BIOMONITORING OF TOXIC HEAVY METALS AND PREVAILING MICROBIAL LOAD IN WHITELEG SHRIMP Litopenaeus vannamei (BOONE, 1931) FARMS OF VELLAKULAM VILLAGE, THIRUVALLUR DISTRICT, TAMIL NADU

Shrimp farming is a multi-billion dollar industry contributing a major income to several countries in Asia and South America. India is the second largest country in aquaculture production in the World, the share of brackish-water sector includes culture of the exotic white-leg shrimp, Litopenaeus vannamei (Boone, 1931) for its ability to grow and survive in low salinity environments (Luke, 2010) for inland aquaculture.

Biomonitoring is the use of biological responses to assess the changes in the environment. It is a valuable assessment tool that is receiving use in water quality monitoring programs of all types. Certain contaminants, particularly metals and organic compounds, may be accumulated in the tissues of organisms. The study focusses on analyzing the presence of toxic heavy metals (like lead, cadmium, chromium, mercury and arsenic), present in the shrimp, soil and water samples. Heavy metal concentration is determined by direct aspiration of water samples and acid digestion prior to filtration and then analyzed using ICP-MS. The major threat to the shrimp farmers is the incidence of diseases that attack culture ponds which results in devastating loss. The infections include a wide range of microorganisms viz. bacteria, fungi, and viruses, among which a few prevailing diseases in India are chosen for detection in this study

Fresh shrimp, water and soil samples were collected from the ponds from the time of stocking of seeds till the period of harvest were collected from three ponds located in Vellakulam village, Ponneri taluk (13.3378°N, 80.1929°E), Thiruvallur district, TamilNadu. Shrimp samples were also collected in containers with freshly prepared Davidson's fixative, for histological purposes (Janakiram et al., 2018). Microbial screening for total fungal count, total plate count, vibrio profiling and the diagnosis of Enterocytozoon hepatopenaei was done at each stage of the culture period. This study of biomonitoring thus aware us at each stage and between the cultures about the toxicity and disease spreads in the farms