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The coastal aquaculture areas have been subject to a variety of anthropogenic pressures in recent studies, and reasonable environmental quality assessment is essential for both ecological conservation and production practices. However, there are significant differences between the results produced from various environmental quality assessment regarding the focus of the evaluation and the fundamental methodology. Furthermore, many of these methods are very specific and difficult to adapt to general applications. Here, we utilized the Modelling-Ongrowing fish farms-Monitoring B investigation system (MOM-B), we assessed the benthic habitat quality of benthic bivalve aquaculture areas in the Xiaoqing River estuary located in Laizhou Bay, China. The aim was to validate the accuracy and practicality of this system. The biological, chemical, and sensory parameters of the MOM-B system, temperature, chlorophyll a (Chl-a), food availability, and planktonic larvae were evaluated throughout the investigation area during the summer of 2021. The MOM-B results indicated that the benthic habitat quality in the survey area was good and lightly disturbed, but the quality in the middle tide area began to deteriorate in August, the hottest month of the summer. Environmental factors indicated that the combined effects of high temperatures and fine sedimentation had led to increased environmental stress in the middle tide area. Food availability and population recruitment also suggested that the benthic habitat quality was better in the high tide and low tide areas than in the middle tide area, and more favorable for the survival of Manila clams. The accuracy, sensitivity, and discriminatory ability of the MOM-B system were demonstrated by environmental and biological indicators. This work showed that the MOM-B system is a practical, simple, and sensitive environmental assessment tool that is easy to implement in estuarine and benthic bivalve aquaculture areas. It can be used for long-term continuous monitoring and as an early warning tool for benthic habitat quality., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Evaluating the performance of AquaCrop models under the drip irrigation of maize with soil conditioners is of great significance for improving coastal saline–alkali land crop management strategies. This study aimed to evaluate the performance of an AquaCrop model for maize growth simulation under different soil conditions (humic acid (HA) and sodium carboxymethyl cellulose (CMC)) and dosages and different levels of irrigation in the Shandong coastal saline–alkali area, China, and to optimize the amount of irrigation. Three years of experiments were carried out in the growing season of maize (Ludan 510) in 2019, 2020, and 2021. The dosages of HA were 5, 15, 25, and 35 g/m2, the dosages of CMC were 1, 2, 3, and 5 g/m2, and the levels of irrigation from 2019 to 2021 were all 120 mm. The model was calibrated with data from 2019, and the model was verified with data from 2020 to 2021, according to the recommended corn parameters in the AquaCrop model manual. The results showed that the model had a good simulation effect on canopy coverage, with a root-mean-square error (RMSE) of less than 15.2%, and the simulated aboveground biomass and yield were generally low. The simulated value of soil water content was generally high, with some treatments having errors of more than 15.0%. The simulation effect of irrigated maize from 2019 to 2020 was better than maize in 2021. The simulation effect of HA was better than that of CMC, while the simulation effect of a low-gradient modifier was better than that of high-gradient conditioner when compared with CMC. In conclusion, the AquaCrop model could be a viable method for predicting maize development under different soil conditioners in this area. The suitable levels of irrigation under HA and CMC treatments were 47.0–65.9 mm and 61.0–92.4 mm, respectively, according to the principle of high yield and water use efficiency. The results provided a reference for optimizing the drip irrigation of maize under the application of soil conditioners in coastal saline–alkali areas. [ABSTRACT FROM AUTHOR]

We measured the organic content and sinking velocities of biodeposits from two scallop species ( Chlamys farreri, Patinopecten yessoensis) and abalone ( Haliotis discus hannai) that were cultured on suspended long-lines. Measurements were conducted every two months from April 2010 to February 2011. The shellfish were divided into three size groups (small, middle, and big sizes). At each sample point, we assessed biodeposit organic content, average sinking velocity, the frequency distribution of sinking velocities, and the correlation between organic content and sinking velocity. The organic content of biodeposits varied significantly among months ( P<0.05) and the pattern of change varied among species. Sinking velocities varied significantly, ranging from <0.5 cm/s to >1.9 cm/s. The sinking velocities of biodeposits from C. farreri and P. yessoensis were 0.5-1.5 cm/s and from H. discus hannai were <0.7 cm/s. The organic content was significantly negatively correlated to the sinking velocity of biodeposits in C. farreri ( P<0.001) and P. yessoensis ( P<0.05). [ABSTRACT FROM AUTHOR]

