Algae bloom is one of the symptoms of eutrophication process in an estuary, causing in some ecological and societal problems for the aquatic environments and human activities. Algae blooms observation was conducted in the dry season period between 2014 to 2016, in an eutrophic embayment of Jakarta Bay, Indonesia. Observations were made by conducting transect-boat survey and plankton sampling once the bloom was observed. Samples of chlorophyll-a and net plankton were taken and measured in the laboratory for phytoplankton biomass analysis, cell counting, and identification of bloom-forming species. In the 3 consecutive years of observation, the most frequent bloom-forming species observed were Skeletonema costatum, Pseudonitzschia Spp., and Noctiluca scintillans, The most frequent location of the blooms observed was in the inner part of the bay, in the area in front of Marunda, Ancol and Angke. Phytoplankton biomass during the bloom events were ranged between 126.3 to 232.3 μg Chl-a L−1, with the highest was in 2015 of during the Skeletonema costatum bloom. Blooms were also observed but in low frequency and low biomass at the middle part of the bay off Marunda coastline area. Cell phytoplankton counting were ranged from 1.139 ϗ 106 cell L−1 to 7.893 ϗ 106 cell L−1. During period of surveys, there was no mass mortality of fishes were detected.

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Coastal degradation can be determined as mangrove destruction and water quality degradation. Erosion and accretion are the impacts of mangrove destruction in coastal areas. Ecosystem condition and coastal environment destruction were analyzed in Tangerang coastal areas. Soil, mangrove vegetation, and water quality analysis were carried out in this study. Soil quality was analyzed descriptively. Mangrove vegetation and water quality were analyzed with the Important Value Index and STORET Index, respectively. The results indicated that the coastal of Tangerang is damaged both in terms of mangrove and water quality. The causal analysis showed that the damage to the coastal environment in Tangerang is largely influenced by the high amount of plastic, domestic, and industrial waste. Management recommendations that can be carried out on the coast of Tangerang are silvofishery management and mangrove planting right behind the wave breaker.