Based on the daily satellite monitoring data of floating green tides, and the nitrogen nutrients and hydrological environment parameters were collected in spring (April, before green tides) and summer (July, later stage of green tides) cruises in the southern Yellow Sea (SYS) in 2018, we studied the spatio-temporal variation characteristics of the green tides, and the role of nitrogen nutrients in it. The results showed that the small U. prolifera patches were firstly observed in shallow waters off Nantong, Jiangsu Province on April 25, then floated northward and reached its maximum scale on the June 29, followed by decomposition and disappearance in the coast of Shandong Peninsula in the mid-August. The trajectory area of floating green tides was mainly located in the western of 122°E in the SYS, and showed two distinguishable development phases, the rapid growth phase in the south of 35°N, nearshore area of Jiangsu, and the decline phase in the north of 35°N, offshore area of Shandong Peninsula. The nitrogen nutrient components showed regional and seasonal variations, influenced by the freshwater influx, cold water masses, biological activity and other factors. The effects of nitrogen components were different in different development phases of green tides. The rich nitrogen nutrients from a variety of sources (total dissdved nitrogen (TDN) >20 μmol/L and dissolved inorganic nitrogen (DIN) >20 μmol/L) provided sufficient nitrogen for the development of green tides in the dominated form of DIN, and contributed to the fast reproduction and growth of U. prolifera in the rapid growth phase. While the U. prolifera showed a higher affinity for DON in the decline phase area, the urea-N become main nitrogen source for the development of green tides because of the poor bioavailable nitrogen content (DIN<2 μmol/L and urea-N<1.5 μmol/L) condition, which would limit the continuous growth of U. prolifera.

Benthic diatoms are important primary producers in estuarine mudflat system, and the spatial and temporal changes in the communities can significantly impact the productivity of benthic fauna in the estuary. In this study, the ecological parameters in the estuaries of Daliao River, Hangu River and Huanghe River along the Bohai Sea coastline were surveyed and the related environmental factors were discussed, aiming to understand the seasonal variations and spatial differences of benthic diatom communities. The results showed that the species diversity index and absolute abundance of benthic diatoms were the highest in autumn, and the dominant species displayed obviously seasonal succession. The diatom absolute abundance in the estuaries of Daliao River and Hangu River were significantly higher than that of Huanghe River Estuary. The coarser sediments and significant phosphorus limitation in the Huanghe River Estuary are main reasons for the low diatom abundance. The correlation analysis between the benthic diatom communities and environmental factors indicated that the changes of temperature and nutrient concentration have significant effects on the seasonal pattern of the benthic diatom communities, while the sediment size, tidal range and runoff of the three estuaries are more important to explain spatial differences.

In the autumn of 2014, a comprehensive survey of hydrology, chemistry and biology in the Bohai Sea was carried out. The structure characteristics of phytoplankton community in the Bohai Sea were studied. The historical data were combined to analyze the formation of phytoplankton community structure. Three classes, including 42 genera, 96 species were found in the survey. Among of them, diatoms are the main species, with 34 genera and 79 species, accounting for 82% of the total species; 16 species of 7 genera of the dinoflagellates account for 17% of the total species; and 1 species of 1 genera of the Chrysophyta. Among them, the genera of Chaetoceros has the most species, a total of 17 species, followed by the genera of Coscinodiscus, a total of 13 species. The total cell abundance of phytoplankton is between 0.71×10⁴ cells/m³ to 72.15×10⁴ cells/m³, with an average of 13.88×10⁴ cells/m³. The cell abundance ratio of diatom to dinoflagellate is 2∶1. The abundance of diatoms in the Laizhou Bay is significantly higher than that in other sea areas. The cell abundance of dinoflagellates in the central Bohai Sea is significantly higher than that in other sea areas. The dominant species of phytoplankton are mainly Coscinodiscus asteromphalus, C. wailesii, Paralia sulcata, Ceratium fusus and Noctiluca. Scintillans. Horizontal distribution of phytoplankton community diversity in the Bohai Sea is uneven in autumn, and the diversity of local sea area is reduced due to the overproduction of single dominant species, the low value areas in autumn are distributed in the Liaodong Bay and the Bohai Strait. Compared with the historical data, the phytoplankton community in the Bohai Sea have obvious species succession. The genara of Ceratium has gradually emerged, its dominance in the central Bohai Sea and Liaodong Bay have surpassed the genara of Chaetoceros and Coscinodiscus. The phytoplankton community structure transforms from dominating by diatoms to dominating by diatoms and dinoflagellates.

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 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.

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.

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.

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.

According to the demersal trawling survey data in the Haizhou Bay and its adjacent waters in autumn of 2011 and 2013−2018, we studied the habitat suitability of Saurida elongata, using biotic and abiotic factors data, such as bottom water temperature, bottom salinity, water depth, resource density, bait biology, collected synchronously. The weight of each environmental factor was determined by using the model of boost regression tree (BRT), and the habitat suitability index (HSI) model was established by using arithmetic mean method and geometry mean method respectively, and the optimal model was determined by cross validation. The results show that the most suitable bottom water temperature range for the Saurida elongata to inhabit in fall was 17.5−18℃, the most suitable bottom salinity range was 31.3−32, and the most suitable water depth range was 24−37 m. Three main bait organisms were selected as biological factors, namely, Loligo spp., Metapenaeopsis dalei and Amblychaeturichthys hexanema. The HSI model was established with the bottom water temperature, bottom salinity and water depth as the influencing factors. The results show that the feed factors contributed most significantly to the total deviation of spatial distribution, followed by the water depth and bottom water temperature. Through cross validation, it is found that the weighted HSI model with arithmetic mean method algorithm has lower Akaike Information Criterion (AIC). The results show that the most suitable habitat (HSI≥0.7) of Saurida elongata in autumn was 34.5°−36°N, 119°−121°E, among which 35°−36°N was the most suitable habitat, and the HSI increased from near shore to sea.