Discussion on Papers 14–16

PR LACK and MRS COOPER, Paper 14 A major area of concern when designing a sea oucfall is Che prediction of any adverse effects it may have on the sea bed and the creatures that live on it. Effects on ecology tend to occur in benthic rather than pelagic communities. Benthic invertebrates have relatively sessile lifestyles and cannot readily escape the effects of pollution by swimming to another area. The natural environment in which these organisms live is often hostile and can be completely disrupted by storms or changes in tidal currents. Because of this, many benthic organisms tend to be opportunistic in their lifestyle, i.e. they can invade an area as soon as it becomes habitable and increase their numbers rapidly. These naturally large fluctuations in numbers make pollutioninduced changes difficult to detect and virtually impossible to predict. Changes attributable to sewage outfalls are not always adverse in terms of total numbers of animals. The oligochaete worms, in particular, thrive on the high levels of organic matter associated with sewage. The distribution of species may change, resulting in a lower diversity, while the total numbers of individuals may increase.