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

[ACG40-07] Quantifying nutrient fluxes through the benthic animal burrows at a tidal flat in Kesennuma Bay

Taiyo Yuba¹, Keisuke Takeno¹, Toshimi Nakajima¹, Yumi Henmi², *Ryo Sugimoto¹ (1.Faculty of Marine Biosciences, Fukui Prefectural University, 2.Field Science Education and Research Center, Kyoto University)

Keywords:Ecosystem engineer, Submarine Groundwater Discharge, Land-Sea interaction zone, Upogebia

Burrows of benthic animals are spread across the seafloor in coastal ecosystems worldwide. Although the filtration effect through the burrow of the upogebiid shrimp is thought to be significant in nutrient dynamics in coastal ecosystems, little field survey quantifies nutrient fluxes between the burrow and the overlying water. Here, we show the advective fluxes of water and nutrients from the burrow of Upogebia yokoyai at the tidal flat in Kessennuma Bay, assessed by the handmade small current meter. The water flux from the burrow was 217±83 ml burrow^-1 h^-1 in the spring tide and 523±73 ml burrow^-1 h^-1 in the neap tide. These fluxes were five times higher than the seepage flux from the no-burrow sediment measured by the same current meter. The averaged total fluxes (burrow + no-burrow) of dissolved inorganic phosphorus (DIP) and nitrogen (DIN) from the seafloor were +23.63 mmol m^-2 h^-1 and +1.50×10³ mmol m^-2 h^-1, respectively. Regarding DIN, the fluxes of nitrate and ammonium were negative and positive, respectively. Furthermore, the total fluxes of DIP and DIN from the tidal flat (~2000 m^-2) were 0.89 and 0.65 times higher than those from the rivers. The fluxes from animal burrows accounted for approximately 31% of DIP and 16% of DIN, although burrows occupied only 5% of the seafloor surface in the tidal flat. These results show that animal burrows would be non-negligible nutrient sources in coastal seas.