Toxicity of Nitrite to Freshwater Invertebrates

摘要

Aquatic invertebrates are important components of river biota, providing the vital link in the food chain between their food sources (e.g. algae, bacteria and detritus) and fish, to which they themselves become prey. Due to the nature of the aquatic environment, freshwater organisms are particularly vulnerable to the input of pollutants. Northern Ireland rivers are subjected to seasonal nitrite (NO_2) fluctuations, which are linked to large inputs of agriculturally derived nitrogenous (N) substrates (Smith et al, 1995, Smith et al, 1997). Greater than 60% of these rivers exceed the E.E.C. drinking water directive guideline of 0.03 mg NO_2~--N L~(-1) (European Economic Community, 1980) and even larger proportions are above the 0.003 and 0.009 mg NO_2~--N L~(-1) recommended for supporting salmonid and cypinid fisheries, respectively (European Economic Community, 1978). The greater proportion of the NO_2~-originates from sediment-water interface transformations of nitrogenous substrates rather than from direct inputs. The impending increase of sewage and sludge applications to agricultural land with a consequent increase in nitrate (NO_3~(TM)) leaching to streams and the transformation of this to NO_2~- could provide added hazards to aquatic biota.