Supriyadi Supriyadi

The diel variations of viruses (< 0.2 μm), picoplankton (0.2—2 μm; heterotrophic bacteria, Syn-echococcus spp., Prochlorococcus spp. and picoeukaryotes) and nanoplankton (2—20 μm; hetero-trophic nanoflagellates and pigmented nanoflagellates) were investigated for 2 days with about 4 hours of temporal sampling in spring 2024 in coastal surface waters of the subtropical western Pacific. A period of wind change associated with rain and increased turbulence, disrupted diel patterns of the overall microbial communities during the second cycle. The abundance of bacteria did not follow a consistent diel pattern, while viral abundance positively correlated with bacterial abundance. Synechococcus spp. and Prochlorococcus spp. grew during the light period and with peak abundance at night, exhibited marked diel variability, however, opposite patterns were observed in picoeukaryotes. According to Synechococcus spp. and Prochlorococcus spp. diel changes, nano-flagellate grazing could control their abundances and may explain temporally varying picocyanobacteria abundances. As we observed in the culture experiments, the results showed a significant increase in picoeukaryotic abundance from noon to nighttime, and a decrease in bacterial abundance during nighttime, to show the prey-predator cycle. Our study suggests picoeukaryotes could serve as bacteria predators by being mixotrophs. Future studies aiming to understand the interactions between prokaryotes and picoeukaryotes within marine microbial communities should take these differences into account.

We used flow cytometry to follow diel variations of viruses, picoplankton, and nanoflagellates for 2 days with about 4 hours of temporal sampling in spring 2024 in coastal surface waters of the subtropical western Pacific. An event of wind change, associated with rainfall and increased turbulence, disrupted diel patterns of the overall microbial communities during the second cycle. We observed that bacterial abundance did not follow a consistent diel pattern and that viral abundance was positively correlated with bacterial abundance. Synechococcus spp. and Prochlorococcus spp. grew during the light period and with peak abundance at night, exhibited marked diel variability, however, opposite patterns were observed in picoeukaryotes. According to Synechococcus spp. and Prochlorococcus spp. diel changes, nanoflagellate grazing could control their abundances and may explain temporally varying picocyanobacterial abundances. As we observed in the culture experiments, the results showed a significant increase in picoeukaryotic abundance from noon to nighttime, and a decrease in bacterial abundance during nighttime, to show the prey-predator cycle. Our study suggests picoeukaryotes could serve as bacteria predators by being mixotrophs. Future studies aiming to understand the interactions between prokaryotes and picoeukaryotes within marine microbial communities should take these differences into account.

Atapupu is a coastal area that has a strategic location because it is directly adjacent to the country of Timor Leste. This study aims to analyze the differences in marine culture at Atapupu Beach in supporting the blue economy in maritime security. This study uses a qualitative method with a descriptive approach. The data source comes from primary data by interviewing local and migrant fishermen and secondary data comes from journals. Data analysis in this study used descriptive qualitative. This study found that the differences between the local and migrant fishermen could be differentiated based on their time to go to sea, the fishing gear, and the type of boat used by the fishermen. The migrant fishermen, which come from Buton, are Muslim, so they do not go to sea on Fridays due to Fridays Prayers. They use fishing rods as gear and bigger boats than the local fishermen. Meanwhile, the local fishermen have no special days to go to sea, they go to sea depending on the weather conditions. The local fishermen only use nets as fishing gear and their boats are smaller compared to the migrant fishermen’s boats. These conditions are affecting their range of fishing areas, the type of fish caught, and the average income per month. Cultural differences at sea between local and migrant fishermen will certainly affect maritime security in the blue economy sector. The existence of differences in types and income from catches can lead to less optimal utilization of fishery resources.