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The extreme geographical and climatic conditions of the Tibetan Plateau result in lakes spanning a diverse range of environmental conditions. Studying microbial response to extreme environmental conditions is important for understanding their adaptation and evolution in the natural environment. In this study, the microbial community composition in the surface sediments from 12 lakes with different salinities on the Tibetan Plateau were analyzed using the Illumina high-throughput sequencing platform. The results showed that the phyla Proteobacteria and Bacteroidota were the major bacteria, and Crenarchaeota was the major group of archaea in low and moderately saline lakes (salinity 0.64–33.88PSU), whereas Firmicutes and Halobacterota increased significantly in high saline lakes (salinity 44.25–106.9PSU). Salinity was the most important factor impacting bacterial α-diversity, characterized by a significant decrease in microbial diversity indices with increasing salinity. Salinity was also the main driving factor determining the microbial community composition of these lakes. Other factors, including Chl-a, OM and glacial meltwater, also had important effects to some extent. In contrast, geographic factors had no remarkable effect on microbial community composition.

With the wide application of plastic products, microplastics are now ubiquitous in coastal wetlands, representing a serious threat to the health of coastal organisms. In East Asia, millions of migratory shorebirds depend on the tidal flats of Yellow Sea in China, and they have experienced rapid populations declines due at least partially to the environmental pollution. However, our understanding about the specific exposures and hazards of microplastics, and the factors affecting the bioavailability of microplastics to different shorebird species remains limited, which hinders our ability to address the potential detrimental effects of microplastic accumulation to these fast-disappearing birds. Therefore, this study aims to assess the risk of microplastic exposure in shorebirds, determine the enrichment of microplastics in different tissues, and establish the relationship between shorebirds' foraging strategies and microplastic intake. We extracted and identified microplastics in different tissues sample from the carcasses of 13 individuals in four shorebird species, and measure the abundance, color, size, and roughness of all microplastics found. Microplastics were found in all species except one red-necked stint (Calidris ruficollis). Polyethylene, silicone, polypropylene, and polyurethane were the main polymers identified in shorebirds. Microplastics found in shorebirds that use mixed tactile and visual foraging strategy were smaller, less rough, and low in color diversity, compared to those found in shorebirds that forage predominately using visual cues. In addition, ingested microplastics were disproportionately enriched in different tissues; in particular, the abundance and size of microplastics in the digestive tract were significantly higher than those in the pectoral muscles. Understanding the stress of microplastics posed to coastal shorebirds is critical to facilitate more effective and targeted measurements in coastal pollution control.

Eukaryotes exist widely in aquatic ecosystems. It is of great importance to study their species composition, diversity, and relationship with environmental factors to protect and maintain ecosystem balance. Salt lakes are essential lakes rich in biological and mineral resources and have significant research value. To understand the characteristics of eukaryotic diversity in salt lake sediments, we conducted a sampling survey of the benthos in Kyêbxang Co, Tibet, in July and August 2020. The sampling area was divided into littoral, sublittoral, and profundal zones. A total of 42 species of Metazoa, 159 species of Protozoa, 63 species of Viridiplantae, and 46 species of Fungi were identified by the high-throughput sequencing of 18S ribosomes. Alpha diversity analysis revealed significant differences in species composition among the three study zones. The littoral zone had the highest Sobs index and Chao index, indicating that the eukaryotic diversity and richness in this zone were significantly higher than those in the profundal and sublittoral zones. Redundancy analysis (RDA) showed that water depth, temperature, and sediment organic matter content significantly affected the community structure of eukaryotes zones, especially the distribution of dominant genera such as Dunaliella, Psilotricha and Brachionus. Cooccurrence network analysis showed that Dunaliella, Aphelidium, temperature, water depth, and organic matter represent essential nodes in the entire network. This study can provide baseline data and new insights for eukaryotic diversity research for salt lakes.

Adaptation to seasonal change is essential for survival, and is especially critical for organisms living in physically harsh environments. Brittle stars (Ophiothrix), known as a keystone species, inhabiting the intertidal rocky ecosystem are affected by multiple stressors, but molecular insights into their adaptation remain poorly studied. In the present study, transcriptomic responses of Ophiothrix exigua from the intertidal habitats of the North Pacific Ocean during summer and winter are reported. A total of 12,844 differentially expressed genes (DEGs) were identified. Of these, 7102 genes were up-regulated and 5742 genes were down-regulated in summer relative to winter. One hundred fifty-two key DEGs, including 31 up-regulated and 121 down-regulated genes, were categorized into three major subcategories and seven subclasses. The key DEGs included heat shock cognate protein 70 (HSC70), toll-like receptor-2 (TLR2), cAMP-dependent protein kinase catalytic subunit beta-like isoform X2 (PKA), serine/threonine-protein kinase mTOR (MTOR), and ras-related c3 botulinum toxin substrate 1 isoform X1 (RAC1). Glutathione peroxidase-like (GPX) and tubulin superfamily members (TUBA, TUBB) were consistent across seasons. The main defense-related pathways in brittle star were phagosome, apoptosis, and glutathione metabolism. These findings would greatly enhance our understanding of the genomic basis of environmental adaptation in intertidal invertebrates.

