SS3.16 Lentic-Lotic Linkages in Freshwaters: Comparisons from Different Ecosystems
Date: Monday, June 10, 2002
Time: 2:45:00 PM
Location: Colwood
 
SmedbergE, Stockholm University, Dept. of Systems Ecology, Stockholm, Sweden, erik@system.ecology.su.se
BlomqvistS, Stockholm University, Dept. of Systems Ecology, Stockholm, Sweden, sven.blomqvist@system.ecology.su.se
Humborg, C, , Stockholm University, Dept. of Systems Ecology, Stockholm, Sweden, christop@system.ecology.su.se
Moerth, M, , Stockholm University, Dept. of Geology and Geochemistry, Stockholm, Sweden, magnus.morth@geo.su.se
 
VEGETATION CHANGES AND HYDROLOGICAL ALTERATIONS WITH DAMMING-FAR-REACHING IMPLICATIONS FOR WEATHERING AND RIVER BIOGEOCHEMISTRY
image
This case study tests the hypothesis that damming leads to a depletion of major elements in river systems. Differences in river chemistry have been observed between regulated and unregulated river systems in northern Sweden. Dissolved silicate (DSi) and major nutrient concentrations have been found to be much lower in the regulated systems. Previously, this was regarded as an effect of diatom sequestering DSi in the reservoirs. However, this seems not to be the case in the studied oligotrophic river systems. We suggest that the lower and uniform concentration throughout the river course is an effect of decreased weathering rates, which in turn are caused by vegetation losses and alterations in hydrology in the riparian zone. In the study area, the ratio of forest to lake area in the headwaters changed dramatically with damming, from 2.65 to 0.84. Damming, especially in high mountainous areas, seems to be crucial for river biogeochemistry, and thus land sea fluxes of nutrients and main elements. Also, this study suggests that changes in vegetation coverage in the Quaternary altered significantly DSi inputs to the global oceans.