Water Quality and Phytoplankton as Indicator of Coastal Health in the Southeast Coast of Sumenep, Indonesia

This study investigated seasonal variations in water quality and phytoplankton community composition in the coastal waters of East Java, Indonesia, to assess their implications for coastal health. Water samples were collected during wet and dry seasons, and phytoplankton composition, diversity indices, trophic status (using the Nygaard Index), along with key water quality parameters (pH, dissolved Oxygen, salinity, temperature, turbidity, nitrates, and phosphates) were analyzed. Results revealed higher nutrient levels (nitrates and phosphates) during the wet season, coinciding with increased turbidity and lower dissolved oxygen. These conditions corresponded with a shift in phytoplankton assemblages from diatom dominance in the dry season to a more diverse community during the wet season. The Nygaard Index indicated fluctuations between eutrophic and mesotrophic conditions, correlating with observed changes in water quality and phytoplankton composition. These findings suggest a coastal ecosystem susceptible to seasonal variations and nutrient fluctuations, highlighting the importance of integrated coastal management strategies, including regular monitoring and consideration of other ecosystem components, to ensure long-term coastal health and sustainability.