STUDY THE EFFECT OF SALINITY AND NUTRIENTS FOR THE GROWTH OF Najas marina AND ITS IMPACT TO AQUATIC BIODIVERSITY IN MADU GANGA RAMSAR WETLAND IN SRI LANKA

Abstract

Species cornpostion, abundance md distnbution of aquanc oligochaetes in Colonbo (Beta) Lake were investigated fiom May 1993 io Apdl 1994 Twenty two species of oligochaetes were identified rcpresenting 3 species of Aeolosomahdae, 17 species of Naidid"e and 2 specles of Tubificidae. Seven species were recorded for the ftst time ftom Sri Lanta These species ar€ ,leolosona f! ucarcnse, Aealosona rnidae, l ot1ax g' liorcnsk, Derc dorsal6, Derc i dica, Pristins slaclite: ad Stephensiniana nivandrdna The popuiations of aquatic oligochaetes fluctuated considerably in size ttuoughout the study period ,'{,/op}o,?r nichaebeni, Branchiodrtus senperi, Prbnna loryisetd and Aulodtilus piguen werc ti,e most abunddt species Abundance of sonle species of olgochaetes was positively correialed with Iainfall, orgmic malter content h dr€ bottom sedrment, pH, dissolved oxygen conten! biochemical oxygen demand, Ditrate ed phosphate conient in the bottom waler whereas negativ€ corelatiois were obsened with salinity and conducbvity in the bottom q'ater (P<0 05). The nunber of speci€s and tl€ densiiy of wolms in the saline areas of ihe lake were cornparatively low. lulo?halus nichael:eni aad Aulodnlts'pi81€, \'rcre the most abundant sp€cies m these areas Introduction