Temporal dynamics of the plankton community structure in Madura Strait: Algae bloom study case

In March 2019 there was a phenomenon in the waters around the Suramadu Bridge in the Madura Strait, where surface water appeared in a different color layer. Madura Strait has a surface current with a range of 0.013 - 0.77 m/sec. In the west season to transition I (December- May) surface flows move from West to East and vice versa in the east season to Transition II (June-November) surface currents tend to move from East to West. Madura Strait is a river estuary in the city of Surabaya which tends to have poor / moderate polluted water quality due to the large amount of organic material input into the waters. Both of those causes the Madura Strait tends to have a high concentration of organic matter and primary productivity. Research aims on temporal dynamics in the structure of the plankton community in Madura Straits after blooming algae to analyze the abundance, distribution, diversity, and dominance index with temporal water quality indicators. Water samples were collected using Kitahara net for phytoplankton by filtering from bottom to surface. The density of plankton for each station was measured base on their biovolume bases. Genus of phytoplankton was identified for each station. Phytoplankton community consists of 15-21 species with Chaetoceros sp. as a dominant species. At least five species of Chaetoceros were identified when sea water had a color stratification and declined in subsequent observations. Chaetoceros sp.2 is the dominant species with abundance range 12,018 ind/L - 47,580 ind/L. The diversity index (Shannon Wiener index) shows the waters in poor condition with phytoplankton H'value range 0.2511 - 0.9543, and zooplankton H' value range 1.2566 - 2.0201. The dominance index (D) of phytoplankton 0.5282 - 0.9263 and zooplankton 0.1639 - 0.3882.