Coastal ecosystems are among the most productive and dynamic ecosystems on the planet. Phytoplankton biomass is considered as one of the most primary indicators of coastal ecosystem health because of its vital function in the food web. The rapid adaptation capability of phytoplankton makes them a critical component in the any aquatic ecosystem and a sensitive indicator of changes in the system concerned. A shift in phytoplankton abundance can alter the food web and impact fisheries production. Therefore, to maintain a healthy coastal ecosystem, it is important to understand the dynamics of phytoplankton communities. A total of 45 genera of mesophytoplankton were recorded from these coastal shelf waters. Of these, Chrysophyta was represented by thirty four (34) genera, Pyrrophyta by eight (8) genera, Cyanophyta and Chlorophyta by two (2) & one (1) genera, respectively. The results showed that chrysophytes predominated the phytoplankton community among these, Centrales (82.36% to 95.74% at S1; 69.22% to 96.81%) seemed to be the dominant Chrysophytes at both the stations over that of pennate (4.26% to 17.64% at S1; 3.19% to 30.78% at S2) diatoms

Phytoplankton, Coastal continental shelf, Salinity, Chlorophyll

The current study provides valuable insights into the seasonal dynamics and community structure of mesophytoplankton in the coastal shelf waters of the Arabian Sea off Mangalore. The dominance of Chrysophyta throughout the study period, emphasizes the significant role of diatoms in these coastal shelf waters. The observed fluctuations in Cyanophyta and Chlorophyta highlight the influence of freshwater influx on phytoplankton composition. These findings underscore the importance of continuous monitoring of phytoplankton communities as indicators of coastal water quality and ecosystem health. Understanding these dynamics is crucial for managing and conserving the productivity of coastal fisheries, which are directly linked to the health of the phytoplankton populations that form the base of the food web, the present study also will contribute to the valuable information data set on the coastal waters of the west coast of India, for broader understanding of these valuable ecosystems in the face of environmental changes

K. Madhavi, A. Padmanabha, N. Jesintha, N. Chetan and Adnan Amin (2024). Abundance and Composition of Mesophytoplanktonic Community in the Coastal Shelf, Arabian Sea, Karnataka. Biological Forum – An International Journal, 16(6): 198-202