Cochin Estuary Research Articles

Demographics and Reproductive Characteristics of Orange Chromidae, Pseudetroplus maculatus (Bloch, 1975) from Cochin Estuary, Southern India

Demographics and Reproductive Characteristics of Orange Chromidae, Pseudetroplus maculatus (Bloch, 1975) from Cochin Estuary, Southern India

Eliciting heavy metal contamination on selected native organisms from Cochin estuary using contemporary biomarker approach

Eliciting heavy metal contamination on selected native organisms from Cochin estuary using contemporary biomarker approach

Characterization of phytoplankton size-structure based productivity, pigment complexes (HPLC/CHEMTAX) and species composition in the Cochin estuary (southwest coast of India): special emphasis on diatoms

Seasonal studies on size-fractionated phytoplankton productivity (biomass and primary production), marker pigments, and species composition and abundance were carried out in the Cochin estuary (CE), located on the southwest coast of India, to identify the critical environmental factors that control the consistent preponderance of diatoms. The overall results of the study showed a significant contribution of small-sized phytoplankton, specifically nanophytoplankton (2–20 µm), to the total chlorophyll a and primary production in the estuary, regardless of seasons. Diatoms constituted the major phytoplankton taxa, showed an exceptional seasonal scale increase in numerical abundance during the post-southwest monsoon. The relative increase in fucoxanthin (biomarker of diatoms) over other marker pigments substantiated the numerical dominance of diatoms throughout the sampling periods. This is the first study in the CE in which phytoplankton marker pigments have been detected and elucidated the seasonality of functional groups based on HPLC/chemotaxonomy analytical approaches. The prevalence of high DiatDP and diatom chlorophyll a equivalent (estimated by CHEMTAX), further confirmed the preponderance of diatoms in the CE, despite the intermittent dominance of cyanophytes and cryptophytes (monsoon period). The consistent increase in SPM levels (> 25 mg L–1), established at all sampling stations, indicated that the water column turbidity might be one of the significant environmental factors hindering the growth of large-sized phytoplankton (ca. >20 µm) in the CE even if the system invariably holds high inorganic nutrients, irrespective of seasons.

Metagenomic phage biodiversity: New insight into the tropical estuarine ecosystem process and microbial risk assessment

Viruses infecting unicellular organisms were shown to have a significant influence on aquatic ecosystem processes. Their role in biogeochemical cycles, primary production and microbial risk assessment in the tropical estuarine systems remain unresolved. The present study is the first approach of Next Generation Sequence (NGS) based viral metagenomic analysis of Cochin estuarine sediment. Viral particles were purified from 1.5 kg sediment samples collected from Cochin estuary, employing flocculation, and the purity was confirmed using epifluorescence microscopy. The flocculate was subjected to whole genome amplification using Illumina. Present NGS data provides information about the abundance of major bacteriophages, especially, cyanophages which play a significant role in ecosystem engineering and the biogeochemical cycle. In the present study, bacteriophages such as phages of Aeromonas, Bacillus, Salmonella, Vibrio, Burkholderia, Acanthocystis turfacea, Acidianus, Clostridium and Escherichia represented a major fraction. NGS result confirmed Aeromonas phages (19.78%) to be the most abundant communities present in the Cochin estuarine sediment. Cyanophages and phytoplankton attacking phage communities included A. turfacea virus, Chlorella virus, Acidianus filamentous virus, Ectocarpus siliculosus virus, Phaeocystis globosa virus, Chrysochromulina ericina virus, Emiliania huxleyi virus, Micromonas pusilla virus, Ostreococcus lucimarinus virus, Ostreococcus tauri virus, Synechococcus virus and Prochlorococcus virus. Unicellular photosynthetic Synechococcus and Prochlorococcus, abundant in oceans and estuaries, contribute to a substantial proportion of primary productivity, so the presence of these low-light adapted cyanobacteria attacking phages in estuarine sediments reveals that they are the key factor that controls the primary production and are also essential in preventing pathogenic bacterial population explosions. The data can be used as a road map for modelling efforts to link the role of viruses in determining carbon and nutrient availability in tropical estuarine ecosystems and the microbial risk assessment.

