ENVIRONMENTAL-STRESS IN LAKE MARYUT AND PHYSIOLOGICAL-RESPONSE OF TILAPIA-ZILLI GERV

This study was initiated to evaluate the effect of hazardous exposure to water pollutants on Tilapia zilli Gerv inhabiting Lake Maryut at 3 different sites with varying degrees of physicochemical and organic cr iteria. As compared to other sites, the lower water turbidity and alka linity plus lesser metal content in site #1, signify its picking as re ference. The expected anoxicity of the polluted sites (#2 & #3) was ev idenced by the elevated chemical and biological-oxygen demands added t o reduced dissolved oxygen. Abundant phytoplankton and sewage effluent s coupled with the high productivity of the lake have elevated water p H and nutrient salts; thus causing a chronic eutrophication problem. E merging evidence suggests that T. zilli responded differently accordin g to the environmental stress index in each catch area. In polluted fi sh, serum hyper-alpha 1-, alpha(2)-, and beta-globulinemia plus low al bumin added to the enhanced activities of serum transaminases and lact ate dehydrogenase suggests chronic functional damage in the liver. How ever, the hyper-gamma-globulinemia implies an indirect challenge respo nse toward the invasion of endo and ectoparasites. Serum enzymes, prot ein, lipid, cholesterol, creatinine, and glucose fluctuated ill a posi tive correlation contra the guidelines of water pollutants; they are t hus validated as beneficial ''biochemical markers'' for contamination stress. Unlike other biological principles investigated, alkaline phos phatase proved to be a promising ''model'' for appraising moderate, su blethal, or metal- restricted contamination. Other water pollutants, a s petroleum oil, seem to interfere with this peculiarity.