Abstract:
Zooplankton serves as a productive base of marine ecosystems and most recently they are used as a biological indicator to assess the ecological status of aquatic environments. The purpose of this study was to determine the diversity, abundance and biomass of zooplankton in 4 areas (defined as; area A; Beruwala coastal area B; Weligama coastal area C; Beruwala offshore area and area D; Weligama off shore area) off south-western coast of Sri Lanka. Total of 22 plankton samples were collected by using R/V "Samudrika" during March and April, 2014. The sampling was carried out by using the WP-2 plankton net of 180 vim mesh-size with an opening area of 0.25 m2.
Preserved zooplankton sample were analyzed using microscope up to genes and species level To determine the net-plankton biomass, a number of techniques such as displacement volume, wet weight, dry weight, ash-free dry weight method was done and tested for significant difference of biomass among different stations by ANOVA. Various diversity indices such as Shannon-Weainer, Margalef and Evenness were used to assess the zooplankton diversity in the ocean. Multiple correlation analysis revealed that there was a positive significant correlation diversity indices in different areas.
94 genera and 9C spp. of zooplankton were found in all A, B, C, and D areas. Only Beruwala area was found species are the Microcalanus, Ophiothrix, Polychaeta larvae and Callianassa, Monstrilloida, Scaphocalanus, Necora, Poecilostomatoid, Anapagurus, Calycophorae, Diogenes, Euchaeta, Eudoxoides was only found in weligama area. Zooplankton density of the area varied from 1.41 - 2.03 individuals per liter. Biomass in terms of organic matter was high compared to other areas around Sri Lanka with a range of 93.03 + 1.67 %.
The distribution pattern of major constituents of zooplankton community indicated the Weligama area is most productive in terms of secondary productivity in comparison with other areas.
Keywords: zooplankton, diversity, abundance, coastal area, offshore area, Sri Lanka
