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, particularl y onto hard substrata. This study experimentally compared the rates of colonization of hard substrata (bricks) in a lake by benthic macroinv ertebrates from two sources - the water column and the bottom. Coloniz ation onto bricks (as mimics of stones) placed on the bottom of the la ke was compared with colonization onto bricks suspended in the water c olumn, where they could not be reached by crawling fauna. Almost all t axa colonizing bottom bricks also colonized suspended bricks, includin g taxa usually considered benthic (e.g. gastropods, mites, oligochaete s and planarians). Water-column samples confirmed the presence of thes e taxa in open water These results suggest that many benthic animals i n lakes may move through the water column more readily than previously considered; constant movement by lake benthos may be in response to s hortage of resources.