Thermal Responses in Global Marine Planktonic Food Webs Are Mediated by Temperature Effects on Metabolism
Thermal Responses in Global Marine Planktonic Food Webs Are Mediated by Temperature Effects on Metabolism
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DOI：
10.1029/2022jc018932
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发表时间：
2022-12-01
影响因子：
3.6
通讯作者：
Moeller, Holly, V
中科院分区：
文献类型：
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作者：
Archibald, Kevin M.;Dutkiewicz, Stephanie;Moeller, Holly, V
海洋温度上升直接影响海洋微生物生态系统，因为代谢率（例如，光合作用、呼吸作用）都依赖于温度，但温度也通过物理环境的变化产生间接影响。对生物量和生产力长期趋势的经验性观察衡量了这两种效应的综合反应，使得独立的组成部分难以分开。我们使用了建模方法的组合来隔离温度升高对微生物代谢的直接影响，并探讨了食物网动态和全球生物地球化学的后果。我们在两种情况下评估了温度敏感性的影响：第一，假设所有的代谢过程具有相同的温度敏感性，或者，异养过程比自养过程具有更高的温度敏感性。高温下的微生物生态系统的特点是生产力增加，但由于短暂的高输出事件减少了表层海洋中的营养物质供应，生物量储存减少。营养动态也介导社会结构的变化，导致在较高的温度下增加异养自养比。当异养生物的温度敏感性高于自养生物时，这些生态系统的热响应被放大。这些结果为理解食物网对直接和间接温度影响的综合反应提供了重要背景，并为气候预测中使用的地球系统模型的构建和解释提供了信息。简明扼要的语言摘要海洋变暖给海洋生态系统带来了无数变化，包括生物体本身的生物变化和环境的物理变化。在这里，我们使用数学模型来隔离温度对代谢率的影响直接引起的变暖的影响，以及由此产生的海洋食物网和全球碳循环的变化。我们专注于不同的代谢率（例如，海洋生态系统（包括光合作用、放牧）对温度的敏感性可能不同，这些差异对海洋生态系统的总体热敏感性产生的后果也不同。我们发现，海洋食物网有较高的生产力，但整体生物量较少，当温度升高。当放牧对温度的敏感性大于光合作用时，这些效应被放大。温度升高也对群落和食物网结构产生影响。这些结果为气候变化预测中使用的各种全球模式提供了重要背景。
Rising ocean temperatures affect marine microbial ecosystems directly, since metabolic rates (e.g., photosynthesis, respiration) are temperature-dependent, but temperature also has indirect effects mediated through changes to the physical environment. Empirical observations of the long-term trends in biomass and productivity measure the integrated response of these two kinds of effects, making the independent components difficult to disentangle. We used a combination of modeling approaches to isolate the direct effects of rising temperatures on microbial metabolism and explored the consequences for food web dynamics and global biogeochemistry. We evaluated the effects of temperature sensitivity in two cases: first, assuming that all metabolic processes have the same temperature sensitivity, or, alternatively, that heterotrophic processes have higher temperature sensitivity than autotrophic processes. Microbial ecosystems at higher temperatures are characterized by increased productivity but decreased biomass stocks as a result of transient, high export events that reduce nutrient availability in the surface ocean. Trophic dynamics also mediate community structure shifts resulting in increased heterotroph to autotroph ratios at higher temperatures. These ecosystem thermal responses are magnified when the temperature sensitivity of heterotrophs is higher than that of autotrophs. These results provide important context for understanding the combined food web response to direct and indirect temperature effects and inform the construction and interpretation of Earth systems models used in climate projections.Plain Language Summary Warming oceans cause a myriad of changes to marine ecosystems, including both biological changes to the organisms themselves and physical changes to the environment. Here, we use mathematical models to isolate the effects of warming that arise directly from temperature's effect on metabolic rates, and the resulting changes to marine food webs and the global carbon cycle. We focus on how different metabolic rates (e.g., photosynthesis, grazing) may have different temperature sensitivities and the consequences of those differences on the overall thermal sensitivity of marine ecosystems. We found that marine food webs had higher productivity, but less overall biomass, when temperatures increase. These effects were amplified when grazing had greater temperature sensitivity than photosynthesis. Increased temperature also had effects on community and food web structure. These results provide important context for the kinds of global models that are used in climate change projections.