Influence of hydrological factors on bacterial community structure in a tropical monsoonal estuary in India.

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.

Nutrient concentrations and distribution of phytoplankton pigments in recently deposited sediments of a positive tropical estuary

Investigation of nutrients in the water column and phytoplankton pigments in recently formed modern sediments (0–5 cm) was carried out in Cochin estuary. The anthropogenic impacts were assessed using nutrients, nitrate, and phosphate in combination with phytopigments in sediments. The nitrate and phosphate concentration during the study ranged from 0.81 to 42.53 μmol/L and from 0.1 to 5.81 μmol/L, respectively. The mean values of the pigment showed the following order: zeaxanthin (791.53 ng/g) > lutein (347.57 ng/g) > fucoxanthin (335.30 ng/g) > pheophytin (308.84 ng/g) > pheophorbide (172.06 ng/g) > chlorophyll a (161.63 ng/g). The increase in the concentration of zeaxanthin indicated the presence of cyanobacteria, associated with eutrophication. Correlation analysis revealed that water column nutrients have a strong relationship between fucoxanthin and lutein, indicating the coexistence of diatoms and prasinophytes in the sampling sites. The principal component analysis showed positive loading of nutrients concomitant with pigment fucoxanthin and lutein, thus establishing that nutrient input controls the phytoplankton biomass of this estuary.

Toxicity of copper on marine diatoms, Chaetoceros calcitrans and Nitzchia closterium from Cochin estuary, India

The effects of copper (Cu) toxicity on the growth, pigments, protein, carbohydrate, lipid and antioxidant enzyme activities of two endemic microalgae, Chaetoceros calcitrans and Nitzchia closterium from Cochin estuary were studied and compared. The 96 h median inhibition concentration (IC50) of Cu for C. calcitrans was 143.8 µg L-1 and that for N. closterium was 204.5 µg L-1. No observable effect concentration (NOEC), lowest observable effect concentration (LOEC) and chronic value of Cu on C. calcitrans were 17.93 µg L-1, 31.91 µg L-1and 24.92 µg L-1 respectively, whereas that for N. closterium were 18.35 µg L-1, 36.04 µg L-1 and 27.2 µg L-1 respectively. Chlorophyll a and c showed significant variation from the control at NOEC in both species. Carotenoid content showed significant increase at LOEC. The chlorophyll a/c ratio significantly decreased at NOEC and LOEC of N. closterium. In N. closterium catalase (CAT) activity showed significant increase at NOEC and LOEC, but in C. calcitrans it varied significantly above LOEC. Protein content showed a significant decrease at NOEC of C. calcitrans. No significant variation was observed for N. closterium. Carbohydrate showed significant variation between the species at NOEC. Lipid content varied significantly at NOEC of C. calcitrans. Chaetoceros calcitrans was observed to be more sensitive to copper toxicity than N. closterium. The metal stress tolerance mechanism of N. closterium and its bioremediation capacity can be established in further studies. This study also provides an insight on the biochemical changes that happened at NOEC.

Faecal contamination and prevalence of pathogenic E. coli in shellfish growing areas along south-west coast of India

Seasonal prevalence of faecal coliforms in Indian black clam (Villorita cyprinoides), sediment and harvesting waters from shellfish harvesting areas along Cochin estuary was evaluated. Enumeration was done by 5 tube most probable number (MPN) method. High prevalence of faecal coliforms was observed in shellfish, sediment and harvesting waters during monsoon and post-monsoon seasons compared to pre-monsoon season. Escherichia coli was isolated and identified by biochemical methods and further confirmed by PCR based detection of uid A gene. A total 125 E. coli strains were isolated; out of which 99 (79.2%) could be serotyped and comprised of 17 diverse serotypes. Approximately 89.06% of the serotyped strains belonged to 5 different pathogenic serotypes. Enterotoxigenic strains were the most prevalent, followed by enterohaemorrhagic, uropathogenic, enteropathogenic and enteroinvasive strains. Enterohaemorrhagic E. coli O157 strains were isolated from shellfish and sediment samples (7.07%). Multiplex PCR analysis revealed the presence of shiga toxin genes (stx1, stx2), intimin (eae) gene and enterohemolysin gene (hlyA). The overall prevalence of toxigenic genes among the strains was 78.1%; in shellfish (84%), sediment (78.1%) and water (69%). Shiga toxin gene stx2, showed the highest prevalence (54.3%), followed by eae (36.2%), stx1(20%), and hlyA (6.7%) genes. To the best of our knowledge, the present study is the first report on the isolation of E. coli O157 from shellfish harvesting areas along the Indian coast. Higher levels of faecal contamination along with the presence of pathogenic E. coli may pose potential health hazards to the consumers.

