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The concentrations of eight heavy metals (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn) were measured in the sediment, the isolated microplastics from the sediment and the body wall of sea cucumbers from farms in China. Accordingly, the heavy metal concentrations in the sediment were below the class I upper limit of Chinese sediment quality guidelines. Among heavy metals, the median concentrations of Cd and As were higher in the body wall than in the corresponding sediment. Additionally, the median concentrations of Cd, Pb, and Zn were higher on the microplastics than in the corresponding sediment. Furthermore, there was no significant correlation among heavy metals in sediment, sea cucumber and microplastics. This study contributes to the understanding of the heavy metal accumulation in the sediment, the microplastics and the body wall of the sea cucumber., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Microplastic ingestion by the farmed sea cucumber is undocumented. Microplastics were isolated from the sea cucumber Apostichopus japonicus that was collected from eight farms along the Bohai Sea and the Yellow Sea in China. To examine microplastic ingestion, the intestines were isolated, digested and then subjected to the floatation test. The microplastic abundance in the sediment ranged from 20 to 1040 particles kg -1 of dry sediment, while the ingested microplastics ranged from 0 to 30 particles intestine -1 . After filtering the coelomic fluid, the extracted microplastics from the coelomic fluid ranged from 0 to 19 particles animal -1 . Thus, we speculated that microplastics may transfer to the coelomic fluid of sea cucumber. The ingested microplastics did not correlate with the animal body weight but was site dependent, suggesting that sea cucumber may serve as sentinel for microplastic pollution monitoring in the sediment. The microplastics were identified by Fourier transform infrared micro spectroscopy, and the polymer types were mainly cellophane, polyester, and polyethylene terephthalate. This study revealed that, microplastics widely existed in sea cucumber farms, and that sea cucumbers ingest microplastics as suitable with their mouth open. Moreover, the microplastics might transfer to the coelomic fluid of the sea cucumber. Further investigations are needed to assess the chronic effect of the microplastics on the growth and physiological status of the sea cucumber., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Industrial aquaculture wastewater contains large quantities of suspended particles that can be easily broken down physically. Introduction of macro-bio-filters, such as bivalve filter feeders, may offer the potential for treatment of fine suspended matter in industrial aquaculture wastewater. In this study, we employed two kinds of bivalve filter feeders, the Pacific oyster Crassostrea gigas and the blue mussel Mytilus galloprovincialis, to deposit suspended solids from marine fish aquaculture wastewater in flow-through systems. Results showed that the biodeposition rate of suspended particles by C. gigas (shell height: 8.67 ± 0.99 cm) and M. galloprovincialis (shell height: 4.43 ± 0.98 cm) was 77.84 ± 7.77 and 6.37 ± 0.67 mg ind(-1) • d(-1), respectively. The total solid suspension (TSS) deposition rates of oyster and mussel treatments were 3.73 ± 0.27 and 2.76 ± 0.20 times higher than that of the control treatment without bivalves, respectively. The TSS deposition rates of bivalve treatments were significantly higher than the natural sedimentation rate of the control treatment (P < 0.001). Furthermore, organic matter and C, N in the sediments of bivalve treatments were significantly lower than those in the sediments of the control (P < 0.05). It was suggested that the filter feeders C. gigas and M. galloprovincialis had considerable potential to filter and accelerate the deposition of suspended particles from industrial aquaculture wastewater, and simultaneously yield value-added biological products.

China has the world’s largest fisheries industry that has provided a healthy and high-quality food source. Currently, guaranteeing national food security, implementing an all-encompassing approach to food, and establishing a diversified food supply system all pose a great demand for the high-quality development of China’s fisheries industry. This study explores the development status and trend of fisheries in China from the aspects of fishery resources and capture, aquaculture and marine ranching, and aquatic product processing and circulation, and examines major problems through industry research and extensive discussion. Industry development goals and key measures are further proposed. Results found that the pressure on offshore capture is too high, understanding of deep-sea and polar resources is insufficient, the independent capability of technologies and equipment is inadequate, the mechanized, automatic, and intelligent levels of aquaculture are low, high-quality feed and raw materials rely heavily on imports, the basic software and hardware capabilities of the intelligent fisheries are deficient, and the aquatic product processing capacity is lagging behind. Therefore, the following key measures are proposed: conservation and restoration of offshore fishery resources, development and scientific utilization of deep-sea fishery resources, construction and application of a new technology system for green and healthy aquaculture, research and application of deep-sea aquaculture platform technologies, construction and promotion of new aquaculture models, and green processing and high-value utilization of aquatic products.Through the high-quality development of fisheries, China is expected to become advantageous in fisheries science and technology by 2035, with a total output of 8.1×107 t of aquatic products. By 2050, intelligent fisheries is expected to be realized in China, outputting 1×108 t of aquatic products.

