Phytoplankton functional groups and harmful algae species in anthropogenically impacted waters of the NW Mediterranean Sea

Abstract

Phytoplankton assemblages were analysed by multivariate analysis techniques in highly modified waterbodies (harbours) of the northwestern Mediterranean Sea over an annual cycle. The phytoplankton functional groups that characterise these anthropogenically impacted waters were identified and related to HAB events. Four functional groups can be distinguished from the analysis: (1) bloom-forming dinoflagellates, (2) winter diatoms, (3) summer-autumn diatoms, and (4) large dinoflagellates and elongated diatoms. The species that characterise these functional groups occurred at all sampling stations. Potentially harmful species are distributed through all the clusters. However, bloom-forming dinoflagellates occur particularly in large harbours and during summer months. The results indicate that: (1) functional groups indicate where and when there is a high risk of blooms, but they cannot determine the risk of a toxic or fish-killing event; and (2) large harbours in tideless seas must be considered as areas with a high risk of high-biomass bloom occurrences.