Fractionation and accumulation of selected metals in a tropical estuary, south-west coast of India.

Estimating the fractional distribution of sediment-bound heavy metals is highly significant for its ecological risk assessment in contaminated aquatic systems, since environmental factors enhance the mobility of heavy metals and its accumulation in different ecological matrices. In this study, the fractional distribution of Zn, Cd, Pb and Cu in the sediments of the Cochin estuary, along the south-west coast of India, was estimated along with its accumulation in four edible crustaceans. The high mobility of heavy metals in the Cochin estuary was evident from the distribution in fractions other than residual fraction. The exchangeable fractions of Zn and Cd were high in the Cochin estuary, indicating its high bioavailability. Even though the exchangeable fraction is negligible, Pb poses the risk of bioaccumulation due to the presence of oxidisable and reducible fractions. The level of heavy metals varies in different species of edible prawns, and high accumulation of all metals was observed in Metapenaeus dobsoni. Various risk assessment indices show that Cd and Pb pose significant ecological and human health risks in the Cochin estuary.

In situ measurements of bioluminescence response of Gonyaulax spinifera to various mechanical stimuli

A conspicuous bioluminescence during nighttime was reported in an aquaculture farm in the Cochin estuary due to Gonyaulax spinifera bloom on March 20, 2020. In situ measurements on bioluminescence was carried out during nighttime to quantify the response of G. spinifera to various mechanical stimuli. The bioluminescence intensity (BI) was measured using Glowtracka, an advanced single channel sensor, attached to a Conductivity–Temperature–Depth Profiler. In steady environment, without any external stimuli, the bioluminescence generated due to the movement of fishes and shrimps in the water column was not detected by the sensor. However, stimuli such as a hand splash, oar and swimming movements, and a mixer could generate measurable bioluminescence responses. An abundance of ~ 2.7 × 106 cells L−1 of G. spinifera with exceptionally high chlorophyll a of 25 mg m−3 was recorded. The BI in response to hand splash was recorded as high as 1.6 × 1011 photons cm−2 s−1. Similarly, BI of ~ 1–6 × 1010 photons cm−2 s−1 with a cumulative bioluminescence of ~ 2.51 × 1012 photons cm−2 (for 35 s) was recorded when there is a mixer with a constant force of 494 N/800 rpm min−1. The response of G. spinifera was spontaneous with no time lapse between application of stimuli and the bioluminescence response. Interestingly, in natural environment, application of stimulus for longer time periods (10 min) does not lower the bioluminescence intensity due to the replenishment of water thrusted in by the mixer from surrounding areas. We also demonstrated that the bioluminescence intensity decreases with increase in distance from the source of stimuli (mixer) (av. 1.84 × 1010 photons cm−2 s−1 at 0.2 m to av. 0.05 × 1010 photons cm−2 s−1 at 1 m). The BI was highest in the periphery of the turbulent wake generated by the stimuli (av. 3.1 × 1010 photons cm−2 s−1) compared to the center (av. 1.8 × 1010 photons cm−2 s−1). When the stimuli was applied vertically down, the BI decreased from 0.2 m (0.3 × 1010 photons cm−2 s−1) to 0.5 m (0.10 × 1010 photons cm−2 s−1). Our study demonstrates that the BI of G. spinifera increases with increase in mechanical stimuli and decreases with increase in distance from the stimuli.

