CS26 Organic Carbon Dynamics
Date: Thursday, June 13, 2002
Time: 10:15:00 AM
Location: Carson C
 
Kaiser, E, , EAWAG, CH-8600 Duebendorf, Switzerland, edith.kaiser@eawag.ch
SulzbergerB, EAWAG, CH-8600 Duebendorf, Switzerland, sulzberger@eawag.ch
 
LIGHT-INDUCED TRANSFORMATION OF RIVERINE DISSOLVED ORGANIC MATTER (DOM): IMPACT ON DOM BIOAVAILABILITY
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The impact of solar radiation and iron on the bioavailability of DOM was investigated in the Tagliamento River, Italy. Ultrafiltration and C18 solid phase extraction of DOM, sampled along the river continuum on a seasonal base, revealed that up to 80% of riverine DOM consisted of hydrophilic, low-molecular weight (LMW) organic compounds. The bacteria dominantly utilized LMW DOM. In general, a 4-hour exposure of all DOM fractions to the simulated full solar spectrum resulted in a release of less soluble, higher oxidized hydrophilic LMW organic compounds, and a concomitant net production of Fe(II) and hydrogen peroxide. After 1 h of incubation with riverine bacteria in the dark, a significant reduction (20-90%) of bacterial utilization of irradiated DOM was observed with all DOM fractions. Reactive species, such as organic peroxides and hydroxyl radicals appear to inhibit bacterial growth on a short term, followed by its partial recovery. Light-induced, iron-catalyzed transformation of DOM significantly decreased the microbial turnover of organic carbon compounds, and therefore appears to play a critical role in the cycling and transport of DOM in this highly oligotrophic system.