Abstract
In the present study, we analyzed variations in bacterial community structure along a salinity gradient in a tropical monsoonal estuary (Cochin estuary [CE]), on the southwest coast of India, using Illumina next-generation sequencing (NGS). Water samples were collected from eight different locations thrice a year to assess the variability in the bacterial community structure and to determine the physico-chemical factors influencing the bacterial diversity. Proteobacteria was the most dominant phyla in the estuary followed by Bacteroidetes, Cyanobacteria, Actinobacteria, and Firmicutes. Statistical analysis indicated significant variations in bacterial communities between freshwater and mesohaline and euryhaline regions, as well as between the monsoon (wet) and nonmonsoon (dry) periods. The abundance of Betaproteobacteria was higher in the freshwater regions, while Alphaproteobacteria and Epsilonproteobactera were more abundant in mesohaline and euryhaline regions of the estuary. Gammaproteobacteria was more abundant in regions with high nutrient concentrations. Various bacterial genera indicating the presence of fecal contamination and eutrophication were detected. Corrplot based on Pearson correlation analysis demonstrated the important physico-chemical variables (temperature, salinity, dissolved oxygen, and inorganic nutrients) that influence the distribution of dominant phyla, class, and genera. The observed spatio-temporal variations in bacterial community structure in the CE were governed by regional variations in anthropogenic inputs and seasonal variations in monsoonal rainfall and tidal influx.
Highlights
Marine microbial communities are vital to global biogeochemical cycles of carbon, nitrogen, sulphur, and phosphorous
The duration from June to September was considered as wet period, which received an average rainfall of 528.75 mm, whereas the dry period, sub classified into the Dry period I and II, received an average rainfall of 151.75 mm and 133 mm, respectively (Fig. S1)
The present study demonstrated that the most dominant bacterial phyla, class and genus using high throughput metagenomic analysis
Summary
Marine microbial communities are vital to global biogeochemical cycles of carbon, nitrogen, sulphur, and phosphorous. They are the engines of every ecosystem and constitute a massive biomass, diversity and activity in the global oceans (Graham et al 2016). It is extremely important to understand the microbial community structure to appreciate the way in which ecosystems function and to recognize factors that control microbial communities. Physicochemical factors directly affect microbial diversity and community composition and variations in microbial community structure affects ecosystem functioning. Very little is known about the complex factors influencing bacterial community composition or the effects these communities have on estuarine ecosystems (Dolan 2005; Teira et al 2008)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
