Macroinvertebrate colonization of the marginal zone of a small impoundment in Eastern Canada

Abstract

Colonization of the marginal macroinvertebrate fauna of Laurel Creek Reservoir was followed from the time of first filling in the spring of 1967 until the reservoir was drained in mid-October of the same year. Of the 55 taxa found during this period 34 (61.8%) were facultative species which had maintained populations in the lotic environment before impoundment. Colonization was an active process which accelerated as the water temperature increased. Passive colonization by species swept into the reservoir by flooding of the creek and the resultant rapid filling of the reservoir was negligible. For the first 3 months after subsequent filling in the spring of 1968 the marginal fauna was very similar to that of the previous year although colonization was more rapid as a result of overwintering of many limnophilic species in various refugia in the reservoir basin. Colonization of the marginal zone appeared to approach completion, with respect to the prevailing environmental conditions, during the first summer period of the reservoir's existence.