Ocean acidification threatens marine organisms continuously. To ascertain if adaptation of marine species to ocean acidification enhanced over multiple generations, we studied the transgenerational effects of ocean acidification on the development, reproduction, ingestion rate, and ATPase activity of a copepod Tigriopus japonicus Mori, 1938. In the first mode, individuals were exposed to either one of the pH levels (8.1 (control), 7.7, 7.3) for five successive generations. In the second mode, each successive generation was exposed to a lower pH level (pH levels: 8.1, 7.9, 7.7, 7.5, 7.3). After prolonged exposure to a constant seawater acidification level, the capacity to adapt to the stress increased. However, when exposed to seawater of descending pH, the detrimental effects gradually increased. Energy allocated to development and reproduction was reduced although the ingestion rate continued to improve in successive generations. Therefore, ongoing ocean acidification might lower the energy transfer of copepods to higher trophic levels.

Functional diversity of macrofaunal assemblages can reflect the composition and differences of functional traits, indicating their response to various contaminants, especially heavy metal pollution. We explored the effects of environment variables over gradients of heavy metal pollution on macrofaunal assemblages, using biological traits analysis, generalized linear model (GLM), AZTI marine biotic index (AMBI), and various biodiversity indexes. The RLQ (co-inertia analysis) and fourth-corner approaches were used to investigate the specific response of functional traits to heavy metal pollution. Most sites were environmentally degraded by heavy metal pollution and macrofaunal body size had a miniaturization trend. There was a significant correlation between functional diversity indexes and AMBI. The RLQ and fourth-corner analysis and GLM models showed that heavy metal and natural environmental gradients had a profound effect on functional diversity. The functional divergence and dispersion indexes, along with the abundance of some specific species, were appropriate indexes for heavy metal pollution.

The coastal ecological environments are heavily affected by anthropogenic activities as well as global climate change. Macrofauna can be used as good indicators for benthic ecological quality status due to its relatively slow movement ability under disturbance and a variety of assessment approaches have been established based on the characteristics of macrofauna. The benthic ecological quality of the Bohai Sea, China, is increasingly threatened by anthropogenic activities. In order to accurately assess the benthic ecological quality status in this region, Shannon-Wiener diversity index, ABC curve, AMBI, M-AMBI and macrofaunal feeding evenness index were used. Results showed that the northern Laizhou Bay and Bohai Bay were under slight disturbance while Liaodong Bay, the central Bohai Sea and Bohai Strait were under moderate disturbance. Overall, the ecological quality indicated by the assessment results of AMBI, Shannon-Wiener diversity index and feeding evenness index were better than that by M-AMBI and the ABC curve.

Eleven heavy metals (V, Cr, Mn, Co, Fe, Ni, Cu, Zn, As, Cd, and Pb) in surface sediment in the intertidal zones of the Yellow River Estuary, China were analyzed by inductively coupled plasma-mass spectrometry in summer and autumn 2019. Results indicated that the 11 heavy metals had the same sources. Sediment particle size and total organic matter were the main factors influencing the distribution of heavy metals. Most sites in the intertidal zones of the study area were not contaminated with V, Cr, Fe, Co, Zn, Pb, Cu, As, Mn and Ni, while Cd was the priority pollutant. Heavy metal pollution risk in autumn was higher than that in summer, which may be due to hydrodynamic effects. The present study showed that the heavy metal concentrations in the study area had a temporal decreasing trend compared to previous studies, which may be due to the reduction in human activities.

The prevalence of microplastics in water bodies such as oceans and rivers has received considerable attention in recent years. The present study contributes to this research effort by assessing microplastics in 12 remote lakes on the Tibetan Plateau, China. Despite the limited extent of human activities, at least 17 items and up to 2644 items of microplastics were found per kg of dried sediments collected from the lakes in Tibet. These values were considered high compared to the levels of microplastics reported in other lake areas worldwide. Our results showed that the most prevailing types of microplastics in the sediments were black or transparent fibers in the size range of 0.05–0.5 mm, which were mainly identified to be polyamide and polyethylene terephthalate using Fourier-transform infrared microspectroscopy. The number of microplastics found appeared to be higher in sediments with a higher silt and clay content. Atmospheric long-range transport, glacial meltwater and surface runoff represent potential pathways to carry microplastics from elsewhere to the remote lakes in Tibet. This study shall be of great significance in understanding the transport and distribution of microplastics in the environment at regional or global scale.

