Communities In Coastal Waters Research Articles

Compositional change of bacterial communities in oil-polluted seawater amid varying degrees of nanoplankton bacterivory

Petroleum hydrocarbons are being released into the marine environment continuously. They will undergo weathering and may eventually be biodegraded by bacteria and other microbes. While nanoplankton (2–20 μm) are the major consumers of marine bacteria, their effect on the process of biodegradation of oil hydrocarbons is still debated. A 14-day microcosm experiment was conducted to investigate the effects of crude oil hydrocarbons on nanoplankton bacterivory and bacterial community in coastal waters. The coefficients of population growth (0.56–1.80 d−1 for all treatments considered) and grazing mortality (0.38–1.65 d−1 for all treatment considered) of bacteria estimated with the dilution method did not differ among the treatments of control (Ctrl), low dose chemically dispersed oil (LDOil, 2 μL L−1 of crude oil), and high dose chemically dispersed oil (HDOil, 8 μL L−1 of crude oil). Bacterial abundance ranged between 0.21–0.86 × 106 cells mL−1 on average for all treatments. The lack of drastic increases in the cell density of bacterial cells in the oil-loaded treatments was observed throughout the experiment period. Sequencing analysis of the 16S rRNA gene revealed the progressive changes in the community compositions of bacteria in all treatments. The relatively high abundance of oil-degrading bacteria, including Cycloclasticus and Alcanivorax on Days 3–14 of the experiment reflected the presence of biodegradation of oil in the LDOil and HDOil treatments. Throughout the 14 days, the community composition of bacteria in the LDOil and HDOil treatments became more similar and they both differed from that in the Ctrl treatment. This study concluded that, in oil-polluted seawater, the changes in the bacterial community composition were mainly resulting from the addition of chemically dispersed crude oil.

Organic matter composition fluctuations disrupt free-living bacterial communities more than particle-associated bacterial communities in coastal waters

Marine organic matter fuels the growth of microbial communities, shaping the composition of bacteria that specialize in its breakdown. However, responses of free-living (FL) and particle-associated (PA) bacterial communities to the changing pools of dissolved organic matter (DOM) and particulate organic matter (POM) remained unclear. This study investigates the composition of size-fractionated bacterial communities, DOM and POM in coastal waters over a 22-day period that includes a diatom bloom. Co-occurrence analysis showed that the FL bacterial communities were significantly less stable than PA communities. During the diatom bloom, we observed a significant increase in DOM molecules, particularly those derived from amino acids and peptides. In contrast, the relative intensities of major POM molecule classes remained stable despite the algal bloom's influence. Our study revealed a strong negative correlation between bacterial alpha-diversity and the amount of molecules in the organic matter pool. Similarly, bacterial community beta-diversity was found to be related to the composition of organic matter pool. However, the composition of organic matter was more strongly related to the composition of FL bacterial communities compared to PA communities. This suggests that FL bacteria exhibit greater variations in temporal dynamics and higher sensitivity to the specific structure of organic matter molecules.

Temporal variations of bacterial and eukaryotic community in coastal waters—implications for aquaculture

Despite increased attention to the aquaculture environment, there is still a lack of understanding regarding the significance of water quality. To address this knowledge gap, this study utilized high-throughput sequencing of 16S rRNA and 18S rRNA to examine microbial communities (bacteria and eukaryotes) in coastal water over different months through long-term observations. The goal was to explore interaction patterns in the microbial community and identify potential pathogenic bacteria and red tide organisms. The results revealed significant differences in composition, diversity, and richness of bacterial and eukaryotic operational taxonomic units (OTUs) across various months. Principal coordinate analysis (PCoA) demonstrated distinct temporal variations in bacterial and eukaryotic communities, with significant differences (P = 0.001) among four groups: F (January-April), M (May), S (June–September), and T (October-December). Moreover, a strong association was observed between microbial communities and months, with most OTUs showing a distinct temporal preference. The Kruskal–Wallis test (P < 0.05) indicated significant differences in dominant bacterial and eukaryotic taxa among months, with each group exhibiting unique dominant taxa, including potential pathogenic bacteria and red tide organisms. These findings emphasize the importance of monitoring changes in potentially harmful microorganisms in aquaculture. Network analysis highlighted positive correlations between bacteria and eukaryotes, with bacteria playing a key role in network interactions. The key bacterial genera associated with other microorganisms varied significantly (P < 0.05) across different groups. In summary, this study deepens the understanding of aquaculture water quality and offers valuable insights for maintaining healthy aquaculture practices.Key points• Bacterial and eukaryotic communities displayed distinct temporal variations.• Different months exhibited unique potential pathogenic bacteria and red tide organisms.• Bacteria are key taxonomic taxa involved in microbial network interactions.

