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The diversity and distribution of culturable fouling bacteria in shellfish, fish and non-mariculture zones in Daya Bay were investigated by using a traditional culture-dependent approach combined with an analysis of bacterial 16S rRNA gene sequences. A total of 129 isolates of fouling bacteria belonging to 37 species in 25 genera were collected and identified, which indicated that the three different mariculture zones harbored abundant and diverse fouling bacterial community. At the genus level, Pseudomonas, Arcobacter and Curtobacterium dominated the fouling bacterial community. Moreover, approximately 46% of the 37 representative isolates could form biofilms. After comparing the diversity and distribution of the biofilm-forming bacteria in three different mariculture zones, it was concluded that the ratios of biofilm-forming bacteria in shellfish (68.4%) and fish (63.4%) in mariculture zones were much greater than those in non-mariculture (42.0%) zone. These results provide important information, for the first time, regarding the fouling bacterial community in typical mariculture zones in South China, which will establish a foundation to develop strategies for biofilm control and disease defense.

The grass carp is one of the most important herbivore consumers in aquatic ecosystems and plays key roles in controlling macrophyte abundance. To assess the trophic role of grass carp and their potential grazing pressure on macrophytes in their native range, we quantified their relative abundance (RA), diet composition and trophic niches in two major tributaries and the central delta of the Pearl River using a fish capture survey, high-throughput analysis of the 18S rDNA sequences of their gut contents, and stable isotope analysis. The grass carp RA variation among the sampling regions was explained most by river discharge range. The RA was the highest in the West River with high discharge range, and the lowest in the central delta with low discharge range. The grass carp fed primarily on Streptophyta (relative read abundance: 0.40 ± 0.33) and facultatively on Arthropoda, Rotifera, Ascomycota, and Chlorophyta. The Streptophyta proportion increased from the tributaries to the central delta. Such variation contributed most to the dietary difference among regions. Grass carp belonged to the second trophic level. The position and size of isotopic niche of grass carp differed among regions, and their niche breadth decreased from the tributaries to the central delta, as indicated by the corrected standard ellipse areas (SEAs) and the Bayesian SEAs. The regional differences in hydrological regime and grass carp RA probably affected the macrophyte distribution. The availability of macrophytes likely further contributed to the regional difference in the Streptophyta proportion in grass carp diet.

The precipitation of the water-leaching solution of Baotou mixed rare earth (RE) concentrate roasted with sulfuric acid using ammonium bicarbonate for producing RE carbonate produces a mass of ammonia-nitrogen wastewater because of the relatively low solubility of rare earth sulfate. To solve the serious problem of ammonia-nitrogen pollution, new precipitators need to be developed urgently so as to meet the requirements of environmental protection and impurities content of the product (SO42−

Deep-sea sediments are now recognized as a home for rich and largely microbial community. Recently, it has been believed in an increasing number of studies that bacteria could be abundant in deep-sea sediments of many types; however, fungi in deep-sea sediments remain relatively unknown. The phylogenetic diversity and bioactivity of culturable deep-sea-derived fungi from Okinawa Trough sediments were investigated in traditional method combined with fungal identification of molecular biology in this study. A total of 76 isolates belonged to 15 fungal taxa were recovered in a harsh condition of low nutrient and low temperature, indicating that the fungal communities in deep-sea sediments from Okinawa Trough were relatively abundant and diversified. Aspergillus, Cladosporium, and Penicillium were the dominant fungal genera, while Mycosphaerella, Purpureocillium, and Schizophyllum were relatively rare in the deep-sea sediments from Okinawa Trough. Among the six genera recovered, Mycosphaerella was firstly recovered from deep-sea sediments in this study. Moreover, about 75% of the extracts from the 15 fungal representative isolates displayed distinct bioactivity against at least one indicator bacterium or marine macrofouler, emphasizing the potentials of these deep-sea-derived fungi from Okinawa Trough as producers of bioactive metabolites. Notably, isolates Cladosporium oxysporum SCSIO z001 and Penicillium citrinum SCSIO z049 displayed a wide spectrum of bioactivities, isolates Cladosporium cladosporioides SCSIO z015, Cladosporium sphaerospermum SCSIO z030, and Penicillium verruculosum SCSIO z007 exhibited a strong anti-bacterial-growth activity, and isolate Penicillium chrysogenum SCSIO z062 displayed a strong anti-larval-settlement activity. These results suggest that these isolates deserved further study as potential sources of novel bioactive metabolites.

In acid treatment technology of Baotou mixed rare earth ore, large quantities of ammonia-nitrogen wastewater are produced in the step of ammonium bicarbonate precipitation to transform rare earth sulfate. In this paper, we adopted a green precipitant magnesium bicarbonate (Mg(HCO3)2) to substitute ammonium bicarbonate to eliminate ammonia-nitrogen pollution. The effects of n(HCO3−):n(RE3+), aging temperature and aging time on the crystallization using Mg(HCO3)2 precipitation method were investigated. The results indicate that the rare earths could be completely recovered when n(HCO3−):n(RE3+) is higher than 3.15:1. The crystal water content of rare earth carbonates is affected by the aging temperature. The precipitate has a bad filterability when the aging temperature is over 40 °C. This can be attributed to the less crystallized water molecules of the hydrated rare earth carbonate precipitation. The mixed rare earth carbonates are prone to be crystalline, and have a good filterability at aging temperatures below 40 °C. Meanwhile, the evolution mechanism of crystalline mixed rare earth carbonates is reasonably deduced, the amorphous rare earth carbonates are first dissolute and then recrystallized. Under the optimized aging conditions, the purity of the crystalline precipitate meets the requirements of the fine product standard (GB/T 16479-2008). The filtrated could be used to produce Mg(HCO3)2, thus to realize the recycling of magnesium sulfate.

