Colonization by lake benthos of hard substrata in the water column versus on the bottom

Little work has been done on colonization by lake benthos, particularly onto hard substrata. This study experimentally compared the rates of colonization of hard substrata (bricks) in a lake by benthic macroinvertebrates from two sources - the water column and the bottom. Colonization onto bricks (as mimics of stones) placed on the bottom of the lake was compared with colonization onto bricks suspended in the water column, where they could not be reached by crawling fauna. Almost all taxa colonizing bottom bricks also colonized suspended bricks, including taxa usually considered benthic (e.g. gastropods, mites, oligochaetes and planarians). Water-column samples confirmed the presence of these taxa in open water. These results suggest that many benthic animals in lakes may move through the water column more readily than previously considered; constant movement by lake benthos may be in response to shortage of resources.