Coral reef is one of the most diverse ecosystem in the ocean, and benthic shellfish is an important component of this ecosystem. We used the SCUBA diving line intercept transect quantitative method to investigate the community status and characteristics of benthic shellfish in the coral reef area of Weizhou Island, Beibu Gulf, covered 6 sites. Sectional benthic shellfish were qualitatively and quantitatively collected in the fall (October 2015) and spring (May 2018). The species composition, abundance, biodiversity index and so on were analyzed. Based on the two survey results, 128 species of benthic shellfish were found in the coral reefs of Weizhou Island, belonging to 1 family, 1 genera, 3 species of Polyplacophora, and 25 families, 46 generas, 68 species of Gastropoda, and 22 families, 31 generas, 57 species of Bivalvia. Dominant species are Parahyotissa numisma, Beguina semiorbiculata, Thais echinata, Trochus maculatus, Euplica versicolor, Barbatia obliquata, Atrina verxillum, Cantharus cecillei, Cerithium dialeucum, Drupa margariticola. We recorded 2 class, 14 family, 43 species in quantitative transects in spring of 2018 and the total species, biomass, Shannon-Wiener index, Margalef index and Pielou index are 3.39 ind./m², 86.94 g/m², 3.31, 3.50 and 0.37. By comparing and analyzing the ecological indices of benthic shellfish in different years, the shellfish biomes in the coral reefs showed good succession development during 2015 to 2018. The shellfish community in the coral reef area of the South China Sea may be affected by both the intensity of anthropogenic disturbance and latitude. This study provided valueable data to rationally develop and utilize marine biological resources, biological protection and ecological restoration for the coral reef ecosystem in the Weizhou Island.

To better understand the ecological characteristics of the macro-fouling community in the northeastern waters of Pingtan Island, East China Sea, a study was conducted by test panels from June 2017 to May 2018. A total of 92 species of fouling organisms belonging to 13 phyla were recorded. The community composition was dominated by coastal warm-water species, and the main dominant species were sessile Amphibalanus reticulatus, Biflustra grandicella, Balanus trigonus, Ectopleura crocea, and motile Jassa falcata, and Maeropsis serratipalma. Bioattachment occurred throughout the year, the main period of settlement extended from June to August (the biomass ranged from 7 326.0 g/m² to 12 970.0 g/m²), and the off-seasons of settlement extended from December to February of next year (the biomass ranged from 39.5 g/m² to 1 580.5 g/m²). The main functional feeding group of macro-fouling organisms was suspension feeder. Temperature and salinity were the most important environmental factors affecting the geographical distribution of macro-fouling organisms. Water transparency, hydrodynamic conditions, surface runoff as well as human activity (such as aquaculture production) also had important impact on the settlement of macro-fouling organisms.

To elucidate the characteristics of macro-fouling communities on discus buoys, an assessment was conducted on 4 buoys deployed in offshore waters southeast of the Zhujiang River Delta and the northeastern Beibu Gulf, respectively. The abundance and biomass of macro-fouling organisms colonizing the side of buoys were 400.00−78 296.00 ind./m² and 659.42−62 276.00 g/m², respectively, whereas those on the bottom were 412.00−66 585.00 ind./m² and 1 861.60−60 784.00 g/m². At most stations, the abundance and biomass of macro-fouling organisms on the bottom of buoys were higher than on the side. The diversity index (H′) on the bottom of buoys ranged from 2.39 to 3.06, the richness index (d) from 4.02 to 6.98 and the evenness index (J′) from 0.88 to 0.91; and those on the side of buoys were from 0.64 to 2.79, 1.10 to 4.89 and 0.58 to 0.96, respectively. Both of the H′ and the d on the bottom of buoys were higher than on the side. According to the results of Hierarchical Cluster Analysis and Non-metric Multi-Dimensional Scaling, the macro-fouling communities of buoys could be clustered into 4 groups at 30% similarity. Of them, the communities on the bottom of the buoys could be basically clustered into a group while those on the sides varied with locations. Moreover, one-way Analysis of Similarities and Similarity Percentages-Species Contributions not only indicated that the macro-fouling community structure differed significantly between the side and bottom of the offshore buoys but also highlighted that the cirripedians and cnidarians made the greatest contribution to the difference. Overall, macro-fouling organisms preferentially colonized the bottom of discus buoys rather than the side.

