SS3.10 Ecological Implications of Terrestrial Inputs into Lakes and Ponds
Date: Tuesday, June 11, 2002
Time: 2:30:00 PM
Location: Esquimalt
 
WetzelRG, University of North Carolina, Chapel Hill, USA, rwetzel@unc.edu
Tuchman, N, C, Loyola University of Chicago, Chicago, IL, USA, ntuchma@luc.edu
 
SOLAR RADIATION AS THE SIMULTANEOUS AUTOTROPHIC AND HETEROTROPHIC MODULATOR OF AQUATIC ECOSYSTEMS
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Organic matter of allochthonous terrestrial and wetland-littoral origins massively subsidizes autotrophic productivity of all river and lake ecosystems. Except for some headwater streams (< 3rd order), nearly all of the imported organic matter is dissolved organic matter (DOM). Results from ongoing research exemplify different mechanisms by which DOM regulates biogeochemical fluxes of carbon and nutrient availability, including alteration of free and membrane-associated enzyme activities, macronutrient and trace element availability, and organic carbon subsidies. In every instance, solar radiation can alter bioavailability of organic substrates and nutrients. It is argued that although UV-B and especially UV-A are important in partial and total photolysis of DOM, the blue portion (400 - 500 nm) of the visible spectrum plays a dominant role because of its greater photic zone. From a thermodynamic standpoint, imported DOM, originating in large part from lignocellulose structural tissues of higher plants, provides essential chemical stability to community and ecosystem metabolism at all levels. Anthropogenically induced alterations of the chemical composition of influent DOM or photolytic degradation rates of DOM will significantly alter the collective metabolism of the ecosystems.