Zooplankton assemblages in Sematan River, Sematan, Sarawak

A study on the zooplankton assemblages in Sematan River, Sematan, Sarawak was carried out to evaluate the species composition, species diversity, species similarity, abundance, distribution and selected water physicochemical parameters. Zooplankton and water samples were collected from six sampling stations at 7-8 August 2010 for dry season and 15-16 January 2011 for wet season. Zooplankton and water samples be analyzed using standard methods in interpreting infonnation about zooplankton assemblages and its relationship to environmental parameters. A total 900 zooplankton belonging to seven groups, four taxa and 14 genera were identified. Copepoda dominated the zooplankton population which made up of 68.44 % of total abundance. Zooplankton abundance followed the order: Copepoda > Cladocera > Mollusca > Protozoa > Ostracoda > Anostraca> Rotifera. A dominant genus identified in this study was Limnocalanus which represented 29.56% of total amount. The seasonal pattern was observed which recorded zooplankton composition was much higher during dry season (866 individuals) compared to wet season with lowest present (31 individuals). Species diversity values vary from 0.562 to 2.042 and recorded mostly in high value for each station during dry season. The Sorensen's index value falls were much larger in range between 13.33 % to 76.19 % among all stations. Water temperature of different season, turbidity, dissolve oxygen, pH and nutrients were main environmental parameters which were found to influence zooplankton composition in Sematan River.