Microplastics have adverse effects on marine organisms. However, there are limited data on microplastics distribution patterns in various tissues of marine organisms. Microplastics in seawater and nine types of tissues of the Zhikong scallop (Chlamys farreri) from three coastal aquaculture areas were analysed. The results showed that in seawater, microplastics were mainly fibrous. There were no significant differences in microplastics abundance among the three areas. The concentrations of microplastics in the scallop anus, intestinal tract and kidney were substantially higher than those in the other tissues. Microplastics abundance ranged from 8 to 13 particles per scallop. Microplastics colours were mainly black, transparent and blue, and there were no significant tissue distribution patterns. Microplastics size ranged from 5 μm to 1 mm. The microplastics abundance in the haemolymph was significantly correlated with those of the surrounding seawater. Additional study is necessary to determine the toxic effects of microplastics on marine organisms.

Microplastics, emerging contaminants in the ocean, are thought to sink and accumulate in sediments, and thus may pose a potential ecological risk to benthic communities. In this study, abundances and characteristics of microplastics in sediments and benthic organisms from the South Yellow Sea were investigated. First, we optimized the sediment sampling for microplastic analysis and found that the top layer (0-5 cm) had the highest abundance, and microplastic abundances decreased significantly with increase in sediment depth. The abundance of microplastics was 560-4205 n/kg dry weight in the surface sediments (the topmost 3 cm) of 14 sites and 1.7-47.0 n/g wet weight in the tissues of benthic organisms. Moreover, microplastic abundances in sediments and benthic organisms were both positively correlated with water depth. Fibers, transparent microplastics, and small microplastics (0.5 mm) were the most dominant types in sediments and organisms. FTIR analysis showed that polypropylene (PP, 31%), polyester (PE, 24%), nylon (19%), and polystyrene (PS, 15%) were the most abundant polymers in sediments. The results of SEM showed rough surfaces and obvious cracks on the microplastics isolated from sediments. In addition, characteristics of microplastics in Ophiura sarsii, Crangon affinis, and Acila mirabilis were compared. Our results demonstrate that a comprehensive investigation of microplastics in sediments and benthic communities will help to fully understand the ecological risk of microplastic pollution.

To evaluate the impact of bottom aquaculture on benthic ecosystems, characteristics of benthic food web were studied using stable isotope techniques during four seasons in a Manila clam (Ruditapes philippinarum) bottom aquaculture area in a semi-enclosed bay, China. Results showed that although nitrogen stable isotope values of food sources (particulate organic matter and phytoplankton) had significant seasonal differences, there were no significant seasonal changes for benthic food web structure. Manila clam bottom aquaculture can enhance the secondary productivity and improve the basic trophic pathways by providing bio-deposits. Besides particulate organic matter and phytoplankton, Manila clam could feed on self-generated feces with high nitrogen stable isotope values, and benthic micro- and macroalga with high carbon stable isotope values. Secondary productivity of the stations with a high degree of aquaculture was higher than that of stations with a low degree. Bivalve bottom culture may have a positive impact on benthic ecosystem functioning.

The adjacent waters of the Yangtze River Estuary are influenced by heavy anthropogenic activities. The benthic ecological status was assessed using the Shannon-Wiener diversity index, the AZTI Marine Biotic Index (AMBI), and the multivariate AMBI (M-AMBI) based on macrofaunal data collected in this area at 51 sites in June 2013 and June 2014. In total, 321 species of macrofauna were identified. Polychaetes were the most dominant, followed by mollusks and crustaceans. The AMBI results showed that 72.55% of the sites were under slight disturbance with a decreasing disturbance trend from inshore to offshore. M-AMBI showed that most of the sites were under lower disturbance level than those shown by AMBI. The Shannon-Wiener diversity index showed that only two sites, near the Yangtze River Estuary and the Zhoushan Islands, respectively, were under moderate status. Other sites were under good or high status, which is consistent with the M-AMBI results.

The meiofauna represent a highly informative faunal group for ecological evaluation in marine ecosystems, but few studies have investigated their spatial distribution patterns in tidal creeks. As an important component of the tidal flat, tidal creeks tend to have unique, contrasting habitats associated with erosion and accretion beds within a short distance of each other. The gradient represented by these habitats is expected to have consequences on the meiofauna and nematode communities. Based on sediment samples from two tidal creeks on a tidal flat covered with very fine-grained sediments, we show that there are distinct relationships between the benthic habitats, meiofauna/nematode communities and the erosion/accretion status of the tidal creek bed. Although there were no differences in sediment grain size between the eroding and accretion sides of the creek, higher sedimentary phaeopigment, total organic carbon and water contents were observed at the accreting side compared to the eroding side. The meiofauna exhibited a significant spatial variability between the two sides. The dominant taxon, nematodes, was more abundant on the accretion side, whilst copepods were more abundant on the erosion side of the creeks. The nematode/copepod ratio was in agreement with the observation that more pollutants and/or organic matter settled down on the accretion side. A total of 53 nematode genera were identified, belonging to 3 orders and 22 families. The prevalence of tolerant nematode genera such as Desmodora, Sabatieria and Viscosia , suggested that nematodes inhabiting highly dynamic environments are well adapted to the physical disturbance. Our results show that geomorphic evolution as implied by erosion/accretion patterns are reflected in the meiofauna and nematode communities and can be assessed using different community characteristics.

