Beaver pond biogeochemical effects in the Maryland Coastal Plain

Abstract

The fluxes and concentrations ofmaterials from two contiguous second-order watershedsin the Coastal Plain of Maryland, U.S.A. were measuredfor six years prior to and six years subsequent to theformation of a 1.25 ha beaver pond near the bottom ofone of the watersheds. The watersheds have a clayaquiclude and were equipped with V-notch weirs andcontinuous volume-integrating water samplers. Thebeaver pond reduced annual discharge of water,total-N, total-P, dissolved silicate, TOC, and TSS by8, 18, 21, 32, 28, and 27%, respectively. Most ofthe total-N reduction was due to increased retentionof nitrate in the winter and spring and TON in thewinter and summer. Most of the total-P reduction wasthe result of retention of both TPi and TOP in thewinter and summer. Dissolved silicate retentionpeaked in the spring, while TOC and TSS retentionpeaked in the winter. Prior to the formation of thebeaver pond, concentrations of TON, TPi, TOP, TOC, andTSS had highly significant correlations with streamdischarge, especially in the winter, but subsequent tothe pond there was little or no relationship betweenthese concentrations and stream discharge. However,concentrations of nitrate in the spring and ammoniumin the summer were highly correlated with streamdischarge both before and after the formation of thebeaver pond and regressions of discharge versusconcentrations of these nutrients explained more ofthe variation in concentrations after the formation ofthe pond.