EurOCEAN 2000 - Vlaams Instituut voor de Zee

BIOLOGICAL PROCESSES
ESPED recognises that bioerosion is an important element in platform evolution. The project
aims to investigate the role of plants and animals in shore platform downwearing through a
combination of field observations and laboratory experimentation. A preliminary study has
been completed of the range and character of bioerosion mechanisms active on the shore
platforms at each site. Seasonal changes in seaweed cover are being monitored to determine
their role in shore platform development and sediment accumulation. Also being studied are
seasonal changes in the populations of animals that contribute to rock destruction by boring
and/or grazing. The ultimate objective is to assess the mass loss of platform material by
biological organisms and to investigate how the rates of loss relate to the geotechnical
properties of the rocks, and the rates of physical and chemical weathering. Special attention is
being given to the analysis of faecal pellets of limpets and other organisms in order to estimate
their contribution to platform downwearing.
MEASURING PLATFORM DOWNWEARING
ESPED is making innovative use of a new laser scanner which was originally developed at the
University of Karlstad for field monitoring of the decay of rock art exposed to the weather
(Swantesson, 1994; Williams, Swantesson and Robinson, 2000). This equipment has been
specially adapted for use on the shore platforms, particular attention being paid to portability
and speed of data acquisition. Computer software for the scanner has been further developed.
Field trials of the new scanner have been successfully completed and it is now being used
(together with two suitably modified and updated earlier versions of the scanner) to make
detailed maps of small areas of the platform surface, enabling variations in microrelief (surface
roughness and micromorphology) to be measured. By overlaying maps taken at regular
intervals rates of change over time can be mapped. Information obtained by scanning is being
combined with measurements taken with mechanical micro-erosion meters and detailed
topographic surveying to determine current rates of platform downwearing. Tests will be
carried out to compare the performance of the laser scanner with other available methods of
measuring downwearing, including the micro-erosion meters and photogrammetry.
PROGRESS TO DATE
The ESPED project has run for only 18 months, and the data so far collected have been mostly
of a baseline nature. However, much useful information has been gathered on geotechnical
matters, platform morphology, cliff retreat and biological processes. Moreover, the successful
deployment of the new scanner means that work can now progress rapidly on measuring
platform downwearing. Micro-erosion meter measurements were made at all monitoring sites
in 1999 and are due to be repeated this year (2000). Laser scans were completed at all sites in
1999, except those in France, which will be scanned for the first time this year.
Oil spilt from the Malta-registered tanker, Erika, which sank on 12 December 1999, washed
ashore along the Brittany coast, destroying most of the littoral flora and fauna at the Le Croisic
monitoring sites. Biological inventories were completed before the spillage, and will be
repeated at intervals over the lifetime of the ESPED project (when it is safe to return to the site)
to monitor rates of recolonisation by seaweeds and invertebrates.
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