[A-HW32] [EE] Biodiversity, nutrients and other materials in ecosystems from headwaters to coasts

[AHW32-08] Quantification of phosphorus and nitrogen uptake in a tropical freshwater ecosystem in Southeast Asia suggests N limitation

*Irisse Bianca Baldovino De Jesus¹, Jonathan Carlo A Briones^1,2,3, Osbert Leo A Privaldos⁵, Elfritzson Martin Peralta², Yoshitoshi Uehara⁷, Takuya Ishida⁷, Adelina Santos Borja⁵, Francis S Magbanua⁴, Rey Donne S Papa^1,2,3, Tomoya Iwata⁶, Noboru Okuda⁷ (1.University of Santo Tomas (UST) - Graduate School, 2.UST - Research Center for Natural and Applied Sciences, 3.UST - College of Science, 4.University of the Philippines, Diliman - Institute of Biology, 5.Laguna Lake Development Authority, 6.University of Yamanashi - Faculty of Life and Environmental Sciences, 7.Research Institute for Humanity and Nature)

Keywords:Tracer Addition for Spiralling Curve Characterization, Philippines, nutrient dynamics

Nitrogen and phosphorus kinetics plays an essential role in the sustainability of watersheds but their increased availability also brings adverse impacts to water quality, species diversity, human health and ecosystem balance. This study reports on nitrogen limitation in headwater streams in Silang-Santa Rosa Subwatershed (SSRS). Moreover, this is the first attempt in studying nutrient spiralling in Philippine headwater streams using Tracer Addition for Spiralling Curve Characterization (TASCC). Phosphorus uptake kinetics showed shortest uptake length (Sw_amb = 25.27m), highest aereal uptake rate (U_amb= 37.46 mg-P/m²/min) and uptake velocity (Vf_amb = 162.12 mm/min) in an agricultural site and longest uptake length (Sw_amb= 109.24m), lowest aereal uptake rate (U_amb= 0.31 mg-P/m²/min) and uptake velocity ( Vf_amb =2.76 mm/min) in a residential site. Nitrogen uptake showed undetected peaks that is suspected as N limitation supported by significant correlations for U_amb-P and NH₃ (R=0.919, 95%) and N:P ratio (0.4923). Overall, this research aids in the Philippine land use planning and watershed management for ecological sustainability and serves as a contribution in tropical studies particularly in nutrient dynamics.