Department of Ecology and Animal Biology, Marine Science Faculty, University of Vigo, Vigo, Spain.
Toralla Marine Science Station (ECIMAT), University of Vigo, Vigo, Spain.
Glob Chang Biol. 2018 Aug;24(8):3766-3779. doi: 10.1111/gcb.14278. Epub 2018 May 8.
Algal wrack subsidies underpin most of the food web structure of exposed sandy beaches and are responsible of important biogeochemical processes that link marine and terrestrial ecosystems. The response in decomposition of algal wrack deposits to global warming has not been studied in ocean-exposed sandy beaches to date. With this aim, passive open top chambers (OTCs) were used to increase soil temperature within the range predicted by the IPCC for western Europe (between 0.5 and 1.5°C), following the hypothesis that the biogeochemical processing of macroalgal wrack subsidies would accelerate in response to temperature increase. The effect of temperature manipulation on three target substrates: fresh and aged macroalgae, and bare sand, was tested. Results indicated that a small warming (<0.5°C) affected the wrack decomposition process through traceable increases in soil respiration through CO flux, inorganic nutrients within the interstitial environment (N and P), sediment organic contents measured through the amount of proteins and microbial pool through the total soil DNA. The different responses of soil variables in the studied substrates indicated that the decomposition stage of stranded macroalgae influences the biogeochemical processing of organic matter in sandy beaches. Thus, CO fluxes, releases of organic and inorganic nutrients and microbial activity intensify in aged wrack deposits. Our results predict that expected global warming will increase the release of inorganic nutrients to the coastal ocean by 30% for the N (21 Gg/year) and 5.9% for P (14 Gg/year); that increase for the flow of C to the atmosphere as CO was estimated in 8.2% (523 Gg/year). This study confirms the key role of sandy beaches in recycling ocean-derived organic matter, highlighting their sensitivity to a changing scenario of global warming that predicts significant increases in temperature over the next few decades.
海藻垫料补贴支撑着大部分暴露沙滩的食物网结构，并负责将海洋和陆地生态系统联系起来的重要生物地球化学过程。迄今为止，尚未在海洋暴露的沙滩上研究过海藻垫料沉积物对全球变暖的分解反应。为此，使用被动开顶式气室 (OTC) 将土壤温度升高到 IPCC 预测的西欧范围内 (在 0.5 和 1.5°C 之间），假设随着温度升高，大型海藻垫料补贴的生物地球化学处理会加速。测试了温度处理对三个目标底物的影响：新鲜和老化的大型藻类和裸沙。结果表明，较小的升温 (<0.5°C) 通过 CO 通量的土壤呼吸可追踪增加，间隙环境中的无机养分 (N 和 P) 、通过蛋白质数量测量的沉积物有机含量以及通过总土壤 DNA 测量的微生物库，对海藻垫料分解过程产生了影响。研究底物中土壤变量的不同反应表明，搁浅大型藻类的分解阶段会影响沙滩上有机物的生物地球化学处理。因此，在老化的海藻垫料沉积物中，CO 通量、有机和无机养分的释放以及微生物活性增强。我们的结果预测，预计全球变暖将使向沿海海洋释放的无机养分增加 30%（N 为 21 Gg/年）和 5.9%（P 为 14 Gg/年）；作为 CO 的 C 通量增加估计为 8.2%（523 Gg/年）。这项研究证实了沙滩在回收海洋来源有机物方面的关键作用，突出了它们对未来几十年内全球变暖预测的温度显著升高的情景的敏感性。
