Effects of temporal, spatial, and environmental factors on ciliates community in northeastern South China Sea, with notes on co-occurrence patterns of environment, phytoplankton, and ciliate.

Unlabelled: Little is known about temp-spatial variations and determining mechanism of microplankton community from continental shelf to deep basin. Here, the distribution and determinants of ciliates in the northeastern South China Sea were investigated in summer and winter. We found that the alpha diversity were generally similar, but community composition showed clear difference in summer and winter.

Insights into prokaryotic communities and their potential functions in biogeochemical cycles in cold seep.

Unlabelled: Microorganisms are significant drivers of organic matter mineralization and are essential in marine biogeochemical cycles. However, the variations and influencing factors in prokaryotic communities from cold-seep sediments to the water column and the specific role of these microorganisms in biogeochemical cycles in the water column above cold seep remain unclear. Here, we investigated prokaryotic communities and their roles in nitrogen/sulfur cycling processes and conducted dissolved organic matter (DOM) enrichment experiments to explore the effects of diverse sources of DOM on prokaryotic communities.

Cold seep nitrogen fixation and its potential relationship with sulfur cycling.

Unlabelled: Dinitrogen (N) fixation is a crucial source of bioavailable nitrogen in carbon-dominated cold seep systems. Previous studies have shown that diazotrophy is not necessarily dependent on sulfate-dependent anaerobic oxidation of methane for energy, and diverse catabolism can fuel the high-energy-demanding process in sediments. However, it remains unclear whether diazotroph can obtain energy by sulfur oxidation in sulfur-rich cold seep water column.

Size-dependent zoogeographical distribution of gelatinous thaliaceans associated with current velocity and temperature.

Thaliaceans are globally distributed and play an important role in the world's biological carbon pump and marine ecosystems by forming dense swarms with high feeding rates and producing large amounts of fecal pellets and carcasses. The contribution of thaliacean swarms to the downward transport of carbon depends not only on their abundance but also on their body size. However, the key factors influencing the distribution of different-sized thaliaceans remain unstudied.

Dissolved organic phosphorus promotes growth and adaptability in eutrophic tropical estuaries.

Dissolved organic phosphorus (DOP) is an important nutrient for phytoplankton growth in oligotrophic oceans. However, little is known about the impact of DOP on phytoplankton growth in eutrophic waters. In the present study, we conducted field monitoring as well as and laboratory experiments in the Pearl River estuary (PRE).

Distinct diversity patterns and assembly mechanisms of prokaryotic microbial sub-community in the water column of deep-sea cold seeps.

Methane leakage from deep-sea cold seeps has a major impact on marine ecosystems. Microbes sequester methane in the water column of cold seeps and can be divided into abundant and rare groups. Both abundant and rare groups play an important role in cold seep ecosystems, and the environmental heterogeneity in cold seeps may enhance conversion between taxa with different abundances.

Phytoplankton Communities Miniaturization Driven by Extreme Weather in Subtropical Estuary under Climate Changes.

Estuarine ecosystems are subject to extreme weather and climatic events, particularly global climate change. To characterize the effects of extreme weather, such as heavy precipitation and cold waves, on phytoplankton communities, four seasonal cruises were conducted in the subtropical Pearl River Estuary. Among the main phytoplankton taxa, small (pico- and nano-sized) phytoplankton accounted for approximately 50% and 70% in the upstream estuary.

Role of jellyfish in mesozooplankton community stability in a subtropical bay under the long-term impacts of temperature changes.

To understand zooplankton community changes in the context of climate change and anthropogenic disturbances, we analyzed mesozooplankton samples from four seasons in the subtropical Daya Bay, which is susceptible to perceived disturbances in the South China Sea. The zooplankton community was found to be divided into two clusters, namely the Outer-bay Cluster (OC) comprising Noctiluca scintillans, Temora turbinata, and Paracalanus spp., and the Inner-bay Cluster (IC) which was dominated by Pseudevadne tergestina, Oikopleura rufescens, and Paracalanus spp.

Effects of terrestrial inputs and seawater intrusion on zooplankton community structure in Daya Bay, South China Sea.

Daya Bay is a eutrophic coastal region with dynamic physico-chemical conditions influenced by terrestrial inputs and seawater intrusion. Zooplankton is a crucial trophic intermediary for energy transfer and fishery resources. In this study, we assessed the distribution and composition of zooplankton in Daya Bay during summer and winter of 2015.

Distribution of C/N/P stoichiometry in suspended particulate matter and surface sediment in a bay under serious anthropogenic influence: Daya Bay, China.

