Publication Abstract

Bedrock Geology Governs Benthic Habitat in the Central English Channel

M. Diesing*, K. Vanstaen* and R. Coggan*

The European Union Habitats Directive obliges member states to protect marine species and habitats in their territorial waters and exclusive economic zones through a coherent network of marine protected areas by 2008. Among the listed habitats, which need protection, are reefs, whether they are biogenic or geogenic. A better understanding of the extent and character of rocky reefs in the central English Channel is required to inform policy and create a profound scientific basis for the selection of marine protected areas. Therefore, we acquired bathymetric data and processed the datasets with Benthic Terrain Modeler to derive benthic zones, structures and rugosity.

In this tide-swept environment, which is characterised by a thin and discontinuous cover of coarse lag deposits, a close correlation between bedrock geology and physical habitat exists. Where soft and uniform Upper Cretaceous chalk is present at the seafloor, slope and rugosity are low and the seabed is flat and smooth, with a thin gravel lag on top. Conversely, Upper Jurassic and Lower Cretaceous bedrock comprises a varied and partly cyclic lithology, displaying a differential resistance to erosion. Consequently, slope and rugosity are highly variable where these bedrock types are found at the seafloor. Such areas are dominated by series of bedrock ridges of up to several tens of kilometres length. Seabed photography showed distinct biological communities associated with these differing physical habitats, supporting a growing evidence base that underlying geology has the potential to be used as a proxy when mapping benthic habitats in support of marine management.

Reference

M. Diesing*, K. Vanstaen* and R. Coggan* (2008) Bedrock Geology Governs Benthic Habitat in the Central English Channel. Association of American Geographers Annual Meeting, 15-19 April 2008, Boston, USA