Publication Abstract

Benthic Responses to Sewage-Sludge Disposal and Climate Events in the Western North Sea

H.L. Rees, M.A. Pendle, D.S. Limpenny, C.E. Mason, S.E. Boyd*, S. Birchenough and C.M.G. Vivian

Macrofaunal assemblages inhabiting stable offshore muddy sand substrata responded predictably to the effects of mild organic enrichment arising from sewage-sludge disposal off the northeast coast of England (western North Sea). At the disposal site, densities were elevated up to two-fold, but classical 'indicator' species were only marginally enhanced and there was no evidence of a significant waste-induced change in assemblage structure. The response following cessation of disposal was equally predictable, with a decline in densities to 'reference' levels some 3 years later. However, physical manifestations of disposal, including tomato pips and non-biodegradable artefacts, were still evident after this time.

Changes in diversity at selected monitoring stations tended to track each other over time, suggesting comparability in the influence of natural environmental factors. The employment of treatment/reference ratios and limit values for acceptable change provided a useful model for the simplified expression of trends and hence has value as a management tool in the regulation of waste disposal activity.

Temporal trends in the benthic fauna were also correlated with winter values of the North Atlantic Oscillation Index for the preceding year. Explanations for this relationship, including variation in the supply of food to the sea bed, are sought in relation to earlier studies in the area, and elsewhere. Finally, the increasing importance of extended time-series data for the investigation of man-made impacts on the marine environment is highlighted, along with the accompanying requirement for continuity and quality assurance of sampling programmes.

Reference:

H.L. Rees, M.A. Pendle, D.S. Limpenny, C.E. Mason, S.E. Boyd, S. Birchenough and C.M.G. Vivian (2006) Benthic Responses to Sewage-Sludge Disposal and Climate Events in the Western North Sea. Journal of the Marine Biological Association UK, 86(1): 1-18