A new approach for detecting and mapping sewage impacts

Increased nitrogen loading has been implicated in eutrophication occurrence s worldwide. Much of this loading is attributable to the growing human popu lation along the world's coastlines. A significant component of this nitrog en input is from sewage effluent, and delineation of the distribution and b iological impact of sewage-derived nitrogen is becoming increasingly import ant. Here, we show a technique that identifies the source, extent and fate of biologically available sewage nitrogen in coastal marine ecosystem. This method is based on the uptake of sewage nitrogen by marine plants and subs equent analysis of the sewage signature (elevated delta N-15) in plant tiss ues. Spatial analysis is used to create maps of delta N-15 and establish co efficient of variation estimates of the mapped values. We show elevated del ta N-15 levels in marine plants near sewage outfalls in Moreton Bay, Austra lia, a semi-enclosed bay receiving multiple sewage inputs. These maps of se wage nitrogen distribution are being used to direct nutrient reduction stra tegies in the region and will assist in monitoring the effectiveness of env ironmental protection measures. (C) 2001 Elsevier Science Ltd. All rights r eserved.