Abstract Economically important marine organisms face severe environmental challenges, such as high temperature and low dissolved oxygen, from global climate change. Adverse environmental factors impact the survival and growth of economically important marine organisms, thereby negatively influencing the aquaculture industry. However, little is known about the responses of sea cucumbers to combined environmental co-stressors till now. In this study, ultra-performance liquid chromatography (UPLC) was utilized to obtain metabolic profiles of sea cucumbers. Changes in the concentrations of 84, 68, and 417 metabolites related to the responses of sea cucumbers to heat (26 °C), hypoxia (2 mg/L) and the combined stress, respectively, were observed and analyzed. Representative biomarkers were discussed in detail, including deltaline, fusarin C, halichondrin B and rapanone. The concentration of metabolites involved in the regulation of energy metabolism, including amino acid, carbohydrate and lipid metabolism were significantly changed, and the tricarboxylic acid (TCA)-cycle was significantly altered under heat plus hypoxia. We interpreted these changes partly as an adaptation mechanism in response to environmental stress. Based on the decreased accumulation of glutamine, we hypothesized that heat stress is the main factor that interferes with the process of glutamic acid-glutamine metabolism. The present study showed that combined environmental stressors have a more extensive impact on the metabolites of the respiratory tree in sea cucumbers than single stress. These results would facilitate further development of the sea cucumber as an echinoderm model to study mechanisms of response to adverse environments, as well as to help advance knowledge of the adaptation of marine organisms to global climate change. Highlights • UPLC was utilized to obtain metabolic profiles of sea cucumbers under heat, hypoxia and the combined stress. • Synergistic effect of environmental stressors has an additive impact on the primary metabolome in sea cucumbers. • Ten representative potential biomarkers of heat and hypoxia in sea cucumber are illustrated. • The levels of metabolites involved in the regulation of energy metabolism were significantly changed. • The tricarboxylic acid (TCA)-cycle was significantly altered under the combined stress of heat and hypoxia. [ABSTRACT FROM AUTHOR]

Shrimps ( Litopenaeus vannamei) were intensively cultured in a recirculating aquaculture system for 98 days to investigate effects of 0.3 mg/L Cu on its performance, Cu budget, and Cu distribution. Shrimps in Cu-treated systems had greater mean final weight (11.10 vs 10.50 g), body length (107.23 vs 106.42 mm), survival rate (67.80% vs 66.40%), and yield (6.42 vs 5.99 kg/m), and lower feed conversion ratio (1.20 vs 1.29) than those in control systems but the differences were not significant. Vibrio numbers remained stable (10-10 colony forming units/mL) in the rearing tanks of both control and treated systems. Total ammonium-N, nitrite-N, nitrate-N, pH, chemical oxygen demand, 5-day carbonaceous biochemical oxygen demand, and total suspended solids were similar in controls and treatments. Dissolved Cu concentration in the treated systems decreased from 0.284 to 0.089 mg/L while in the control systems it increased from 0.006 2 to 0.018 mg/L. The main sources of Cu in the treated systems were the artificially added component (75.7% of total input), shrimp feed (21.0%), water (2.06%), and shrimp biomass (1.22%). The major outputs of Cu occurred via the mechanical filter (41.7%), water renewal (15.6%), and draining of the sediment trap (15.1%). The foam fractionator removed only 0.69% of total Cu input. Harvested shrimp biomass accounted for 11.68% of Cu input. The Cu concentration of shrimps in the Cu-treated systems (30.70 mg/kg wet weight) was significantly higher than that in control systems (22.02 mg/kg). Both were below the maximum permissible concentration (50 mg/kg) for Cu in seafood for human consumption in China. Therefore, recirculating systems can be used for commercial on-growing of Litopenaeus vannamei without loss of shrimp quality, even in water polluted by 0.30 mg/L Cu. The mechanical filter is the main route for Cu removal. [ABSTRACT FROM AUTHOR]

