OR/14/015 Summary

Lark R M. 2014. Mapping seabed sediments of the Swallow Sand and South-west Deeps (West) MCZs. British Geological Survey Internal Report, OR/14/015.

This report is on work undertaken for the JNCC under an Addendum to the Memorandum of Agreement dated 20 February 2014 between The Scottish Ministers, Natural Environment Research Council (NERC) and JNCC Support co. (JNCC). Under the terms of this Addendum JNCC requested that BGS carry out geostatistical analysis of sediment sample data from the CEND 8/12 survey of Swallow Sand MCZ and CEND 6/13 survey of South-west Deeps (West) MCZ in order to produce maps of sediment distribution in the sites.

For each of the MCZ a geostatistical analysis of the data is reported leading to the selection of a robust linear model of corregionalization for the composition of the sediment, based on the additive log-ratio transformation of data on mud, sand and gravel content. This model is then used for spatial prediction on a 250-m grid. At each grid node a prediction distribution is obtained, conditional on neighbouring data and the selected model. By sampling from this distribution, and back-transforming onto the original compositional simplex of the data, we obtain a conditional expectation for the proportions of sand, gravel and mud at each location, a 95% confidence interval for the value at each node, and the probability that each of the four sediment texture classes that underly the EUNIS habitat classification is found at the node.