The suspension-feeding sea cucumber Cucumaria frondosa has become commercially important in recent years. Finding proper diets is the first important step for intensive aquaculture of this sea cucumber. In this study, adult C. frondosa were exposed to one of the following diet treatments: control (no diet provided), two powdered seaweeds (Ascophyllum nodosum and Saccharina latissima), a commercially available microalgal diet (shellfish diet) and natural seston. The effects of diets on the feeding behavior and physiological properties of sea cucumbers were investigated after a 5-week rearing period. Results show that sea cucumbers fed with shellfish diet exhibited a significantly higher tentacle insertion rate (1.80±0.20 insertion/min) than these fed with seaweed powders, and there was no significant different between the two groups fed by seaweed powders. No significant difference was found on the fecal production rate among the feeding groups. The minimum oxygen consumption rate was observed in the control group (5.76±0.99 μg O 2/(g·h)), which is significantly lower than individuals fed with A. nodosum, shellfish diet, and natural seston; however, no significant difference was shown between those of control and S. latissimi groups. The maximum ammonium excretion rate was found in the A. nodosum group (0.03±0.01 μmol/(g·h)), which is significantly higher than other groups. The minimum O/N ratio was observed in the A. nodosum group (14.57±1.04), which is significantly lower than the S. latissima, shellfish diet, and natural seston groups. Individuals fed with seaweed powders had similar physiological properties with these fed with microalgae diet and natural seston, indicating that A. nodosum and S. latissima can be explored as promising diets for intensive aquaculture of C. frondosa.

Cancer remains the primary cause of death worldwide. To develop less toxic anti-cancer drugs to relieve the suffering and improve the survival of cancer patients is the major focus in the anti-cancer field. To this end, marine creatures are being extensively studied for their anti-cancer effects, since extracts from at least 10% of the marine organisms have been shown to possess anti-tumor activities. As a classic Chinese traditional medicine, sea cucumbers and compounds extracted from the sea cucumbers, such as polysaccharides and saponins, have recently been shown to exhibit anti-cancer, anti-inflammatory, and anti-oxidant effects.

Finfish cage culture is the most predominant form of mariculture. The rapid expansion of fish cage culture systems has raised concerns about their environmental impact, such as nutrient release. In this study, for the first time, we estimated the release of nitrogen (N) and phosphorus (P) from fish cage culture in Daya Bay, southern China, by constructing N and P budget models based on a mass balance principle. In addition, the contribution and importance of nutrients from fish culture and other nutrient sources, including submarine groundwater discharge, benthic sediments, local rivers, and atmospheric deposition were assessed. The annual amount of N and P released from fish cage culture was 205.6 metric tons (hereafter tons) of N and 39.2 tons of P, including 142.7 tons of dissolved inorganic nitrogen (DIN) and 15.1 tons of dissolved inorganic phosphorus (DIP). Among the analyzed nutrient sources, the contributions of DIN and DIP from fish culture were 7.0% and 2.7%, respectively. For cages consuming conventional trash fish, 142 kg of N and 26 kg of P were released into the environment per ton of fish products, much higher than the values (72 kg N and 17.3 kg P) for cages using formulated feed. In fish culture, the dissolved nutrients were more N rich, but the particulate nutrients were more P rich. The ratio of cage-derived N and P was 21.1, higher than the ratio of coastal seawater (27.1), indicating that cage culture may also impact the local nutrient forms around farming regions. Oyster cultivation and harvest removed 126.3 tons of N and 35.1 tons of P from of the bay. Replacing trash fish with formulated feed and co-culturing of nutrient extractive species (e.g., bivalves, macroalgae) and deposit-feeding species (e.g., sea cucumber) in fish culture zones can be efficient nutrient mitigation strategies.

A safe, effective and simple method for ammonia nitrogen and nitrite removal in farming water has always been a goal of environmentally friendly farming models aimed at water saving and reducing the discharge of farming wastes. In this study, it was shown that a bacterial strain LPN080 isolated and screened from a shrimp culture pond can efficiently remove both ammonia nitrogen and nitrite. When supplemented with ammonia nitrogen and glucose in water samples, ammonia nitrogen (as the only nitrogen source) was reduced from an initial 8 mg/l to 0.3 mg/l in 48 h, and a removal rate of ammonia nitrogen of up to 96% was achieved. With the same addition of glucose in the water samples, nitrite (as the only nitrogen source) reduced from an initial 5 mg/l to 0.8 mg/l, and the removal rate was approximately 81% in 48 h. The LPN080 strain was identified as a member of Sphingomonas using 16S rDNA sequencing. Sphingomonas sp. LPN080 could indirectly inhibit the growth of Vibrio spp. in water supplemented with glucose and the inhibition was not caused by the production of antimicrobial substances. Sphingomonas sp. LPN080 showed high biosafety toward shrimp Litopenaeus vannamei. All these results demonstrated that Sphingomonas sp. LPN080 has a potential economic value in aquaculture and even in wastewater treatment.

