Biodiversity of shipwrecks from the Southern Bight of the North Sea
The seabed of the Southern Bight of the North Sea is mostly composed of sandy soft sediments. Natural hard substrates like pebbles are rare and only occur locally. Lost cargos or shipwrecks lie on the seabed as results of unintentional processes, but because of their inherent structure, they effectively act as artificial reefs deprived of an a priori defined set of functions. On Belgian waters, 231 shipwrecks and other artificial hard structures are dispersed on the continental shelf. Together with the sunken vessels of the neighbouring countries, they create a network of individually isolated hard substrates available for the colonization of the epifauna. The faunal diversity of these shipwrecks has never been studied before.
This thesis analyzed the diversity as well as spatial and temporal variation in community structure of ten Belgian shipwreck sites.
A total of 224 macrospecies have been identified, with at least 50 species new or rare for the Belgian fauna and Southern North Sea. All shipwrecks are strongly dominated by cnidarians in terms of biomass and by amphipods in terms of abundances. The artificial hard substrate communities isolate strongly from the surrounding soft sediment communities by sharing few species, being dominated by different faunal groups and having a distinct trophic organization. Looking at a cross-shore gradient of sites, three groups of shipwrecks could be determined. Metridium senile, a sea anemone, dominates a species poor community of the coastal sites. Channel water masses influence the offshore sites causing a more stable abiotic environment. The hydrozoan Tubularia indivisa dominates this community. Intermediate sites are also dominated by T. indivisa, but a higher biomass is here observed.
It also appears that this T. indivisa is a key species allowing for the settlement of a large set of secondary epibionts.
The shipwreck network is further discussed in the context of the regional diversity, dispersal of species and fisheries based applications
School:Université catholique de Louvain
Source Type:Master's Thesis
Keywords:communities communautés epaves artificial reef récif artificiel mer du nord epifauna biodiversité poissons fish
Date of Publication:02/26/2007