Detecting environmental change using stable isotopes

Changing land use is one of the primary causes of increased sedimentation and nturient levels in aquqatic systems, resulting in contamiantion and reduction of biodiversity. Detecting and quantifying these inputs is the first step of remediation, to enable targeted reduction of transport processes into waterways from human impacted land surfaces. More recently, stable isotope analyses are being used as a detection and quantification tool in aquatic environments. Carbon and nitrogen isotopes of sediments, algae and invertebrates from aquatic systems can be used as proxies to record both short and long term enviornmental cahgne. Excess nutrients derived from urbanization, industry, forestry, farming and agriculture increase the bio-availability of nitrogen to aquatic organisms, changing their natural 15N isotopic signatures. Allochthonous (terrestrial) input from soil destabilization and human activity in surrounding catchments changes the 13C isotope ratios and increases the C:N ratio of sediments. Heavy metal and other organic pollutants can also be used to indicate urbanization and industrial contamination. The comined use of carbon and nitrogen isotopes, C:N ratios and heavy metals are powerful environmental monitoring tools which are useful indicators of source and transport pathways of terrestrial derive dmaterial and anthropogenic pollutants into strams, rivers and estuaries. (author). 56 refs., 10 figs., 3 tabs