Effects of solar radiation on the abiotic and bacterially mediated carbon flux in aquatic ecosystems
Research output: Thesis › Doctoral Thesis (compilation)
In this Thesis, I studied some of the current aspects of organic matter photochemistry. I analyzed abiotic phototransformations of several types of dissolved (DOM) and particulate organic matter (POM). I also evaluated the effects of phototransformation of several types of DOM on bacteria. Finally, in a field experiment, I analyzed net effects of solar radiation on organic matter decomposition. DOM undergoes several transformations due to solar irradiation. One such transformation is photooxidation of organic matter into inorganic carbon. Results of this Thesis show that photooxidation is ubiquitous to all kinds of organic matter in both dissolved and particulate forms. The intensity of this process depends on several factors, including DOM composition, radiation type and time of exposure. Besides mineralization to inorganic carbon, DOM undergoes other chemical transformations due to UV radiation, with profound consequences to DOM availability for bacteria. Bioavailability was tested by measuring bacterial growth and respiration on irradiated and non-irradiated DOM from several types of humic matter and plant leachates. Irradiation of freshly-leached DOM often produced negative effects on bacteria, whereas irradiation of humic material was followed by stimulation of bacterial growth. The degree of stimulation seems to be related to the initial bioavailability of the DOM and to the capability of the DOM to produce hydrogen peroxide upon irradiation. Other factors also accounted for differences in bacterial response to photochemical modification of DOM, including length and type of irradiation exposure. The effects of solar radiation on litter decomposition were also evaluated using experiments that more closely mimic natural conditions. I could not observe differences between dry weight loss of leaves and culms exposed to solar radiation or kept in darkness, which may be explained by the fact that abiotic decomposition under solar radiation is counterbalanced by negative effects of solar radiation on decomposers.
|Research areas and keywords||
Subject classification (UKÄ) – MANDATORY
|Award date||2000 May 5|
|Publication status||Published - 2000|
Defence details Date: 2000-05-05 Time: 10:15 Place: Department of Ecology, Sölvegatan 37, at the Blue Room External reviewer(s) Name: Cole, Jonathan J. Title: Dr Affiliation: Institute of Ecosystem Studies, New York --- The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Limnology (Closed 2011) (011007000)