Holothuria leucospilota (Echinodermata: Holothuroidea) is a widespread tropical sea cucumber with strong value for the ecological restoration of coral reefs. Therefore, some studies regarding the artificial breeding and cultivation of H. leucospilota have been undertaken recently. However, the biological functions of the digestive system of this species have not been elucidated. In this study, a cDNA coding for α-amylase, an indicator of digestive maturity in animals, was identified from H. leucospilota and designated Hl-Amy. The full-length cDNA of the Hl-Amy gene, which is 1734 bp in length with an open reading frame (ORF) of 1578 bp, encodes a 525 amino acid (a.a.) protein with a deduced molecular weight of 59.34 kDa. According to the CaZy database annotation, Hl-Amy belongs to the class of GH-H with the official nomenclature of α-amylase (EC 3.2.1.1) or 4-α-D-glucan glucanohydrolase. The Hl-Amy protein contains a signal peptide at the N-terminal followed by a functional amylase domain, which includes the catalytic activity site. The mRNA expression of Hl-Amy was abundantly exhibited in the intestine, followed by the transverse vessel with a low level, but was hardly detected in other selected tissues. During embryonic and larval development, Hl-Amy was constitutively expressed in all stages, and the highest expression level was observed in the blastula. By in situ hybridization (ISH), positive Hl-Amy signals were observed in different parts of the three different intestinal segments (foregut, midgut and hindgut). The Hl-Amy recombinant protein was generated in an E. coli system with codon optimization, which is necessary for Hl-Amy successfully expressed in this heterogenous system. The Hl-Amy recombinant protein was purified by immobilized metal ion affinity chromatography (IMAC), and its activity of starch hydrolysis was further detected. The optimal temperatures and pH for Hl-Amy recombinant protein were 55°C and 6.0, respectively, with an activity of 62.2 U/mg. In summary, this current study has filled a knowledge gap on the biological function and expression profiles of an essential digestive enzyme in sea cucumber, which may encourage future investigation toward rationalized diets for H. leucospilota in artificial cultivation, and optimized heterogenous prokaryotic systems for producing recombinant enzymes of marine origins.

Trehalases are a group of enzymes that catalyse the conversion of trehalose to glucose, and they are observed in most organisms. In this study, the first echinoderm trehalase, designated Hl-Tre, was identified from a tropical sea cucumber, Holothuria leucospilota. The full-length cDNA of H. leucospilota trehalase (Hl-Tre) is 2461 bp in length with an open reading frame (ORF) of 1788 bp that encodes a 595-amino-acid protein with a deduced molecular weight of 67.95 KDa. The Hl-Tre protein contains a signal peptide at the N-terminal and a functional trehalase domain, which includes the signature motifs 1 and 2. The mRNA expression of Hl-Tre was ubiquitously detected in all selected tissues, with the highest level being detected in the intestine. By in situ hybridization (ISH), the positive Hl-Tre signals were observed in the brush borders of the intestinal mucosa. In embryonic and larval stages, the transcript levels of Hl-Tre decreased during embryonic development and increased after the pentactula stage. After a challenge of starvation, the intestinal Hl-Tre mRNA levels were observed to be first decreased and partially recovered thereafter. Overall, our study provided the first evidence for trehalase in echinoderms and showed that this enzyme was potentially linked to a trehalose metabolic pathway in sea cucumbers.

The tropical sea cucumber Holothuria leucospilota (Echinodermata: Holothuroidea) is one of the most widespread sea cucumber species with high economic value. To develop the artificial breeding methods of H. leucospilota, we conducted the first detailed study on the processes of spawning, embryonic and larval development, and juvenile growth of the species. The results showed that the suitable breeding season of H. leucospilota in the Daya Bay might be from June to October and that at least 30 days were needed for embryos to develop into juveniles at a temperature of 29−33 °C, a salinity of 27−30‰, and a pH of 7.9−8.2. The survival rate of the juveniles were approximately 8.5%, the average growth rate during days 31−49 of culture was 0.11 mm per day and increased to 0.72 mm per day during days 73−120. The body color of the juveniles was transparent yellow at approximately 55 days of culture, and it began to darken at 79 days later. These results indicated that an artificial culture method of H. leucospilota was realized. Our research might contribute a feasible way to the artificial breeding, natural resource restoration, and sustainable use of tropical sea cucumbers.

China is the largest kelp (Saccharina japonica) producing country in the world. Kelp consumption is a tradition in many Asian countries. However, S. japonica accumulates trace elements that exhibit potential health risks upon ingestion. Here, we selected six sampling sites, from the shelf to offshore waters, in a maricultural area of Ailian Bay in Rongcheng City, northern China and investigated the spatiotemporal distributions of trace elements in kelp and seawater from 2016 to 2018. We then evaluated the bioremediation potential and food safety of S. japonica. Most trace elements in S. japonica and seawater demonstrated no marked spatial variations. The trace element concentrations in the tested kelp did not exceed the food safety standards, indicating that it is safe for human consumption. Moreover, S. japonica has a high bioremediation capability for trace elements, and the kelp in the coastal waters of Rongcheng (with annual yield of 1.7 × 104 t DW) removed 28.60 kg Cr, 165.51 kg Cu, 682.54 kg Zn, 34.00 kg Cd, 52.53 kg Pb, 3.60 kg Hg, and 1305.53 kg As from the seawater per year. Our results will be useful for evaluating the bioremediation potential of S. japonica and for food safety management.

