[A-CG51] Coastal Ecosystems-2. Coral reefs, seagrass and macroalgal beds, and mangroves

[ACG51-02] Determination of tropical seagrass nutrient uptake rates and application in ocean-ecosystem numerical modelling

*Yuta A. Takagi¹, Takashi Nakamura¹, Yuichi Kawakami¹ (1.School of Environment and Society, Institute of Science Tokyo)

Keywords:Tropical seagrass, Nutrient uptake, Ecosystem nutrient budget, Numerical modeling

Seagrass beds play an important role in tropical coastal systems. They are often found in shallows between river discharge and coral reefs or intergrown with corals and help to regulate water conditions by sinking nutrients and carbon. This study experimentally determined nutrient uptake rates for Thalassia hemprichii and Halodule uninervis with an eye towards applications in numerical modelling. Seagrasses can uptake nutrients through both their leaves and roots (unlike macroalgae) making it particularly challenging to accurately characterize their ecological nutrient budget and interactions. Samples of the target species were collected from Bise, Okinawa, and a novel methodology was developed to simultaneously and independently measure the nutrient uptake rates of leaves and roots. Uptake rate curves were derived as a function of nutrient concentration, and these equations were implemented in a seagrass ecology module within a holistic numerical ocean simulation system (COAWST). It was found that both leaves and roots contribute a roughly equally significant portion of total seagrass nutrient uptake potential, meaning neither can be discounted in consideration of nutrient uptake dynamics, and both sources must be considered when assessing the water filtering function of seagrasses in ecosystems.