Simulation of the spring phytoplankton bloom of the Socheongcho Ocean Research Station in the Yellow Sea using a lower trophic level ecosystem model

Abstract

Investigating the temporal variability of biogeochemical and ecological processes in shelf seas is important for obtaining an in-depth understanding of marine ecosystem. In this study, the lower trophic ecosystem and related variables for the Socheongcho Ocean Research Station (SORS; 37.42 °N, 124.74 °E) waters were simulated using a 1-D physical-biological model (ERSEM-GOTM). The simulation was compared with the observations of total Chl-a concentration, sea surface nutrient concentration, and size-fractionated Chl-a during the spring bloom periods from 2017 to 2020. The observed nitrate and phosphate concentrations were up to ~10 uM and ~1 uM, respectively, before the bloom, and almost depleted after the bloom decline, which was represented in the model as well. The silicate was hardly consumed in the model contrary to the observation, however. In addition, given that 1) the model reproduces the dominance of nanophytoplankton well, 2) the diatoms of SORS are mostly classified as nanophytoplankton, and 3) the physiological properties of diatoms in the model were considered those of microphytoplankton, it can be inferred that the growth of diatoms might be underestimated. To improve this and make the model more universally applicable, the allometric relationships between cell sizes and the functional performance of diatoms were additionally incorporated in the model. We will discuss the universality of the new size-structured dynamics we developed in this presentation.