The effects of sewage-works effluent on riverine extracellular aminopeptidase activity and microbial leucine assimilation

Extracellular aminopeptidase activity and microbial leucine assimilation, b oth processes related to protein degradation and biopurification of organic pollutants, were investigated in relation to sewage-works discharges, The rivers studied were the Swale, and its tributary the Wiske in which there w as less dilution of effluent. Localized increase in planktonic leucine amin opeptidase activity and leucine assimilation, associated with increased bac terioplankton abundance, potentially enhanced biopurification in both river s. In contrast, epilithic leucine aminopeptidase activity was not consisten tly elevated in response to discharges. Epilithic leucine assimilation and bacterial abundance did, however, tend to increase; this response might hav e favoured biopurification, despite the lack of enhanced aminopeptidase act ivity. General downstream increase in aminopeptidase activity and amino-aci d assimilation, previously described along the Swale, was shown not to be a simple response- to successive sewage-works discharges. (C) 2000 Elsevier Science Ltd. All rights reserved.