L. Edler

Connection between trace metals, chelators and red tide blooms in the Laholm Bay, SE Kattegat: an experimental approach

The influence of the trace metals, copper, aluminum and iron, and of the strong complexing agents, EDTA and NTA, on phytoplankton growth in water from a brackish water bay was investigated through bioassay experiments. A diatom (Skeletonema costatum (Grev.) Cleve) and a dinoflagellate (Prorocentrum minimum (Pav.) J. Schiller) were used as test organisms. The growth of both phytoplankton species was strongly inhibited by copper. This inhibition was generally eliminated by EDTA and NTA. Both phytoplankton species were considerably less inhibited by aluminum than by copper at the same total metal concentration. While S. costatum responded to copper and chelator additions in the same way in sea water samples from different seasons, the growth of P. minimum exhibited pronounced seasonal variation. Other parameters than the values of pCu must be considered in order to account for the experimental results. This work supports the theory that alterations in contents of trace metals and natural chelators in sea water are important factors behind shifts in phytoplankton species composition.

Dinoflagellate distribution in the Southeastern Kattegat during an autumn bloom

Abstract Distribution and density of selected dinoflagellates in relation to the salinity distribution was studied in Laholm Bay, southeastern Kattegat in the autumn 1985. Obvious heterogeneity and patchiness was observed on four sampling occasions during an autumn bloom. During strong west winds some dinoflagellate species accumulated along the salinitygradients towards the coast, while one showed a gradient perpendicular to the salinity gradient. During calm and sunny conditions the dinoflagellates appeared in well defined patches, coinciding with areas of slightly lower salinity. This supports the viewthat.patchiness is size-determined by salinity gradients. The distinct patches formed in the central Laholm Bay covered an area of 21.4 and 8.3 km2 for Proroeentrum minimum (PAV.) SCHILLER and Ceratium furca (EHR.) CLAP. et LACHM. respectively. The calculated patch stability revealed critical patch lengths ranging from 1.2 to 9 km, depending on diffusion scales used. During the stable weather conditions p...