The oyster Crassostrea angulata is a major species for shellfish aquaculture in southern China. In this study, the in situ biodeposition method was used to estimate the clearance rate (CR) of C. angulata cultivated in Dapeng Cove, southern China, from January 2012 to January 2013. Relationships between CR and the dry tissue weight (DW) of the oyster were estimated for each experimental period. Results indicated that the CR of C. angulata related to DW by allometric relationships (CR = a × DWb) (the a values, representing CR of an oyster with 1 g DW) varied with time. The maximum value (7.678) was observed in November 2012, and the minimum value (0.655) in August 2012, when the oysters were in their reproductive period. The exponent value of b was low when oysters were large, and the minimum (0.215) occurred in August 2012; the b values were all > 0.9 during November and December 2012 when oysters were small. The relationship between the standardized CR (1 g DW; outside the reproductive period) and water temperature (T) can be described by non-linear regression: CRstd = − 0.098 T2 + 4.885 T − 53.476 (n = 6, R2 = 0.949, p = 0.012), and the CRstd increased with T until a theoretical maximum (7.400 L g− 1 h− 1) was reached at 24.92 °C. No statistically significant relationship was observed between CRstd and other environmental parameters (all p > 0.05). These results may facilitate oyster aquaculture management in southern China.

In this study, shell growth, shell microstructure, and expression levels of shell matrix protein genes (aspein, n16, and nacrein) that play a key role in the CaCO3 crystal polymorphism (calcite and aragonite) of the shell were investigated in the pearl oyster Pinctada fucata at pH 8.10, 7.70, and 7.40. We found that the shell length and total weight index did not vary significantly between oysters reared at pH 8.10 and 7.70, but was significantly lower at pH 7.40. Calcium content and shell hardness were not significantly different between pH 8.10 and 7.70, but were significantly different at pH 7.40. At pH 7.40, the shell exhibited a poorly organized nacreous microstructure, and showed an apparent loss of structural integrity in the nacreous layer. The prismatic layer appeared morphologically dissimilar from the samples at pH 8.10 and 7.70. The internal layer was corroded and had dissolved. At pH 7.40, the expression levels of nacrein, aspein, and n16 decreased on day 1, and remained low between days 2 and 42. The expression levels of these genes were significantly lower at pH 7.40 than at pH 8.10 and 7.70 during days 2-42. These results suggest that ocean acidification will have a limited impact on shell growth, calcification, and associated gene expression levels at a pH of 7.70, which is projected to be reached by the end of the century. The negative effects were found on calcification and gene expression occurred at the lowest experimental pH (7.40).

Though the breeding and the rearing of Acanthaster planci larvae had been reported before, the descriptions of them are not all-around, and there are no clear and detailed pictures indicating the whole process of embryonic and larval development. Besides, some methods described previously for culturing A. planci larvae are troublesome and even not available. In this study, adult A. planci were artificially induced to spawn and fertilized eggs were incubated and cultured indoor with disinfected seawater. A. planci developed from fertilized eggs to early bipinnaria by 50 h. Once a large number of late brachiolaria occurred, the diets were replaced by mixed benthic diatoms on settlement plates. Five-armed juveniles were reached after 23-day rearing when enough live Chaetoceros mueller and oceanic red yeast were supplied. It is critical to prevent infections by protozoa and pathogenic bacteria. The diets used here are universal in larval rearing and easily obtainable, which guarantees constant supply ...

Estuaries are important in terms of biodiversity, biogeochemical function, and ecological balance due to their intense land-sea interactions. The sustainability of estuarine ecosystem function relies on a good understanding of the ecological processes related to microbial communities. However, microbial community assembly in such ecosystems is still not well understood. Here, based on 16S rRNA sequencing, we investigated the bacterioplankton community structure in the Pearl River Estuarine system during the wet and dry seasons. Results showed that there were significant seasonal and spatial variations in the bacterioplankton communities of the estuary, with seasonal variations being more remarkable. Multiple bacterioplankton with different abundances in the wet and dry seasons were observed, e.g., the class Actinobacteria and Oxyphotobacteria were enriched in the wet season, whereas Alphaproteobacteria and Saccharimonadia were more abundant in the dry season. Both variation partitioning and null model analysis revealed that environmental filtering dominated the bacterioplankton community assembly in the Pearl River Estuary. Water physical properties (e.g., salinity and temperature), nutrient content (e.g., nitrate), and upstream land use (e.g., urban land cover) together determined the distribution of the bacterioplankton composition in this highly urbanized estuarine ecosystem. These findings would help improve our understanding of the bacterioplankton communities in estuarine ecosystems and provide a theoretical foundation for estuarine ecological health management.

