Analysis and interpretation of recurrent spatio-temporal patterns in zooplankton dynamics: a case study on Noctiluca scintillans (Dinophyceae) in the German Bight (North Sea)

Data from theHelgolandRoads time series and from two series of quasi-synoptical zooplankton surveys in 1979 and 1984 were analysed with respect to recurrent patterns of dynamics of the dinoflagellate Noctiluca scintillans. Based on a Lotka–Volterra model, the patterns were interpreted in terms of potential interactions. The work was conducted as a comparative analysis consisting of spatial, temporal moving window correlations and cross-correlations. In a reverse of the principle of spacefor-time substitution in ecosystem analysis, space-andtime concordance of results was applied to indicate the relevance of interactions in time and space. A time series model on intra-annual dynamics significantly reproduced the dynamics of N. scintillans in 1979 and 1984. Results indicate that the dynamics of N. scintillans populations were linked to the population dynamics of Pleurobrachia pileus (Ctenophora), Sagitta spp. (Chaetognatha), hydromedusae, especially Rathkea octopunctata and Lizzia blondina, and copepod nauplii. Evaluation of historical data sets from the Wadden Sea and the Bulletin Trimestrial series supported the statistical analysis. A food web model for the postulated relationships is discussed. The statistical method did not allow us to distinguish between predatory or competitive interactions.