According to two years (2018−2019) spring plankton surveys in the Zhoushan coastal waters, the zooplankton community structure (species composition, abundance of dominant species) were investigated, the canonical correspondence analysis (CCA) was used to study spring interanuual difference of zooplankton community and causes of their dynamics, the mechanism of community dynamics were discussed according to our results.The results show that the study region is divided into three groups according to cluster analysis of sea surface temperature (SST) and sea surface salinity (SSS): Hangzhou Bay water masses (Area I), upwelling water masses in Zhoushan Island (Area II), and water masses in Zhoushan offshore area (Area III). Water mass groups have significant influence on the composition of zooplankton community. The main species contributing to the difference between the three water masses in spring 2018 and spring 2019 (contribution rate >10%) are Calanus sinicus. The contribution species of the same water mass in two years were: Tortanus derjugini (56.91%) and Labidocera euchaeta (12.34%) in Area I, Calanus sinicus (72.64%) and Muggiaea atlantica (13.35%) in Area II, Calanus sinicus (41.93%) and Noctiluca scintillans (22.94%) in Area III. CCA shows that the first CCA axis (CCA1) and the second CCA axis (CCA2) explained 46.14% of the accumulated variance of the dominant species of zooplankton and 97.82% of the species-environment accumulated variance in spring 2018 and spring 2019. CCA1 mainly reflects the spatial difference between the offshore water mass and the Hangzhou Bay water mass. CCA2 mainly reflects the interannual difference between the stations in 2018 and 2019. Salinity is the main factor influencing the spatial difference of zooplankton community structure in spring, while temperature and chlorophyll a concentration are the main factors controlling the interannual difference of zooplankton community structure in spring.

Based on the data obtained from bottom trawl investigation in the Haizhou Bay and adjacent waters in 2018, a mass-balance model for the Haizhou Bay ecosystem was constructed by Ecopath with Ecosim software, consisting of 26 functional groups. Using Ecopath model, we evaluated the trophic structure, trophic impact relationship and ecosystem characters of the Haizhou Bay to provide a theoretical basis for the implementation of ecosystem-based fisheries management. The result showed that in this ecosystem trophic levels of functional groups varied from 1.00 to 4.19, and the range of fish trophic level was wide, ranging from 3.22 to 4.19. Phytoplankton and molluscs were in important nutritional positions in the ecosystem facing with the pressure from both the primary producers and predators. The evaluation of the ecosystem structure and function showed that the total primary production/total respiration (TPP/TR) was 7.096, total primary production /total biomass (TPP/B) was 56.866, the connectance index (CI) and system omnivory index (SOI) were 0.429 and 0.204, indicating that the Haizhou Bay ecosystem was in an immature, unstable state and was susceptible to external disturbances. Through the study of the Haizhou Bay and its adjacent waters ecosystem model, we analyzed the nutrient structure and phylogenetic status of the sea area, which would provide a theoretical basis for the sustainable utilization and scientific management of fishery resources in the Haizhou Bay.

In this paper, the net primary productivity (NPP) of the northern islands of Miaodao Archipelago in 2005, 2010 and 2017 was estimated by using ArcGIS10.2, ENVI5.1, SPSS26 and other software based on the classic CASA model, and analyzed the spatial-temporal heterogeneity of NPP from the perspectives of season, individual of island, landscape type, terrain gradient, and then analyzed the spatial-temporal heterogeneity of the landscape pattern of the five northern islands in 2005, 2010 and 2017. The relationships between them and the reasons were discussed. The results showed that: the total NPP for the five northern islands of Miaodao Archipelago was 7 520.54 t/a in terms of carbon; the mean density of NPP was 406.07 g/(m²·a) in terms of carbon; the distribution of NPP showed a significant spatial-temporal heterogeneity; the order of the average area of each landscape type from largest to smallest was coniferous forest, broad-leaved forest, construction land, grassland, arable land; the mean density of NPP from largest to smallest was broad-leaved forest, coniferous forest, arable land, grassland, construction land; the mean density of NPP of each landscape increased first with the increase of slope and height difference, and then decreased slowly; the aspect had a great influence on the NPP of forest, and the mean density of NPP of half shady slope is the largest; the annual mean density of NPP of different terrain gradients decreased with the time; the high value of NPP appeared in the mountainous area, and the low value of NPP is mainly in the flat area; due to the natural geographical conditions and the plant growth strip, the distribution of NPP was influenced by season, geographical location and landscape type.

In present study, the morphology and species identification of the Neobenedenia parasites (Isolate Batam/IB) in the cage aquaculture were studied via morphological and molecular marker methods at Batam Island, Indonesia. The isolate Batam is morphological similar with Neobenedenia girellae, and it is considered to belong to the Neobenedenia genera. 394 bp of the 28S rRNA was amplified, and its similarity with other genera was between 85.86%−99.47%. The phylogenetic tree shows that IB, Neobenedenia melleni and Neobenedenia girellae are in a same cluster, and other Benedeniinae species form their own cluster. To sum up, IB is identified as the specie of Neobenedenia girellae and we support the theory that N. melleni and N. girellae are synonyms.