The red alga Gracilaria lemaneiformis was cultivated with the scallop Chlamys farreri in an integrated multi-trophic aquaculture (IMTA) system for 42 h at Sanggou Bay, located in north China. Variation in inorganic carbon in the IMTA system was determined. The experiment included three treatments each with three replicates and three scallop monoculture systems as controls. Scallop density (399.1 ± 7.85 g per microcosm) remained the same in all treatments while seaweed density differed. The seaweed density was set at three levels (treatments 1, 2, 3) with thallus wet weights of 125.3 ± 4.72 g, 252.3 ± 7.50 g, and 378.7 ± 6.51 g per microcosm, respectively. This produced bivalve to seaweed wet weight ratios of 1:0.31, 1:0.63, and 1:0.96 for treatments 1, 2, and 3, respectively. In control groups, continuous dissolution of carbon dioxide (CO) produced by scallops into the seawater not only caused an ongoing increase in partial pressure of CO ( pCO), 5.5 times higher than that of natural seawater, but also acidified seawater by 0.8 units after 42 h of culture. However, in all seaweed-scallop groups, the higher the algal density, the more CO was absorbed; pCO was lowest in treatment 3. The results suggest that a ratio of bivalve to seaweed less than 1:0.96 may produce an even stronger CO sink. Overall, the integrated culture of seaweed and scallop could provide an efficient and environmentally friendly means to reduce CO emissions from bivalve mariculture. [ABSTRACT FROM AUTHOR]

The amphipod crustacean Eogammarus sinensis has useful features that make it suitable for use in the aquaculture of fish and large decapod crustaceans. In this study, we investigated the effects of temperature and salinity on the development, fecundity, survival, and growth rate of E. sinensis. The results show that temperature significantly affected E. sinensis development, but salinity. As temperature increased, the duration of E. sinensis embryonic development decreased. Fecundity was affected significantly by temperature and the combination of temperature and salinity, but by salinity alone. In addition, high temperatures accelerated E. sinensis juvenile growth rates, whereas high salinity reduced it. Therefore, our data suggest that E. sinensis tolerates a wide range of salinities and that temperature has more significant effects than salinity on the embryonic development, fecundity, and growth of E. sinensis. Our results shall be useful for mass production of this species for use in aquaculture. [ABSTRACT FROM AUTHOR]

The growth and survival of the scallop Chlamys farreri exposed to different initial densities were evaluated in culture systems from inshore and offshore areas of Sungo Bay, China, from May 2007 to March 2008. Water quality data (e.g. temperature, salinity, current speed, chlorophyll a and total particulate material) were measured concurrently. The C. farreri reached the market size after 10 months of cultivation. Average survival rates for the same initial densities were lower in the inshore area than those in the offshore area. Survival rates also were inversely proportional to the initial densities. Scallops in offshore area with initial densities of 20 and 30 individuals per disc resulted in significantly greater shell heights, soft tissue weights and muscle weight compared with the other experimental groups. Tissue weight increased rapidly from May to September. However, scallops in offshore area had a second growth peak during October to November. Scallops in the offshore area had higher growth and survival rates, which may be attributed to high water current speed resulting in increased food supplies. Results indicate that the scallop C. farreri has an aquaculture potential in offshore cultivation systems. [ABSTRACT FROM AUTHOR]

