SS3.10 Ecological Implications of Terrestrial Inputs into Lakes and Ponds
Date: Tuesday, June 11, 2002
Time: 9:30:00 AM
Location: Esquimalt
PaceML, Institute of Ecosystem Studies, Millbrook, USA,
I will present an overview that considers DOM loading rates as well as DOM influences on lake metabolism, food webs, and stability. An analysis of 553 Adirondack watersheds in New York reveals that loading rates are in the range of 30-300 kg/ha/y for the main land cover types in this region. Areal loading rates from wetlands are 6-fold greater than uplands but uplands dominate total loading as they account for 90% of land cover. DOM-inputs clearly influence lake ecosystem metabolism as many systems consume more carbon than they produce and hence are net heterotrophic. However, it is unclear the extent to which DOM supports consumers other than bacteria. Current studies are addressing this problem using stable isotopes. The concept of stability has been used in two ways in the context of DOM. First, theory suggests that high DOM lakes are resistant to some perturbations but have low resilience (long return times) when perturbed. Second, DOM is argued to stabilize metabolism by providing a steady source of energy to consumers. There are, however, few empirical tests either of resistance and resilience or whether DOM is associated with lower variance in productivity and fluxes. This is an area ripe for experimental and comparative analysis.