The extracellular enzyme activity of seawater can indicate the distribution characteristics of organic and the nutritional status of microorganisms. Activities of eight extracellular enzymes, including alkaline phosphatase, lipase, leucine aminopeptidase, chitinase, cellulose, xylosidase, α-D-glucosidase and β-D-galactosidase, were measured in the surface seawaters collected from 44 stations of the Yellow Sea and the East China Sea from March 25 to April 15, 2017 and from 10 stations of the Jiaozhou Bay nearby waters from April 28 to 29, 2018. In the spring of 2017, the high-value areas of alkaline phosphatase and lipase appeared in the northern coast of Jiangsu and the middle of the Yellow Sea, alkaline phosphatase activity and phosphate concentration were positively correlated. High activity areas of the other six enzymes (leucine aminopeptidase, chitinase, cellulose, xylosidase, α-D-glucosidase and β-D-galactosidase) appeared in the open sea outside the east of the Changjiang River Estuary. The average activities of β-D-galactosidase and xylosidase were significantly higher in the East China Sea than in the Yellow Sea. The decreasing order of average enzyme activities of the eight enzymes was as follows: alkaline phosphatase, lipase, leucine aminopeptidase, chitinase, α-D-glucosidase, β-D-galactosidase, cellulose, xylosidase, the values of α-D-glucosidase and β-D-galactosidase are proximate. The activities of alkaline phosphates, lipase and xylosidase in the Jiaozhou Bay nearby waters in spring 2018 decreased from nearshore to far shore. The decreasing order of the average enzyme activity of the eight enzymes was as follows: alkaline phosphatase, lipase, leucine aminopeptidase, xylosidase, α-D-glucosidase, β-D-galactosidase, cellulose, chitinase, the values of cellulose and chitinase are proximate. The alkaline phosphatase and lipase activities in the Yellow Sea were significantly higher than those in the East China Sea and Jiaozhou Bay. The average enzymatic activities of polysaccharide hydrolases (chitinase, cellulose, α-D-glucosidase, β-D-galactosidase and xylosidase) were the lowest in the Yellow Sea compared with those in the East China Sea and Jiaozhou Bay nearby waters. Our results are beneficial to understand the degradation of organic carbon by plankton and heterotrophic bacteria and the distribution of marine organic carbon in the coastal water of China.

This study investigated the oxidative stress and energy utilization responses of juvenile cobia (Rachycentron canadum) to environmental hypoxia stress, and provided reference for the healthy cultivation of cobia. Through the hypoxia stress-reoxygenation test, the oxidative stress and energy utilization indexes of liver and muscle tissues were measured after hypoxia ((2.64±0.25)mg/L) stress for 3 h and reoxygenation ((6.34±0.15)mg/L) stress for 8 h, 24 h and 48 h. The results showed that after hypoxia stress, the activity of malondialdehyde (MDA), catalase (CAT) and glutathione reductase (GR) in the liver were significantly lower than that in the control group (p<0.05), and the activity of lactate dehydrogenase (LDH) was significantly higher than that in the control group (p<0.05). MDA and lipid peroxidase (LPO) activities in muscle were significantly lower than those in control group (p<0.05), and superoxide dismutase (SOD) and LDH activities were significantly higher than those in control group (p<0.05). The contents of muscle glycogen and liver glycogen were significantly lower than those of control group (p<0.01). During reoxygenation, the contents of MDA, LPO, SOD, CAT, glutathione peroxidase (GPx) and GR in liver and muscle all increased differentially. Liver glycogen content was significantly higher than that of the control group 24 h after reoxygenation (p<0.05), and significantly lower than that of the control group 48 h after reoxygenation (p<0.05). Muscle glycogen content was significantly lower than that of control group after reoxygenation for 8 h, 24 h and 48 h (p<0.05). In conclusion, hypoxia stress can cause some oxidative damage to the body of cobia, and the enzyme activity and energy supply of liver and muscle tissues change. The reoxygenation environment after hypoxia stress causes more severe oxidative damage to the body, which can be gradually restored to the normal level through physiological regulation.

As one of the most abundant species of family Notothenioidei, rock cod (Patagonotothen ramsayi) plays an important role in energy transfer in the food web in the Patagonian Shelf. Currently, the work on feeding ecology of this species mainly bases on the conventional stomach content analysis, which only reflects short-term variation in feeding. Therefore, this study analyzed the distribution of fatty acids in three tissues (muscle, liver and gonad) of rock cod, and analyzed whether fatty acids in these tissues can characterize their feeding habits and transfer of diet. The results indicate that 27 kinds of fatty acids were detected in the tissues of rock cod. The storage and use of fatty acids in liver and gonad tissues are not suitable for indicating the diet of rock cod because they are involved in growth and reproduction. Compared to liver and gonad tissues, the longer renewal cycle of muscle tissue may better reflect its absorption of fatty acids from food. For the analysis of fatty acids in the muscle tissue of the rock cod in different size groups, it is inferred that the small-size rock cod (immature individual, 100−240 mm) mainly fed on planktonic organisms. The benthic feeding characteristics of rock cod increase with the increasing of size, and the feeding pattern transfer from planktonic feeding to planktonic-benthic feeding. In addition, due to the consumption of a certain amount of fishery discards by rock cod, the contribution rate of saprophytic food chain to predatory food chain is weakened. The results derive from this study further demonstrate that, compare to tissues of liver and gonad, the fatty acids of muscle tissue can be more suitable to indicate the food source of oceanic fish species.