The Effects of Benthos on Physical Properties of Freshwater Sediments

Abstract

In this chapter we review the effects of freshwater benthos on the physical (as opposed to chemical) properties of the bottom. Specifically, we will focus our discussion on the effects of macrobenthos (adult length >1 mm) on fine-grained bottoms (sediments that contain approximately 50% by weight silt—clay-sized particles) of lakes and slow-flowing rivers. There are three reasons for this approach. The first is that there is simply too little known about freshwater meio- and microbenthos to merit a review of their effects on sediment properties. More importantly, the macrobenthos are probably the most potent modifiers of sediment properties by virtue of their size relative to sediment grains, their population density, their ability to move through a relatively large volume of sediment, and their feeding and respiratory habits. Finally, we have restricted ourselves to fine-grained bottoms because these comprise the bulk of freshwater lake sediments and because the structure of this sediment is more easily altered than is that of sediments with larger grain size. Some information from slow-flowing river bottoms is included with lakes because their sediments and faunas are very much alike (Hynes, 1970).