Community assembly patterns and processes of microbiome responses to habitats and Mytilopsis sallei invasion in the tidal zones of the Pearl River Estuary.

The sustainability of estuarine ecosystem functions depends on the stabilization of microbial ecological processes. However, due to the unique and variable habitat characteristics of estuarine areas, in-depth studies on ecological processes such as the spatial distribution and assembly patterns of microbial community structure are lacking. As methods to elucidate this structure, we used 16S rDNA, 18S rDNA and ITS sequencing technologies to study the composition, diversity, spatial pattern and aggregation mechanism of the bacterial, protist and fungal communities in the tidal zones of the Pearl River Estuary (PRETZ). The abundance of bacterial communities was much higher than that of protists and fungi, and the spatial pattern was obvious in PRETZ. The application of neutral and null models revealed the assembly process of three microbial communities dominated by stochastic processes. Among the stochastic processes, undominated processes (64.03 %, 62.45 %, and 59.29 %) were the most critical processes in the assembly of bacterial, fungal and protist communities. Meanwhile, environmental variables, geographic locations, and biological factors were associated with the composition and assembly of bacterial, protist, and fungal communities. Among the environmental variables, dissolved oxygen and salinity were the main predictors that jointly affected the differences in the community structure of the three microorganisms, and geographic location was the second predictor affecting the community structure of the three microorganisms and had a more pronounced effect on the diversity and network structure of the bacterial and fungal communities. However, biological factors exerted a weaker effect on the microbial community structure than spatial factors and only affected bacteria and protists; the invasive species Mytilopsis sallei only affected the process of protist community assembly. In addition, environmental variables affected the relative importance of stochastic processes. In summary, the formation of microbial communities in the PRETZ was affected by random processes, environmental variables, geographic location, and invasive species.

Seasonal and spatial variation of protist communities from reef water and open ocean water in patchy coral reef areas of a semi-enclosed bay.

Protists are an important component of the marine ecosystem and play an essential role in material cycle and energy flow, but the distribution of protists in coral reefs have not been fully studied. In this study, high-throughput amplicon sequencing technology was used to study the biodiversity and community structure of protists from coral reefs and open sea areas, with the typical semi-enclosed bay Daya Bay as the research field. There were significant seasonal differences in the dominant phyla of protists, biodiversity index values and ßeta diversity (P < 0.05) but no significant differences in the different sampling areas (P > 0.05). The topological parameters of the co-occurrence network showed the protist co-occurrence network in the open sea had more complex interactions and stronger stability than in the coral reef areas because of the hydrodynamics, waves, and relatively poor nutrients. Redundancy analysis and the Mantel test showed that the structure of the protist community was affected by seawater temperature, pH, salinity, and dissolved oxygen. This study analysed the temporal and spatial differences in protists in the coral reef and open sea areas of Daya Bay to provide important information for the study of protist biodiversity and community structure in semi-enclosed bays.

Ecological implications of purple sea urchin (Heliocidaris crassispina, Agassiz, 1864) enhancement on the coastal benthic food web: evidence from stable isotope analysis.

A responsible approach to marine stock enhancement is an effective approach to restore fishery resources. While the release strategy of target species has been well investigated, the impacts on local ecological equilibrium and habitat qualities have only been poorly considered. In the present study, we evaluated how the macro-benthic food web in Daya Bay was affected by purple sea urchin (Heliocidaris crassispina (Agassiz, 1864) stock enhancement using stable isotope analyses (δ13C and δ15N). Our results indicated that the distribution of local species and trophic diversity were influenced to a certain degree by release of purple sea urchins and changes in the feeding habit of the urchins were observed in line with food abundance, which seasonally varied. When food is abundant, the main food source of sea urchins was microphytobenthos and no significant differences were observed among sites; significant differences in the diet of purple sea urchins were detected when food is less abundant. These results suggested that optimization of the release strategy should include information on seasonal productivity of local recipient sites, food web structure and feeding habits of released species. Such information is essential for building a responsible release approach to maximize production enhancement.

[Evaluation of ecosystem service and emergy of Wanshan Waters in Zhuhai, Guangdong Province, China].

The method for monetary value and emergy value analysis of ecosystem service was used in this paper to analyze the change in value of marine ecosystem service of Wanshan District, Zhuhai from 2007 to 2012. The result showed that the monetary value and emergy value of marine ecosystem service of Wanshan District, Zhuhai rose to 11512840000 yuan and 1.97 x 10(22) sej from 7721630000 yuan and 1.04 x 10(22) sej, respectively. Both monetary value and emergy value could forecast the change in the value of marine ecosystem service, but they reflected different value structures and ecological energy, which could be used to more objectively evaluate the ecosystem service. Ecological civilization development, as an inherent driving force to impel the development of marine ecosystem service structure, was important for rational exploitation of marine resources and optimization of marine ecosystem service.