INHIBITORY EFFECTS OF HIGH-MOLECULAR-WEIGHT DISSOLVED ORGANIC-MATTER UPON METABOLIC PROCESSES IN BIOFILMS FROM CONTRASTING RIVERS AND STREAMS

SUMMARY. 1. The effect of removal of organic manor >1000 apparent molecular weight (AMW) upon biofilm processes was determined in three contrasting streams in West Germany and three contrasting rivers in the U.K. This process removed 66–85% of the dissolved organic matter supply. 2. Elevations in extra cellular enzyme activity (β‐glucosidase, phosphatase and esterase), metabolic heat‐output, bacterial density and poly‐beta‐hydroxy alkanoate (PHA) content (a prokaryote storage product) were noted throughout the study in response to the removal of organic matter. This suggests that there are inhibitory substances present in the dissolved organic matter pool >1000 AMW. Evidence is presented to suggest that phenolics play a role in this inhibition. 3. Decreases in metabolic heat output, β‐glucosidase activity and PHA content were noted at four sites in response to the removal of >1000 AMW material. 4. The divergent responses of the six river/stream biofilms are indicative of radically differing metabolic/catabolic processes, on a spatial and/or temporal basis, to a major organic supply perturbation. Copyright © 1990, Wiley Blackwell. All rights reserved