Dynamics of phytoplankton succession in the Ulleung Basin, East Sea (Sea of Japan): the role of vertical mixing

Abstract

Stratification/destratification and vertical mixing and have been recognized as playing an important role in controlling the timing and magnitude of phytoplankton blooms in the upper layer of the ocean. We used a zero-dimensional European Regional Seas Ecosystem Model (ERSEM) to study how changes in vertical mixing affect the dynamics of phytoplankton succession in the Ulleung Basin for the years 2000-2012. The model results showed shallow winter mixing reduced the nutrient supply to the upper layer and led to an early growth limitation of diatoms. On the other hand, shallow winter mixing was responsible for early formation and long duration of dinoflagellate blooms. Furthermore, enhanced stratification during the late winter/spring period resulted in a rapid shift in seasonal succession of phytoplankton from diatoms to picophytoplankton, flagellates and then to dinoflagellates. The temporal variability of phytoplankton communities in response to the changes in vertical mixing therefore was associated with differences in nutrient/light limited growth and differences in grazing. These results suggest that changes in the water column structure by climate change may induce a large shift in phytoplankton community succession and have certain implications for food availability for zooplankton caused by match-mismatch effect. Regional Seas Ecosystem Model (ERSEM) to study how changes in vertical mixing affect the dynamics of phytoplankton succession in the Ulleung Basin for the years 2000-2012. The model results showed shallow winter mixing reduced the nutrient supply to the upper layer and led to an early growth limitation of diatoms. On the other hand, shallow winter mixing was responsible for early formation and long duration of dinoflagellate blooms. Furthermore, enhanced stratification during the late winter/spring period resulted in a rapid shift in seasonal succession of phytoplankton from diatoms to picophytoplankton, flagellates and then to dinoflagellates. The temporal variability of phytoplankton communities in response to the changes in vertical mixing therefore was associated with differences in nutrient/light limited growth and differences in grazing. These results suggest that changes in the water column structure by climate change may induce a large shift in phytoplankton community succession and have certain implications for food availability for zooplankton caused by match-mismatch effect.