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Effects of solar radiation on the abiotic and bacterially mediated carbon flux in aquatic ecosystems

Anesio, Alexandre Magno LU (2000) In Department of Ecology, Limnology, Lund University, Sweden 1043.
Abstract (Swedish)
Popular Abstract in Swedish

Solljusets effekter på abiotiska och bakteriella kolflöden i akvatiska system



I denna avhandling behandlar jag solljusets effekter på organiskt material. Jag har analyserat hur solljus förändrar olika sorters löst organiskt kol och partikulärt organiskt kol. Vidare har jag utvärderat de indirekta effekterna som förändringar av löst organiskt kol har på bakterier. Slutligen har jag, i fältexperiment, analyserat nettoeffekten av solstrålning på nedbrytningen av organiskt material. Solstrålning orsakar flera olika förändringar av löst organiskt kol. En sådan förändring är oxidation till oorganiskt kol. Av resultaten i avhandlingen framgår att allt organiskt material, både löst och... (More)
Popular Abstract in Swedish

Solljusets effekter på abiotiska och bakteriella kolflöden i akvatiska system



I denna avhandling behandlar jag solljusets effekter på organiskt material. Jag har analyserat hur solljus förändrar olika sorters löst organiskt kol och partikulärt organiskt kol. Vidare har jag utvärderat de indirekta effekterna som förändringar av löst organiskt kol har på bakterier. Slutligen har jag, i fältexperiment, analyserat nettoeffekten av solstrålning på nedbrytningen av organiskt material. Solstrålning orsakar flera olika förändringar av löst organiskt kol. En sådan förändring är oxidation till oorganiskt kol. Av resultaten i avhandlingen framgår att allt organiskt material, både löst och partikulärt, i varierande utsträckning oxideras som ett resultat av solstrålning. Hur betydande denna process är beror på flera faktorer, bland annat sammansättningen av det organiska kolet, exponeringstiden och typen av strålning. Förutom oxidation till oorganiskt kol så kan löst organiskt kol omvandlas kemiskt som ett resultat av UV-strålning. Detta påverkar kolets tillgänglighet för bakterier. Tillgängligheten har testats genom mätning av bakterietillväxt och bakterierespiration på bestrålat och icke-bestrålat löst kol från flera typer av humöst material och växtexudat. Bestrålning av nyligen exuderat kol påverkade ofta bakterier negativt, medan bestrålning av humusmaterial ledde till en ökad bakterietillväxt. Ökningens storlek tycks vara relaterad till den ursprungliga tillgängligheten av det lösta kolet, samt dess benägenhet att bilda väteperoxid under bestrålning. Även andra faktorer, såsom exponeringstid och typ av strålning, orsakade olika respons hos bakterierna. Solljusets effekt på nedbrytningen av döda växtdelar utvärderades genom experiment som efterliknade naturliga förhållanden. Jag kunde inte observera några skillnader mellan torrvikt hos löv och vass-strån som exponerats för solljus respektive hållits i mörker. Detta kan bero på att negativa effekter på nedbrytande organismer uppväger en eventuellt ökad kemisk nedbrytning. (Less)
Abstract
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... (More)
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. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Dr Cole, Jonathan J., Institute of Ecosystem Studies, New York
organization
publishing date
type
Thesis
publication status
published
subject
keywords
bacteria, dissolved inorganic carbon (DIC), bioavailability, aquatic macrophytes, photooxidation, detritus decomposition, Ultraviolet radiation, dissolved organic carbon (DOC), fungi, Hydrobiology, marine biology, aquatic ecology, limnology, Marinbiologi, limnologi, akvatisk ekologi
in
Department of Ecology, Limnology, Lund University, Sweden
volume
1043
pages
130 pages
publisher
Department of Ecology, Lund University
defense location
Department of Ecology, Sölvegatan 37, at the Blue Room
defense date
2000-05-05 10:15
external identifiers
  • other:ISRN: SE-LUNDS/NBLI-00/1043+130pp
ISSN
1100-6366
ISBN
91-7105-135-x
language
English
LU publication?
yes
id
3b6751f1-26e6-475f-a30d-bc27ab9a5851 (old id 40369)
date added to LUP
2007-06-20 10:51:23
date last changed
2016-09-19 08:44:56
@phdthesis{3b6751f1-26e6-475f-a30d-bc27ab9a5851,
  abstract     = {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.},
  author       = {Anesio, Alexandre Magno},
  isbn         = {91-7105-135-x},
  issn         = {1100-6366},
  keyword      = {bacteria,dissolved inorganic carbon (DIC),bioavailability,aquatic macrophytes,photooxidation,detritus decomposition,Ultraviolet radiation,dissolved organic carbon (DOC),fungi,Hydrobiology,marine biology,aquatic ecology,limnology,Marinbiologi,limnologi,akvatisk ekologi},
  language     = {eng},
  pages        = {130},
  publisher    = {Department of Ecology, Lund University},
  school       = {Lund University},
  series       = {Department of Ecology, Limnology, Lund University, Sweden},
  title        = {Effects of solar radiation on the abiotic and bacterially mediated carbon flux in aquatic ecosystems},
  volume       = {1043},
  year         = {2000},
}