Eutrophication and distribution of dinoflagellates as an indicator of water quality in the Probolinggo coast, East Java, Indonesia

Eutrophication can trigger the spread of phytoplankton which is toxic and dangerous for the other aquatic biota. Dinoflagellates are a type of plankton that is dangerous and toxic. This study aimed to analyze the status of eutrophication and distribution of dinoflagellates in the coastal waters of Probolinggo, East Java. The method used in this study is a survey method with descriptive data analysis. The research was carried out in June-September 2022, during a period which is divided into two seasons, namely the west season and the east season. The results obtained were the level of eutrophication in the Mayangan and Binor waters, included in the oligotrophic to eutrophic category. The distribution of dinoflagellates in Mayangan from June to September comprises Alexandrium, Gambierdiscus, Glenodinium, Gymnodinium, Pyrodinium, Prorocentrum, Ceratium, Peridinium, Dinophysis, Ostreopsis, and Amphidinium. The distribution of dinoflagellates in Binor from June to September comprises Scrippsiella, Amphidinium, Alexandrium, Glenodinium, Protoperidinium, Dinophysis, Cochlodinium, Gymnodinium, Bysmatrum, Peridinium, Ceratium and Pyropharus. The abundance of phytoplankton in Mayangan and Binor waters consisted of 81–11,214 cells ml^-1. Mayangan and Binor waters showed almost the same water quality characteristics between locations and seasons. Nitrate and phosphate affect the abundance of dinoflagellates in both Mayangan and Binor waters, while temperature and pH only affect the abundance of dinoflagellates in Binor waters. The conclusion of this study is the high level of eutrophication in Mayangan and Binor waters resulting in several species of dinoflagellates that can endanger the environment. Therefore, it is necessary to control the quality of water and nutrients that enter the waters on a regular basis to protect the aquatic environment, especially the coastal areas of Probolinggo, by avoiding high eutrophication and an abundance of harmful phytoplankton such as dinoflagellates.