Fish and shellfish aquaculture industries in Dapeng Cove, South China, have profound impacts on the coastal marine ecosystem in recent years. In this study, the local seaweed Sargassum hemiphyllum was introduced into oyster and fish farms as a biofilter during winter and early spring of 2013. Results showed that S. hemiphyllum grown in the fish farm suffered greater fouling and herbivory than these in the oyster farm. Thalli grown in both sites could achieve high growth rates during January and February; meanwhile, the specific growth rates for wet weight (SGR W ) of seaweeds in the oysters farm at January, February and April samplings (7.16, 6.16 and 2.25% d − 1 , respectively) were all higher than those in the fish farm at the same sampling period (2.89, 3.19 and 0.90% d − 1 , respectively). The mean fresh-weight biomass increments for thalli grown in the oyster and fish farms were ~ 40 and 7 times, respectively, during the 4-month culture period. The N and P contents of S. hemiphyllum grown in both sites all varied significantly over time, and P contents of thalli in the oyster farm always higher than those of the fish farm at the same sampling period. The C, N and P bioaccumulation capacities of S. hemiphyllum cultured in the oyster farm were 15016.90 ± 6241.78, 1112.45 ± 459.81 and 134.69 ± 55.46 mg thallus − 1 , respectively, over the study period, which were all significantly higher than those in the fish farm (2457.46 ± 1073.78, 180.27 ± 75.23 and 13.69 ± 5.88 mg thallus − 1 , respectively). The nutritional composition of S. hemiphyllum in both sites were always comparable or higher than those of the seaweeds used as holothurian feed, and the heavy metal contents (Pb, Cd and Cr) were all well below the maximum allowable concentration for aquatic feed; thalli grown in the oyster farm were always with higher crude protein and fat contents, but lower heavy metal levels than those in the fish farm. We consider large-scale cultivation of S. hemiphyllum in Dapeng Cove can efficiently relieve the total environmental impact of aquaculture on the ecosystem of the whole bay, while give high yield of seaweed product with better quality. Statement of relevance This article provides useful information on the seaweed-based integrated multi-trophic aquaculture in fish and shellfish farms, and it can also give suggestion for the practice of large-scale cultivation of Sargassum and sustainable aquaculture in coastal area.

Alpha-2-macroglobulin (A2M) is essential for hosts defending against pathogen infections. In this study, two distinct A2Ms were identified from sea cucumbers Stichopus monotuberculatus and Holothuria atra, which belong to different genera in the Phylum Echinodermata, and named StmA2M and HaA2M, respectively. Structural analysis of StmA2M and HaA2M revealed that all contain the bait region domain, thioester domain, and receptor-binding domain. Phylogenetic analysis indicated that StmA2M and HaA2M all belong to the echinoderm A2Ms. The cleavage site RXXR and the catalytic histidine residue for complement component C3 were found in StmA2M and HaA2M. Compared with human A2M, the three-dimensional structures of StmA2M and HaA2M were more similar to that of common carp A2M. Both StmA2M and HaA2M showed the strongest response at transcriptional levels to lipopolysaccharide (LPS) at 12 h and polyriboinosinic polyribocytidylic acid [Poly (I: C)] at 24 h, respectively. Activity of StmA2M showed the strongest response to Poly (I: C) at 6 h, while the strongest change of HaA2M activity was induced by LPS at 24 h. The differential mRNA expression and enzyme activity levels suggested that A2M in sea cucumbers might be involved in different immune responses to LPS or Poly (I: C) challenge.

The non-specific protease inhibitor alpha-2-macroglobulin (A2M) is a key macromolecular glycoprotein that involved in host immune defense against pathogens in vertebrates and invertebrates. However, no research regarding A2M has been developed in echinoderms to date. In this study, the full-length cDNA of A2M was cloned from the sea cucumber (Holothuria atra), which is a tropical species widely distributed along the coasts of the South China Sea and designated HaA2M. HaA2M possesses all three conserved functional domains of known A2M proteins, including the bait region domain, thioester domain and receptor-binding domain. Compared to fish and shrimp A2Ms, the histidine residue from the catalytical regions is well conserved in HaA2M. HaA2M mRNA was predominantly expressed in coelomocytes and, to a lesser extent, in the body wall, intestine and respiratory tree. A2M activity was detected in the coelomic fluids of H. atra. The mRNA expression and activity levels were investigated in the major immune tissues and coelomic fluids of H. atra after challenge with inactivated Vibrio alginolyticus or polyriboinosinic polyribocytidylic acid [Poly (I: C)]. RNA interference (RNAi)-mediated knockdown of HaA2M resulted in a significant reduction of HaA2M gene transcript level (86%). RNAi-mediated silencing of HaA2M gene significantly decreased the A2M activity (38%) and increased the number of viable bacteria (2.8-fold) in the coelomic fluids of H. atra infected by V. alginolyticus. Our study, as a whole, supplied the evidences for HaA2M as an immune-relevant molecule and it might have multiple functions in the innate immune system of H. atra.

Phytoplankton pigment concentrations in the sur-face sediments of a fish and oyster farm in Dapeng Cove, South China Sea, were measured monthly to investigate the effects of mariculture on the envi-ronment from December 2011 to December 2012. The highest contents of the identified phytopig-ments, sulphides and total organic carbon in the surface sediments were all found at the fish farm, followed by the oyster farm; the lowest contents were detected at the control site. Fucoxanthin in the surface sediments was the most abundant car-otenoid and was significantly correlated with chlorophyll a (Chl a; r = 0.922, P < 0.01). This finding suggested that the deposited diatoms could be the main source of the Chl a concentration. Besides a differential sedimentation of phytoplank-ton (i. e. higher downflux at fish and oyster site than that at control site), we assume that the extent of pigment diminution from the fish site to control site was also controlled by the chemical conditions of the surface sediments. The fish farm provided the most optimum preservation condi-tions for the phytopigments and was a good sink for phytodetritus among the three sites because of its anoxic and reductive characteristics. Phyto-plankton pigments could be useful biomarkers to evaluate the influence of mariculture on sediment environment.

