Impact of sewage disposal on a nematode community of a tropical sandy beach

Abstract

Free-living marine nematodes from an intertidal sandy beach from Goa near the Panjim city, central west coast of India was investigated along a gradient of sewage pollution. High nematode diversity (11 species) and abundance was observed near the sewage discharge point, which decreased gradually away from the discharge site. The salinity and dissolved oxygen of the estuarine water increased from the discharge point whereas reverse trend was observed for the sedimentary organic carbon. The total nematode densities indicated three-fold increase (from 523 to 1769 ind.10 cm sup(-2)) in 25 yr with a contrasting gradient of nematode abundance, spatially from the source point of sewage discharge. Daptonema sp is known to be a good indicator of stressed and polluted habitats and was observed to be the most dominant species at the study site. Being exposed to the domestic sewage, the area also has high counts of pathogenic bacteria (e.g. E. coli and other colifrom types). Daptonema sp are known to consume bacteria and presence of high bacterial biomass due to nutrient enrichment from the discharged sewage enhanced their abundance. Thus, the increasing nematode densities specifically like Daptonema sp at organically polluted sites can be of immense aid to reduce pathogenicity and can potentially be applied in pollution management and act as agents of natural bio-remediation.