SS3.10 Ecological Implications of Terrestrial Inputs into Lakes and Ponds
Date: Tuesday, June 11, 2002
Time: 3:00:00 PM
Location: Esquimalt
 
HouserJN, Oak Ridge National Laboratory, Oak Ridge, USA, houserjn@ornl.gov
 
COLORED DISSOLVED ORGANIC MATTER AFFECTS THE SURFACE TEMPERATURE, HEAT CONTENT, AND EPILIMNETIC LIGHT INTENSITY OF SMALL LAKES
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I used data from whole-lake experiments (1991-99) to investigate the effects of water color and algal biomass on thermal characteristics and light intensity of lakes. Water color varied widely among lakes (g440 = 1.5 - 19.8 m-1) because of natural variability in colored dissolved organic matter (CDOM) inputs. Chlorophyll concentrations varied among lakes and years (2.9 - 62.6 ug chlorophyll L-1) because of experimental nutrient enrichment. As water color or chlorophyll concentration increased, light penetration decreased more rapidly than thermocline depth leading to reduced mean epilimnetic light intensity in the colored lakes. Epilimnetic temperatures in the colored lakes were cooler than the all lake mean 13 out of 15 sampling days (range: +0.8 to -2.1 C), and warmer in the clearest lakes 21 out of 30 sampling days (range: -1.5 to +3.5 C). Maximum heat content was lower, and relative resistance to mixing at the thermocline was ~3 fold higher in colored lakes vs clear lakes. These results show novel ways that input rates of nutrients and CDOM from the watershed affect lake thermal characteristics and light intensity.