Phytoplankton species potentially Harmful Algal Blooms (HABs) in Jakarta Bay

The occurrence of algal bloom causes problems in many parts of the world, including in tropical Indonesian coastal waters. Harmful algal bloom events in Jakarta Bay have been increased since several years ago and causing massive fish kills which lead to economic losses in local fisheries, a decrease of water quality, and threat to people consuming fish from the bay. Research was conducted in Jakarta Bay in 2008, 2009, 2010, 2011, 2013 and 2015, to study the variability of phytoplankton species that potentially as bloom maker. The samples were taken by 20 μm mesh size plankton net which deployed vertically to a depth of 7 - 10 meter at each station. The results showed that the abundance of phytoplankton ranged from 10⁶ to 10⁸ cells.m⁻³. The population composed of 27 taxa, mostly belong to diatoms and dinoflagellates. We observed there are nine genera of phytoplankton which potentially as harmful algal bloom species, occurring in Jakarta Bay. Three of them are known as the predominant species of algal bloom in this bay, namely: Skeletonema, Chaetoceros, and Thalassiosira. Besides that, there are some species also playing a role in the tragedy of fish-killing due to oxygen depletion during blooms events in Jakarta Bay.