The Role of Community Structure for Invasion Dynamics in Marine Fouling Communities in the North Sea.

Lauterbach, Lars (2007) The Role of Community Structure for Invasion Dynamics in Marine Fouling Communities in the North Sea. (Diploma thesis), Universität Stuttgart, Stuttgart, Germany, 87 pp.

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Biological invasions can markedly influence the biodiversity of marine fouling communities and cause considerable economic damage. Ship hulls and ballast water tanks are possible vectors for the dispersal of invasive species. The number of invasions facilitated by these vectors is expected to increase due to the expansion of shipping routes and an increase in the number of ocean-going ships. In this context, little is known about the invasion ecology of entire fouling communities consisting of macroalgae and macroinvertebrates. It is also not fully understood how the age of a community influences its stability towards environmental change. The longer introduced communities persist after a transport, the more likely it is that single species reproduce and release propagules, which could initiate a new invasion. To
investigate this subject, an experiment was conducted using natural fouling assemblages. I translocated fouling assemblages, differing in species richness and composition, between two shallow, sub-tidal habitats on the north-east coast of England. In this study, assemblage age was experimentally manipulated at two levels: I let fouling organisms establish on settlement panels for 2 months and 8 months, respectively. The same experiment was repeated during a different season with 2 month and 4 month old assemblages. The community dynamics were observed over a period of 18 weeks after translocation. At the one site, Bugula angustiloba, Ascidiella aspersa, Ciona intestinalis, Botryllus schlosseri and Didemnum spp from the introduced assemblages temporarily invaded the resident assemblages, despite high levels of environmental stress. I assume that a low productivity of the recipient site and large amounts of available settlement substrata present in the resident communities, the species identity of the introduced species (e.g. short larval dispersal), their repeated introduction during the second experiment were responsible for facilitating the transient establishment of the introduced species.
At the other site, the introduced assemblages underwent a process of structural convergence towards resident assemblages after transplantation. Based on the data obtained from the experiment, I calculated the convergence rates between resident and translocated communities.
Generally, older, species-rich assemblages showed slower rates of convergence than younger, less rich assemblages. Intrinsic characteristics of the assemblages at the time of
transplantation, such as diversity, species identity and the amount of available settlement substrata were considered as possible determinants of the convergence rate. In this context, the influence of diversity on community stability has been controversially discussed for
several years. Different diversity measures (Species Richness, Shannon- Weaver index, and functional diversity) were correlated with the convergence rate i.e. community stability towards environmental change. Shannon Weaver index was the only diversity measure that was significantly negatively correlated with the convergence rate of both experiments. This correlation between Shannon Weaver index and community stability may be considered as a “sampling effect”. The more species are present in a community the higher is the probability that species that stabilise the community are present. The availability of settlement substrata was significantly positively correlated with the
convergence rate. In conclusion, species identity, diversity and available settlement space are good stability predictors. As a practical implication for the control of bio- invasions I recommend the frequent cleaning of ship hulls and cleaning of oil platforms before transport
as fully matured fouling communities have a high potential to initiate invasion.

Document Type: Thesis (Diploma thesis)
Thesis Advisors: UNSPECIFIED
Additional Information: 1st supervisor: Prof. Dr. Franz Brümmer 2nd supervisor: Prof. Dr. Martin Wahl
Keywords: Benthic Ecology; GAME; marine fouling; bioinversion
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-B Experimental Ecology - Benthic Ecology
Refereed: No
Projects: GAME
Date Deposited: 07 Sep 2011 12:27
Last Modified: 06 Jul 2012 14:55

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