PROGRAMME

Study was carried out to assess the ecotoxicity and interaction of polystyrene (PS) microspheres and trace element, cobalt (Co). Stage II nauplii of Amphibalanus amphitrite were exposed to environmentally relevant (250 and 1000 particles/ml) and future high (2000 particles/ml) concentrationss of 3µm PS microspheres in 3 different forms (unwashed, washed and aged). Series concentrations of Co were prepared, 24h LD50 was determined and 0.01, 0.1 and 1ppm Co concentrations were selected for use in individual and combined toxicity assays. It was found that microspheres of all types did not significantly affect the survival of nauplii (Mortality≤20%) at low concentrations. With increase in no. of particles in the medium (upto 2000 particles/ml), treatments consisting of unwashed and aged particles resulted in percentage mortality as high as 39% and 56% respectively however washed particles were still nontoxic. r. With regards to Co, mortality appeared to be a linear function of concentration.. When nauplii were exposed to a mixture of PS and Co, there was a shift in percentage mortality either towards low or high. Percentage mortality after combined exposure to Co at 0.01 ppm and unwashed/washed particles at 250 particles/ml was 13% and 37% greater than the mortality at same concentration of Co alone however with increase in no. of particles in the medium, a decrease in toxicity of cobalt was observed. Antagonistic effect of microplastics was more pronounced in the presence of aged particles and when present at 2000 particles/ml, toxicity of 1 ppm Co dropped down to half It is concluded that aging of microplastics, which is a real environment scenario, reduces the toxicity of cobalt even if present in higher concentrations in the environment.