Metabarcoding reveals a high diversity and complex eukaryotic microalgal community in coastal waters of the northern Beibu Gulf, China.

Beibu Gulf is an important semi-enclosed bay located in the northwestern South China Sea, and is famous for its high bio-productivity and rich bio-diversity. The fast development along the Beibu Gulf Economical Rim has brought pressure to the environment, and algal blooms occurred frequently in the gulf. In this study, surface water samples and micro-plankton samples (20-200 μm) were collected in the northern Beibu Gulf coast. Diversity and distribution of eukaryotic planktonic microalgae were analyzed by both metabarcoding and microscopic analyses. Metabarcoding revealed much higher diversity and species richness of microalgae than morphological observation, especially for dinoflagellates. Metabarcoding detected 144 microalgal genera in 8 phyla, while microscopy only detected 40 genera in 2 phyla. The two methods revealed different microalgal community structures. Dinoflagellates dominated in microalgal community based on metabarcoding due to their high copies of 18 s rRNA gene, and diatoms dominated under microscopy. Altogether 48 algal bloom and/or toxic species were detected in this study, 34 species by metabarcoding and 19 species by microscopy. Our result suggested a high potential risk of HABs in the Beibu Gulf. Microalgal community in the surface water samples demonstrated significantly higher OTU/species richness, alpha diversity, and abundance than those in the micro-plankton samples, although more HAB taxa were detected by microscopic observations in the micro-plankton samples. Furthermore, nano-sized taxa, such as those in chlorophytes, haptophytes, and chrysophyceans, occurred more abundantly in the surface water samples. This study provided a comprehensive morphological and molecular description of microalgal community in the northern Beibu Gulf.

Spatio-seasonal variations in functional trait composition and diversity patterns of marine fish communities in coastal waters

Spatio-seasonal variations in functional trait composition and diversity patterns of marine fish communities in coastal waters

Lack of strong seasonality in macrobenthic communities from the northern Barents Sea shelf and Nansen Basin

The Barents Sea has been coined ‘the Arctic hotspot’ of climate change due to the rapidity with which environmental changes are taking place. This transitional domain from Atlantic to Arctic waters is home to highly productive benthic communities. This system strongly fluctuates on a seasonal basis in its sympagic-pelagic-benthic coupling interactions, with potential effects on benthic standing stocks and production. Recent discoveries have questioned the marked seasonality for several high Arctic seafloor communities in coastal waters of Svalbard. Still, the seasonal variability of benthic process in the extensive Barents Sea open shelf remains poorly understood. Therefore, we studied the seasonality of macrofauna communities along a transect in the northwestern Barents Sea comprising two hydrographic domains (Arctic vs. Atlantic Water, across the Polar Front) and three geomorphological settings (shelf, continental slope and abyssal plain). Overall, we did not find strong signs of seasonal variation in taxonomic community structure and functional diversity. However, we found some weak signs of seasonality when examining each station separately, especially at a station close to the Polar Front, with high seasonal fluctuations in abiotic drivers indicating a stronger pelagic-benthic coupling. The lack of seasonality found both at the shelf stations south and north of the Polar Front could be related to organic matter stored in the sediments, reflected in constant levels of total organic carbon in surface sediment across time for all stations. We did observe, as expected, highly spatially structured environmental regimes and macrofauna communities associated to them from shelf to slope and basin locations. Understanding the underlying spatio-temporal mechanisms by which soft-bottom benthic communities are structured along environmental gradients is necessary to predict future impacts of climate change in this area. Our results indicate that short-term climate driven changes in the phenology of pelagic ecosystem components might not be directly reflected in the Arctic benthic system, as seafloor processes seem to be partially decoupled from those in the overlying water.