The distributions and relationships of O2, CO2, and dimethylsulfide (DMS) in the Changjiang (Yangtze) Estuary and its adjacent waters were investigated in June 2014. In surface water, mean O2 saturation level, partial pressure of CO2 (pCO2), and DMS concentrations (and ranges) were 110% (89%–167%), 374 μatm (91–640 μatm), and 8.53 nmol L−1 (1.10–27.50 nmol L−1), respectively. The sea-to-air fluxes (and ranges) of DMS and CO2 were 8.24 μmol m−2 d−1 (0.26–62.77 μmol m−2 d−1), and −4.7 mmol m−2 d−1 (−110.8-31.7 mmol m−2 d−1), respectively. Dissolved O2 was oversaturated, DMS concentrations were relatively high, and this region served as a sink of atmospheric CO2. The pCO2 was significantly and negatively correlated with the O2 saturation level, while the DMS concentration showed different positive relationships with the O2 saturation level in different water masses. In vertical profiles, a hypoxic zone existed below 20 m at a longitude of 123°E. The stratification of temperature and salinity caused by the Taiwan Warm Current suppressed seawater exchange between upper and lower layers, resulting in the formation of a hypoxic zone. Oxidative decomposition of organic detritus carried by the Changjiang River Diluted Water (CRDW) consumed abundant O2 and produced additional CO2. The DMS concentrations decreased because of low phytoplankton biomass in the hypoxic zone. Strong correlations appeared between the O2 saturation level, pCO2 and DMS concentrations in vertical profiles. Our results strongly suggested that CRDW played an important role in the distributions and relationships of O2, CO2, and DMS.

Macrofauna are useful indicators of benthic ecological quality status, which were studied in summer and autumn of 2020 in the southern Yellow Sea, China. A total of 134 species were identified, and polychaetes represented the most dominant group. The dominant species across both seasons were Ophiura sarsii vadicola, Trigonothracia jinxingae, Heteromastus filiforms, Ninoё palmata, Thyasira tokunagai, Sigambra hanaokai, Ehlersileanira incisa hwanghaiensis, and Portlandia japonica. The average values of macrofaunal abundance and biomass were 386.68 ind./m2 and 28.21 g/m2, respectively. Species diversity during the autumn was slightly higher than that in the summer. Seasonal variations in functional diversity were also observed. BIOENV results indicated that water depth, bottom water temperature, and sediment phaeophorbide content was the optimal combination of parameters to explain macrofaunal assemblage variation. Bioassessment results, based on H’, AMBI, and M-AMBI, showed that most sites in the southern Yellow Sea could be classed as moderate or good status.

Sediment samples were collected in the intertidal zone of the Dagu River Estuary, Jiaozhou Bay, China in April, July and October 2010 and February 2011 for examining seasonal dynamics of meiofaunal distribution and their relationship with environmental variables. A total of ten meiofaunal taxa were identified, including free-living marine nematodes, benthic copepods, polychaetes, oligochaetes, bivalves, ostracods, cnidarians, turbellarians, tardigrades and other animals. Free-living marine nematodes were the most dominant group in both abundance and biomass. The abundances of marine nematodes were higher in winter and spring than those in summer and autumn. Most of the meiofauna distributed in the 0–2 cm sediment layer. The abundance of meiofauna in hightidal zone was lower than those in low-tidal and mid-tidal zones. Results of correlation analysis showed that Chlorophyll a was the most important factor to influence the seasonal dynamics of the abundance, biomass of meiofauna and abundances of nematodes and copepods. CLUSTER analysis divided the meiofaunal assemblages into three groups and BIOENV results indicated that salinity, concentration of organic matter, sediment sorting coefficient and sediment median diameter were the main environmental factors influencing the meiofaunal assemblages.

Functional diversity can reflect the overall differences in functional traits and indicate their response to environmental disturbance. Macrofaunal feeding functional groups and functional diversity were studied in the adjacent waters of the Yangtze River Estuary. The detritivorous group had the highest species number, abundance and secondary productivity while the canivorous group had the highest biomass. Pearson correlation analysis showed that functional evenness was negatively correlated with species number and Shannon-Wiener index. Functional divergence was negatively correlated with Simpson dominance index. Functional dispersion was positively correlated with species evenness, Shannon-Wiener index and Simpson dominance index. High values of functional diversity mainly cooccurred with high species diversity, uniform trait distribution and small niche overlap, indicating weak interspecific competition and high resources utilization. The dominant species were miniaturized and their biological traits analysis indicated that the study area has been disturbed for long time, resulting in the decline of the benthic ecosystem stability.

