THE RECOVERY OF BENTHIC COMMUNITIES ALONG THE COUNTY DURHAM COAST AFTER CESSATION OF COLLIERY SPOIL DUMPING

Large amounts of coal tailings and minestone have been dumped off the County Durham coast since at least the beginning of the twentieth century. Three sites which have been subjected to colliery waste dumping were studied to assess the effect of the waste on the marine benthos, and the degree of recovery of the benthic communities after the cessation of dumping. A control site was chosen to the north of the impacted sites and presumed to be unaffected by dumping operations. At each site three replicate grabs were taken for macrofaunal analysis and one for sediment analysis (sand-silt ratio and percentage coal by loss on ignition). The colliery waste appears to have had an effect on the benthic fauna present, indicated by the multidimensional scaling (MDS) configurations, which showed a clear separation between the control and the three sites subjected to dumping. The highest diversity was at Easington (6 months after the cessation of dumping) followed by Blackhall and the control, with the lowest at Horden. This suggests that the level of disturbance is such as to result in an increase in diversity of the affected sites. There were clear signs of recovery from the effects of mine waste dumping at Horden 7 1/2 years after the cessation of dumping, although at Blackhall the community is still perturbed 12 1/2 years after the cessation of dumping. This is probably caused by the prevailing southbound current transporting coal waste down to this site, where it appears to accumulate.