16:00 〜 16:15
[ACG38-08] Modeling the effect of terrestrial nutrients on phytoplankton communities in coral reefs from field-based incubation experiments
キーワード：phytoplankton, incubation experiment, ecosystem modeling, terrestrial nutrient input, coral reefs, interdisciplinary research
Coral reefs around the world are facing significant impacts by climate change and socio-economic development. Although seemingly disconnected, terrestrial human activities such as agriculture, livestock farming, and urbanization, have important consequences in marine coastal areas. Particularly, excessive nutrient and sediment inputs into the ocean are becoming important stressors and causing changes in the ecosystem functioning and balance. Within these areas, phytoplankton organisms play a fundamental role in linking inorganic nutrients with both planktonic and benthic food webs. By understanding phytoplankton dynamics and their responses to terrestrial inputs, we can unravel the effects and connections shaping marine coastal ecosystems from the base, while quantifying their influence in higher-scale processes, including carbon and material cycling. In this study, a natural phytoplankton community from a coral reef area in Ishigaki Island (Okinawa, Japan), was used to test their responses to terrestrial nutrient input. To achieve this, phytoplankton incubation experiments were conducted under natural conditions in the field and enriched with varying concentrations of nitrate (NO3-), phosphate (PO43-), and silica (SiO2). The results showed a strong co-limitation of nutrients on phytoplankton growth with direct effects on the community composition, size structure, chlorophyll-a concentration, and carbon biomass. Additionally, numerical simulations were conducted to replicate the phytoplankton dynamics (low-trophic ecosystem) and to estimate possible scenarios under diverse nutrient conditions. This interdisciplinary research integrates field-based experimental findings with ecosystem modeling to quantify the effects of terrestrial influences on marine coastal areas. Hence, this approach offers a comprehensive analysis that facilitates the study of complex ecosystems such as coral reef areas.