North Atlantic Oscillation primary productivity and toxic phytoplankton in the Gullmar Fjord, Sweden (1985-1996)

The evaluation of the time-series data set of primary production, chlorophyll a (1985-1996) and toxic phytoplankton species abundance measurements (1986-1996) in the Gullmar Fjord as part of the Swedish Monitoring Program, revealed the importance of considering climatic and environmental forces among the factors that may be responsible for the observed fluctuations. The results suggested that the occurrence of toxic phytoplankton blooms in the Skagerrak may be related to changes in the phase of the North Atlantic Oscillation (NAO). The Dinophysis species were related to the NAO, temperature and salinity and the fluctuations in the phytoplankton biomass expressed as chlorophyll a were also shown to be related to the NAO. The results pointed to the need to understand further the role played by climatic and environmental forces in relation to the formation and duration of harmful algal blooms and the need for continuous quality monitoring programmes and novel statistical methods for detecting trends and cycles in ecological time-series related to environmental forces.