Autumnal Processing of Dissolved Organic Matter in a Small Woodland Stream Ecosystem

Abstract

A mass—balance approach was used to construct a dissolved organic matter (DOM) budget for Roaring Brook, a small New England stream, in autumn. Total litter input to the stream ecosystem during the 77—day study period was 345 g/m2, 21% of which occurred as the lateral transport. Nearly 17% of litter input was released to the water as DOM within 3 days of entry. This leachate input represents 42% of total DOM input to the 1260—m study section. The remainder entered by way of inflowing surface and subsurface water. Autumn uptake of DOM was equivalent to 77% of leachate input and 33% of total DOM input. Approximately 88% of DOM removed from the water column is retained within the system and at least 67% is energetically degraded by consumer respiration in autumn. Based upon total annual energy budgets for similar streams, we estimate that DOM utilization in autumn accounts for from 7% to 11% of annual ecosystem respiration in Roaring Brook.