Eutrophication induced changes in benthic community structure of a flow-restricted tropical estuary (Cochin backwaters), India

Abstract

The influence of anthropogenic loading on the distribution of soft bottom benthic organisms of a tropical estuary (Cochin backwaters) was examined. The industrial activities were found to be high in the northern and central part of the estuary, where dissolved inorganic nitrogen (DIN > 210 μM) and phosphorus (DIP > 6.5 μM) have caused high abundance of chlorophyll a (up to 73 mg m(-3)) and accumulation of organic carbon in sediments (up to 5%). Principal component analysis distinguished three zones in the estuary. The central zone (Z1) was characterized by organic enrichment, low species diversity, and increased number of pollution tolerant species. Long-term deterioration of the estuary is indicated by an increase in the nutrients and chlorophyll a levels by sixfold during the last few decades. Flow restrictions in the lower estuary have lead to a fourfold increase in sediment organic carbon over the period of three decades. The reduced benthic diversity followed by an invasion of opportunistic polychaetes (Capitella capitata), are indicative of a stress in the estuary.

Heavy Metals Pollution Influence the Community Structure of Cyanobacteria in Nutrient Rich Tropical Estuary

“…The level of heavy metal pollution gradually reduces from S4 at river mouth to S1 at bar mouth, owing to its accumulation in sediment [9]. Earlier studies recorded accumulation of heavy metals in the sediment samples and benthic organisms collected from CE [9,23,[40][41][42]. In a previous study, we recorded an 18 times increase in the level of Zn in sediments of CE during the past three decades [9].…”

“…Cochin Estuary (CE) is the largest wetland ecosystem along the southwest coast of India, covering an area of ~25600 ha, extending from 9° 30'-10° 12' N to 76° 10'-76° 29' E. CE is reported to be nutrient rich, and its composition is greatly influenced by anthropogenic and terrestrial inputs from six rivers, seawater influx from two bar mouths and prolonged monsoon [23]. CE also receives high concentrations of industrial effluents (104 × 10 3 m 3 per day) and untreated domestic waste (260 m 3 ).…”

Southwest monsoon influences the water quality and waste assimilative capacity in the Mandovi estuary (Goa state, India)

“…We have also compared the water quality conditions of other estuaries/coastal water bodies ( Table 9) situated on the west coast of India with that of the Mandovi estuary. [4,40,44,[50][51][52][53][54][55][56][57][58][59][60][61] The prevailing estuarine water quality of the Mandovi estuary is found to be good and acceptable as compared to most of the other regions along the west coast of India.…”

Sediment Oxygen Demand in Cochin backwaters, a tropical estuarine system in the south-west coast of India

“…In fact, SOD and BOD are equally important in determining the oxic/anoxic status of the estuarine ecosystem. Considering the fact that the CBS receives large amount of untreated industrial and domestic wastes per day (Martin et al, 2011), SOD might prove to be an additional tool in assessing its environmental quality. In this regard, the present study forms a pioneering attempt to evaluate the SOD of the CBS.…”