Understanding the mechanisms of the interannual variability of phytoplankton in the Ulleung Basin, East Sea: A modeling study

Abstract

We investigated the seasonal dynamics of phytoplankton responding to the changes in the mixed layer depth andatmospheric deposition in the Ulleung Basin for the years 2001-2012. To address the effect of vertical mixing andatmospheric deposition on interannual variability of phytoplankton communities, we used a zero-dimensionalEuropean Regional Seas Ecosystem Model (ERSEM). We compared the years of deep winter mixing with theyears of shallow winter mixing during the period. The model results showed that the deep winter mixing increasedthe nutrient supply to the upper layer. It led to a better growth of diatoms. On the other hands, the shallowwinter mixing advanced the initiation of spring blooms of diatoms because of enhanced light availability butreduced the production in spring by poor nutrient supply. Also the model indicated that the nutrient supply byatmospheric deposition controls the phytoplankton community in warm season. but it had little effect on regulatingthe phytoplankton blooms. These results suggest that in the Ulleung Basin, the balance between the verticalmixing and the atmospheric deposition process can induce a shift in phytoplankton communities. We discuss theimplication of this results in light of climate change and anthropogenic N production.position on interannual variability of phytoplankton communities, we used a zero-dimensionalEuropean Regional Seas Ecosystem Model (ERSEM). We compared the years of deep winter mixing with theyears of shallow winter mixing during the period. The model results showed that the deep winter mixing increasedthe nutrient supply to the upper layer. It led to a better growth of diatoms. On the other hands, the shallowwinter mixing advanced the initiation of spring blooms of diatoms because of enhanced light availability butreduced the production in spring by poor nutrient supply. Also the model indicated that the nutrient supply byatmospheric deposition controls the phytoplankton community in warm season. but it had little effect on regulatingthe phytoplankton blooms. These results suggest that in the Ulleung Basin, the balance between the verticalmixing and the atmospheric deposition process can induce a shift in phytoplankton communities. We discuss theimplication of this results in light of climate change and anthropogenic N production.