Eelgrass ecosystems have a wide variety of ecological functions in which living tissues and detritus may be a food source for many marine animals. In this study, we conducted a laboratory simulating experiment to understand the trophic relationship between the eelgrass Zostera marina L and the sea cucumber Apostichopus japonicus. A mixture of decaying eelgrass debris and seafloor surface muddy sediments was used as food to feed A. japonicus, and then specific growth rates (SGR) and fecal production rates (FPR) were measured. According to the proportion of eelgrass debris, we designed five treatment diets, i.e., ES0, ES10, ES20, ES40, and ES100, with eelgrass debris accounting for 0%, 10%, 20%, 40%, and 100% in dry weight, respectively. Results showed that diet composition had a great influence on the growth of A. japonicus. Sea cucumbers could use decaying eelgrass debris as their food source; and when the organic content of a mixture of eelgrass debris and sediment was 19.6% (ES40), a relatively high SGR (1.54%·d−1) and FPR (1.31 g·ind.−1 d−1) of A. japonicus were obtained. It is suggested that eelgrass beds can not only provide habitat for the sea cucumber A. japonicus but can also provide an indirect food source for the deposit feeder. This means that the restoration and reconstruction of eelgrass beds, especially in coastal waters of China, would be a potential and effective measure for sea-cucumber fisheries, in respect to both resource restoration and aquaculture of this valuable species. [ABSTRACT FROM AUTHOR]

Abstract: Powdered algae is an essential ingredient in the artificial diet of the sea cucumber Apostichopus japonicus (Selenka) in aquaculture systems. In this study, growth performance, apparent digestibility coefficients, and ammonia-nitrogen production of A. japonicus fed six different granulated macroalgae diets (Sargassum thunbergii, Sargassum polycystum, Zostera marina, Ulva lactuca, Laminaria japonica and boiled L. japonica) were quantified for 60d to identify the optimal diet for this species. The type of seaweed ingested greatly affected the growth, ingestion rate, digestibility, and ammonia-nitrogen production of A. japonicus. Sea cucumbers grew faster when fed the U. lactuca or L. japonica diet than when fed the S. thunbergii or S. polycystum diet. The ingestion rate was much higher when fed the U. lactuca, L. japonica, Z. marina, or boiled L. japonica diet than when fed the S. thunbergii or S. polycystum diet. The apparent digestibility coefficients of the test diets ranged from 9.63% to 15.84%. Ammonia-nitrogen production was much lower in A. japonicus fed the U. lactuca or L. japonica diet compared to the other seaweed diets. The results of this study indicate that U. lactuca and L. japonica are optimum seaweeds for use in the culture of the commercially valuable sea cucumber A. japonicus. [Copyright &y& Elsevier]

The association of heavy metals with plastics could represent a source of contamination, presenting acute metal exposure to ecosystems. Here, we aimed to evaluate the level of 20 metals on plastics employed in aquaculture areas and their surrounding water. All the selected metals were detected on six different polymers/types of plastics. Despite the difference in sampling sites, there was no significant difference among metal concentrations on plastics. However, some metals showed a significant difference in the surrounding seawater among sites or were not detected. Additionally, the median concentrations of all heavy metals were higher on plastic than in their surrounding water at all sites. Furthermore, multivariate analysis showed that metals accumulate on plastics in a similar pattern among sites but distinct from the surrounding water. This study contributes to understanding the accumulation of metals on plastics used in aquaculture areas. • Twenty metals were detected on plastics collected from aquaculture areas. • Metal levels in plastics were higher than those in the surrounding water. • PE and PVC polymers had similar levels of heavy metals. [ABSTRACT FROM AUTHOR]

Abstract: Aestivation is an indispensable state in the life history of sea cucumbers, Apostichopus japonicus. The immune characteristics of the coelomic fluid of A. japonicus, were investigated during aestivation. Samples were collected between July and November 2006 from a coastal pond located off the Yellow Sea in Jiaonan, Shandong Province, China. The total coelomocytes counts (TCC), total superoxide dismutase (T-SOD), catalase (CAT), myeloperoxidase (MPO), and lysozyme (LZM) in the coelomic fluid were measured. The activities of catecholamines, [adrenaline (AD), noradrenaline (NA), and dopamine (DOP)] were estimated. TCC decreased from July to September, indicating weakness of the cellular immune activity at that time. Activities of SOD, CAT, MPO, and LZM changed significantly from July to October. Catecholamines AD and NA in coelomic fluid were significantly higher on August 21 and November 27. There was no significant variation in DOP during the sampling period. Thus, immune characters in coelomic fluid of A. japonicus changed significantly during aestivation. Water temperature was significantly and negatively correlated with TCC, and salinity was significantly and positively correlated with AD and NA. The mechanism of aestivation in A. japonicus is complex and might not be attributed only to environmental changes, such as temperature and salinity, as shown in previous studies. [Copyright &y& Elsevier]

