Sewage and environmental impacts on rocky shores: necessity of identifying relevant spatial scales

摘要

The concentration of contaminants usually decreases with increasing distance from a point-source disturbance, so sampling to detect ecological impacts is usually done at 1 spatial scale, often at regular intervals from the point of discharge. There is, however, concern that the choice of that inappropriate scale will cause failure to detect impacts or failure to identify and estimate the size of impacts. In this study, the putative impact of a shoreline sewage outfall on the abundance of green ephemeral algae and gastropods was sampled at 2 spatial scales(tens of metres and several kilo- metres from the point of discharge)in order to determine whether the ecological impact of effluent was comparable across these, as would be expected if the abundance of species follows the gradient of contaminants.