Nitrogen degradation of water quality in a phosphorus-saturated catchment: the case of Lough Neagh, Northern Ireland

摘要

The damaging effects of eutrophication on lakes have been recognised for at least 40 years, yet the disruption of aquatic ecosystems by nutrient fertilisation remains a potent environmental problem throughout the world (Schindler 2001). Although eutrophication has been linked with nutrients from urban waste-waters (e.g. Hall et al. 1999), agricultural activities can saturate soils with phosphorus (P) and nitrogen (N), to the extent that excess nutrients from diffuse terrestrial sources degrade aquatic ecosystems (Carpenter et al. 1998). In general, P loading has been identified as the principal factor degrading water quality in lakes; however, recent evidence suggests that N inputs may also contribute to lake eutrophication (James et al. 2003), especially in watersheds where soils have high P content. In this paper, annually-resolved fossil records of nutrient inputs (as stable N isotopes), algal abundance (as fossil pigments) and gross phytoplankton community composition (as non-siliceous algal microfossils) were compared with long-term historical records of nutrient supplements to agricultural lands, urban pollution, limnological conditions and climatic change to identify the correlates of water quality change in Lough Neagh, Northern Ireland, during the 20th century.