Dataset Information

Virioplankton dynamics are related to eutrophication levels in a tropical urbanized bay.

ABSTRACT: Virioplankton are an important and abundant biological component of marine and freshwater ecosystems. Often overlooked, aquatic viruses play an important role in biogeochemical cycles on a global scale, infecting both autotrophic and heterotrophic microbes. Viral diversity, abundance, and viral interactions at different trophic levels in aqueous environments are not well understood. Tropical ecosystems are less frequently studied than temperate ecosystems, but could provide new insights into how physical and chemical variability can shape or force microbial community changes. In this study, we found high viral abundance values in Guanabara Bay relative to other estuaries around the world. Viral abundance was positively correlated with bacterioplankton abundance and chlorophyll a concentrations. Moreover, prokaryotic and viral abundance were positively correlated with eutrophication, especially in surface waters. These results provide novel baseline data on the quantitative distribution of aquatic viruses in tropical estuaries. They also provide new information on a complex and dynamic relationship in which environmental factors influence the abundance of bacterial hosts and consequently their viruses. Guanabara Bay is characterized by spatial and seasonal variations, and the eutrophication process is the most important factor explaining the structuring of virioplankton abundance and distribution in this tropical urbanized bay.

SUBMITTER: Cabral AS

PROVIDER: S-EPMC5376344 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Virioplankton dynamics are related to eutrophication levels in a tropical urbanized bay.

Cabral Anderson S AS Lessa Mariana M MM Junger Pedro C PC Thompson Fabiano L FL Paranhos Rodolfo R

PloS one 20170331 3

Virioplankton are an important and abundant biological component of marine and freshwater ecosystems. Often overlooked, aquatic viruses play an important role in biogeochemical cycles on a global scale, infecting both autotrophic and heterotrophic microbes. Viral diversity, abundance, and viral interactions at different trophic levels in aqueous environments are not well understood. Tropical ecosystems are less frequently studied than temperate ecosystems, but could provide new insights into how ...[more]

PMID: 28362842

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Project description:BackgroundOysters in coastal environments are subject to fluctuating environmental conditions that may impact the ecosystem services they provide. Oyster-associated microbiomes are responsible for some of these services, particularly nutrient cycling in benthic habitats. The effects of climate change on host-associated microbiome composition are well-known, but functional changes and how they may impact host physiology and ecosystem functioning are poorly characterized. We investigated how environmental parameters affect oyster-associated microbial community structure and function along a trophic gradient in Narragansett Bay, Rhode Island, USA. Adult eastern oyster, Crassostrea virginica, gut and seawater samples were collected at 5 sites along this estuarine nutrient gradient in August 2017. Samples were analyzed by 16S rRNA gene sequencing to characterize bacterial community structures and metatranscriptomes were sequenced to determine oyster gut microbiome responses to local environments.ResultsThere were significant differences in bacterial community structure between the eastern oyster gut and water samples, suggesting selection of certain taxa by the oyster host. Increasing salinity, pH, and dissolved oxygen, and decreasing nitrate, nitrite and phosphate concentrations were observed along the North to South gradient. Transcriptionally active bacterial taxa were similar for the different sites, but expression of oyster-associated microbial genes involved in nutrient (nitrogen and phosphorus) cycling varied throughout the Bay, reflecting the local nutrient regimes and prevailing environmental conditions.ConclusionsThe observed shifts in microbial community composition and function inform how estuarine conditions affect host-associated microbiomes and their ecosystem services. As the effects of estuarine acidification are expected to increase due to the combined effects of eutrophication, coastal pollution, and climate change, it is important to determine relationships between host health, microbial community structure, and environmental conditions in benthic communities.

Project description:Urbanized bays are vulnerable to fecal bacterial pollution, and the extent of this pollution, in marine recreational waters, is commonly assessed by quantifying enterococcus concentrations. Recent reports have questioned the utility of enterococci as an indicator of fecal bacterial pollution in subtropical bays impaired by non-point source pollution, and enterococcus data alone cannot identify fecal bacterial sources (i.e., hosts). The purpose of this study was to assess relationships between rainfall, fecal bacterial pollution, antimicrobial resistance, and microbial diversity in an urbanized subtropical bay. Thus, a comprehensive bacterial source tracking (BST) study was conducted using a combination of traditional and modern BST methods. Findings show that rainfall was directly correlated with elevated enterococcus concentrations, including the increased prevalence of Enterococcus faecium, although it was not correlated with an increase in the prevalence of antimicrobial-resistant strains. Rainfall was also correlated with decreased microbial diversity. In contrast, neither rainfall nor enterococcus concentrations were directly correlated with the concentrations of three omnipresent host-associated fecal markers (i.e., human, canine, and gull). Notably, the human fecal marker (HF183) was inversely correlated with enterococcus concentrations, signifying that traditional enterococcus data alone are not an accurate proxy for human fecal waste in urbanized subtropical bays.IMPORTANCE The presence of human enteric pathogens, stemming from fecal pollution, is a serious environmental and public health concern in recreational waters. Accurate assessments of fecal pollution are therefore needed to properly assess exposure risks and guide water quality policies and practices. In this study, the absence of a direct correlation between enterococci and source-specific human and animal markers disputes the utility of enterococci as an indicator of fecal pollution in urbanized subtropical bays. Moreover, the inverse correlation between enterococci and the human-specific marker HF183 indicates that recreational beach advisories, triggered by elevated enterococcus concentrations, are a misleading practice. This study clearly demonstrates that a multiparameter approach that includes the quantitation of host-specific markers, as well as analyses of microbial diversity, is a more effective means of assessing water quality in urbanized subtropical bays.

Dataset Information

Virioplankton dynamics are related to eutrophication levels in a tropical urbanized bay.

Publications

Virioplankton dynamics are related to eutrophication levels in a tropical urbanized bay.

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