|Monitoring van exotische macro-invertebraten in de Vlaamse havens|
Hebbelinck, L. (2010). Monitoring van exotische macro-invertebraten in de Vlaamse havens. MA Thesis. Universiteit Gent. Faculteit Bio-ingenieurswetenschappen: Gent. 87 pp.
Marien; Brak water; Zoet water
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In recent years increased attention has been paid to the worldwide spread of non-indigenous species due to the potential severe consequences for the global biodiversity and the functioning of ecosystems, the economy and the society. The fast worldwide spread of exotic species is mainly due to the growing international traffic of cargo vessels, which introduce non-indigenous species in brackish water systems around the world by means of their ballast water. A high number of international important harbors are located in these brackish water areas and form important stepping stones in the invasion process of many exotic species. In this masterthesis a profound analysis of the current macrobenthos community in brackish water systems was conducted, based on own collected data in four harbors along the Belgian coast. Several research hypotheses were formulated, which deal with several potential decisive parameters in the introduction, establishment en subsequent spread of exotic species. The influence of the salinity, the chemical water quality, hydromorphological characteristics of the environment and the type of shipping traffic on the success of the introduction, establishment and further expansion of the sampled exotic species was investigated. De exotic macrobenthos community in the brackish water systems is dominated by the species Hemigrapsus penicillatus, Caprella mutica, Dikerogammarus villosus and Gammarus tigrinus. The Site-Specific Biocontamination Index reveals that the present non-indigenous species in the sampled watercourses along the Flemish coast have a significant effect on the indigenous community. Moreover, the more inland waterways and artificial canals seem to be more sensitive to invasion, while the actual harbors seem more or less resistant. The research about the influence of the salinity reveals the importance of this parameter in the presence and spread of exotic species. The abundance, diversity (Shannon-Wiender index) and biomass of non-indigenous species reaches a maximum at a salinity between 2 and 5 gNaCl/L, which coincides with the minimum in the abundance, diversity (Shannon-Wiener index) and biomass of the indigenous species. Thereby most of the exotic species present in the sampled brackish water systems are characterized by a great salinity tolerance, which facilitates the establishment en consequent spread. Other results indicate that the presence of artificial substrates seem to have a positive influence on the presence of most of the dominant exotic species due to the creation of suitable niches. The results considering the influence of the type of shipping traffic on the abundance of the non-indigenous species reveal that cargo vessels are the most important transport vector of exotic species. Nevertheless, the results indicate that the traffic of yachts has a significant contribution to the spread of non-indigenous species, which emphasizes the importance of hull fouling as a transport mechanism of exotic species. The results of this masterthesis indicate a number of interesting relations between the investigated parameters and the presence and spread of exotic species, which may form the basis for a effective legislation and management programs for the prevention of further introductions and spread of non-indigenous species in the Flemish watercourses.