Olivier Marini

Friday 1st June 12.30
IMAS seminar room, Sandy Bay 

Abstract: 
Nutrients, Phytoplankton, Zooplankton and Detritus (NPZD) models provide a relatively simple means to describe and model the basis of ocean food webs. Based on four essential components, Nutrients, Phytoplankton, Zooplankton and Detritus, these models can be used to capture important ecosystem interactions. The complex dynamics of the water column in the Southern Ocean has a strong influence on primary production and food web dynamics. Satellite chlorophyll a estimates indicate that chlorophyll concentrations are higher towards the north of the SR3 transect (around 52°S), as compared with more southerly latitudes (around 58°S). In order to investigate ecosystem dynamics at these locations, we implemented an NPZD model and performed optimisations for a subset of model parameters. This model was reasonably successful at representing seasonal changes in primary production at both locations, although some features of phytoplankton blooms were not captured. Results from parameter optimisation for these implementations emphasised the importance of zooplankton grazing pressure and nutrients inputs in the system. We explore the relative roles of different forcing variables in influencing NPZD dynamics at different latitudes and provide some suggestions regarding further modelling approaches that might better capture physical-ecological interactions for the region.