Seasonal and spatial dynamics of phylogenetic structure of fish communities in coastal waters

Understanding community assembly has long attracted the attention of ecologists. There are a lot of studies on how community assembly mechanisms work through phylogenetic analysis. Nevertheless, phylogenetic structures have generally been assumed to be stable over time in most studies, and little attention has been paid to seasonal shifts in phylogenetic structure, which is important to mobile animals. In this study, phylogenetic distance was measured as the mean pairwise distance (MPD) and as mean nearest taxon distance (MNTD). The phylogenetic structures of fish communities in different regions, subregions and at sampling stations were examined using the standardized effect sizes of MPD and MNTD (SES.MPD and SES.MNTD) under null model independent swap over four seasons in the coastal waters of Shandong Province, China. Generalized additive model (GAM) was used to detect which environmental factors have an important impact on phylogenetic structure indices at each sampling station. The fish communities were phylogenetically clustered in most seasons in the whole survey waters, indicating environmental filtering tended to shape the whole fish assemblage. Two phylogenetic indices indicated that the phylogenetic structure (phylogenetic over-dispersion or phylogenetic clustering) was inconsistent on the different regions and subregions. For fish assemblages at each sampling station, the phylogenetic structure of fish communities presented patchy distribution patterns in different seasons. GAM analysis showed that phylogenetic structure responded differently to different environmental factors over four seasons, and the change in phylogenetic structure indices was significantly associated with environmental factors, especially in autumn and winter. SES.MPD can better respond to environmental changes than SES.MNTD. Spatial factors (longitude and latitude) were important factors influencing fish community assembly, indicating that fish communities at offshore stations with low latitude exhibit a relatively high degree of phylogenetic overdispersion. It was difficult to draw consistent conclusions about seasonal changes in phylogenetic structure of fish communities on different temporal and spatial scales. It is possible that seasonal variations and spatial scales in assembly mechanisms contribute to maintaining marine fish diversity in temperate waters, resulting in different phylogenetic structures in fish community.

Usage of antibiotics in aquaculture and the impact on coastal waters

For decades, coastal marine ecosystems have been threatened by a wide range of anthropogenic pollutants. Recently, there has been increasing concern about the accumulation and impacts of antibiotic compounds on marine ecosystems. However, information regarding the accumulation of antibiotics and the impacts they may have on microbial communities in coastal water bodies and on human health is sparse in literature. Antibiotics from aquacultures are constantly discharged into marine environments via rivers. Large rivers transport tons of antibiotics every year into coastal waters, e.g., 12 tons of sulfonamide by the river Mekong. Here, we discuss a potential influence of such imported antibiotics on bacterial communities in coastal waters. Potential accumulation of antibiotics in the uppermost surface layer of aquatic ecosystems, the so-called sea surface microlayer (SML), is of interest. Because of the ability of the SML to accumulate anthropogenic pollutants, it may serve as a pool for antibiotics and correspondingly also for resistant organisms. Also, due to its biofilm-like structure, the SML could serve as a hotspot for horizontal gene transfer, speeding up the spread of antibiotic resistant strains to encompassing marine environments. The emergence of antibiotic resistant bacteria is a global threat and scientists projected that it could pave the way for the next pandemic that could ravage the world in the next decades. For this reason, it is time to focus research on understanding and minimizing the impact of antibiotics on the sustainability of coastal waters and on the health of humans who depend on coastal resources for food and recreational purposes. Also, knowledge about antibiotics in the SML is necessary to understand the effects they are likely to have on bacterial abundance, diversity, and metabolic activities in coastal water bodies.

Annual cycle of mesozooplankton at the coastal waters of Cyprus (Eastern Levantine basin).

This study is the first to explore monthly and seasonal succession of the zooplankton community in coastal waters of Cyprus using a 12-month period time series. A total of 192 taxa of mesozooplankton (MZ), 145 of which were copepods, were identified at three sites at the southern and one site at the northern coasts of the island. Zooplankton distribution and community structure were influenced mostly by stratification, temperature and Chl-a. The combination of upwelling and advection from the Rhodes Gyre during summer, causing cooler waters in the southern coast of Cyprus, seems to control the food supply and offered favorable feeding conditions to zooplankton, enhancing their numbers. The proximity to a fish farm also positively affected MZ abundance and biomass. This study also revealed the importance of smaller species (e.g. Clausocalanus paululus) and juvenile stages (e.g. Clausocalanus, Oithona and Corycaeus spp.) in composition, structure and functionality of the copepod community. These species seems to be more important in low Chl-a environments, where the relative size of primary consumers is expected to be smaller and the microbial components dominant. This baseline study paves the way for further investigation of the elements of marine food webs in the ultra-oligotrophic environment of the Eastern Mediterranean.

