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

The evaluation of the time-series data set of primary production, chlorophy ll a (1985-1996) and toxic phytoplankton species abundance measurements (19 86-1996) in the Gullmar Fjord as part of the Swedish Monitoring Program, re vealed the importance of considering climatic and environmental forces amon g the factors that may be responsible for the observed fluctuations. The re sults suggested that the occurrence of toxic phytoplankton blooms in the Sk agerrak may be related to changes in the phase of the Worth Atlantic Oscill ation (NAO). The Dinophysis species were related to the NAO, temperature an d salinity and the fluctuations in the phytoplankton biomass expressed as c hlorophyll a were also shown to be related to the NAG. The results pointed to the need to understand further the role played by climatic and environme ntal forces in relation to the formation and duration of harmful algal bloo ms and the need for continuous quality monitoring programmes and novel stat istical methods for detecting trends and cycles in ecological time-series r elated to environmental forces.