The shellfish–algae mode of integrated multitrophic aquaculture (IMTA) is a sustainable aquaculture method that benefits the environment and the carbon cycle. However, most current shellfish–algae aquaculture modes are based on the expansion of kelp aquaculture. Due to the low tolerance of kelp to high temperatures, integrated shellfish–algae aquaculture areas often become shellfish monocultures in summer, which may lead to both high mortality rate of shellfish and to economic loss while causing serious environmental harm via eutrophication, decreases in dissolved oxygen (DO), and decreases in pH. In this study, we investigated the effects of different ratios of seaweed (Gracilaria lemaneiformis), which is tolerant of high temperatures, to Japanese scallop (Patinopecten yessoensis) on water quality and environmental parameters. A two-day small-scale enclosure water body experiment was conducted in Sanggou Bay (Shandong, China) in August 2019. The results demonstrated that culturing shellfish alone significantly affected pH, DO, eutrophication, and other environmental indicators, as well as the carbonate system. The negative environmental impact of the shellfish–algae aquaculture system was much smaller. However, too high a proportion of algae might consume excessive amounts of dissolved inorganic nitrogen (DIN) and nutrients, while too low a proportion of algae might not fully absorb the nutrients released by the cultured shellfish, in turn leading to an increased risk of eutrophication. The shellfish–algae aquaculture system not only improved the inorganic carbon system, but also the organic carbon system. At the end of the experiment, all the parameters of the inorganic carbon system had decreased significantly, while all the parameters of the organic carbon system had increased significantly. The results of this study illustrate the need to include macroalgae rotations in summer, and that an appropriate ratio of shellfish to algae is necessary to achieve a sustainable aquaculture system. Moreover, this research has also confirmed the importance of the future and related research in the actual production, which will provide useful information to guide governmental strategies for summer aquaculture rotations and insight into the controversy concerning whether aquaculture is a carbon source or sink. [ABSTRACT FROM AUTHOR]

A biophysical model was used to study bivalve-seaweed integrated culture in Sungo Bay, a typical intensive longline mariculture site in China. Based on this model, the observed variations in pelagic variables and growth of cultivated species were reasonably reproduced. The results showed that the nutrients carried by water exchange were more than sufficient to support the growth of kelp, while the growth of oysters was mainly supported by the local accumulation of phytoplankton, and the majority of scallop's food was supplied by water exchange. A reduction of water exchange would lead to a decrease in the quality of scallops, whereas the growth of oysters would be promoted. Considering the interactions among species and areas, the growth potential of mariculture in Sungo Bay was evaluated. From an area-scale perspective, mariculture in specific areas has certain growth potential. From a bay-scale perspective, the seeding density in the bay should be reduced. In addition, a precise assessment of growth potential should be a tradeoff between seeding density and water exchange. Although further improvement is needed, this model is an effective tool to assist with the management of spatially heterogeneous aquaculture systems, and similar approaches can be applied to other aquaculture sites. • A biophysical model was used to study the growth potential of mariculture. • Interactions among species and areas were considered. • The effects of water exchange and phytoplankton were highlighted. • The model provides a tool for managing spatially heterogeneous culture systems. [ABSTRACT FROM AUTHOR]