Abstract: The survival, growth, food availability and assimilation efficiency of the bottom-cultured sea cucumber Apostichopus japonicus were investigated at a subtropical fish farm in Dapeng Cove, Daya Bay, during an 8-month field study. Our aim was to assess the possibility of producing commercial-sized A. japonicus under fish farms and developing an integrated multi-trophic aquaculture (IMTA) system on the southern China coast. Survival of A. japonicus cultured at the fish farm and reference site (1km away from the fish farm) was 100% from December 9, 2011 through June 29, 2012, though all animals at both sites died at the July sampling because of anoxia caused by water stratification. Factors including time, culture site and stocking density had significant effects on the growth of A. japonicas. Growth during winter and early spring varied significantly with density and site; however, growth over the whole study period was significantly affected by time, site and the interactions between time/site and time/density. Specific growth rates of A. japonicus at the fish farm (0.40–0.71%) and reference site (0.15–0.54%) were always positive from winter through early spring (December to April). The faster growth recorded at the fish farm site during this period was mainly due to accessing more food of better quality from the surrounding environment. A. japonicus underwent aestivation and suffered weight loss with the increase of water temperature after the April sampling. Only A. japonicus cultured at low density (10indm−2) at the fish farm site reached a commercial size (>100g wet weight) during the entire study period. Organic matter contents of the foregut material were higher than the surrounding sediments, indicating that A. japonicus had a high food selection capability. The assimilation efficiency of A. japonicus in the experimental areas was relatively high, with average values of 13.78±5.83% at the fish farm and 15.13±7.75% at the reference site. This study demonstrated that fish farm debris can be efficiently used by A. japonicus, and bottom culture is an economical and environmentally friendly system of producing commercial-sized A. japonicus in subtropical fish farms in southern China. We recommend harvesting bottom-cultured A. japonicus specimens before May, thereby avoiding weight loss during aestivation. We also suggest improving product size through enhanced seed size and/or reducing stocking density. [Copyright &y& Elsevier]

Abstract: Rates of respiration and excretion of the Pacific oyster, Crassostrea gigas, were measured seasonally from June 2002 to July 2003 under ambient conditions of food, water temperature, pH, and salinity in Sanggou Bay, an important mariculture coast in north China. The aim of this study is to obtain fundamental data for further establishing an energy budget model and assessing the carrying capacity for cultivation of C. gigas in north China. Oysters were collected monthly or bimonthly from the integrated culture areas of bivalve and kelp in the bay. Oxygen consumption and ammonium and phosphorus excretion rates were measured, and ratios of O/N and N/P were calculated. One-way ANOVA was applied to determine differences among these parameters that act as a function of seasonal variation. All the physiological parameters yielded highly significant variations with season (P <0.01). The rate of respiration varied seasonally, with the highest oxygen consumption rate in July and the lowest rate in January, ranging from 0.07 to 2.13 mg O2 h− 1 g− 1dry tissue weight (DW). Maximum and minimum ammonium excretion rates were recorded in August and January, respectively, ranging from 0.51 to 5.40 μmol NH4–N h− 1g− 1 DW. Rates of phosphorus excretion varied from 0.11 (in January) to 0.64 (in July) μmol PO4–P h− 1g− 1 DW. The O/N and N/P ratios changed from 9.2 (in January) to 59.8 (in July) and from 4.6 (in January) to 10.9 (in August), respectively. For each season, the allometric relationship between the physiological response (e.g., rate of oxygen consumption, ammonium and phosphorus excretion) and DW of the animal was estimated using the formula: Y = a ×DW b . [Copyright &y& Elsevier]