Characteristics of macrofaunal assemblages and their relationships with environmental factors in a semi-enclosed bay were studied seasonally in China. A total of 251 species were identified, including polychaetes (104 species), crustaceans (73 species), mollusks (51 species), and other phyla (23 species). Mean values of macrofaunal abundance were 1210, 2483, 3209, 3600 ind./m2 while those of biomass were 56.88, 176.15, 136.28, 265.55 g/m2, respectively. Ranges of species richness index, evenness index, Shannon-Wiener index were 1.54–8.16, 0.17–0.90, 0.69–4.78, respectively. The diversity indices were affected by bottom water salinity and pH. BIOENV analysis showed that water depth, phaeophorbide, and silt-clay proportion had important impacts on macrofaunal assemblages while abundance and biomass were affected by bottom water temperature, salinity, and water depth. Compared with historical data, macrofaunal species number, abundance and biomass showed a slight increasing trend, which may be due to the water quality improvement of this bay.

Microbial communities are a large component of abyssal and hadal benthic environments, especially in deep-sea areas like Yap Trench, they provide a continuous source of nutrients and energy in their unique ecosystems. However, due to sampling difficulties, these microbial communities are relatively understudied. In the summer of 2017, sediment samples were collected from 21 stations around Yap Trench in the Western Pacific Ocean (mostly in the West Caroline Basin), at depths ranging from 3156 to 7837 m. Sediment samples from deep water depths and shallow water depths differed in organic matter content, median grain size, silt-clay content, and biodiversity. The structure of the microbial communities in the surface sediments had distinct relationships with environmental factors and their co-occurrence networks exhibited a clear spatial pattern. In addition, for both prokaryotes or eukaryotes, a combination of variables including silt-clay content, organic matter content, median grain size, and depth had the greatest impact on community structure. It was notable that fungi played important roles in the co-occurrence networks of deep water depth sediment samples while bacteria dominated those of shallow water depth samples. The differences in structure and ecological niches in the different networks were due to differences in sediment texture and organic matter content. Since clay had a positive effect on the diversity of bacteria, it had an indirect positive effect on fungi, leading to differences in biodiversity among different groups. More organic matter meant more nutrients were available for the growth and reproduction of microbes, which led to fewer niche overlaps. This study conducted an extensive and systematic sequencing survey of surface sediments around Yap Trench in the Western Pacific Ocean, providing insight into microbial responses to environmental heterogeneity in deep-sea benthic ecosystems.

Bottom aquaculture of bivalves is a high-yield culture method, which is increasingly adopted by shellfish farmers worldwide. However, the effects of bottom aquaculture on benthic ecosystems are not well-known. Manila clam (Ruditapes philippinarum), is a widely distributed bottom aquaculture mollusk species. To assess the ecological impacts of Manila clam bottom aquaculture, clams and other macrofaunal assemblages were investigated during four cruises (July and November 2011, February and May 2012) at six sampling sites in Jiaozhou Bay, China. Correlation analysis showed that macrofaunal assemblages had significant negative correlations with the abundance of Manila clams. However, according to the results of several biotic indices, a low disturbance was detected by Manila clam bottom aquaculture. In conclusion, AMBI (AZTI'S Marine Biotic Index) and M-AMBI (Multivariate AZTI Marine Biotic Index) indices are more suitable for assessing ecological quality than polychaete/amphipod ratios when the disturbance is slight, such as at a bivalve bottom aquaculture.

The Fildes Peninsula has a maritime Antarctic climate and has attracted the interest of scientists for decades. The soil bacterial community and the environmental factors shaping it have been well documented. However, the bacterial community of intertidal sediments, which has been determined to play crucial roles in biogeochemical cycles in temperate regions, has been comparatively neglected. Here, the diversity and abundance of bacteria in intertidal sediments represented by 18 samples from the Fildes Peninsula were revealed by 16S rRNA gene pyrosequencing and qPCR. The results showed distinct bacterial community structure, and lower diversity and abundance relative to low-latitude areas. Proteobacteria, Bacteroidetes, and Actinobacteria were the predominant phyla, accounting for ~90 % of the total community. Among the measured environmental factors, chlorophyll a (Chl a), total organic matter (TOM), and standard deviation (σ) of sediment grain size explained the bacterial community variation in the redundancy analysis across all samples, and had consistent relationship with bacterial diversity and abundance. Granulosicoccus, the most abundant genus within Chromatiales Gammaproteobacteria in this study, showed positive correlation with standard deviation of sediment grain size. The present study demonstrated a distinct bacterial community different from temperate regions and provided insights into the potential ecological roles of specific taxa in the Antarctic environment.

Meiofauna particularly marine nematodes around the Caiwei Guyot in the northwest Pacific Ocean and a Polymetallic Nodule Field in the northeast Pacific Ocean were studied. Due to the geographic structure, the Caiwei Guyot and the Polymetallic Nodule Field had different environmental characteristics. Meiofaunal abundances around the Guyot area ranged from 9.18 to 25.59 ind./10 cm2, which were much lower than those in the Polymetallic Nodule Field. Marine nematode was the most dominant group. A total of 123 species, belonging to 74 genera and 29 families were found. Xyalidae (21.43%), Cyatholaimidae (9.82%), Linhomoeidae (8.03%) were the dominant families. The values of species number, Margalef's species richness and Shannon-Wiener diversity index ranged from 15 to 62, 4.75 to 12.84 and 2.58 to 3.93, respectively. The combination of water depth, silt-clay content and chlorophyll-a concentration can best explain the differences of nematode community. This study provides a baseline for deep-sea meiofauna distribution.

