An examination of the spatial scale of impact on the marine benthos arising from marine aggregate extraction in the central English Channel

Surveys were designed to investigate the nature and footprint of biological effects arising from both trailer and static suction hopper dredging in UK waters. Two transects of stations located at increasing distance from active centres of dredging activity in the central English Channel were sampled for macrofauna and sediments using a 0.1m2 Hamon grab. Multivariate statistical analyses indicated that macrofaunal community composition was distinct and there was a clear gradient of change with increasing distance from the dredging activity. Spatial differences in species distribution patterns correlate with levels of dredging intensity and the physical characteristics of the sediments. Effects on the benthos of the different dredging practices were similar within the zone of active dredging, although there were notable differences in the scale of impact and the nature of effects beyond the margins of the extraction sites. The two principal methods of dredging for sand and gravel in the UK are discussed in relation to their potential for impacting the benthos.