The C/N/P stoichiometry of organic matter can provide useful information for better understanding of the effects of human activities on aquatic ecosystems. The Daya Bay is a semi-closed bay under serious anthropogenic influences in the southeastern China. This study investigated the contents and ratios of C, N, and P in suspended particulate matter (SPM) and surface sediment in Daya Bay during the spring of 2017.

Distribution of Geochemical Fractions of Phosphorus in Surface Sediment in Daya Bay, China.

Surface sediment samples were collected from 19 sites throughout Daya Bay, China, to study the concentrations, and spatial distributions of different fractions of phosphorus through sequential extraction methods. Like many coastal and marine areas, De-P was the dominant form of P, contributing 47.5% of TP, followed by O-P, contributing 25.

Phosphorus deficiency induced by aluminum in a marine nitrogen-fixing cyanobacterium Crocosphaera watsonii WH0003.

Large amounts of aluminum (Al) enter the ocean through atmospheric dust deposition and river runoffs. However, few studies have reported the effects of Al on marine phytoplankton, especially nitrogen-fixing cyanobacteria. By using the isotope tracer method and quantitative reverse transcription PCR (RT-qPCR), we examined the physiological effect of Al (0.

Utilization of different dissolved organic phosphorus sources by Symbiodinium voratum in vitro.

This study examines the physiological responses of the Symbiodiniumvoratum (clade E) to two types of phosphates having different chemical bonds-phosphoesters (C-O-P bonds) and phosphonates (C-P bonds) to explore Symbiodinium cell growth and the molecular perspective of the P utilization process. Alkaline phosphatase (AP), PhnX, PhoA and PhoX expression was profiled for different P conditions using the RT-qPCR method. In a sterile system, Symbiodinium could decompose phosphoesters, such as ATP and glucose 6-phosphate (G-6-P), into dissolved inorganic P (DIP) to supplement inorganic phosphorus but could not directly use phosphoesters for growth.

Synechococcus bloom in the Pearl River Estuary and adjacent coastal area-With special focus on flooding during wet seasons.

Based on the field surveys aimed at understanding the variations of Synechococcus (Syn) abundance in the Pearl River Estuary during different seasons. We found that heavy terrestrial precipitation result in significant riverine runoffs and promote Syn growth, extension and blooms during warm and wet seasons. To understand the ecological role of Syn play in this estuary during wet seasons, we combined flow cytometry and high throughput sequencing (HTS) of 16S rDNA to investigate the phytoplankton distribution patterns and the potential shaping mechanisms during a typical wet season.

The key to dinoflagellate (Noctiluca scintillans) blooming and outcompeting diatoms in winter off Pakistan, northern Arabian Sea.

The Arabian Sea is prone to large-scale algal blooms during winter monsoon annually. However, it is unclear why dinoflagellate, especially Noctiluca scintillans, replaced diatoms as the main bloom species. Based on in situ, remote sensing and numerical-model data off Pakistan, we found a stratified water with less salty, suitable temperature (~24 °C) and low-light conditions at the subsurface, as well as the organic nutrient accumulation and silicate limitation, were crucial for the growth of N.

Significantly depleted N in suspended particulate organic matter indicating a strong influence of sewage loading in Daya Bay, China.

The influence of anthropogenic nutrient loading on the stable isotopic signatures (δC and δN) in the suspended particulate organic matter (SPOM) is still not fully understood. Water quality and the values of δC and δN in the SPOM were investigated in the surface water of Daya Bay during the spring of 2016 and 2017. The results indicated that the Dan'ao River is the main point source of nutrient pollution in Daya Bay.

Beneficial effects of aluminum enrichment on nitrogen-fixing cyanobacteria in the South China Sea.

Few studies focus on the effects of aluminum (Al) on marine nitrogen-fixing cyanobacteria, which play important roles in the ocean nitrogen cycling. To examine the effects of Al on the nitrogen-fixing cyanobacteria, bioassay experiments in the oligotrophic South China Sea (SCS) and culture of Crocosphaera watsonii in the laboratory were conducted. Field data showed that 200 nM Al stimulated the growth and the nitrogenase gene expression of Trichodesmium and unicellular diazotrophic cyanobacterium group A, and the nitrogen fixation rates of the whole community.

Subsurface low dissolved oxygen occurred at fresh- and saline-water intersection of the Pearl River estuary during the summer period.

