Heavy metal contamination along different tidal zones of a tropical Bay of Bengal coastal environment influenced by various anthropogenic activities

Trace metals and pesticides in water-sediment and associated pollution load indicators of Netravathi-Gurupur estuary, India: Implications on coastal pollution

Various environmental indicators were used to evaluate the water and sediment quality of the Netravathi-Gurupur estuary, India, for trace metals and pesticide pollution. The descended order of studied metal concentrations (μg/L) in the water was Fe (592.71) > Mn (98.35) > Zn (54.69) > Cu (6.64) > Cd (3.24) > Pb (2.38) > Cr (0.82) and in sediment (mg/kg) was Fe (11,396.53) > Mn (100.61) > Cr (75.41) > Zn (20.04) > Cu (12.77) > Pb (3.46) > Cd (0.02). However, pesticide residues were not detected in this estuarine environment. The various metal indexes categorised the water as uncontaminated, whereas contamination factor, enrichment factor, geo-accumulation index, degree of contamination and pollution load index indicated low to moderate sediment contamination. Multivariate statistics showed that the dominance of natural sources of trace metals with little anthropogenic impact. Improvement in water/sediment quality during the study period might be due to COVID-19 imposed lockdown.

Heavy metals concentration in zooplankton (copepods) in the western Bay of Bengal

Along the coastline, urbanisation and industrialization pose significant challenges to marine habitats and biodiversity. Most wastewater that reaches the marine environment contains toxic metals, which, as they are non-biodegradable, accumulate in the biota and enter the marine food chain. This study presents the concentration of nine heavy metals (Fe, Zn, Cu, Co, Cr, Mn, Ni, Pb, and Cd) in zooplankton (copepods) during the Spring Intermonsoon/Pre-Monsoon (April 2019) in the western Bay of Bengal (BoB). Higher Fe concentrations were found in copepods both nearshore (42,352 µg/g) and offshore (9835 µg/g). However, the relative amounts of heavy metals in copepods from 16 locations (eight nearshore and eight offshore) varied in the order of Fe > Zn > Cu > Co > Cr > Mn > Ni > Pb > Cd. The copepods in the nearshore locations had higher concentrations of heavy metals than those offshore. Compared to earlier data on heavy metals, particularly those that are physiologically non-essential and toxic, the current study demonstrates higher amounts of these metals in copepods in the inshore BoB [Ni (avg. 58.7 ± 5.5 µg/g), Pb (avg. 25.6 ± 4.7 µg/g), and Cd (avg. 16.4 ± 0.9 µg/g)]. Considering the strong East India Coastal Currents in the western BoB, trace metal-concentrated copepods could be transported too far along the Indian coastline from the current study area.