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Title: Warming enhances the stimulatory effect of algal exudates on dissolved organic carbon decomposition
Abstract The current paradigm in peatland ecology is that the organic matter inputs from plant photosynthesis (e.g. moss litter) exceed that of decomposition, tipping the metabolic balance in favour of carbon (C) storage. Here, we investigated an alternative hypothesis, whereby exudates released by microalgae can actually accelerate C losses from the surface waters of northern peatlands by stimulating dissolved organic C (DOC) decomposition in a warmer environment expected with climate change. To test this hypothesis, we evaluated the biodegradability of fenDOCin a factorial design with and without algalDOCin both ambient (15°C) and elevated (20°C) water temperatures during a laboratory bioassay.WhenDOCsources were evaluated separately, decomposition rates were higher in treatments with algalDOConly than with fenDOConly, indicating that the quality of the organic matter influenced degradability. A mixture of substrates (½ algalDOC + ½ fenDOC) exceeded the expected level of biodegradation (i.e. the average of the individual substrate responses) by as much as 10%, and the magnitude of this effect increased to more than 15% with warming.Specific ultraviolet absorbance at 254 nm (SUVA254), a proxy for aromatic content, was also significantly higher (i.e. more humic) in the mixture treatment than expected from SUVA254values in single substrate treatments.Accelerated decomposition in the presence of algalDOCwas coupled with an increase in bacterial biomass, demonstrating that enhanced metabolism was associated with a more abundant microbial community.These results present an alternative energy pathway for heterotrophic consumers to breakdown organic matter in northern peatlands. Since decomposition in northern peatlands is often limited by the availability of labile organic matter, this mechanism could become increasingly important as a pathway for decomposition in the surface waters of northern peatlands where algae are expected to be more abundant in conditions associated with ongoing climate change.  more » « less
Award ID(s):
1651195
PAR ID:
10457143
Author(s) / Creator(s):
 ;  
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
Freshwater Biology
Volume:
65
Issue:
7
ISSN:
0046-5070
Page Range / eLocation ID:
p. 1288-1297
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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