Plankton Diversity in Coastal Waters near Kalu Ganga River Mouth; Sri Lanka

The plankton community plays a significant role in the stability of coastal ecosystems. They serve as key players marine food webs. present study investigated diversity waters near Kalu Ganga river mouth. Six sampling locations were chosen randomly, three along right side coastline (CR1-CR3) and left-side (CL1-CL3) from Zooplankton phytoplankton at each location sampled September 2020 to February 2021 using 55μm net surface on monthly basis. Plankton morphologically identified nearest possible taxonomic level. Shannon-Weiner index (H) Simpson's Index Diversity (SID) calculated determine diversity. number species found during wet months (September-October) dry (January-February) 62 68 respectively, while similar zooplankton (43) recorded both periods. Altogether, 81 53 research period. Bacillariophyta (72%) Copepods (68%) dominant groups respectively. Dinoflagellates including, Peridinium sp., Protoperidinium Ceratium Noctiluca Gonyaulax Alexandrium which are well-known form harmful algal blooms (HABs) accounted for 17%. Chlorophyta Cyanophyta less dominated only (CL1 CR1) Rotifera (11%), foraminifera (9%), protozoa (10%) ichthyoplanktons (<1%) also reported. H SID values be between 2.7 3.1 0.90 0.96 not significantly different (p>0.05) location. According values, area has moderate-high level Further should conducted temporal spatial variation area.