CHANGES IN THE BENTHIC MACROINVERTEBRATE COMMUNITY IN 2 YEARS OF COLONIZATION OF NEW EXPERIMENTAL PONDS

The objective of this study was to determine if the benthic macroinvertebrate community structure in a set of experimental ponds changed significantly during the second year of their existence. This is an important factor in pesticide registration testing using this type of facility. One year has been established as sufficient time to develop a complete community but this has never been tested. Comparison of the community at the end of year 1 to the community at the end of year 2 showed no significant differences for community summary measures (total density, taxa richness, diversity, Bray-Curtis similarity index); however, some individual taxa densities were significantly lower at the end of year 2. Physicochemical parameters measured indicated that the ponds were oligotrophic. Submerged macrophytes colonized and became established in most of the ponds during year 2. With the exception of a few noninsect taxa, the experimental pond communities appeared similar to mature communities in shallow lentic environments. Additionally, the seasonal changes observed in the pond communities followed expected patterns.