Effect of heavy metals, textile dyes and pesticides on growth and biochemical composition in tropical marine chlorophytes

The detection and monitoring of toxic contaminants in the aquatic environment continues to be an expensive and tedious exercise. It becomes even more complex when contaminants exist at low levels that go undetected by conventional analytical techniques. Examples of such contaminants are the genotoxic pollutants, which not only cause mortality in the exposed organisms but potentially may induce higher order changes such as alterations in population dynamics and changes in biodiversity. Such changes may initiate direct and catastrophic ecological consequences. Algae have been widely used as bioindicators for pollution due to toxicants such as heavy metals, pesticides and xenobiotics (Gin et al., 2006). They have also been used as organisms in toxicity testing and bioassay. Range-finding toxicity test using 25 algal species with cadmium chloride at concentrations 10mg/L and 100mg/L, CdCl2 were conducted. Four tropical marine chlorophytes including microalgae (Chlorella sp. UMACC 245, Tetraselmis tetrahele UMACC 144) and seaweeds (Boergesenia forbesii and Ventricaria ventricosa) were selected for further toxicity tests. The effect of seven heavy metals ( Cd,Co,Cr,Cu,Fe,Mn,Zn), three types of textile dyes (Supranol Br, Red 3Bur, Astrazon Red FBL, Laraset Red 2GA) and two types of organophosphate pesticides (malathion, DDVP) on the growth of the four species of marine algae, were carried out in 1L conical flasks with test volumes of 500 ml. The algae were exposed to 0.01, 0.1, 1.0, 10, 100 and 500 mg/L concentration of toxicant in Provasoli medium without EDTA for 96 hours and 10 days under controlled conditions. The growth parameters (Chl a, ODsub 620 nm), biochemical composition (protein, lipid fatty acids, carbohydrates) and IC sub50 values (concentration of toxicants estimated to inhibit 50% algal growth relative to control were determined after 96 hours and 10 days based on chl a content. Chlorella sp. UMACC 245 was more tolerant than Ventricaria ventricosa to the toxicants tested. This is due to the presence of the thick cell wall in Chlorella sp. UMACC 245 and Boergesenia forbesii.