|Potential risk of organic micropollutants on marine phytoplankton in the greater North Sea: integration of modelling and experimental approaches|
Everaert, G. (2015). Potential risk of organic micropollutants on marine phytoplankton in the greater North Sea: integration of modelling and experimental approaches. PhD Thesis. Ghent University: Ghent. ISBN 978-90-5989-793-9. 175 pp.
A complex chemical cocktail, with unknown composition and concentrations, is present in marine waters. Although the awareness of the vulnerability of marine ecosystems to pollution induced changes increased, the ecotoxicological effects of chemical pollutants on marine ecosystems are poorly understood. Even in intensively monitored regions such as the North Sea, current knowledge of the ecotoxicological effects of chemicals is limited to few (priority) substances and few (model) species (discussed in chapter I). To partly address this knowledge gap, in the present work, using phytoplankton, it is assessed how marine ecosystems respond to the presence of organic chemicals. By analyzing existing data and performing laboratory experiments, ecotoxicological effects of organic chemicals to marine organisms and ecosystem functions are quantified. Specific aims of this work are: (1) to infer spatiotemporal trends of concentrations of organic chemicals; (2) to investigate the impact of primary and secondary emissions on the spatiotemporal trends of organic chemicals; (3) to examine the partitioning of organic chemicals in different environmental compartments; (4) to assess the potential ecotoxicological effect of realistic mixtures of organic chemicals along environmental gradients; and (5) to quantify the relative contribution of organic chemicals to the phytoplankton growth dynamics. Spatiotemporal trends of polychlorinated biphenyl (PCB) concentrations are inferred based on an extensive set of concentrations monitored between 1991 and 2010 in sediments of the Belgian Coastal Zone (BCZ) and the Western Scheldt estuary in chapter II. The time trends unravel two to three-fold PCB concentration decreases in the BCZ during the last 20 years. In the Western Scheldt estuary, time trends are spatially heterogeneous and not significantly decreasing. These results demonstrate that international efforts to cut down emissions of PCBs have been effective to reduce concentrations in open water ecosystems like the BCZ but had little effect in the urbanized and industrialized area of the Scheldt estuary. Most likely, estuaries are subject to secondary emissions from historical pollution.