Water chemistry responses to vacant and active beaver dams.

Abstract

This study was conducted to examine the effects of active and abandoned beaver dams on stream water chemistry and primary productivity. We expected to find an increase in downstream nutrients and productivity at actively maintained sites, since beavers excrete a considerable amount of nutrient-rich waste material. Four dam sites were selected and analyzed to determine their temperature, pH, dissolved oxygen, nitrogen, phosphorus, silica, and chlorophyll. These factors were measured using samples from both above and below the beaver dams, and the results of these tests were compared and contrasted between active and abandoned sites. We found there was no significant differences in any of the variables above and below the beaver dam. However, there were significant differences between active and abandoned sites in nitrogen and silica levels, indicating higher nutrient availability at active sites. Finding this, we would expect to see higher productivity at active sites, but chlorophyll levels showed no significant differences. We can conclude that the presence of beavers at dams has the effect of increasing nutrient levels in the stream, but this does not directly result in an increase in productivity. There are many other environmental factors that need to be considered to actually determine how productive an aquatic ecosystem may be.