Publication Abstract

Invertebrate recolonisation of fine-grained beneficial use schemes: an example from the south-east coast of England

S. Bolam and P. Whomersley

The disposal of maintenance dredged material constitutes one of the most important problems in coastal zone management. To minimise ecological impacts, a number of ‘beneficial use’ options have developed whereby the material is regarded as a potential resource and used to recharge or recreate intertidal habitats. This paper presents the results of a sampling programme to investigate the macrofaunal recovery rates, and the underlying mechanisms responsible for them, following a beneficial use scheme involving the placement of fine-grained dredged material on a saltmarsh in south-east England.

Three stations in the recharge area and 3 reference stations, located within the same saltmarsh system, were selected. These stations were sampled prior to recharge (recharge stations only) then 1 week, 3, 6, 12 and 18 months after the recharge. Sediment redox potentials (1, 2 and 4 cm sediment depths) were also measured on each sampling occasion. The results indicated a rapid recolonisation of the fauna typical of the surrounding saltmarsh channels. All univariate parameters had recovered after 3 months after the recharge. Active post-juvenile immigration is likely to have been the predominant recovery process. Multivariate data analysis revealed that the community structure of the recharge stations, however, did not progress towards those of the reference sites. Natural spatial variability in community structure at the scale of the recharge-reference station distance, and differences in eventual tidal elevations are factors responsible for these differences. The need to carefully assess reference site suitability in monitoring beneficial use schemes is discussed.

Reference:

S. Bolam and P. Whomersley (2004) Invertebrate recolonisation of fine-grained beneficial use schemes: an example from the south-east coast of England. Journal of Coastal Conservation, 9: 159-169