Fluctuations in the rotifer population of a tropical estuary in Kerala concurrent to the century’s largest deluge

Rotifers, because of their small size, slow motility, and high calorific value forms an important live feed in aquaculture. The present study was conducted to elucidate the impact of the massive flood that occurred in Kerala during August 2018 on the estuarine hydrography and rotifer community of Cochin estuary, the largest tropical monsoonal estuary along the southwest coast of India. Sampling conducted in seven stations from the inlets to the upstream during the pre-flood, flood, and post-flood periods revealed conspicuous changes in the zooplankton community of the estuary, especially the rotifers. The decline in the rotifer abundance from pre-flood (17.6 ± 26.3 ind 100 m−3) to flood (1.3 ± 2.6 ind 100 m−3) followed by a sharp increase in the post-flood period (86 ± 129.8 ind 100 m−3) indicated the impact of the flood on the rotifer population. A conspicuous change was also noticed in their community structure with the genus, Keratella dominating during the low saline, pre-flood, and flood periods and the genus, Brachionus and specifically the species, Brachionus plicatilis dominating during the relatively high saline post-flood period. The species, Filinia longiseta var. acaudata (Filinia saltator, Gosse, 1886), hitherto not recorded from the study area, was observed exclusively after the flood. Cochin estuary (CE), being a monsoonal estuary where the high freshwater discharges associated with monsoon results in the washing out of a majority of the rotifer population, this scenario was much more aggravated by the massive flood that occurred during August 2018. However, with the reduction in the floodwater discharges, the concomitant increase noticed in the rotifer abundance indicates their rapid adaptation and proliferation strategies towards favourable hydrographic conditions in the estuary.

Microbial community shifts along an estuarine to open ocean continuum

The water bodies along a continuum from estuaries to open ocean display significant changes in their physical, chemical and biological characteristics. In the current study, we report the influence of such changes on the abundance and community structure of bacteria and archaea in a continuum from Cochin Estuary, in the southwest coast of India, to the open ocean of Arabian Sea. The bacterial and archaeal abundances were in the range of 104 to 106 and 103 to 105 cells ml−1 respectively in all the stations and showed a clear dependence on nutrients. The bacterial abundance decreased with depth in the open ocean, whereas the archaea showed a similar reduction at both shelf and open ocean stations. The α- Proteobacteria (35 %) and Cyanobacteria (23 %) were dominant in the estuary. More than 70 % of the community of bacteria on the shelf and in the open ocean were similar. The α- and γ-Proteobacteria contributed 37 & 27 % of the OTUs in the clone library of shelf and 20 & 29 % in the open ocean. The archaeal community structure in the open ocean and shelf were similar (90 %) composed mostly of Nitrosopumilaceae (70%–75%), while they were highly diverse in the estuary. In short, our study shows that the archaea are more diverse in the estuary compared to shelf and open ocean, while bacteria are equally diverse in all ecosystems.

The Circulation and Politics of Knowledge Climate Change and Livelihood Struggles in a Coastal Fishing Community

Exploring the role of knowledge circulation in everyday life could provide interesting insights on how different forms of knowledge shapes the lifeworld and subjective realities of people. In the context of everyday livelihood struggles of a coastal fishing community, this paper examines the nature of knowledge circulation at the local level and its micropolitics in wider social arenas. Exploring the nature of local knowledge systems prevalent among small-scale fishworkers, this paper further examines the politics of knowledge, when it circulates from the local social worlds to their solidarity networks. This paper is based on a qualitative study conducted in a coastal fishing village at Munambam situated along the Cochin Estuary in Kerala, India. The study was conducted in two phases. In the first phase of the study, data was collected through in-depth interviews by using a semi-structured interview schedule. In the second phase, a content analysis of media reports was carried out with an aim to analyse the discourses prevalent among diverse solidarity networks of fishworkers. The findings of this paper show that local knowledge is situated and intersectional. Further, the everyday lives of fishworkers are shaped by different knowledge claims that also signify their everyday struggles to access basic livelihood resources. It is amidst these diverse knowledge claims that one needs to critically examine the narratives of modernisation, climate change and the role of solidarity networks among fishworkers.

