Distribution of benthic diatom assemblages in the Westerschelde (Zeeland, The Netherlands)

The benthic diatom assemblages of the Westerschelde-estuary were studied by means of multivariate analysis. Two main groups and eight subgroups were distinguished. The relation with salinity and sediment composition was investigated. A clear relation between grain size and the distribution of the assemblages was found

Coccolithophore bloom dynamics shape bacterioplankton community in the northern Bay of Biscay

This is the first study to apply a comparative analysis of environmental parameters, phytoplankton pigment data, and bacterioplankton community structure combined with 16S rRNA clone libraries in an Emiliania huxleyi bloom assemblage, as revealed by denaturing gradient gel electrophoresis (DGGE) and clone libraries. With the majority of the DGGE phylotypes identified, domination by Flavobacteria in the particle-associated bacterial assemblage and by Alfaproteobacteria and SAR86 in the free-living bacterial assemblage was apparent. Stations showed distinct bacterial assemblages, as indicated by ordination of the bacterial community composition. Moreover, changes in particle-associated bacterial assemblage detected by DGGE were weakly yet significantly correlated with changes in phytoplankton community composition

Bacterial community structure during a coccolithophorid bloom in the northern Gulf of Biscay

As part of a study on the ecosystem dynamics and carbon fluxes (PEACE project) during a coccolithophorid (Prymnesiophyceae, Haptophyta) bloom, DNA samples were taken to assess the bacterial community structure associated with the bloom. Here we report on the bacterial community profiles, generated by DGGE fingerprinting of PCR products derived from 16S rRNA encoding genes, of seven different oceanographic stations located near the shelf slope area in the northern part of the Gulf of Biscay, each sampled at six different depths. Both the particle-associated (>3µm) and the free-living size fraction (<3µm) were analysed, showing a marked difference in bacterial community composition between the two size fractions. The bacterial assemblages tend to be specific for a particular oceanographic station, even after a one week sampling interval. Depth related variation in bacterial community profiles appeared only in two of the stations sampled. The influence of environmental variables, such as chlorophyll a, TEP (Transparent Exopolymeric Particles), POC, and PIC concentrations, on the observed variation in bacterial community structure is assessed as well

Ecological implications of life-forms in intertidal benthic diatoms in macrotidal estuaries

Diatom communities inhabiting intertidal estuarine sediments are composed of different life-forms, ranging from adnate epipsammic to free-living epipelic and tychoplanktonic forms. A detailed study of the spatial and temporal distribution patterns of various life-forms in the macro-tidal Westerschelde estuary (South-West Netherlands) revealed that the specific life-form composition of a community has an important influence on its temporal dynamics and might also have major implications for the transfer of diatom-fixed carbon to higher trophic levels. The importance of substrate structure and availability, stochastic (e.g. climate-induced and anthropogenic) hydrodynamic events and the nature and rate of sediment development in regulating the dynamics of these communities are evaluated

Diversity, ecology and the role of protist communities in the Schelde estuary: research by the "Protistology & Aquatic Ecology" group, University Gent (poster)

The section ‘Protistology & Aquatic Ecology’ has been studying the diversity and ecology of planktonic and benthic communities of unicellular eukaryotes (or protists) in the Schelde estuary. The study area involves the entire estuarine gradient, going from the freshwater tidal reaches in the Belgian part of the estuary to the estuary mouth in The Netherlands. Large research efforts were invested in the diversity of protistan communities (diatoms and other micro-algae, heterotrophic flagellates and ciliates) and the biotic and abiotic factors that regulate their structure and composition. In addition, several studies dealt with the role of microbial plankton and benthos in the functioning of estuarine food webs. In these studies, attention was paid to the importance of diversity of microbial communities for fluxes of matter and energy through the estuarine microbial ecosystem. This poster aims at illustrating certain aspects of this research

Late quaternary climate history of Heart Lake and Pup Lagoon (Larsemann Hills, East Antarctica)

Information on East-Antarctic coastal environments during the Holocene is relatively sparse. This is surprising as sedimentary records from the interface between land and sea can provide chronologies of climate change, isostatic uplift, relative sea level and the colonisation of newly formed biomes. Here we examine a sediment core from Pup Lagoon and Heart Lake (Larsemann Hills, East Antarctica). Sediment stratigraphy, fossil pigments and diatoms were used to infer the sequence of Holocene environmental and climate change. Results show that between 5800 and 4785 corr. yr BP the marine coast of Prydz bay was characterized by stratified, open water conditions during spring and summer and seasonally warm conditions. From 4785 to 2615 corr. yr BP sea ice duration in Prydz Bay increased with the coast being ice-free for 2-3 months each year, conditions which are similar to the present day. A return to stratified, open water conditions and a reduction in winter sea ice extent between 2615 corr. yr BP - 2200 uncorr. yr BP is signaled by enhanced biogenic production and more open water diatom taxa