Biogeographic Patterns and Community Assembly Processes of Bacterioplankton and Potential Pathogens in Subtropical Estuaries in China.

Microbial communities in coastal waters are diverse and dynamic and play important roles in ecosystem functions and services. Despite the ecological impact of bacterioplankton or pathogens, little is known about whether bacterioplankton and pathogen communities exhibit similar patterns. Here, using 16S RNA gene amplicon sequencing, the geographic patterns and assembly processes of bacterioplankton and pathogen communities in 30 subtropical estuaries were studied. Results showed that the estuarine bacterioplankton communities mainly consisted of Proteobacteria (49.06%), Actinobacteria (17.62%), and Bacteroidetes (16.33%), among which 31 pathogen genera (186 amplicon sequence variants [ASVs]) were identified. Under the influence of salinity, bacterioplankton and pathogens showed similar biogeographic patterns. Redundancy and correlation analyses indicated that the bacterioplankton communities were strongly correlated with estuarine environmental factors, but potential pathogens were less influenced. Co-occurrence network analysis revealed a close relationship between bacterioplankton and potential pathogens, with two pathogens identified as connectors (i.e., ASV340 [Clostridium perfringens] and ASV1624 [Brevundimonas diminuta]), implying potential impacts of pathogens on structure, function, and stability of estuarine bacterioplankton communities. Null-model analysis revealed that deterministic processes (heterogeneous selection) dominated bacterioplankton community assembly, while stochastic processes (undominated effect) shaped the potential pathogen community. Our findings illustrate the biogeographic patterns and community assembly mechanisms of bacterioplankton and pathogens in estuaries, which should provide guidance and a reference for the control of potential pathogenic bacteria. IMPORTANCE Bacterioplankton play an important role in estuarine ecosystem functions and services; however, potentially pathogenic bacteria may exhibit infectivity and pose a serious threat to environmental and human health. In this study, geographic patterns and assembly processes of bacterioplankton communities in 30 subtropical estuaries were explored, and potential pathogenic bacteria in the estuaries were detected and profiled. Our results demonstrate here that bacterioplankton and pathogens show similar biogeographic patterns under the influence of salinity. Interestingly, heterogeneous selection dominated bacterioplankton assembly, while stochasticity dominated pathogen assembly. This study provides important information for future risk assessment of potential pathogenic bacteria as well as management in estuarine ecosystems.

Turnover in Life-Strategies Recapitulates Marine Microbial Succession Colonizing Model Particles.

Particulate organic matter (POM) in the ocean sustains diverse communities of bacteria that mediate the remineralization of organic complex matter. However, the variability of these particles and of the environmental conditions surrounding them present a challenge to the study of the ecological processes shaping particle-associated communities and their function. In this work, we utilize data from experiments in which coastal water communities are grown on synthetic particles to ask which are the most important ecological drivers of their assembly and associated traits. Combining 16S rRNA amplicon sequencing with shotgun metagenomics, together with an analysis of the full genomes of a subset of isolated strains, we were able to identify two-to-three distinct community classes, corresponding to early vs. late colonizers. We show that these classes are shaped by environmental selection (early colonizers) and facilitation (late colonizers) and find distinctive traits associated with each class. While early colonizers have a larger proportion of genes related to the uptake of nutrients, motility, and environmental sensing with few pathways enriched for metabolism, late colonizers devote a higher proportion of genes for metabolism, comprising a wide array of different pathways including the metabolism of carbohydrates, amino acids, and xenobiotics. Analysis of selected pathways suggests the existence of a trophic-chain topology connecting both classes for nitrogen metabolism, potential exchange of branched chain amino acids for late colonizers, and differences in bacterial doubling times throughout the succession. The interpretation of these traits suggests a distinction between early and late colonizers analogous to other classifications found in the literature, and we discuss connections with the classical distinction between r- and K-strategists.