First recorded bloom of Akashiwo sanguinea (Dinophyceae) from the Cochin backwaters, a tropical estuarine system along the South Eastern Arabian Sea

Abstract Akashiwo sanguinea, a cosmopolitan red tide-forming dinoflagellate, is reported for the first time as a bloom from the Cochin estuary along the South Eastern Arabian Sea. Monthly sampling showed the continuous presence of A. sanguinea with occasional blooms. Blooms of A. sanguinea with the highest abundance of 2.8 × 105 cells l−1 were observed during the monsoon season (June 2019) with chlorophyll a of 17.2 mg m−3. The bloom period was characterized by higher concentrations of nitrate (26 μmol l−1) and phosphate (3.8 μmol l−1). Routine monitoring of the bloom region showed the survival of the Akashiwo sanguinea population in the temperature (26 to 30°C) and salinity (22 to 24 PSU) range indicating its eurythermal and euryhaline characteristics.

Biofouling inhibition for aquaculture cage nets through a coating nano zinc and silicon oxides incorporated with polyaniline

Biofouling is one of the problems faced by cage aquaculture farmers, and its management is expensive. In this present study, polyethylene aquaculture cage nets were coated with the nano structured oxides of zinc and silicon incorporated with polyaniline. Fourier transform infrared spectroscopy and scanning electron microscope data evidenced that a thick coating of nano particle was formed on polyethylene. The oxides were attached to the quinoid part of polyaniline. The antifouling efficiency of treated cage net was tested by exposing in the Cochin estuary for three months. A webbing treated with 0.01% of each of the nano zinc oxide (ZnO) and silicon dioxide (SiO2) exhibited the highest biofouling resistance. Reinforcement of nano SiO2 with ZnO increased biofouling resistance as the former complemented the coating to make the system more efficient.

Microplastics distribution and contamination from the Cochin coastal zone, India

Microplastics are small plastic fragments less than 5 mm in diameter, and microplastic pollution is an emerging threat in our day to day life. Microplastic pollution was estimated in water, sediment and fish samples from selected stations along the Cochin estuary and nearby coastal areas in Kochi. The estuarine water and sediment samples recorded a larger number of microplastics than in beach samples with a mean abundance of 751.7 ± 452.21 particles/m3 and 1340 ± 575.22 particles/kg, respectively. Study stations near to the busiest city locations showed significantly high levels of microplastic pollution (p < 0.001). A total number of 46 fishes belonging to five species were dissected, from which nine microplastics were isolated. All of the isolated plastic materials were identified as secondary microplastics. Among different types, fibres were abundant in all the sampling sites. Selected particles were identified with Fourier Transform Infrared Spectroscopy analysis as cellophane, polystyrene, polyethylene, polypropylene, and nylon. The study found that the water and sediment samples from the Cochin estuary are seriously polluted with microplastics, and this is the first attempt to compare the microplastic pollution status of the Cochin estuary with the associated beaches.

Trace metal dynamics in mysids from the Cochin estuary

Trace metal concentrations in two species of mysids, Mesopodopsis orientalis and Rhopalophthalmus indicus, from the Cochin estuary, were investigated during the monsoon and pre-monsoon periods. Metal concentration (ppm, dry weight) ranges in mysids during the monsoon and pre-monsoon periods were: Fe (775.75 to 1254.12), Mn (7.85 to 14.57), Co (0.76 to 1.75), Ni (11.19 to 20.00), Cu (20.02 to 47.42), Zn (66.83 to 106.62), Cr (14.30 to 28.45), Cd (0.53 to 1.70) and Pb (7.16 to 14.19). Trace metal bioaccumulation in mysids was found to be species-specific with higher metal concentrations in R. indicus than M. orientalis. Data on trace metal concentrations in mysids are important for environmental forensic investigations, useful for bio-monitoring (i.e., tracing) sources of contaminants (i.e., metal pollutants) and their impacts, and valuable for tracking the dispersal pathways of contaminants in estuarine environments.

