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[ACG23-02] Variety of impacts of the freshwater-derived nutrients on the marine ecosystem
Keywords:Marine Ecosystem, Freshwater Input, Fishery Resources
Rapidly grown phytoplankton during rainy season due to nutrient-rich freshwater could also contribute to the formation of the hypoxic water mass. Because organic matters derived from phytoplankton are generally labile components, they are accumulated and decomposed by bacteria under the thermocline in summer. Many studies suggest that the content of silica frustules, sulfur compounds such as dimethylsulfoniopropionate (DMSP) and other compounds varies depending on phytoplankton species and environmental conditions, which means that the decomposition rate and oxygen consumption rate in the water column should vary as well. Although this hypoxic water is known to cause mass mortality of benthic organisms, our recent studies suggest that the anaerobic autotrophic bacterial mat itself can be a potential food source for benthic filter feeders and the other organisms at a higher trophic level.
Therefore, to evaluate the impact of freshwater discharge on the fishery resources, it is important to consider various environmental changes and carefully monitor the marine environments in the long-term.