Impact of nutrient concentration and composition on shifting of phytoplankton community in the coastal waters of the Bay of Bengal

Nutrients from different sources with different concentrations can make significant changes in the phytoplankton community of coastal water. The experiment was conducted for ten days by adding nutrients from various sources such as a river, ground, sewage, aerosol, and bottom seawater to surface seawater of the Bay of Bengal to test this hypothesis. Higher nitrate, phosphate concentrations were observed in sewage water. Higher silicate was observed in groundwater during the study period. Upon spiking, dissolved inorganic nitrogen increased from 3.91 to 169.10μmol L−1, and the N:P ratio increased from 9.31 to 58.53. This enhanced phytoplankton biomass by four times in river water added bottles, five times in aerosol and Bottom seawater added bottles, 10 and 15 times in ground and sewage water added bottles. Initial days of the experiment in all experimental bottles, Fucoxanthin was the dominant pigment. Later in sewage and aerosol bottles, Peridinin was the dominant pigment and showed linear relation with N: P.In contrast, in all other experimental bottles still, Fucoxanthin was the dominant pigment and showed a linear connection with silicate. This indicates that silicate availability will alter the phytoplankton composition and community in the coastal waters of the Bay of Bengal. This experiment also revealed that sewage nutrients are the highest contributes to primary production (9%–35%), followed by groundwater (8%–23%), aerosol (9%–13%), river (2.5%–12%) and bottom seawater (3%–10%) in the coastal Bay of Bengal. This study suggests that the changes in the composition of nutrients from different sources enhance phytoplankton biomass in coastal waters of the Bay of Bengal and modify the phytoplankton community in coastal waters, supporting the hypothesis stated above.

Habitat heterogeneity: A confounding factor for the effect of pollutants on macrobenthic community in coastal waters

Discrepancies were found between Ecological Status of sediments evaluated though the analysis of macrobenthic community and chemical analyses along a heavily trafficked and contaminated maritime seaway in Tyrrhenian Sea. Chemical analyses showed some sites highly contaminated by PAHs and metals with values exceeding thresholds for Good Chemical status and representing potential toxicological risk for benthic animals. Conversely, macrobenthic communities were highly rich and diverse, with Ecological Status (through M-AMBI) Good and High at each site. Sampling depth, total organic carbon, and total nitrogen were the major factors influencing biotic indices (AMBI, M-AMBI, S, H), even if concentrations of PAHs and metals (V, As, and Fe) contributed in explaining a part of indices variability. Habitat heterogeneity of sampled sites is likely acting as a confounding factor for two reasons: (1) high variability of environmental parameters leads to high richness and diversity, to which M-AMBI is sensitive, and (2) environmental parameters explained part of the variability of indices, together with contaminants. Our results suggested the importance of considering natural variability as a fundamental step of environmental impact assessment, for the correct interpretation of biotic indices.

Terrestrial input of herbicides has significant impacts on phytoplankton and bacterioplankton communities in coastal waters

AbstractHerbicide use has increased very rapidly worldwide in recent decades, and some of these herbicides eventually enter the ocean. At present, herbicide pollution in the ocean has become a global environmental problem. Here, in a field investigation of 22 commonly used herbicide residues (triazine, phenylurea, and amide) in the Bohai Sea and the Yellow Sea, we found that the detection rate of herbicide residues within 100 km from shore was 100%. Notably, triazine herbicides have reached concentrations (up to 12.07 nmol L−1) that can significantly disturb phytoplankton and bacterioplankton communities in microcosm experiments. Under exposure to triazine herbicides at close to their total in situ concentrations, the photosynthesis of the phytoplankton community was significantly inhibited, which was reflected by the significant decrease of Fv/Fm (28.7–63.8%) of the phytoplankton community and dissolved oxygen content (18.1–32.2%) in seawater. Concurrently, the phytoplankton community structure underwent significant changes with the dominant group shifting from diatoms to dinoflagellates, due to the higher atrazine sensitivity of diatoms compared to facultative dinoflagellates. Triazine herbicide also significantly altered the bacterioplankton community structure and inhibited their metabolism of many carbon sources including carbohydrates, amino acids, and carboxylic acids. As phytoplankton and bacterioplankton are closely related, the impact of herbicide on the bacterioplankton community was clearly aggravated by the phytoplankton community. In view of the significance of phytoplankton and bacterioplankton communities in supporting marine food webs and biogeochemical cycles, a continuous increase in herbicide input in the future may seriously affect the stability of coastal oceans.

