Modulation effects of different dissolved nitrogen compositions on the phytoplankton community structure based on combined field experiments and the NbPD model in Jiaozhou Bay

Abstract

The dissolved nitrogen (DN) regime in Jiaozhou Bay (JB) has shifted recently, and the phytoplankton community structure showed decreased diatom and increased dinoflagellate concentrations. This study combined field microcosm experiments, the Nutrients–bi-Phytoplankton–Detritus (NbPD) biogeochemical model, and statistical analysis, and obtained some results. The growth/death of dominant phytoplankton populations were comprehensively determined by the processes of nutrient uptake, excretion and decomposition of phytoplankton in JB. Kinetic parameters indicated that Skeletonema costatum preferentially absorbed NH4-N and NO3-N, while Protoperidinium pellucidum preferentially absorbed domestic-derived dissolved organic nitrogen. Moreover, S. costatum, as R-strategists, needed a faster uptake rate and slower excretion rate to achieve high growth efficiency but with faster decomposition, while P. pellucidum, as K-strategists, could maintain stability with a more active metabolism. Overall, this study discussed the key factors modulating the diatom dinoflagellate community structure changes in JB, providing a scientific basis for ecosystem-based management.