Role of vertical mixing and atmospheric deposition in controlling the phytoplankton community in the Ulleung Basin, East Sea: a modeling study

Abstract

We used a zero-dimensional European Regional Seas Ecosystem Model (ERSEM) to investigate the interannual variability of phytoplankton in response to the changes in the vertical mixing and atmospheric deposition in the Ulleung Basin for the years 2001-2012. The model results show that the changes in winter vertical mixing had varying effects on the competitive advantages of phytoplankton functional types and thereby altered the composition of phytoplankton functional types in the mixed layer. The model results also indicate that the changes in the balance of nutrient supply from external sources could influence the composition of phytoplankton functional types. With the increase in atmospheric deposition, the picophytoplankton and the flagellates increased in summer, whereas the dinoflagellates and the diatoms relatively decreased. For this period, relative contribution of vertical mixing, atmospheric deposition and Tsushima Warm Current&#8722 transport to the annual nutrient supply to the surface layer was estimated 59.10:2.83:38.07%. These results suggest that the changes in the balance between nutrient sources may induce a significant shift in phytoplankton community. We discuss the implication of these results in light of climate change and anthropogenic nitrogen production.years 2001-2012. The model results show that the changes in winter vertical mixing had varying effects on the competitive advantages of phytoplankton functional types and thereby altered the composition of phytoplankton functional types in the mixed layer. The model results also indicate that the changes in the balance of nutrient supply from external sources could influence the composition of phytoplankton functional types. With the increase in atmospheric deposition, the picophytoplankton and the flagellates increased in summer, whereas the dinoflagellates and the diatoms relatively decreased. For this period, relative contribution of vertical mixing, atmospheric deposition and Tsushima Warm Current&#8722 transport to the annual nutrient supply to the surface layer was estimated 59.10:2.83:38.07%. These results suggest that the changes in the balance between nutrient sources may induce a significant shift in phytoplankton community. We discuss the implication of these results in light of climate change and anthropogenic nitrogen production.