Short-term temporal variation in coastal zooplankton communities: the relative importance of physical and biological mechanisms

Drogues were deployed off the coast of Northumberland (north-east England), as they were tracked zooplankton were collected, by four vertical hauls of a UNESCO WP-2 net (200 μm), adjacent to the drogue at hourly intervals Sampling covered a full tidal cycle, at least once each month from February to April, and in July and August 1993. Short-term changes in the community structure (in terms of species composition and abundance) were investigated with respect to the local wind field and tidal advection. It was observed, from a cluster analysis that during horizontal transport, the zooplankton maintained the same community structure for at least three consecutive hours on each sampling occasion [Pearson correlation (r) ≥0.70; P≤0.01] even during periods of high turbulent mixing, driven by wind stress Multiple regression models including parameters of the wind field and the rate of horizontal transport only accounted for a maximum of 52% of the temporal variation in zooplankton community structure. The unaccounted for variation provides the basis for the consideration of the zooplankton as ‘active drifters’ rather than ‘passive particles’, this is discussed.