AbItnct. Observations were made on the colonization of test panels (8 x 5 em) by fouling organisms in the coastal waters and the cooling circuit (forebay) of Madras Atomic Power Station for a year. In coastal waters, hydroids settled as a pioneer species followed by barnacles and ascidians, whereas at the forebay, sea anemones were the important settlers. Species abundance, diversity indices and fouling biomass showed relatively low values at the forebay as compared to coastal waters. Species richness however was more in forebay than in coastal waters. Low species diversity with high species richness indices observed at the forebay could be attributed to species selection under altered environmental factors (chlorine levels, high flow rates and lack of predators).The settlement and growth of fouling organisms on surfaces associated with the power plant cooling water systems can interfere with the efficient operation of the plant (Hillman 1977). An evaluation of the type and abundance of such fouling communities from the cooling circuit of power stations provide information not only regarding efficiency of antifouling treatment adopted in such systems but also about the impacts of such antifoulants on the local ecosystem (Markowski 1959). Moreover, most of these organisms are sedentary or semisessi1e and thus are best indicators to assess any stress to the ecosystem.Several studies from Indian coastal waters (Karande 1983; Satyanarayana Rao and Balaji 1987; Nair et at 1988; Sasikumar et at 1989) have reported very heavy fouling biomass build-up. Reports in the literature also indicate possibility of fouling biomass levels being different even in adjacent habitats. Most of the reports of the Indian authors have so far been on the development of fouling communities in natural habitats, there being very little data available on the fouling communities in impacted habitats. In the present paper, observations on the colonization of fouling organisms in a natural habitat (coastal waters) and inside the cooling circuit (forebay) of Madras Atomic Power Station (MAPS) are reported.MAPS is located approximately 65 km south of Madras city, on the east coast of India. The power station uses seawater for cooling the condensers. Seawater is drawn through a 468 m long sub-seabed tunnel (figure 1) and is discharged through an outfall structure. Seawater enters the tunnel through subsurface intake gates (I m depth) and reaches the forebay. From the forebay seawater is pumped at a rate of 35 m 3/s for cooling the condensers. Chlorine is used as a biocide/ to reduce settlement of foulants in the cooling circuit. Chlorine dosing levels are maintained in such a way as to obtain a chlorine residual of 0-5 to I ppm at the forebay. The 525
Results of a study on mortality response of Megabalanus tintinnabulum when exposed to chlorine and different temperatures are presented. At 1.5 ppm chlorine residuals, 5 mm barnacles showed 100% mortality in 101 h and 30 mm barnacles in 156 h. At relatively high levels of chlorine residuals (15 ppm), all the size groups showed 50% and 100% mortality at identical exposure times. Exposure to a temperature of 35°C showed 100% mortality of the 5 mm size group in 9.9 h and 50% mortality in 3.98 h. All the size groups showed 100% mortality at identical exposure times above 40°C. While chlorination appears to be the method of choice in operating power plants, heat treatment can be considered for use in new plants. The heat treatment method that is reportedly successful in California can be more economical if practised in India. This paper emphasises application of the two methods in power plants and the need for more biological information to control power plant biofouling in Indian waters.
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