Estuarine oxygen depletion is one of the worldwide problems, which is caused by the freshwater-input-derived severe stratification and high nutrients loading. In this study we presented the horizontal and vertical distributions of dissolved oxygen (DO) in the Pearl River estuary, together with temperature, salinity, chlorophyll a concentration and heterotrophic bacteria abundance obtained from two cruises during the summer (wet) and winter (dry) periods of 2015. In surface water, the DO level in the summer period was lower and varied greater, as compared to the winter period.

Effects of resource availability and hydrological regime on autochthonous and allochthonous carbon in the food web of a large cross-border river (China).

Resource availability and flooding disturbance restrict the amount of energy available to the upper trophic level consumers and thus determine the trophic structure and energy mobilization in river food webs. In this study, we evaluated the availability of primary and secondary food resources, food web structure (determined by δC and δN) and relative contributions of autochthonous and allochthonous particulate carbon to aquatic consumers in the Irtysh River, which spans from northwest China to Kazakhstan and suffers from a long frozen period. Despite higher density and biomass, epilithic algae did not make large contributions to aquatic consumers due to the restriction of flow velocity, water depth and turbidity.

Distribution of picoplankton in the northeastern South China Sea with special reference to the effects of the Kuroshio intrusion and the associated mesoscale eddies.

We investigated picoplankton distribution patterns and environmental variables along an east-to-west transect in the northeastern South China Sea (SCS) during late winter 2016, giving us the opportunity to examine the impacts of the Kuroshio intrusion and the associated eddies. The results indicated that the subsurface (50-75m) phytoplankton biomass chlorophyll (Chl a) maximum (SCM) disappeared and was replaced by higher Chl a in the middle part of the transect due to the impacts of the Kuroshio intrusion and mesoscale eddies. Both flow cytometry and pyrosequencing data revealed that picoplankton abundance and community structure were significantly influenced by perturbations in complex physical processes.

Characteristics of picoplankton abundances during a Thalassiosira diporocyclus bloom in the Taiwan Bank in late winter.

To understand the variations of picoplankton (Prochlorococcus, Synechococcus, picoeukaryotes, and heterotrophic bacteria) abundances during diatom bloom, the distribution of picoplankton in the Taiwan Bank, South China Sea was investigated using flow cytometry during a Thalassiosira diporocyclus bloom in March 2016. The results indicated an abrupt abundance decrease for Prochlorococcus, Synechococcus, and picoeukaryotes within the bloom area while the abundance of heterotrophic bacteria showed no significant difference between the bloom and non-bloom areas. We found two sub-groups of heterotrophic bacteria: high- and low-nucleic acid content (HNA and LNA) bacteria with HNA dominated in the bloom area whereas LNA dominated in the non-bloom area.

Spatial distributions of δC, δN and C/N ratios in suspended particulate organic matter of a bay under serious anthropogenic influences: Daya Bay, China.

Stable isotopic signatures (δC and δN) and C/N ratios of suspended particulate organic matter (POM) were investigated from the surface water of Daya Bay during summer and winter of 2015. The relatively high δC values suggested the input of C-depleted terrigenous organic matter was low in Daya Bay. There were significant correlations between δC values and chlorophyll a concentrations both during summer and winter, suggesting the δC values were mainly controlled by the phytoplankton biomass in the surface water.

Abnormally high phytoplankton biomass near the lagoon mouth in the Huangyan Atoll, South China Sea.

Nutrient concentration and phytoplankton biomass were investigated in Huangyan Atoll in May 2015. The concentrations of nutrients were very low, and dissolved inorganic nitrogen was composed mainly of ammonia. Nitrogen likely was the primary limiting factor for phytoplankton growth.

Contrasting energy pathways at the community level as a consequence of regime shifts.

Ecological regime shifts typically result in abrupt changes in ecosystem structure through several trophic levels, which leads to rapid ecosystem reconfiguration between regimes. An interesting aspect of the impact of regime shift is that alternative regimes may induce distinct shifts in energy pathways; these have been less tested than structural changes. This paper addresses this by using stable isotopes to establish the energy pathways in fish communities.

[Effects of large bio-manipulation fish pen on community structure of crustacean zooplankton in Meiliang Bay of Taihu Lake].

In 2005, a large bio-manipulation pen with the stock of silver carp and bighead carp was built to control the cyanobacterial bloom in Meiliang Bay of Taihu Lake. This paper investigated the seasonal variation of the community structure of crustacean zooplankton and the water quality within and outside the pen. There were no significant differences in the environmental parameters and phytoplankton biomass within and outside the pen.