Publication Abstract

How can we predict the occurrence of rocky reefs?

M. Diesing*, R. Coggan*, J. Aldridge*

Rocky reefs are among the marine habitats listed in the European Union Habitats Directive, therefore special efforts need to be undertaken for their conservation. It is the aim of the Habitats Directive to protect a certain percentage of representative habitats through a network of Special Areas of Conservation. The knowledge regarding the location, extent and character of rocky reefs on the United Kingdom continental shelf is however limited, yet essential to provide a thorough database for the nomination of protected areas. Here we attempt to establish a relationship between modelled wave and tide-induced bed-stress and occurrence of rocky reef to tackle this problem.

Starting from the observation that a recently discovered area of rocky reef in the English Channel is situated in a bedload parting zone, we hypothesise that high bed-shear stress and divergent transport patterns are responsible for non-sedimentation and hence the outcrop of rock at the seabed. A comparison of the location of bedload parting zones with mapped seabed sediments shows that several exhibit bedrock at the seabed, e.g. in the Bristol Channel, the Pentland Firth (both pre-Quaternary rock) and St. Georges Channel (Quaternary till). Bedrock was also mapped along the coasts of Southwest England and Wales and off the Outer Hebrides. Here, the seabed is kept sediment-free by high wave-induced shear stresses caused by long swell arriving from the open Atlantic. Taking into consideration additional information (e.g. the nature of the bedrock) it should be possible to narrow down areas of high likelihood of rocky reef occurrence.

Reference

M. Diesing*, R. Coggan*, J. Aldridge* (2009) How can we predict the occurrence of rocky reefs? Association of American Geographers Annual Meeting, March 22-27, 2009 Las Vegas, NV, USA