The occurrence of phytoplankton blooms in Jakarta Bay has increased significantly, and resulted in, the mass mortality of fish and other organisms. Phytoplankton bloom events are indicated by a change in the color of the sea's surface. Generally, phytoplankton growth is influenced by the levels of nutrients in the water, while spatial distribution is influenced by the pattern of the current. In connection with this phenomenon, research was conducted in 2010, 2011 and 2013, to determine the abundance and distribution of phytoplankton and their connection with the N/P ratio. The results showed that the abundance of phytoplankton ranged from 40x10 6 cells/m 3 up to 1699.1x10 6 cells/m 3 , with the highest recorded data was during the east monsoon in 2010 and the lowest during the first transition period of 2011. The predominant phytoplanktons were frequently diatoms such as Skeletonema, Chaetoceros and Thalassiosira. The distribution of phytoplankton seemingly follows the nutrient concentration ratio where phosphate acted as the limiting factor and nitrogen as the triggering factor. The higher the N/P ratio, the more potentially uncontrolled growth of phytoplankton occurred. When the availability of nutrients increased an increase in total algal biomass occurred, however, the alteration in nutrient composition led to a change in composition of community.

The frequency of algal bloom's event has been increased in Jakarta Bay, recently. Most of the bloom events were tend to be reoccurred after the rainy season. The research was conducted from 2008 until 2015 to study the linkage of nutrients and the ratios on the growth of the phytoplankton population. Collecting samples were conducted using a canonical plankton net of 20 µm mesh size, 125 cm length and 30 cm diameter of the opening mouth. The results of the study showed that the concentration of phosphate in the waters ranged from 0.01-12.5 µg/l (average 4.58 µg/l) and nitrate ranged from 0.01-15.89 µg/l (average 0.72 µg/l). The N/P ratio during the study ranging from 0.2 up to 45.4. High ratios of nutrients were mostly recorded in 2010 where the overall abundance of phytoplankton is very high. There is a strong correlation of N/P ratio with the community structure or composition of the phytoplankton population. The variability of phytoplankton abundance appears to be related to nutrient ratios of nitrate and phosphate.

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Margalefidinium polykrikoides , an unarmored dinoflagellate, was suspected to be the causative agent of the harmful algal blooms – associated with massive fish mortalities – that have occurred continually in Lampung Bay, Indonesia, since the first bloom event in October 2012. In this study, after examination of the morphology of putative M. polykrikoides -like cysts sampled in bottom sediments, cyst bed distribution of this harmful species was explored in the inner bay. Sediment samples showed that resting cysts, including several morphotypes previously reported as M. polykrikoides , were most abundant on the northern coast of Lampung Bay, ranging from 20.6 to 645.6 cysts g -1 dry sediment. Molecular phylogeny inferred from LSU rDNA revealed that the so-called Mediterranean ribotype was detected in the sediment while M. polykrikoides motile cells, four-cell chain forming in bloom conditions, belonged to the American-Malaysian ribotype. Moreover, hyaline cysts, exclusively in the form of four-cell chains, were also recorded. Overall, these results unequivocally show that the species M. polykrikoides is abundantly present, in the form of vegetative cells, hyaline and resting cysts in an Indonesian area.

Harmful algal blooms (HABs) cause various problems, such as water quality degradation, fauna mass mortality and impairment of human health. Water quality monitoring in Lampung Bay has been conducted by Lampung Marine Aquaculture Office (BBL) of the Ministry of Marine Affairs and Fisheries since 1994. Occurrence of Pyrodinium bahamense var. compressum (Pbc), a causative organism of paralytic shellfish poisoning (PSP), has been recorded but threats caused by HABs have never been reported. A study aimed to know the level of public knowledge and awareness about HABs in Lampung Bay has been conducted. The components of group respondents consisted oflocal governments, academics and coastal communities. Awareness from each component was examined includinggeneral HAB knowledge, HAB impact to the community, HAB occurence and local knowledge of HAB. Data of HAB knowledge were collected through questionnaire and focus group  discussion. The result showed that 40.5% of respondents had knowledge of HABs phenomena and 51.3% respondents only know signs or indicators of HAB occurrence, while only 1.4% respondents had knowledge of local HAB occurences. The direct impact of HABs to the community was not commonly known by the respondents. Only a few cases of poisoning after eating seafood were reported. It can be concluded that there was lack of public knowledge and awareness on HABs in LampungBay. Intensive public awareness programs about HABs should be conducted in order to reduce risk towards HABs in Lampung Bay.