The effects of aquatic macrophytes on the stream microenvironment

Abstract

The effects of aquatic macrophytes on various aspects of the stream microenvironment were observed and compared to conditions found in unvegetated substrate. Specifically, factors of micro-current velocity, substrate surface area, fine particle sediment deposition, detritus deposition and attached diatom availability were examined. Macrophytes were transplanted into substrate trays and microenvironment conditions found within them were compared to conditions found in adjacent trays containing unvegetated substrate. Macrophytes were found to alter flow characteristics and create reduced current velocities near the substrate. They also provided significantly more substrate surface area, more fine particle sediments and more detritus than unvegetated substrates. Macrophytes supported significantly lower attached diatom biomass per m 2 in moderate current regions than stones, but in slow water they may support higher biomasses, because sedimentation adversely affects diatom populations on unvegetated substrate. The possible ecological significance of these effects is discussed.