Microplastic contamination in the ocean has emerged as an environmental issue of global importance. The most effective strategy to control microplastic pollution is to reduce the terrestrial input, but severe weather conditions make it difficult. This study investigated microplastic abundance and characteristics in the seawater, sediments, and cultured oysters (Crassostrea gigas) of Sanggou Bay (China) before and after two typhoons with an average rainfall of 19.2 mm/d over 8 days. Prior to the typhoons, microplastic levels in the seawater, sediment, and oysters were 63.6 ± 37.4 items/L, 2178 ± 369 items/kg, and 41.0 ± 15.5 items/individual, with fibers being the predominant shape. Typhoons increased the average concentrations of microplastics in the seawater and sediments by approximately 40%, and the proportions of fragments, spherules, and granules in the sediments increased by 9.6%, 4.0%, and 4.3%, respectively. The majority of microplastics in seawater, sediments, and oysters collected before the typhoons could be grouped into sizes of 0.1–0.5 mm (36.7%), 0.05–0.1 mm (42.6%), and 0.1–0.5 mm (47.1%), respectively. After the typhoons, the most abundant size classes of microplastics in the three environmental compartments were 0.05–0.1 mm (39.2%) for seawater, 0.1–0.5 mm (37.1%) for sediments, and 0.05–0.1 mm (29.9%) for oysters. The typhoons also altered color distribution of microplastics and increased the proportions of polypropylene, polystyrene, and polyethylene terephthalate in seawater. Scanning electron microscopy/energy dispersive spectroscopy showed that organic matter and heavy metals were present on the microplastics collected from oysters. Our results suggest that weather conditions should be considered when investigating marine microplastics.

Since the response to ocean acidification is species specific, differences in responses between predator and prey will alter their interactions, hence affect the population dynamics of both species. Changes in predator prey interactions between a predatory muricid gastropod Reishia clavigera and its prey, the barnacle Amphibalanus amphitrite amphitrite and mussel Brachidontes variabilis under three pCO2 levels (380, 950, and 1250 μatm) were investigated. The searching time for barnacles increased and the ability to locate them decreased at higher pCO2 levels. The movement speed and the prey consumption rate, however, were independent of pCO2. There was no preference towards either B. variabilis or A. amphitrite amphitrite regardless of pCO2. Exposure experiments involving multiple generations are suggested to assess transgenerational effects of ocean acidification and the potential compensation responses before any realistic predictions on the long term changes of population dynamics of the interacting species can be made.

The characteristics of phytoplankton assemblages were analyzed by the Utermohl method in the southern Yellow Sea in summer, 2008. A total of 113 species (including varieties and forms), belonging to 51 genera and 3 phyla, were identified. Diatom was the most dominant group. The dominant species included Eucampia zoodiacus, Leptocylindrus danicus, Chaetoceros affinis, Thalassionema nitzschioides, Skeletonema costatum, Paralia sulcata and Chaetoceros tortissimus, which were eurytopic and temperate species. The cell abundance of phytoplankton ranged from 0.04 to 620.08 cells·mL−1 with an average of 27.52 cells·mL−1. Horizontally, the cell abundance showed a decreasing trend from the south to the north. In terms of vertical distribution, the values in surface and subsurface water layers were higher than those in bottom water layers. Results of correlation analysis showed that phytoplankton cell abundance was positively correlated with water temperature, ammonia and nitrite concentrations, and negatively correlated with salinity and silicate concentration.

Sediment characteristics and benthic communities on a finer sampling scale in four contrasting environments in subtropical Hong Kong were analyzed in summer and winter 2012. In two harbour habitats which suffered from historic sewage pollution or hypoxic events, organic carbon, nutrient and trace metal content in the sediment were significantly higher than that in an offshore area and a marine reserve. The relatively low organic and nutrient content in the offshore habitat could be resulted from enhanced resuspension of such materials from the seabed owing to intense water mixing and disturbance caused by bottom trawling. The biotic indices AMBI and M-AMBI were shown to be useful in assessing the benthic ecological status of these habitats. Such indices can also be more sensitive than sediment physico-chemical parameters in differentiating the response of macrofauna to seasonal changes in the benthic environment.

