Modelling the seasonal behavior of two functional groups of phytoplankton in a Mediterranean Bay

Abstract

Alfacs Bay is an estuarine bay located in NW Spain, as part of the Ebro river Delta. It has great interest due to the importance of its fishery and aquaculture industries. However, during the last decades, episodes of Harmful Algal Blooms have been repeatedly observed. Analyses of 14 year-long time series have shown a clear seasonal behavior of the two main functional groups of phytoplankton in the bay. Diatoms present a population peak in autumn while dinoflagellates are more abundant in winter and spring. Factors affecting the variability of the different phytoplankton assemblages include inputs of freshwater into Alfacs Bay, which occur from April to October and influence the amount of nutrients and the stability of the water column. We used a zerodimensional N-PP-Z D model with two phytoplankton functional groups to explore the relationships between physico-chemical variability and the behavior of the two main phytoplankton groups in the Bay, with the aim of defining scenarios that can explain the alternation between these groups