Response of macrophyte litter decomposition in global blue carbon ecosystems to climate change |
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| Authors: | Xiaoguang Ouyang Erik Kristensen Martin Zimmer Carol Thornber Zhifeng Yang Shing Yip Lee |
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| Institution: | 1. Research Centre of Ecology & Environment for Coastal Area and Deep Sea, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, 511458 China;2. Department of Biology, University of Southern Denmark, Odense, 5230 Denmark;3. Leibniz Centre for Tropical Marine Research and University of Bremen, 28359 Bremen, Germany;4. Department of Natural Resources Science, The University of Rhode Island, Kingston, Rode Island, 02881 USA;5. Research Centre of Ecology & Environment for Coastal Area and Deep Sea, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, 511458 China
Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou, 510006 China;6. Simon F.S. Li Marine Science Laboratory and School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, SAR, China |
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| Abstract: | Blue carbon ecosystems (BCEs) are important nature-based solutions for climate change-mitigation. However, current debates question the reliability and contribution of BCEs under future climatic-scenarios. The answer to this question depends on ecosystem processes driving carbon-sequestration and -storage, such as primary production and decomposition, and their future rates. We performed a global meta-analysis on litter decomposition rate constants (k) in BCEs and predicted changes in carbon release from 309 studies. The relationships between k and climatic factors were examined by extracting remote-sensing data on air temperature, sea-surface temperature, and precipitation aligning to the decomposition time of each experiment. We constructed global numerical models of litter decomposition to forecast k and carbon release under different scenarios. The current k averages at 27 ± 3 × 10−2 day−1 for macroalgae were higher than for seagrasses (1.7 ± 0.2 × 10−2 day−1), mangroves (1.6 ± 0.1 × 10−2 day−1) and tidal marshes (5.9 ± 0.5 × 10−3 day−1). Macrophyte k increased with both air temperature and precipitation in intertidal BCEs and with sea surface temperature for subtidal seagrasses. Above a temperature threshold for vascular plant litter at ~25°C and ~20°C for macroalgae, k drastically increased with increasing temperature. However, the direct effect of high temperatures on k are obscured by other factors in field experiments compared with laboratory experiments. We defined “fundamental” and “realized” temperature response to explain this effect. Based on relationships for realized temperature response, we predict that proportions of decomposed litter will increase by 0.9%–5% and 4.7%–28.8% by 2100 under low- (2°C) and high-warming conditions (4°C) compared to 2020, respectively. Net litter carbon sinks in BCEs will increase due to higher increase in litter C production than in decomposition by 2100 compared to 2020 under RCP 8.5. We highlight that BCEs will play an increasingly important role in future climate change-mitigation. Our findings can be leveraged for blue carbon accounting under future climate change scenarios. |
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| Keywords: | blue carbon ecosystems carbon sinks climate change litter decomposition mangroves tidal marshes seagrasses and macroalgae warming |
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