Impacts of Mesoscale Eddies on Biogeochemical Variables in the Northwest Pacific

Mesoscale eddies play an important role in regulating biogeochemical cycles. However, the response of variables to cold and warm has not been well elucidated, mainly due most previous studies relying on remote sensing techniques lacking situ observations below surface water. Here, we used hydrographic biochemical data from one survey northwestern Pacific document vertical structure two eddies. We first compared changes key eddy core relative outside, explained layers (the mixing depth, pycnocline, nutricline, euphotic) causing these changes, then analyzed main environmental factors affecting chlorophyll a (Chla) phytoplankton communities. Finally focused mechanisms The results showed that biological (Chla, microphytoplankton, picophytoplankton), salinity, dissolved inorganic nitrogen (DIN), phosphate (DIP), silicate (DSi) increased by 0.2–134%, while core, they decreased 0.2–70% outside. were able force deep maximum (DCM), which rose or fell with nutricline euphotic depth (Zeu) as whole. Cold raised thermocline could lead about 20 m elevated DCM enhanced biomass when coincident. In contrast, drove isopycnals downward, resulting 10–25 drop decrease nutrient Chla concentrations at center significant difference community between outside might be direct influence both stoichiometry changes. contribution microphytoplankton total was much smaller than picophytoplankton oligotrophic waters where DIN:DIP DSi:DIN ratios are significantly low. Compared nutrients, photosynthetically active radiation (PAR) factor controlling abundance attributed Zeu being consistently deeper mixed (Zm), whereas it likely limiting distribution community.