The aquaculture of Manila clam (Ruditapes philippinarum) is under threat due to its high mortality in summer. To investigate the environmental influence on mortality of the species, we have conducted field surveys in the aquaculture area in Laizhou Bay, during the summers of 2019 and 2020. Environmental and biological data were collected. The results of data analysis have shown that in 2020, large-scale mortality events were not recorded and spatial variations of environmental variables were no significant within the survey area. However, in August 2019, significant variations of environmental variables were detected in the middle tidal area. This area was charactered with relatively high-water temperature (with maximum temperature of 31.49 °C and mean value of 26.17 ± 1.62 °C), elevated hydrogen sulfide concentrations (with a maximum concentration of 24.72 μmol/L and a mean concentration of 7.89 ± 4.14 μmol/L), and low dissolved oxygen concentrations (with a minimum concentration of 3.35 mg/L and a mean concentration of 6.27 ± 0.42 mg/L). Correspondingly, high mortality of the clam was recorded in the area, the abundance of live Manila clams has decreased by 80%. No significant abnormalities of environmental variables and clam growth were observed in other regions in 2019. Glycogen content and condition index of the clam were analyzed to investigate the relationship between environmental stress and the health of the clam. Compared to the condition index, glycogen content is a more sensitive indicator of the health status of the clam because changes in glycogen content appeared earlier than changes in condition index and mortality. A principal component analysis further indicated that the high mortality of the clam corresponds with a few environmental variables, including elevated temperature, hypoxia and the concentration of hydrogen sulfide. The simultaneous presence of these multiple environmental stressors could have triggered alterations in the physiological responses of the clam. [Display omitted] • Elevated temperatures can trigger various environmental alterations. • The combination of multiple sublethal environmental stressors had a devastating impact on the survival of the Manila clam. • There exists a causal relationship between environmental stress, physiological responses, and mortality. • Glycogen content and condition index of bivalves serve as reliable indicators for monitoring their overall health status. [ABSTRACT FROM AUTHOR]

Abstract: A three-dimensional physical–biological coupled aquaculture model is developed to study the aquaculture carrying capacity of kelp in Sungo Bay, a typical aquaculture site in China with intensive suspended raft aquaculture. In the aquaculture model, the hydrodynamic module builds on the Princeton Ocean Model by adding two types of drags due to the aquaculture facilities at surface and kelp in water column. The biological module simulates the renewal of dissolved inorganic nitrogen (DIN), the cycle of phytoplankton biomass, and the growth of kelp, while the contribution of bivalves'' excretion to DIN is set to a constant derived from observations. Thus, the coupling between the growth of kelp and the current variation can be studied by adding drags in the layers reached by kelp. The simulated magnitude and vertical profile of currents agree well with observations. The suspended aquaculture causes a reduction in the average speed of surface current by 40%, decreasing the water exchange with the open sea. The simulation results also show that the seasonal and spatial variations of the DIN concentration and phytoplankton biomass are clearly controlled by the distributions of different species. The estimation of DIN budgets of different periods shows competition between kelp and phytoplankton. The primary source of nutrients for the growth of kelp in Sungo Bay is the DIN from the open sea, and the aquaculture obstruction is the main reason for the deficient DIN in the kelp culture area. The final kelp production decreases from the mouth to the end of the bay, consistent with the spatial variation of water exchange rate. Numerical experiments have been carried out by increasing the aquaculture density of kelp from 0.8 to 1.5 times of the current value. Obtained results indicate that the optimal average density is 0.9 times of the current value. [Copyright &y& Elsevier]

Abstract: The suitability of two algae species, Gracilaria lemaneiformis and Sargassum pallidum, for use as food sources for the abalone Haliotis discus hannai Ino was evaluated. Abalones were fed one of five experimental diets: 1) kelp L aminari japonica; 2) G. lemaneiformis; 3) S. pallidum; 4) a mixed diet of L. japonica and G. lemaneiformis (1:1); and 5) a mixed diet of L. japonica and S. pallidum (1:1) for a period of 4months. The survival, growth (shell length and body weight), condition index (body weight/shell length), and feed utilization were measured. Survival was excellent (100%) in all groups. Growth rate (body weight) was highest in the abalone fed kelp exclusively, followed by the mixed diet of kelp and G. lemaneiformis. The abalone fed S. pallidum had the lowest increase in body weight and the lowest feed intake. The mixed diet of kelp and G. lemaneiformis yielded the biggest increase in shell length. There were no significant differences in the condition index among all the treatment groups. The mean daily feed intake of L. japonica was highest, followed by the mixed diets of kelp and G. lemaneiformis, and was lowest for S. pallidum. Abalone exhibited a preference for L. japonica. The feed conversion efficiency was highest for G . lemaneiformis. Results suggest that G . lemaneiformis can be used as a partial substitute for kelp in the diet of cultured abalone. [Copyright &y& Elsevier]