Using long-term monitoring to investigate the changes in species composition in the harbour of Ghent (Belgium)
The macroinvertebrate community of the harbour of Ghent was studied by analysing 135 samples taken at different sampling locations from 1990 until 2008. The results showed that the current Crustacea and Mollusca communities are mainly represented, in terms of abundances, by alien species. In total, seven alien and four indigenous crustacean species were found. Mollusc diversity was higher, with a total of 14 species, four of which were alien. Macroinvertebrate diversity was very low at the beginning of the 1990s, but increased due to the improvement of the chemical water quality achieved by sanitation and stricter environmental laws. This is reflected by the dissolved oxygen concentration, which increased from an average of 2 mg/l to an average of 9 mg/l, allowing more sensitive species to establish. Since 1993, the number of alien taxa has augmented, whereas the number of native taxa has remained stable. The improvement of the chemical water quality and the simultaneous increase in total number of species were also reflected in an increase of the Multimetric Macroinvertebrate Index Flanders, which is used to assess the ecological water quality in Flanders. Due to intensive international boat traffic and the low species diversity, the harbour of Ghent is highly vulnerable for invasions. Stronger regulations and a better understanding about the contribution of shipping, shortcuts via artificial water ways, habitat degradation and environmental pollution are required to reduce the further spread of alien species.
KeywordsAlien species Macrocrustaceans Molluscs Water quality
We would like to thank the Flemish Environment Agency (VMM) for the opportunity to provide data, and Joost Mertens from the Flemish Environment Agency for providing information about the sampling sites. We would also like to thank Rose Sablon of the Royal Belgian Institute of Natural Sciences for the assistance during the study of the collection. Koen Lock is currently supported by a post-doctoral fellowship from the Fund for Scientific Research (FWO-Vlaanderen, Belgium).
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