Initial recovery of demersal fish communities in coastal waters of Hong Kong, South China, following a trawl ban

Fisheries resources in Hong Kong have been overexploited since the 1970s due to intensive bottom trawling and other fishing activities that have depleted stocks and destroyed marine habitat. To rehabilitate depleted fisheries resources, a permanent ban on trawling in Hong Kong territorial waters came into force on December 31, 2012. In order to determine whether the trawl facilitated recovery of fish communities, trawl surveys were conducted at two sites in each of the eastern, southern and western (estuarine) coastal waters of Hong Kong before and three years after the trawl ban. A total of 315 species and 86 families of fishes in nine feeding groups were encountered during the surveys. Mean trophic level of the fish community, abundance and biomass of total fishes and of predatory fishes increased in eastern and western waters after the ban, but no changes or declines in these metrics were observed in southern waters. Although initial recovery in fish community were observed in eastern and western waters, anthropogenic disturbances might hinder the recovery process, including a large-scale reclamation for construction of coastal infrastructures in the west, illegal trawling, and expansion of non-trawling fishing efforts in the southern and eastern waters. Longer term monitoring is needed to evaluate the effects of the trawl ban, and determine whether recovery in the southern waters will continue to be constrained by the anthropogenic disturbances.Graphic abstract

Influence of Filter Pore Size on Composition and Relative Abundance of Bacterial Communities and Select Host-Specific MST Markers in Coastal Waters of Southern Lake Michigan.

Water clarity is often the primary guiding factor in determining whether a prefiltration step is needed to increase volumes processed for a range of microbial endpoints. In this study, we evaluate the effect of filter pore size on the bacterial communities detected by 16S rRNA gene sequencing and incidence of two host-specific microbial source tracking (MST) markers in a range of coastal waters from southern Lake Michigan, using two independent data sets collected in 2015 (bacterial communities) and 2016–2017 (MST markers). Water samples were collected from river, shoreline, and offshore areas. For bacterial communities, each sample was filtered through a 5.0-μm filter, followed by filtration through a 0.22-μm filter, resulting in 70 and 143 filter pairs for bacterial communities and MST markers, respectively. Following DNA extraction, the bacterial communities were compared using 16S rRNA gene amplicons of the V3–V4 region sequenced on a MiSeq Illumina platform. Presence of human (Bacteroides HF183) and gull (Gull2, Catellicoccus marimammalium) host-specific MST markers were detected by qPCR. Actinobacteriota, Bacteroidota, and Proteobacteria, collectively represented 96.9% and 93.9% of the relative proportion of all phyla in the 0.22- and 5.0-μm pore size filters, respectively. There were more families detected in the 5.0-μm pore size filter (368) than the 0.22-μm (228). There were significant differences in the number of taxa between the two filter sizes at all levels of taxonomic classification according to linear discriminant analysis (LDA) effect size (LEfSe) with as many as 986 taxa from both filter sizes at LDA effect sizes greater than 2.0. Overall, the Gull2 marker was found in higher abundance on the 5.0-μm filter than 0.22 μm with the reverse pattern for the HF183 marker. This discrepancy could lead to problems with identifying microbial sources of contamination. Collectively, these results highlight the importance of analyzing pre- and final filters for a wide range of microbial endpoints, including host-specific MST markers routinely used in water quality monitoring programs. Analysis of both filters may increase costs but provides more complete genomic data via increased sample volume for characterizing microbial communities in coastal waters.

Trophic ecology of a tropical scyphozoan community in coastal waters: Insights from stomach content and stable isotope analyses

Despite the growing concern of scyphozoan jellyfish blooms and their associated threats, there is an acute lack of baseline knowledge regarding the trophic ecology of scyphozoans in tropical waters where blooms of several species sometimes occur at once or successively. Therefore, this study was conducted from June 2010 to December 2011 in the Klang Strait (Malaysia) to elucidate the trophic ecology of eight sympatric species of scyphozoan that occurred in a conjoint mangrove-mudflat habitat. The species diet, trophic position and the relative contribution of primary producers to their nutrition were determined by integrating stomach content examination with stable isotope analysis. Scyphozoans in the Klang Strait are principally carnivores and can be grouped into three major trophic guilds: specialized copepod feeder, copepod and macrozooplankton feeder, and mixed plankton feeder. Bayesian mixing model of δ13C isotope values indicates that the scyphozoans mainly derived their basal carbon source from microphytobenthos and phytoplankton. Analysis of δ15N isotope values reveals that all species are positioned at the third trophic level after mixed zooplankton groups (second) and primary producers (first) in the food web. Scyphozoans thus represent an important trophic link coupling benthic and pelagic primary production to higher-level predators and humans, and are important carbon exporters from nearshore to neritic and offshore waters.

