Bioaccumulation of heavy metals in edible tissue of crab (Scylla serrata) from an estuarine Ramsar site in Kerala, South India

Wetlands are under severe threat due to anthropogenic activities and pollutants. Many pollutants such as heavy metals may accumulate to a hazardous level. In the present study, Scylla serrata, the mud crab and associated sediments were collected from three sites of Ashtamudi lake, the Ramsar site, to investigate the bioaccumulation of heavy metals Cadmium, Chromium, Copper, Lead and Zinc. Elemental analysis in the sediment sample showed that Cadmium and Chromium were found to be above USEPA and CCME limits and Copper was found to be above CCME limit on site 1. In site 2, Chromium was found to be above USEPA and CCME limits. In all the three sites, Lead and Zinc are below the permissible limit. Bioaccumulation status of heavy metals in the muscle of Scylla serrata with respect to the sites are in the order of site 1 > site 2 > site. The heavy metals Cadmium, Chromium and Lead were found to be above the permissible limit in site 1 and site 2, whereas Copper and Zinc concentrations in the muscle of crab from Ashtamudi wetland are below levels of concern for human consumption. A number of histological alterations such as splitting of muscle fibres, focal area of necrosis and muscular oedema were noticed in the samples. The result clearly indicates the fact that S. serrata undergoes intensified stress, when exposed to heavy metal contamination. Knowledge of metal concentrations in shell fish and fin fish are important both with respect to nature management and human consumption of fish.