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 cent ury. Three sites which have been subjected to colliery waste dumping w ere studied to assess the effect of the waste on the marine benthos, a nd the degree of recovery of the benthic communities after the cessati on of dumping. A control site was chosen to the north of the impacted sites and presumed to be unaffected by dumping operations. At each sit e three replicate grabs were taken for macrofaunal analysis and one fo r sediment analysis (sand-silt ratio and percentage coal by loss on ig nition). The colliery waste appears to have had an effect on the benth ic fauna present, indicated by the multidimensional scaling (MDS) conf igurations, which showed a clear separation between the control and th e three sites subjected to dumping. The highest diversity was at Easin gton (6 months after the cessation of dumping) followed by Blackhall a nd the control, with the lowest at Horden. This suggests that the leve l of disturbance is such as to result in an increase in diversity of t he 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 du mping, although at Blackhall the community is still perturbed 12 1/2 y ears after the cessation of dumping. This is probably caused by the pr evailing southbound current transporting coal waste down to this site, where it appears to accumulate.