Are free-living nematodes effective environmental quality indicators? Insights from Bohai Bay, China

Free-living marine nematodes are sensitive biological indicators of environmental quality in marine sediments. This study investigated nematode communities in coastal waters in Bohai Bay, China. Nematode community taxonomic structure, colonizer–persister classes, maturity index (MI), index of trophic diversity (ITD), Shannon–Wiener diversity index (H′), together with the Hakanson’s Ecological Risk Index, were applied to assess the environmental quality of the investigated stations. The taxonomic structure, MI, ITD, and H′ varied among the study stations. In addition to the stochastic causes, variability in environmental variables together with metal concentrations explained, to a certain extent, the observed variations in nematode features. The differentiation in nematode species’ composition was attributed to changes in water depth, temperature, salinity, dissolved oxygen concentration, sediment medium diameter, organic matter, chlorophyll-a and pheophytin-a concentrations, and concentrations of manganese (Mn) and cobalt (Co). Mn was the most influential metal in explaining nematode diversity. MI appeared to be affected more by metals than by other environmental variables. According to the nematode features, the environmental quality ranged from bad to good at the majority of stations, although the rankings varied among different indices. Taxonomic structure, life strategy traits, ITD, and H′ were all effective in highlighting the areas subjected to severe metal contamination in the bay, and could provide more comprehensive assessments when used in combination. These indices suggested a more severe pollution status than the results obtained from the Hakanson’s Ecological Risk Index method, and may be more sensitive to ecological quality deterioration. However, their effectiveness requires further testing over larger spatial ranges and with more data.

High-throughput sequencing reveals the spatial distribution variability of microbial community in coastal waters in Shenzhen.

Seashore habitats are located between terrestrial and marine ecosystems, which are a hotspot for anthropogenic impacts. Shenzhen is one of the most developed cities in south China, but the microbial functions of its coastal ecosystems remain poorly understood. The study applied 16S rRNA gene sequencing methods to identify the bacterial community from twenty sites of Shenzhen inshore waters. The microbial structure of the samples between eastern Shenzhen and western Shenzhen seashores is notably different, suggesting the spatial variability. Proteobacteria, Cyanobacteria, Actinobacteria, and Bacteroidetes were dominant phyla in the community, and the relative abundance of Bacteroidetes was significantly higher in eastern seashores. Specifically, samples from western Shenzhen contained much more Prochlorococcus, while Synechococcus was more abundant in eastern samples. Moreover, the metabolism of terpenoids and polyketides, and transport and catabolism were significantly more abundant in eastern samples, while antibiotic-resistant pathways were enriched in western samples. The results have important significance to understand bacterial ecosystem of coastal water and promote water quality management and protection activity in Shenzhen. This study can also help developing an optimal strategy for the green economy development and the policy planning of Guangdong-Hong Kong-Macao Greater Bay Area.

The ecology of Lepas-based biofouling communities on moored and drifting objects, with applications for marine forensic science

Pelagic biofoulers such as barnacles or bryozoans settle and raft on natural debris like pumice or seeds. Recent influxes of marine debris into the world’s oceans, especially plastic, have increased habitat availability for these biofoulers. Goose barnacles in the genus Lepas are some of the most common biofouling taxa globally, and play an important role in biofouling communities as foundation species. We examined community succession, growth rates and isotopic composition in Lepas and their associated biofouling communities in coastal waters of eastern Australia. Community succession on a fixed surface mooring showed an increase in species diversity over 25 weeks. Using the abundances of L. anserifera, L. anatifera, and the amphipods Caprella danilevskii and Jassa slatteryi, we created an equation to estimate minimum duration at sea. Predators such as the polychaete Amphinome rostrata may influence the biofouling community, as can beach scavengers once floating debris is cast ashore. We report a new maximum growth rate for L. anserifera of 1.45 mm−1, and our study is the first to report growth rates for any species of Lepas faster than 1 mm day−1. Lepas were larger on moored floats than on smaller, free-floating drifters. δ18O content of Lepas shells was a robust predictor of sea surface temperatures during formation for L. anatifera and L. anserifera. Our findings have important applications for estimating drift duration and trajectories of marine debris.