Zooplankton Assemblage in Hambanota Port and Adjacent Coastal Waters of Sri Lanka

Abstract

Present study was to investigate zooplankton assemblage in Hambantota port and adjacent coastal waters in Sri Lanka. Samples were collected from the port before the commencement of commercial operations in order to have baseline information on zooplankton assemblage that can be used in the future to study any community change. Species composition, abundance, spatial distribution and diversity of zooplankton were investigated over a period of six months from January 2011 to June 2011. Monthly samples were collected from both inner-harbor and outer-harbor. Physico-chemical parameters such as temperature, pH, salinity, density, conductivity, nitrate, orthophosphate, DO, BOD5 and Ch a were also measured. Zooplankton diversity, species richness and evenness were calculated using Shannon-Weiner diversity index (Hˊ ), Simpson‟s index (D) and Pielou‟s evenness (E). A total of 72 zooplankton types were identified throughout the research project mainly Calanus sp., Paracalanus sp., Sapphirina sp., Acartia tranteri, Barnacle nauplii, Crustacean cypris larvae, Oikopleura sp., Tunicate larvae, Brachionus calyciflorus calyciflorus, Brachionus forficula, Fish larvae, Discorbis sp., Actinula larvae and Sagitta sp.. Copepod nauplii dominated the zooplankton. According to percentage occurrences arthropods (71%), protozoans (10%) and ichthyoplankton (9%) were abundant in the inner harbor. In the outer harbor also arthropods (66%), ichthyoplankton (11%) and protozoans (7%) were recorded in higher numbers. Highest species diversity (Hˊ =2.685), highest species richness (S=39) and highest evenness (E=0.856) were recorded from outer harbor locations (HFHB1 and HPM). Several species such as Ceratium furca, Chaetoceros sp., Thalassiosira sp., Rhizosolenia sp. and Protoperidinium sp. known to form harmful algal blooms were also observed in this study.