Effects of sedimentary heavy metals on meiobenthic community in tropical estuaries along eastern Arabian Sea

The central west coast of India comprises the 720 km long coastline of Maharashtra state and houses widespread industrial zones along the eastern Arabian Sea. Sediments from seven industrial-dominated estuaries along the central west coast were studied for metal enrichment and benthic assemblages to determine sediment quality status and ecological effects in these areas. The suit of geochemical indices highlighted the contamination of sediment in the estuaries concerning heavy metals. Positive correlations of Hg with Co, Zn, Ni, Cr, and Pb indicated the source similarity and effect of anthropogenic activity. non-Metric Multidimensional Scaling (n-MDS) based on meiofaunal abundance showed a cleared separation of clusters through the gradient of heavy metal concentrations. The Canonical Correspondence Analysis (CCA) results with the Monte Carlo test signified those heavy metals influenced the meiobenthic community. Heavy metals (Cr, Ni, Zn, Cd, Pb, and Hg) were the main drivers shaping the meiofaunal community with a significant (p < 0.05) reduction in taxa richness, diversity, and evenness. Dominant meiofaunal assemblages evidence the tolerance of foraminiferans and nematodes. However, these taxa were affected by decreased abundance at impacted sites compared to other fauna. In conclusion, results demonstrated that impairment occurred in the meiofaunal community in most estuaries (except AB and KK).

Microplastics in zooplankton in the eastern Arabian Sea: The threats they pose to fish and corals favoured by coastal currents

The baseline study of Microplastics (MPs) in zooplankton (copepods, chaetognaths, decapods, and fish larvae) from six different zones along India's west coast (off Kanyakumari/Cape Comorin, Kochi, Mangalore, Goa, Mumbai, and Okha) in the Eastern Arabian Sea (EAS) is presented here with their vast ecosystem impacts. This investigation revealed that zooplankton in all six zones accumulated MPs pellets (52.14%), fibres (28.40%), films (10.51%), and fragments (8.95%). The highest average retention of MPs (MPs/individual) was found in fish larvae (av. 0.57 ± 0.18) while copepods had the lowest (av. 0.03 ± 0.01). The presence of low-density polyethylene, polypropylene, polystyrene, and polyethylene terephthalate was confirmed by Raman Spectra of MPs. The MPs in zooplankton found in this study (av. 22 ± 7 pieces/m³) were nearly 2-fold greater than those found in some of the world's most densely populated areas. It is shown that the strong southerly coastal currents could advect the MPs contaminated water mass too far away, having the potential to affect the fish and corals.

Spatial and seasonal variation of microplastics and possible sources in the estuarine system from central west coast of India

The versatile use of various synthetic polymers, including plastics, generates a large volume of non-degradable waste, which is eventually responsible for forming microplastics (MPs) in aquatic environments. The present study describes the significant spatial and seasonal variation on the abundance of MPs and their physiochemical nature along the Mandovi-Zuari estuarine system of Goa, west coast of India. During the wet season (September), the average abundance of MPs was found relatively higher in water (0.107 particles/m³) and sediment (7314 particles/kg) than those found in the dry season (April) (0.099 particles/m³ in water and 4873 particles/kg in sediment). During the wet season, heavy rain and excessive riverine freshwater influx carry more terrestrial plastic debris in the estuarine system which causes higher averages MPs density in surface water and sediment. <300 μm sized particles and black colored MPs were predominant equally in water and sediment during both seasons. MPs of different shapes like fragments, fibres, films and beads accounted for most collected samples. The Micro-Fourier Transform Infrared Spectroscopy (μ-FTIR) based compositional analysis identified approximately 33 types of polymers, of which polyacrylamide (PAM), polyacetylene, polyamide (PA), polyvinyl pyrrolidone (PVP), polyvinyl chloride (PVC), and polyimide (PI) were abundant. Fragmentation of larger plastic particles due to mismanaged treated and untreated STPs and washing machine effluents are the primary sources of these MPs in the estuarine system. Moreover, these estuaries also receive a variety of domestic, industrial and other wastes from local cities, ports, and fishing jetties. Thus the present study enlightens the current distribution of MPs and their sources in the Mandovi-Zuari estuarine system and thus provides very useful information to the stakeholder and concerned departments for initiating the mitigation measures.

Prevalence of indicator and potential pathogenic bacterial groups in the Chapora bay-estuarine system, Goa, central west coast of India