The Baotou bastnaesite and monazite mixed rare earth ore is one of the most significant rare earth ore in the world and is mainly processed by the sulfuric acid roasting method. However, the high content of Fe and P in the leaching solution contributes to a large amount of radioactive precipitate waste produced in the purification process, and that causes the primary loss of rare-earth elements (REEs) and the environmental issue and safety concern. The goal of this paper is to reduce the solid-waste by improving the selective leaching efficiency of REEs based on a leaching kinetics study of REEs, Fe and P in the H2SO4 system. The experiments were carried out focusing on the effect of acidity, roasted concentrate particle size, temperature, and liquid-solid ratio on the leaching kinetics. The results indicate that the equilibrium leaching time of REEs (

Mariculture has caused negative environmental impacts on the marine ecosystem in Dapeng Cove, Daya Bay, South China Sea. In this study, the brown macroalgae Sargassum henslowianum was introduced into fish and oyster farms as a biofilter to evaluate its bioremediation potential. We examined the temporal dynamics of seaweed growth, tissue nutrients (N and P), and heavy-metal contents (Cu and Zn) over a 100-day culture period (December 2012 to March 2013). The thalli of seaweed grown in the fish farm suffered greater from fouling and predation than those grown in the oyster farm. The specific growth rates by wet weight of S. henslowianum for the first three culture periods were all significantly higher in the oyster farm (at 6.30, 6.90, and 2.18% d−1) than the rates in the fish farm (at 2.77, 4.19, and −1.16% d−1). The tissue nutrients and heavy-metal contents of the seaweed at both sites all varied significantly with time. The estimated N bioaccumulation efficiency of seaweed at the oyster farm increased with time (from −34.44 to 62.91 mg thallus−1 d−1) until late February, but values for the seaweed at the fish farm (−4.70 to 7.19 mg thallus−1 d−1) increased only until late January. N bioaccumulation efficiency was significantly higher for seaweed in the oyster farm than for seaweed in the fish farm up to February 23; similar trends were found for the P, Cu, and Zn bioaccumulation efficiencies. We conclude that large-scale cultivation of S. henslowianum in the oyster farms of Dapeng Cove should be the first choice to alleviate eutrophication and improve water quality, and the seaweed biomass should be harvested by late February, allowing it to accumulate the optimum amount of nutrients and heavy metals from the water column.

The mitochondrial genome of Holothuria leucospilota was 15,906 bp in length, containing 13 protein-coding genes (PCGs), 22 tRNA genes, and two rRNA genes. There were four initiation codons (ATG, ATT, ATC, and ATA) for the PCGs, and the termination codon of most PCGs was TAA, except for nad4 (TAG) and nad6 (TAG). Only one PCG (nad6) and five tRNA genes (tRNASer(UCN), tRNAGln, tRNAAla, RNAVal, and tRNAAsp) were encoded on the light chain; the other genes were encoded on the heavy chain. H. leucospilota was most closely related to Holothuria scabra in a phylogenetic tree.

Fish maws (dried swimbladders of fishes) are regarded as traditional luxurious delicacies, medicine and tonics, which have been recommended and consumed in Asia over many centuries. At the commercial level, they are ranked as different values based on species. However, fish maw species and the trade are still unknown and undocumented. The processing treatments make them difficult for species identification based on morphological characterization. In the present study, the genetic identification of the main commercialized species of fish maws has been carried out, based on the amplification of a fragment of mitochondrial 16S rRNA gene and subsequent BLAST analysis. The applicability of all kinds of processed products was verified, including dried, water soaked, salt fried and salt fried plus water soaked forms. The result indicated this method was applicable to all of them, showed that 53.3% of the products were incorrectly labeled and 58.3% of “croaker” products were substituted with catfish or perch species. Moreover, results indicated that besides traditional trade in Asia, the fish maw trade has been globally expanded to meet the growing demand of market. Therefore, this method can be useful in normative control of processed products, particularly in the authenticity of imported species, verifying the correct traceability in commercial trade, the correct labeling, and also for fisheries control of endangered species to conserve stocks biodiversity.

In this study, the bioremediation potentials of two seaweeds (Sargassum hemiphyllum and S. henslowianum) against pollution in a coastal mariculture area of Shenzhen, South China, were investigated by comparing the growth, nutrient bioaccumulation capacity of plants from the seaweed bed (control site) with plants from the fish farm. Results indicated that both species are potential candidates for bioremediation in the fish farm areas in terms of their high growth rates and high bioaccumulation capacities on inorganic nutrients. Both Sargassum spp. contain high levels of crude protein (11.7-14.0%) and crude fat (2.2-2.7%), suggesting high nutritional values. The S. hemiphyllum may serve as a good aquaculture fodder with high nutritional compositions and low heavy metal contents. However, heavy metals (Cr, Pb and Cd) of S. henslowianum exceed the maximum allowable concentrations as aquatic feed, which restricts its fodder application. In general, the results of this study may contribute to the marine pollution bioremediation in the coastal areas of South China, especially in mariculture zones.

