Warming enhances the stimulatory effect of algal exudates on dissolved organic carbon decomposition
Warming enhances the stimulatory effect of algal exudates on dissolved organic carbon decomposition
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DOI：
10.1111/fwb.13390
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发表时间：
2020-07
影响因子：
2.7
通讯作者：
Kevin H. Wyatt;A. Rober
中科院分区：
文献类型：
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作者：
Kevin H. Wyatt;A. Rober
目前泥炭地生态学的范式是，来自植物光合作用的有机物质输入（例如苔藓凋落物）超过了分解，使代谢平衡倾向于碳（C）储存。在这里，我们调查了一个替代假设，即微藻释放的分泌物实际上可以加速碳损失的表面沃茨的北方泥炭地刺激溶解有机碳（DOC）分解在一个温暖的环境中预计与气候变化。为了验证这一假设，我们在实验室生物测定期间，在环境温度（15°C）和升高的水温（20°C）下，在有和没有藻类DOC的析因设计中评估了fen DOC的生物降解性。当DOC源分别进行评估，分解率较高的处理与藻类DOC仅比与芬DOC，表明有机质的质量影响降解性。基质的混合物（1/2藻类DOC +1/2芬DOC）超过了预期的生物降解水平（即单个基质响应的平均值）高达10%，这种影响的幅度增加到15%以上的变暖。在254 nm处的特定紫外吸光度（苏瓦吸收率），芳香族含量的代理，也显着更高（即更多的腐殖酸）的混合物处理比预期的苏瓦吸收率值在单一基质处理。在藻类DOC的存在下，加速分解加上细菌生物量的增加，表明增强代谢与更丰富的微生物群落。这些结果提出了一个替代能源的途径，异养消费者分解有机物在北方泥炭地。由于分解在北方泥炭地往往是有限的可用性不稳定的有机物质，这种机制可能会变得越来越重要的分解途径，在北方泥炭地，藻类预计将更加丰富的条件下与持续的气候变化。
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 fen DOC in a factorial design with and without algal DOC in both ambient (15°C) and elevated (20°C) water temperatures during a laboratory bioassay. When DOC sources were evaluated separately, decomposition rates were higher in treatments with algal DOC only than with fen DOC only, indicating that the quality of the organic matter influenced degradability. A mixture of substrates (½ algal DOC + ½ fen DOC) 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 SUVA₂₅₄ values in single substrate treatments. Accelerated decomposition in the presence of algal DOC was 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.