Biodiversity patterns of free-living marine nematodes were studied using specific, taxonomic and phylogenetic diversity measures in the southern Yellow Sea, China. The results showed that the average of Shannon-Wiener diversity index (H') in the study area was 3.17. The higher values were distributed in the east part of Shandong coastal waters and north part of Jiangsu coastal waters, while the lower values were distributed in the southern Yellow Sea Cold Water Mass (YSCWM). The average of taxonomic diversity (Δ) was 62.09 in the study region. The higher values were distributed in the transitional areas between the coastal areas and the southern YSCWM, while the lower values were distributed near the north part of Jiangsu coastal waters and the YSCWM. Results of correlation analysis of species diversity and taxonomic diversity showed that some of the two kinds of diversity index were independent, which suggested that combining the two kinds of diversity indices can reflect the ecological characteristics better. A test for 95% probability funnels of average taxonomic distinctness and variation in taxonomic distinctness suggested that Station 8794 (in the YSCWM) was outside of the 95% probability funnels, which may be due to the environmental stress. Results of correlation analysis between marine nematodes biodiversity and environmental variables showed that the sediment characteristics (Mdo and Silt-clay fraction) and phaeophorbide a (Pha-a) were the most important factors to determine the biodiversity patterns of marine nematodes.

In this study, the distribution pattern of meiofauna from nine sandy beaches at six latitudinal gradients along Chinese coast between 18 and 40°N was studied on their meiofauna abundance to examine the effect of latitudinal gradients. In general, meiofauna abundance was lower in four subtropical beaches in Xiamen (24°N) and Zhoushan (29°N) than that in other beaches. Meiofauna abundance differed little between tropical and temperate beaches. The taxonomic structure of meiofauna showed a dominance of nematode in colder area. The relative composition of turbellarians and polychaetes increased in warmer area. In addition to latitudinal gradient, salinity, oxygenation, sediment grain size affect also the meiofauna latitudinal distribution. As for horizontal distribution, the highest meiofauna abundance was found in low tidal zone at tropical beaches, and in middle tidal zone at temperate beaches. The horizontal distribution of meiofauna was controlled by both physical and biotic factors including feeding and anthropogenic activities. Although meiofauna abundance exhibited a horizontal difference, the composition of meiofaunal main taxa was unanimous horizontally at all beaches at the same sampling latitude.

To evaluate spatial distribution pattern of intertidal macrofauna, quantitative investigation was performed in January to February, 2013 around Fildes Peninsula, King George Island, South Shetland Islands. A total of 34 species were identified, which were dominated by Mollusca, Annelida and Arthropoda. CLUSTER analysis showed that macrofaunal assemblages at sand-bottom sites belonged to one group, which was dominated by Lumbricillus sp. and Kidderia subquadrata. Macrofaunal assemblages at gravel-bottom sites were divided into three groups while Nacella concinna was the dominant species at most sites. The highest values of biomass and Shannon-Wiener diversity index were found in gravel sediment and the highest value of abundance was in sand sediment of eastern coast. In terms of functional group, detritivorous and planktophagous groups had the highest values of abundance and biomass, respectively. Correlation analysis showed that macrofaunal abundance and biomass had significant positive correlations with contents of sediment chlorophyll a, phaeophorbide and organic matter.

A quantitative study on the community structure and biodiversity of free-living marine nematodes and their relationship with environmental factors in the northern South China Sea were carried out based on the samples collected at five stations in the deep sea (from 313 to 1 600 m) and one station in shallow waters (87 m) during the cruise in September, 2010. Results showed that the abundance of marine nematodes ranged from 224 to 1 996 ind./(10 cm2). A total of 69 free-living marine nematode genera, belonging to 26 families and three orders, were identified. The most dominant genera were Sabatieria, Linhystera, Aegialoalaimus and Daptonema according to SIMPER analysis. Results of CLUSTER analysis revealed four types of marine nematode community (or station groups) in the sampling area. In terms of trophic structure, non-selective deposit feeders (1B) and selective deposit feeders (1A) were the dominant trophic types with highest genera numbers and abundances, which implied that organic detritus was the main food source of marine nematodes in the northern South China Sea. The percentage of male nematode was low, ranging from 2.22% to 17.81%, while those of juvenile individuals ranged from 36.99% to 82.09%. For genera level diversity of marine nematodes, Shannon-Wiener diversity indices (H’) ranged from 3.76 to 4.57 and had highly significant negative correlation with water depth. In general, diversity indices H’ at the five stations in deep sea (over 200 m) were lower than that at the station in shallow waters (87 m). BIOENV analysis showed that the most important environmental factor controlling marine nematode communities was water depth.

In order to reveal the spatio-temporal distribution of meiofaunal assemblages and its relationship with environmental factors in semi-enclosed bay habitats, meiofaunal and sediment samples were collected in February (winter), May (spring), August (summer) and November (autumn) 2014 in Jiaozhou Bay, China. A total of 20 meiofaunal taxa were identified. The most dominant group was free-living marine nematode, followed by benthic copepod. During the four sampling seasons, the values of meiofaunal average abundance were (912.3 ± 603.1), (1576.4 ± 659.5), (1074.6 ± 417.6), (2152.4 ± 1062.3) ind./10 cm2 while those of biomass were (575.0 ± 398.5), (874.3 ± 518.4), (617.9 ± 337.8), (1203.6 ± 719.6) μg dwt/10 cm2, respectively. In terms of vertical distribution, meiofauna were mainly found in the (0–2) cm sediment layer (59.92%), followed by (2–5) cm layer (28.25%) and (5–8) cm layer (11.82%). Results of correlation analysis showed that bottom water temperature was the main factor influencing meiofaunal distribution and food source (sediment organic matter content) was the main factor influencing meiofaunal assemblages.