This paper describes the prevalence of indicator and pathogenic bacterial groups in water and sediments in OSZ-offshore, ISZ-inshore, IEZ-inner estuary, and UEZ-upper estuary along the river Chapora, central west coast of India, which is influenced by anthropogenic inputs. The abundance of indicator bacterial groups such as total coliforms and Escherichia coli-like organisms in water ranged from non-detectable (ND) to 10³ colony-forming units (CFU)/mL. In contrast, their abundance in the sediments was six orders magnitude higher than water (ND to 10⁹ CFU/g). The abundance of potential pathogenic bacteria in water and sediment samples ranged from ND to 10³ CFU/mL and from ND to 10⁹ CFU/g respectively, with Shigella-like organisms (SHLO) being the most abundant. In the surface waters, SHLO and Pseudomonas aeruginosa-like organisms (PALO) and in bottom waters, Vibrio parahaemolyticus-like organism and PALO increased progressively from OSZ to UEZ. In contrast, Proteus/Klebsiella-like organisms (PKLO) showed a reverse trend. Amongst all four zones, IEZ was the most contaminated in terms of the higher abundance of indicator and potential pathogenic bacterial populations as corroborated by significantly lower water quality index value. Principal component analysis performed using physico-chemical variables and bacterial groups to reduce data set variability revealed that a different set of parameters contributed differently to the total variation in each zone. Considering the eco-sensitivity of the river Chapora, the results of the present study call for precautionary measures to minimize the degree of anthropogenic inputs.

Assessment of micro and macroplastics along the west coast of India: Abundance, distribution, polymer type and toxicity

Considering the magnitude of pollution caused by marine plastics, the present study assessed their abundance, distribution, surface morphology and polymer type in ten sandy beaches spread across three states (Maharashtra, Karnataka and Goa) along the west coast of India (WCI). The total abundance of plastics (∼1-100 mm) in the studied beaches ranged from 4.1 to 23.4% (19±1-346 ± 2 items/m²). Location-wise, the abundances of both micro (43.6 ± 1.1-346 ± 2 items/m²) and macroplastics (21.6±3-195 ± 6 items/m²) were relatively higher in beaches along the Maharashtra coast. Surface morphology-wise, fragments were predominantly abundant in both micro (76±2-346 ± 2 items/m²) and macroplastics (50.6 ± 1.5-195 ± 6 items/m²) followed by pellets (43.3 ± 2.5-245.6 ± 2 items/m²). Fourier-transform infrared spectroscopy (FT-IR) analysis of plastics revealed a dominance of polyethylene (PE) followed by polypropylene (PP). IR spectra of the collected plastics at absorption band at 1750-1700 cm^-1 reflect minimal surface oxidation. White-colored plastics were observed most frequently, followed by pale-yellow, dark-brown, green, blue, transparent and red. A short-term (72 h) experimental study to assess the toxicity of PE microbeads (∼1 mm) in a commercially important shrimp species, Litopenaeus vannamei revealed toxicological changes. An elevated level of lipid peroxidation (LPX)-the tagged biochemical marker, was recorded only at the maximum dose (0.15 mg/L) of PE microbeads. A moderate increase in the levels of enzymatic antioxidants (catalase and glutathione S-transferase) was also recorded at the same dose. Comprehensive information on marine plastics, including ecotoxicity provided in this study, would help in evolving strategies in minimizing plastic pollution along the WCI.

Factors controlling organic matter composition and trophic state in seven tropical estuaries along the west coast of India

To understand the organic matter (OM) sources and trophic states, spatial and seasonal (post-monsoon and pre-monsoon) variation in sedimentary OM compositions was investigated in seven tropical estuaries of the state of Maharashtra along the central west coast of India. Based on the result of cluster analysis, estuaries were segregated into two distinct groups: Northern Maharashtra and Southern Maharashtra owing to dissimilarity in OM characteristics potentially constrained by geomorphology and catchment properties. Enrichment of C_org and major biochemical compounds (lipids, carbohydrates and proteins) in the middle zone of most estuaries highlighted towards the addition of allochthonous OM. Results of principal component analysis highlighted the similar source of OM in most of the estuaries during both seasons and their distribution largely constrained by grain size change. The benthic trophic state indicated the prevalence of eutrophic state in the middle zone of the investigated estuaries, which may be sporadic and dependent upon anthropogenic activities in the study area.

On the relationship between sea surface temperatures, circulation parameters and temperatures over west coast of India

The oceans and the atmosphere are tightly linked and they together form the most dynamic component of the climate system. Topography and proximity to the surrounding seas of the region determine the temperature of the area. West Coast (WC) of India is a high elevated region surrounded by large oceanic area, therefore, an attempt is made in this study to examine the trends and variability in temperature over WC in relation to oceanic phenomena. Temperature over the WC shows considerable year-to-year variation with anomalous cool years in recent warm epoch. Therefore, sea surface temperature (SST) and associated winds have been analyzed to understand possible mechanism behind the variation in temperatures over the WC. During the winter, north-easterlies prevail over the WC which blows from land to ocean. Variations in SSTs alter the strength of these winds to cause anomalies in temperature over the WC. Indian Ocean Dipole (IOD) appears to have a dominant role in climate of the WC, whereas SSTs over the equatorial Pacific do not show any impact on temperatures over the WC. Study indicates that the strengthening of north-easterlies due to negative phase of Indian Ocean Dipole causes cooling over the WC of India.

New record of Norileca indica from the west coast of India

Two hundred and twenty samples of Rastrelliger kanagurta from the Cochin Fisheries Harbour were collected during the month of August 2013. Forty-one specimens (32 females and 9 males) were parasitized by the cymothoid isopod Norileca indica. N. indica is recorded for the first time from the west coast of India.