Occurrence of enhanced herbivory in the microbial food web of a tropical estuary during southwest monsoon

Tropical monsoonal estuaries have a significant role in global fishery as they act as rich feeding and breeding grounds for many commercial species. Food web dynamic studies in these coastal ecosystems are mainly focused on the classic food chain which assumes that microbial food webs contribute more towards the recycling of organic carbon and nutrients rather than production. But recently it is observed that phyto-microbial food web which is largely dependent on pico-autotrophs can contribute significantly towards the higher trophic level. Based on these observations we have analysed phyto-microbial pathway of food web in a highly productive tropical monsoonal estuary. We assessed the grazer-prey interaction in the microbial food web of Cochin estuary during spring intermonsoon and southwest monsoon seasons. Our results show that during spring intermonsoon the food web is dependent more on heterotrophic bacteria, but in southwest monsoon the dependency of grazers switches over to autotrophic picoplankton. We also analysed the growth rate, grazing rate and carbon contribution of autotrophic picoplankton experimentally during both seasons and found that autotrophic picoplankton show higher growth rate during southwest monsoon. The higher grazing rate and clearance rate of autotrophic picoplankton recorded during southwest monsoon indicate the efficient consumption of autotrophic picoplankton crop during the season. We could also observe a change in autotrophic picoplankton community structure between the seasons with the dominance of picocyanobacteria during spring intermonsoon and that of picoeukaryotes during southwest monsoon. Thus we infer that high freshwater influx into the estuary during monsoon results in high turbid and low saline (mesohaline to oligohaline) environment which increases the growth rate of low light adapted autotrophic picoplankton populations and in turn enhances herbivory (phyto-microbial pathway) in the microbial food web. Apart from protists, autotrophic picoplankton were found to be widely consumed by many larval forms of mesozooplankton, gastropods, bivalves, rotifers and large sized filter feeders either as aggregates or as unicellular forms. Thus monsoon enhanced herbivory can have a significant role in the growth and survival of larval forms recruited into the estuary during monsoon season and in turn the fishery.

Hydrological regulation of Vibrio dynamics in a tropical monsoonal estuary: a classification and regression tree approach.

Dynamics of Vibrio populations in aquatic environments are of concern, as they encompass members pathogenic to humans as well as marine flora and fauna. Spatiotemporal distribution of its culturable abundance for a range of physicochemical and biological parameters in the Cochin estuary (CE), one of the largest tropical monsoonal estuary along the southwest coast of India, witnessed a proliferation of this bacterial group (707 ± 196 CFU ml-1) in downstream stations during a relative dry period. The study for the first time employed classification and regression tree (CART) along with multiple linear regression (MLR) based approaches to explore the nonlinear and linear interactions, respectively, among environmental variables regulating Vibrio abundance in CE. Both the techniques were on consensus to ascertain salinity as the primary determinant of Vibrio dynamics, during the entire sampling period regardless of the seasons, viz., dry and wet. Nevertheless, CART outperformed MLR in performance index, suggesting that in a dynamic system like estuaries, usage of the latter is limited by complex nonlinear relationships among environmental variables. According to CART, Vibrio proliferation observed in downstream stations of the estuary (salinity ≥ 13.4 psu) during a relative dry period was driven by eutrophication (dissolved inorganic phosphate ≥ 1.48 μM L-1) associated with reduced flushing resulting in an oxygen-limited environment (dissolved oxygen < 4.56 ml L-1), wherein phytoplankton production diverts to support microbes. Our results imply that anthropogenic activities and sea level rise in future may prompt Vibrio proliferation, to be a concern for public health and impinge on fisheries yield from tropical estuaries.

Aberrations in the microbiome of cyanobacteria from a tropical estuary polluted by heavy metals

The effect of heavy metal pollution on the microbiome of cyanobacteria in Cochin estuary (CE) on the southwest coast of India is reported in the study. Statistically significant difference in heavy metal concentration was observed between water, suspended particulate matter (SPM) and sediment. The Zn, Cd, Cu, Ni and Cr were 2–6 times higher in the SPM compared with the sediment, while Pb was 10 to 25 times higher. Although nearly 60% of the species diversity of microbiome was common between cyanobacteria enriched from the upstream (S1S) and downstream (S11B), there was a difference in the major groups of heterotrophic bacterial associates. Proteobacteria was the dominant phylum (>80%) in S1S, while it was second only (27.5%) after Planctomycetes (37.4%) in S11B. The results of the current study indicate that the pollution can influence an ecosystem at the micro-niche level.