Publication Abstract

Preliminary observations of the effects of dredging intensity on the recolonization of dredged sediments the south-east coast of England (Area 222)

Preliminary observations of the effects of dredging intensity on the recolonization of dredged sediments the south-east coast of England (Area 222)

S.E.Boyd, D.S. Limpenny, H. L. Rees, K.C. Cooper and S. Campbell

The recolonization of a marine aggregate extraction site used for c. 25 years off the south-east coast of the U.K. was examined 4 years after the cessation of dredging. Effects of different levels of dredging intensity on the rate of macrofaunal recolonization were investigated. Values of abundance and total numbers of species were significantly lower (p<0.05) in an area most recently exposed to the highest level of dredging intensity compared with samples taken from an area of low intensity, and those from a reference site. Differences between previously dredged sediments and the reference location were due to the reduced abundance of a range of macrofaunal species characterising nearby sediments. Multivariate measures of community structure also indicated that there were significant differences (p<0.01) in the macrofaunal assemblages between areas exposed to different dredging intensities. Sediment from the area exposed to the highest dredging intensity contained proportionally more sand than other sampled sediments. The extent to which dredging intensity contributed to these differences was difficult to determine due to the absence of any baseline data. Despite this, univariate and multivariate analyses indicated a strong relationship between macrofaunal community structure and dredging intensity at this site. Correlation analyses also demonstrated that the predominant influence on the macrofaunal community was the level of dredging that took place in 1995, the last year that the licensed site was dredged heavily.

Preliminary observations indicated that the fauna remained in a perturbed state some four years after cessation of dredging. Therefore relatively rapid 'recovery' rates commonly cited as 2 to 3 years for European coastal gravelly areas should not be assumed to be universally applicable. Implications for the future management and scientific study of marine aggregate extraction arising from preliminary observations on the physical and biological status of this site are discussed together with the options for selecting a reference site post-extraction.

Reference:

S.E.Boyd, D.S. Limpenny, H. L. Rees, K.C. Cooper and S. Campbell. 2003. Preliminary observations of the effects of dredging intensity on the recolonization of dredged sediments the south-east coast of England (Area 222). Estuarine, Coastal and Shelf Science 57: 209-223pp

S.E.Boyd*, D.S. Limpenny*, H. L. Rees*, K.C. Cooper* and S. Campbell*

Estuarine, Coastal and Shelf Science 57: 209-223pp