A new system for bottom co-culture of scallop, Patinopecten yessoensis, sea cucumber, Apostichopus japonicus (Selenka), and sea urchin, Anthocidaris crassispina, is reported. To evaluate the system, scallops (average shell height, 3.904 ± 0.511 cm) were placed in nine “Hailong” units at densities of 10, 30, and 50 individuals per cell (ind/m2), and the units were placed in shallow waters with a muddy, sandy, or semi-sandy seabed. After more than 9 months, the scallops cultured on the semi-sandy seabed were larger than those cultured on sandy or muddy seabed (p

The bottom culture of southward-transplanted sea cucumber Apostichopus japonicus in a subtropical fish farm was investigated in a field study at Dapeng Cove, Daya Bay, from January 5-August 5 2011, with the aim of finding the ideal period for culturing A. japonicus in fish farms, and developing an integrated multi-trophic aquaculture (IMTA) in southern China. Results showed that the bottom-cultured sea cucumbers survived well (100%) before summer, survival rates decreased to 65.00 +/- 21.21% in July, and all animals had died at the end of the study. Specific growth rates of the sea cucumbers were high during winter (1.05 +/- 0.03% d(-1)), decreased in early spring (0.44 +/- 0.11% d(-1)) and became negative in the following months. Growth rate was mainly influenced by water temperature, dissolved oxygen and sulphide content; the anoxia caused by water column stratification at the sea-floor in the summer were the main causes of mass mortality. Our results indicate that bottom culture in the temperate season (winter and spring, optimally from late November to early April) is a viable way to rear the deposit feeder A. japonicus underneath a subtropical fish farm.

In this study, we conducted a 14-month investigation in Daya Bay, southern China to understand the effects of oyster farming on phytoplankton community and biomass by using size-fractionated phytopigments. Results proved the filtering effects of oysters on phytoplankton biomass. During the oyster culture period, the average concentration of total chlorophyll a (sum of size-fractionated Chl a) within the farming area was approximately 60% lower than that at the reference site. Phytoplankton depletion in the aquaculture zone mainly occurred in micro-sized fractions (>20 μm) of Chl a, fucoxanthin, and peridinin. The influence of oyster filtration on nano-sized (2.7-20 μm) pigments seemed less than that on micro-sized ones. The depletion of peridinin and 19'-hex-fucoxanthin in aquaculture zone was higher than those of the other pigments, which indicated that flagellated cells might be selectively filtered by oysters and could be more easily influenced by oyster aquaculture. The pico-sized Chl a (

The feasibility of co-culturing the sea cucumber Holothuria leucospilota Brandt in a subtropical fish farm was investigated in a field study. Sea cucumbers were cultured in the fish farm in cages suspended at 4 m deep (suspended culture) and directly on the seafloor (bottom culture). The survival and growth of the sea cucumbers were monitored twice during the 3-month, summer experimental period (May 26August 14, 2010). Results showed that the suspension-cultured sea cucumbers exhibited excellent survival rate (100%) during the whole study period. There also occurred no mortality in the bottom-cultured sea cucumbers during the first culture period (May 26July 13); but all these died from anoxia caused by water column stratification during the second culture period (July 14August 14). The specific growth rate of the bottom-cultured sea cucumbers (1.05 +/- 0.21 % day-1) was nearly double that of the suspended culture animals (0.57 +/- 0.21 % day-1) during the first culture period, and the growth rates of the suspended culture sea cucumbers in the second culture periods (0.46 +/- 0.24 % day-1) was only a little lower than that of the first period. The sea cucumbers H. leucospilota could ingest and assimilate sediment with high organic matter content with an average assimilation efficiency of 14.9 +/- 3.9%. This study indicated that fish farm detritus can be effectively used as a food source for the sea cucumber and that it can be turned into a valuable secondary crop in the form of the sea cucumber biomass.

Survival, growth and immune response of the scallop, Chlamys farreri, cultured in lantern nets at five different depths (2, 5, 10, 15, and 20 m below the sea surface) were studied in Haizhou Bay during the hot season (summer and autumn) of 2007. Survival and growth rates were quantified bimonthly. Immune activities in hemolymph (superoxide dismutase (SOD) and acid phosphatase (ACP)) were measured to evaluate the health of scallops at the end of the study. Environmental parameters at the five depths were also monitored during the experiment. Mortalities mainly occurred during summer. Survival of scallops suspended at 15 m (78.0%) and 20 m (86.7%) was significantly higher than at 2 m (62.9%), 5 m (60.8%) or 10 m (66.8%) at the end of the study. Mean shell height grew significantly faster at 10 m (205.0 μm/d) and 20 m (236.9 μm/d) than at 2, 5 or 15 m in summer (July 9 to September 1); however, shell growth rate at 20 m was significantly lower than at the other four depths in autumn (September 2 to November 6). In contrast to summer, scallops at 5 m grew faster (262.9 μm/d) during autumn. The growth of soft tissue at different depths showed a similar trend to the shell. Growth rates of shell height and soft tissue were faster in autumn than in summer, with the exception of shell height at 20 m. SOD activity of scallops increased with depth, and ACP activity was significantly higher at 15 and 20 m than at other depths, which suggests that scallops were healthier near the bottom. Factors explaining the depth-related mortality and growth of scallops are also discussed. We conclude that the mass mortality of scallop, C. farreri, during summer can be prevented by moving the culture area to deeper water and yield can be maximized by suspending the scallops in deep water during summer and then transferring them to shallow water in autumn.

