Simulating Nutrient Uptake Dynamics in Plankton Models: a Case Study for the Cilician Basin Marine Ecosystem

Abstract

The primary productivity in the Cilician Basin is severely constrained by phosphorus limitation due to high N:P ratios in the external nutrient inputs. Therefore, special attention is required when the dynamics of plankton is modelled. Acknowledging that mathematical formulation of nutrient uptake by phytoplankton in ecosystem models is crucial as it determines the degree of realism of the representation of biogeochemical dynamics, a plankton model was developed by utilising two widely adopted approaches; i) Monod nutrient uptake kinetics, and ii) Droop nutrient uptake kinetics, to delineate the seasonality of phytoplankton in an attempt to establish a mechanistic biogeochemical model of the Cilician Basin. The model was validated against field data from Erdemli Time Series stations in the region and differences between the approaches were compared. The model successfully simulated the phosphorus limitation in the basin; however, the scenario with Droop kinetics had a better fit to the field data. Both scenarios reproduced the primary productivity in the region. Overall, the results indicated that implementation of Monod kinetics generally sufficed to represent the seasonality of phytoplankton, whereas in environments with severe temporal nutrient scarcity, i.e. the Cilician Basin, implementation of Droop kinetics is required to represent the phytoplankton dynamics more realistically.