[A-CG40] Coastal Ecosystems - 1. Water Cycle and Land-Ocean Interactions

[ACG40-P02] Effects of fresh groundwater springs on phytoplankton primary productivity in a volcanic sandy beach

Kana Harada¹, *Ryo Sugimoto¹, Toshimi Nakajima¹, Osamu Tominaga¹ (1.Faculty of Marine Biosciences, Fukui Prefectural University)

Keywords:Submarine groundwater discharge, 13C isotope tracer, Field experiment

Research on how SGD nutrients impact marine biota has increased in recent years. The documented response of marine organisms to SGD is quite variable and site-specific, and can be positive or negative from a population or community perspective. Additionally, the response to SGD is sometimes unclear and could change depending on the specific location or time of the year. The most documented response to SGD-derived nitrogen and phosphorus loading is related to increasing the primary productivity of phytoplankton or microphytobenthos. However, in some cases, no response was found near sites receiving fresh groundwater springs, indicating SGD loading does not always induce an increase in primary productivity. Here, we present the phytoplankton primary productivity around fresh groundwater springs in the Chokai volcano coast assessed by the field experiments. Although fresh groundwater springs were significant nutrient sources, the primary productivity of phytoplankton decreased with increasing groundwater impact, possibly due to physical and physiological disturbances such as low salinity and temperature.