Temperature and dissolved oxygen concentration are important abiotic factors that can limit the growth and survival of sea cucumbers by affecting their immune systems. As global warming intensifies, sea cucumbers are increasingly exposed to adverse environmental conditions, which can cause severe economic losses and limit the sustainable development of sea cucumber aquaculture. It is therefore important to better understand how sea cucumbers respond to environmental stress, especially with regard to its effects on immunity. In the present study, the time series of immunity-related gene expression in sea cucumbers under thermal and hypoxic stresses were analyzed separately. The expression trends of 17 genes related to the nuclear factor κB (NF-κB) pathway, the protease family, the complement system, heat shock proteins (HSPs) and the transferrin family during exposure to two stresses at eight time points were concluded. These genes have interconnected roles in stress defense. The expression levels of genes relating to the NF-κB pathways and HSPs were strongly affected in the sea cucumber thermal stress response, while melanotransferrin (Mtf) , ferritin (Ft) and mannan-binding C-type lectin (MBCL) were affected by hypoxia. In contrast, complement factor B (Bf) , myosin V (Mys) and serine protease inhibitor (SPI) were not that sensitive during the initial period of environmental stress. Similar expression patterns under both thermal and hypoxic stress for certain genes, including an increase in Hsp90 and decreases in lysozyme (Lys) , major yolk protein (MYP) and cathepsin C (CTLC) were observed in sea cucumbers. Conversely, NF-κB and Hsp70 were differentially affected by the two stress treatments. Lysozyme-induced immune defense was inconstant in sea cucumbers coping with stress. A gene ontology (GO) analysis of the selected genes revealed that the most co-involved terms related to immunity and iron ion. Our analysis suggests that sea cucumbers demonstrate complex and varied immune responses to different types of stresses. This dynamic image of the immune responses and stress tolerance of sea cucumbers provides new insights into the adaptive strategies of holothurians in adverse environments. • Expressed trends of 17 immune genes under two stresses at 8 time points were concluded. • Genes related to Nf-κB pathway, protease, complement system, HSP and transferrin family were coefficient to defense stress. • Sea cucumber showed complex and different immune pattern towards different stresses. • These dynamic images provide new insights into adaptive strategies in sea cucumber tolerance to adverse environment. [ABSTRACT FROM AUTHOR]

The feeding behavior and digestive physiology of the sea cucumber, Apostichopus japonicus are not well understood. A better understanding may provide useful information for the development of the aquaculture of this species. In this article the tentacle locomotion, feeding rhythms, ingestion rate (IR), feces production rate (FPR) and digestive enzyme activities were studied in three size groups (small, medium and large) of sea cucumber under a 12 h light/12 h dark cycle. Frame-by-frame video analysis revealed that all size groups had similar feeding strategies using a grasping motion to pick up sediment particles. The tentacle insertion rates of the large size group were significantly faster than those of the small and medium-sized groups ( P < 0.05). Feeding activities investigated by charge coupled device cameras with infrared systems indicated that all size groups of sea cucumber were nocturnal and their feeding peaks occurred at 02:00–04:00. The medium and large-sized groups also had a second feeding peak during the day. Both IR and FPR in all groups were significantly higher at night than those during the daytime ( P < 0.05). Additionally, the peak activities of digestive enzymes were 2–4 h earlier than the peak of feeding. Taken together, these results demonstrated that the light/dark cycle was a powerful environment factor that influenced biological rhythms of A. japonicus , which had the ability to optimize the digestive processes for a forthcoming ingestion. [ABSTRACT FROM AUTHOR]

The sea cucumber Apostichopus japonicus (Selenka) tolerates salinity fluctuations when inhabiting the intertidal zone and culture ponds. In this study, green, white and purple morphs of juvenile A. japonicus (1.0 ± 0.1 g) were cultured at salinities of 22, 26, 30, 34 and 38 for 60 days. The influence of salinity on the growth, energy allocation and physiological performance of A . japonicus was determined. The results indicated that the three color morphs tested could survive within the salinity range of 22–38. Salinity had a significant effect on the growth, energy allocation and physiological performance of sea cucumbers ( P < 0.05). Specific growth rates, ingestion rates and feed conversion efficiencies of A. japonicus were generally optimal at a salinity of 30. Similar results were obtained for energy ingested, and the proportion of energy allocated to growth. Significant changes in enzyme activities of sea cucumbers mainly occurred at salinities of 22 and 38, indicating that metabolism was affected by low and high salinities. Green A. japonicus grew faster than the white and purple color morphs at a salinity of 22. Growth rates were the highest in purple, then green and the lowest in white color morphs at salinities of 30, 34 and 38. At a salinity of 22, the green allocated more energy to growth and respiration. The purple morph allocated more energy to growth and respiration when water salinity reached 34 and 38. At salinities of 30, 34 and 38, the purple morph had higher trypsin and superoxide dismutase activities, which supported the higher specific growth rate and food conversion rates compared with the green and white color morphs. The results clearly showed that the green color morph performed better at low salinities, while the purple was better adapted to high salinities within the tolerance range. [ABSTRACT FROM AUTHOR]