Diatoms as a bio-indicator for the coastal environment changes in Pasarbanggi mangrove conservation area, Rembang, Central Java

Abstract The coastal area of Pasarbanggi, Rembang has experienced significant coastline changes in the last 30 years. Changes in the stability of coastal ecosystems can be tracked by using bio-indicators whose traces are recorded in sediment. This research was conducted to determine changes in the ecosystem in the Pasarbanggi coastal area and its relationship to mangrove development using diatoms as the bio-indicator. Diatoms data is calculated to determine the abundance and diversity of its individuals. Based on the diatoms analysis, it is known that in the interval 26–50 cm, the abundance of diatoms is dominated by freshwater species, including Cyclotella meneghiniana and Cyclotella ocellata. From the satellite image, in 2002, the mangrove area has not developed yet and the sedimentation process is dominant. In the layer above it, at intervals of 1-25 cm, the sediment deposited in marsh environment. The diatoms diversity increased with the emergence of brackish and marine diatoms such as Tribionella granulata and Amphora coffeaeformis . In satellite imagery from 2018 to 2022, it appears that the development of mangrove area is significant. This shows that along with the mangrove development, there is an increase in ecosystem stability characterized by an increase in the diversity of diatoms species.