In search of non-indigenous barnacle species on man-made hard substrates in the marine environment (Southern Bight of the North Sea)
Bouwens, J. (2019). In search of non-indigenous barnacle species on man-made hard substrates in the marine environment (Southern Bight of the North Sea). MSc Thesis. Oceans & Lakes, Interuniversity Master in Marine and Lacustrine Science and Management: Antwerpen, Ghent, Brussel. 39 pp.
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Document type: Dissertation
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| Abstract |
The introduction and establishment of invasive non-indigenous species is increasing on a global scale and is posing a threat to local biodiversity, commercially important species and public health. Most of these invasions are linked to the expansion of anthropogenic dispersal mechanisms, such as the worldwide transfer of ballast water through shipping. The construction of artificial hard substrates in the marine environment attracts species that were previously not present. This study focuses on non-indigenous barnacles on groynes in the southern bight of the North Sea. The aim was to map the early phase of invasion and range expansion of Balanus glandula. We determined the present-day geographical distribution of B. glandula on groynes along the entire Belgian coastline and part of the coastline of the Netherlands (i.e. Cadzand), characterized its habitat preference (focusing on tidal zonation and substrate preference) and explored possible competitive interactions with other established barnacle species (i.e. the indigenous Semibalanus balanoides and non-indigenous Elminius modestus). We encountered B. glandula on all ten groynes sampled, which were not equally colonized and showed no East-West gradient in terms of its density. This barnacle had low densities relative to S. balanoides and E. modestus and was most abundant in Raversijde. The most significant environmental variable determining the habitat preference of B. glandula appeared to be the submersion duration. The highest densities were at about 30 to 40% submersion duration, which corresponds to the mid-to-high intertidal zone. Balanus glandula was found on each substrate type, of which conglomerate appeared to be the most preferred, hosting the highest densities. A negative interaction between the recently introduced B. glandula and the indigenous S. balanoides and non-indigenous E. modestus is suggested. However, we concluded from our interspecies regression analysis that our data does not allow to demonstrate a significant effect of B. glandula onto the other two barnacle species. Balanus glandula may affect the intertidal biodiversity in the southern bight of the North Sea, although it is not expected to impact –commercially- important species such as Mytilus edulis (the blue mussel), since this native species occurs towards the sublittoral zone. We conclude that B. glandula has not –yet- displayed its full invasive potential in the southern bight of the North Sea. Yet, due to its competitive advantages, it is very likely that the species will stay here for a longer period of time and possibly will become one of the most abundant barnacle species by outcompeting other barnacles, such as S. balanoides and E. modestus. |
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