Predicting the seasonality of North Sea zooplankton

Phenology and seasonality of the population response patterns of marine Zooplankton provide a measure of the impact of climatic forcing upon the ecosystem, as most metazoans in the sea are periodically planktonic, usually in their propagative phase. The global warming expectancy suggests intensified consideration of this aspect of ecosystem research. On the basis of the “Helgoland Roads Zooplankton” time-series, such population specific investigations have been carried out. They suggest that temperature and wind stress modify the beginning, end, length and intensity of the seasonality of Zooplankton populations. Climatic forcing and solar irradiation forcing of the production driven trophic cycles are basically independent of each other. The response patterns vary, depending on the life-cycle strategy of each population. Positive and negative correlation with water temperature occur, as well as larger or smaller deviations from multi-annual means, and distances from the times of greatest temperature impact and population responses. Examples are given for the different kinds of response. The results are discussed with respect to the influx of the NAO and to the annual recruitment of marine metazoans.