期刊
ARCHIV FUR HYDROBIOLOGIE
卷 156, 期 3, 页码 287-314出版社
E SCHWEIZERBARTSCHE VERLAGS
DOI: 10.1127/0003-9136/2003/0156-0287
关键词
dissolved organic matter; photolysis; mineralization; UV-effects
Carbon, nitrogen and phosphorus associated with dissolved organic matter (DOM) form a large potential source of nutrients and energy for bacterio- and phytoplankton. The role of solar radiation in the transformation of DOM into inorganic and bioavailable forms was investigated in a humic boreal Lake Valkea-Kotinen. The concentrations of nitrate+nitrite, inorganic phosphorus and inorganic carbon increased, but those of ammonium decreased in < 0.2-mum filtered hypolimnetic water during 1-day exposures to solar radiation. In epilimnetic water, solar radiation increased the concentration of ammonium at a rate equivalent to the rate of atmospheric deposition of inorganic nitrogen. When indigenous bacteria of Lake Valkea-Kotinen were inoculated into sunlight-exposed waters, bacteria achieved higher biovolume and productivity and incorporated carbon, nitrogen and phosphorus at greater rates than those grown in non-exposed waters. Bacteria mineralized dissolved organic carbon 92-375% more in exposed than in non-exposed waters. Thus, in addition to direct photochemical mineralization, solar radiation increased metabolic mineralization of organic carbon by bacteria. Solar radiation decreased the activity of phosphomonoesterase during exposures down to <1% of the initial values. However, after 4-d bioassay the activity of phosphomonoestrase in the exposed waters exceeded that in the non-exposed water.
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