The Yellow Sea Cold Water Mass (YSCWM) is a seasonal hydrological phenomenon with significant effects on benthic animals. Based on a range of biological traits, including feeding type, tail shape, adult body length, body shape and life history (c-p value), the biological trait analysis (BTA) of marine nematodes in the southern Yellow Sea was studied in June 2003 (summer) and January 2004 (winter) in order to reveal the effects of YSCWM on benthic animals. In terms of biological traits composition of marine nematode assemblages, results of ANOSIM showed that there were no significant differences among sites inside the YSCMW area. However, for spatial distribution, marine nematode assemblages showed significant differences between sites inside and outside of the YSCWM area in terms of body shape, as there was higher percentage of nematodes with slender body shape while lower percentage with stout and long thin body shape at the sites inside the YSCWM area. Results of BIOENV analysis showed that water depth and sediment silt-clay percentage were the most important factors contributed to the differences of biological traits of marine nematode assemblages in summer, while sediment phaeophorbide content best explained the differences of marine nematode assemblages in winter. The existence of the YSCWM may provide a stable environment for marine nematode assemblages, keeping them in a continuous state during the seasonal changes. The higher percentage of nematodes with slender body may be the response to the YSCWM.

Microbial communities of the Chinese marginal seas have rarely been reported. Here, bacterial and archaeal community structures and abundance in the surface sediment of four sea areas including the Bohai Sea (BS), North Yellow Sea (NYS), South Yellow Sea (SYS), and the north East China Sea (NECS) were surveyed by 16S ribosomal RNA (rRNA) gene pyrosequencing and quantitative PCR. The results showed that microbial communities of the four geographic areas were distinct from each other at the operational taxonomic unit (OTU) level, whereas the microbial communities of the BS, NYS, and SYS were more similar to each other than to the NECS at higher taxonomic levels. Across all samples, Bacteria were numerically dominant relative to Archaea, and among them, Gammaproteobacteria and Euryarchaeota were predominant in the BS, NYS, and SYS, while Deltaproteobacteria and Thaumarchaeota were prevalent in the NECS. The most abundant bacterial genera were putative sulfur oxidizer and sulfate reducer, suggesting that sulfur cycle processes might prevail in these areas, and the high abundance of dsrB (10(7)-10(8) copies g(-1)) in all sites verified the dominance of sulfate reducer in the north Chinese marginal seas. The differences in sediment sources among the sampling areas were potential explanations for the observed microbial community variations. Furthermore, temperature and dissolved oxygen of bottom water were significant environmental factors in determining both bacterial and archaeal communities, whereas chlorophyll a in sediment was significant only in structuring archaeal community. This study presented an outline of benthic microbial communities and provided insights into understanding the biogeochemical cycles in sediments of the north Chinese marginal seas.

In this study, biodiversity patterns of free-living marine nematode communities were assessed in the Yangtze River estuary and its adjacent waters by certain diversity measures. The studied area exhibited spatial variation in nematode biodiversity patterns. According to habitat heterogeneity, two station groups, shallow water near shore area and shallow water continental shelf area, were observed in the Yangtze River estuary and its adjacent waters. In general, nematode abundance and species diversity in the near shore area were significantly lower than the continental shelf area. Salinity, sediment Chlorophyll-a (Chl-a) and Phaeophytin-a (Phaeo-a) concentrations were responsible for the discrimination of species diversity measures. They reflect the reverin influence to nematode species diversity. By contrast, our results showed that the average taxonomic distinctness with presence/absence data (Δ+), and the variation in taxonomic distinctness (Λ+) were not influenced by natural environmental var...

Heavy metal concentrations in surface sediments at 56 stations during two cruises in the Yellow Sea in summer and winter, 2011 were analyzed by inductively coupled plasma-mass spectrometry. The pollution status was assessed via the Geoaccumulation index and Hankanson potential ecological risk index. Higher concentrations of heavy metals (except for Mn) were found in the central Southern Yellow Sea and the western Northern Yellow Sea. The higher contents of Mn were much closer to Shandong Peninsula. Correlation analyses indicated that Pb, Cu, Fe, Ni, Zn and Co probably had the same origin and were controlled by grain size and total organic carbon. Pollution assessment showed that most areas of the Yellow Sea were not or lowly contaminated with the exception of the northwest and south parts of the Southern Yellow Sea showing Cd-contamination. The pollution status of the Yellow Sea in summer was worse than that in winter.