The growth and survival of the Zhikong scallop Chlamys farreri suspended in deep water of Haizhou Bay were studied from July 2007 to June 2008, and the biodeposition method was used to estimate the clearance rate of C. farreri under field conditions. Results showed that the scallop grew fast during all the culture time, with the exception of summer. The condition index of the scallop increased with time and reached the highest value in spring of the second year. The survival of scallops was 60.8 +/- A 3.9% at the end of this study, mortality occurring mainly during the summer and autumn of the first year. The clearance rate fluctuated obviously with season,with the highest value in September 2007, and the lowest value in March 2008. Factors accounting for variations in growth and clearance rate of scallops are also discussed.

We examined the growth, survival and immune response of the scallop, Chlamys farreri, during a 1-year period in deep water of Haizhou Bay. Scallops were cultured using two methods: (1) in lantern nets at a 5 m depth and (2) in a bottom culture system (sleeves) on the seabed at about a 25 m depth. Shell heights, meat dry weight and immune activities in the haemolymph (superoxide dismutase and myeloperoxidase) were measured bimonthly or quarterly from July 2007 to June 2008. Survival was measured at the end of the study and environmental parameters in the experimental layers were monitored during the experiment. The growth and immune activities of scallops were lower when the water temperature was high, which was consistent with the main mortality occurring in summer. The growth and immunity of scallops were higher in the suspended culture than in the bottom culture during the experiment, with the exception of shell growth during the last study period. Survival of scallops in the suspended culture (54.6 +/- 12.3%) was significantly lower than that in the bottom culture (86.8 +/- 3.5%) at the end of this study. We conclude from our results that the high mortality of C. farreri can be prevented by culturing them in a bottom culture system before November of the first year, and then transferring them to a suspended culture to improve scallop production.

The complete mitochondrial genome (mitogenome) sequence of Holothuria scabra, an economically and ecologically important tropical sea cucumber, was first sequenced and annotated. The mitochondrial DNA is 15,779 bp in length and contains 13 protein-coding genes (PCGs), 2 rRNA genes, 22 tRNA genes, and a 456 bp putative control region, of which gene order is identical to the echinoderm ground pattern. Comparative analyses between H. scabra and other holothurians revealed three new findings: (1) the mitogenome of H. scabra is highly compact having five regions with overlapping genes and least intergenic nucleotides among the sequenced holothurians, only accounting for 3.58% of its mitogenome; (2) the genus Holothuria mitogenomes show a pattern of high interspecies divergence at the 13 PCGs, and the genetic p-distance reaches 25.68% between H. scabra and H. forskali; (3) the incomplete stop codon T of cox2 shared with H. forskali may be a common feature in the genus Holothuria.

Summary The survival of the sea cucumber Apostichopus japonicus in various land-based and field aquaculture systems is negatively correlated with the abundance of potential predators. Different predators affect the various life stages. Copepods, such as Microsetella sp. and Tigriopus japonicus , can compete for food and space with sea cucumber larvae, and they can also be predators of juveniles A. japonicus themselves) are potential predators of larvae and newly settled juveniles. Juvenile sea cucumbers with a body length 10 cm have few known predators. Various methods have been developed in an effort to protect the various life stages of A. japonicus against predators. In hatcheries and nurseries, trichlorphon can eliminate copepods without harming early life stages. In grow-on ponds and coastal areas, rocks and artificial reefs are used to provide shelter from predators. Bottom trawling, trapping, and manual removal by divers may also be used to decrease the abundance of predators in aquaculture systems.

The sea cucumber Holothuria (Theelothuria) notabilis for the first time is reported from the Beibu Gulf, South China Sea. A morphological description of this new record with colour figures and scanning electron microcopy images of its ossicles are provided. This finding widens the geographical range of H. (T.) notabilis and indicates that this species may expand northwards in the South China Sea. With our new record, the subgenus theelothuria is now represented by three species in China.

The sea cucumber Holothuria leucospilota is a good candidate for aquaculture, for large-scale production of this sea cucumber, it is imperative to know the effects of salinity on its physiological performance. In this study, ingestion, oxygen consumption and ammonium excretion rates of the adult sea cucumber H.leucospilota (16.98 +/- 1.14g, wet weight) at various salinity levels (18, 23, 28, 33 and 38PSU) were studied in the laboratory. The species were acclimated for 1week at the desired salinity before testing, and were fed with sediment from their natural habitat during this period. Results showed that the minimum ingestion rate (0.02 +/- 0.01gg(-1)d(-1)) at a salinity of 18PSU was significantly lower than those observed at salinities of 28, 33 and 38PSU, and there was no significant difference among the values at 23, 28, 33 and 38PSU. The maximum value of oxygen consumption rate recorded at a salinity of 28PSU was significantly higher than the minimum at 18PSU, no significant differences were observed among other treatments. The ammonium excretion rates of H. leucospilota also changed significantly in response to salinity variations, the maximum value observed at a salinity of 28PSU (0.09 +/- 0.03Mg(-1)h(-1)) being nearly five times higher than the minimum value at a salinity of 38PSU (0.02 +/- 0.01Mg(-1)h(-1)). The O:N ratio varied as a function of salinity. Lower O:N ratios (

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 (1 km 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 (10 ind m(-2)) at the fish farm site reached a commercial size (>100 g 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. (C) 2014 Elsevier B.V. All rights reserved.