological pump." The biological pump is driven by the biological Si pump to a large extent. Therefore, the biogeochemical process of Si has become one of the key research issues for global environmental change.Based on previous studies, the regulation and influence of the Si biogeochemical cycle on the carbon cycle are discussed in this review. The coupling effect and mechanism of the Si and carbon cycles in shellfish culture ecosystems were analyzed and the key research questions were explored. Chemical weathering of silicates and the cycling of their products form the basis of Si biogeochemistry. CO2 is consumed during weathering reactions. Therefore, silicate weathering on land represents an important sink for atmospheric CO2. Furthermore, at the geological timescale, primary silicate mineral weathering is the source of secondary silicate. Terrestrial plants absorb soluble silica through their root system during growth. Amorphous silica deposited in plant tissue after maturity is called phytolith. Phytoliths have excellent geochemical stability and occlude a certain amount of organic carbon during the formation process. The organic carbon occluded within phytolith is called phytolith-occluded carbon (PhytOC) and is buried in the soil. PhytOC is released into the soil with phytolith and may be preserved in soils for several thousands of years. As a consequence, PhytOC in terrestrial ecosystems could be significant potential carbon sinks globally due to the refractory phytolith. Primarily through river input, the dissolved silicate (DSi) is transported into the coastal ocean (approximately 84% of DSi input to the oceans). As the major primary producer, diatoms absorb DSi during growth and account for a large fraction of the total carbon fixation in the modern oceans. DSi is converted into biogenic silica via biological processes, is transported to the deep ocean, and is finally buried into sediments with organic carbon in the marine ecosystem. Thus, by controlling the contribution of diatoms to the total primary production, DSi can affect the carbon cycle in oceans. The carbon pump is driven by the Si pump.Mariculture has developed quickly in recent decades. Shellfish, which are dominated by filter-feeding species, are the main mariculture species. The filter-feeding shellfish consume particulate organic carbon as phytoplankton and use dissolved inorganic carbon to build their shell during growth. Filter-feeding shellfish are an import fishery carbon sink. As one of the important feed sources of filter-feeding shellfish, diatoms form fishery carbon sinks in coastal shellfish culture areas. Silicate is an essential salt for diatom growth. Consequently, the carbon sink of filter-feeding shellfish culture is connected with DSi through diatoms. Si could play an important role in driving the formation of carbon sinks in filter-feeding shellfish culture. Hence, it is necessary to consider all processes and coupling effects in the study of the Si biogeochemical cycle. It is important to understand its role in the carbon sinks of shellfish culture.Nowadays, in many systems, human perturbation has resulted in a decline in the ratio of Si: N to 1:1 or less, with severe impacts on the quality and structure of aquatic ecosystems. DSi limitation has been reported in many studies, in both coastal and marine waters. DSi limitation causes shifts from diatoms to non-siliceous algae and is supposedly related to the decreasing export of carbon. A shift from diatoms to other species would enhance the recycling of organic matter in the upper water column because diatoms are very effective in carbon sequestration. DSi limitation has also appeared in some aquaculture bays in China, such as Jiaozhou Bay and Laizhou Bay, in spring. Regarding future directions, it is suggested that more research be conducted on Si biogeochemistry in shellfish culture systems and coupling with the carbon cycle. The subsequent results could evaluate the role of Si in the carbon sink of filter-feeding shellfish culture. Future studies are expected to provide ideas for alleviating Si deficiency in the aquaculture bay and exploring the expansion path in shellfish farming.

In recent years, the rapid development of the large-scale aquaculture industry has generated substantial economic benefits, positioning it as one of the fastest-growing sectors in global agricultural production. However, improper management practices in aquaculture, including overfeeding, improper feed selection, antibiotic misuse, high stocking densities, inappropriate choice of aquaculture species, and improper discharge of aquaculture wastewater, have resulted in significant watershed pollution in agriculture and the wastage of valuable resources. To address these challenges, extensive research and application of wastewater treatment technologies have been conducted in large-scale aquaculture in China. This review provides an overview of current cases and applications of wastewater treatment in large-scale aquaculture in China, focusing on four common intensive wastewater treatment methods: constructed wetland treatment model, ecological ditch treatment model, Integrated Multi-trophic Aquaculture model, and recirculating aquaculture model. The constructed wetlands utilize plants and microorganisms to purify both organic and inorganic pollutants in water, while ecological ditches employ engineering measures such as sedimentation ponds, interception ditches, and aeration devices to achieve wastewater treatment. Additionally, other aquaculture models are highlighted, such as Integrated Multitrophic Aquaculture (IMTA), which emphasizes synergistic interactions between aquaculture species and the recycling of nutrients, and the Recirculating Aquaculture Systems (RAS), which utilize water circulation and treatment equipment for wastewater treatment. The consequences and benefits of these systems in pollution reduction are described. These treatment technologies have made significant progress, offering theoretical guidance for environmentally friendly aquaculture production and the maintenance of ecological stability in aquaculture water bodies. Each wastewater treatment model has a different function, target, and methodology. Finally, this paper proposes directions and recommendations for future pollution management in large-scale aquaculture in China, including strengthening technological research and development, the combined application of multiple treatment models, promoting industry collaboration, and achieving resource sharing. These efforts will contribute to further promoting the sustainable development of China's aquaculture industry and provide valuable experiences and references for other countries and regions.