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Diversity and dynamics of protist communities in subtidal North Sea sediments in relation to metal pollution and algal bloom deposition

Boek - Dissertatie

The Belgian Coastal Zone (BCZ) is heavily polluted by trace metals, that pose a potential threat to the marine ecosystem in the area, including to humans (a.o. via fisheries). Trace metals accumulate in silty, organically enriched sediments and changes in the environment can lead to the resuspension of the metals, with the activity of the benthic microbes as one potential factor influencing the release of TM into the water column. Benthic microbial activity and dynamics in turn are regulated by the availability of growth substrates, and sedimentation of phytoplankton blooms represents a major source of organic material for the benthic biota in subtidal areas. It remains unclear however, how microbial communities, phytodetritus deposition and TM behaviour interact in subtidal sediments. We aimed to obtain a better insight in the interactions between microbial communities, metal contaminants and algae-derived organic matter in contaminated sediments of the BCZ. Our study focussed on protist (unicellular eukaryotes) communities, which are largely understudied but ecologically very important since they occupy a central position in the benthic food webs, especially in the microbial loop. Both field studies and microcosm experiments were performed, and molecular fingerprinting techniques (18S rDNA and rRNA- based DGGE and clone libraries) were used to characterise protistan diversity and dynamics in the contaminated sediments. A high diversity was found, with members ecologically important as primary producers (mainly diatoms), grazers (Rhizaria, Alveolata, Amoebozoa, heterotrophic stramenopiles), saprobes (Fungi) or pathogen/parasites (e.g. Marine Alveolates Group I, Pirsonia sp.). Our results showed that phytoplankton deposition after the spring algal bloom stimulates microbial activity and activates the development of the microbial loop, and a positive link is suggested between this increased microbial activity and the observed increased mobilisation and upward metal fluxes. Moreover, we found indications that the diversity and structure of the protistan communities in these sediments are affected by the trace metals, as evidenced by both the field and experimental data.
Aantal pagina's: 1
Jaar van publicatie:2011