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 done at 1 spatial scale, often regular intervals the point discharge. There is, however, concern that choice an inappropriate scale will cause failure or identify and estimate size impacts. In this study, putative impact shoreline sewage outfall on abundance green ephemeral algae gastropods was sampled 2 scales (tens metres several kilo- discharge) in order determine whether effluent comparable across these, as would be expected if species follows gradient contaminants. Such also enabled vari- ability taxa examined 3 scales: (1) among quadrats site com- pared variance other sites shore outfall; (2) non-outfall compared con- trol shores; (3) between comparison control shores. A greater Enteromorpha spp. found close than fur- ther away both scales. Patterns many differed sampling. density limpet Patelloida latistrigata much far outfall, when considered large scale. At smaller single shore, completely reversed—densities were outfall. Variances, like abundances, did not always follow contami- nants different patterns seen Thus, should multiple using nested designs. Where possible, which might detected interpreted needs clearly stated because generalisation disturbance has similar all relevant popula- tion being studied cannot made without explicit tests.