Departamento de Ecología y Biología Animal, Facultad de Ciencias del Mar, Universidad de Vigo, Campus Lagoas Marcosende s/n, 36310 Vigo, Spain; Centro de Investigación Mariña, Universidad de Vigo (CIM-UVigo), Illa de Toralla s/n, 36331 Vigo, Spain; Departamento de Ecología, Universidad de Granada, Campus Fuentenueva s/n, 18071 Granada, Spain.
Departamento de Ecología, Universidad de Granada, Campus Fuentenueva s/n, 18071 Granada, Spain; Instituto Universitario de Investigación del Agua, C/Ramón y Cajal, n 4, 18071 Granada, Spain.
Sci Total Environ. 2022 Apr 10;816:151491. doi: 10.1016/j.scitotenv.2021.151491. Epub 2021 Nov 6.
Multiple drivers are threatening the functioning of the microbial food webs and trophic interactions. Our understanding about how temperature, CO, nutrient inputs, and solar ultraviolet radiation (UVR) availability interact to alter ecosystem functioning is scarce because research has focused on single and double interactions. Moreover, the role that the degree of in situ nutrient limitation could play in the outcome of these interactions has been largely neglected, despite it is predominant in marine ecosystems. We address these uncertainties by combining remote-sensing analyses, and a collapsed experimental design with natural microbial communities from Mediterranean Sea and Atlantic Ocean exposed to temperature, nutrients, CO, and UVR interactions. At the decade scale, we found that more intense and frequent (and longer lasting) Saharan dust inputs (and marine heatwaves) were only coupled with reduced phytoplankton biomass production. When microbial communities were concurrently exposed to future temperature, CO, nutrient, and UVR conditions (i.e. the drivers studied over long-term scales), we found shifts from net autotrophy [primary production:respiration (PP:R) ratio > 1] towards a metabolic equilibrium (PP:R ratio ~ 1) or even a net heterotrophy (PP:R ratio < 1), as P-limitation degree was higher (i.e. Atlantic Ocean). These changes in the metabolic balance were coupled with a weakened phytoplankton-bacteria interaction (i.e. bacterial carbon demand exceeded phytoplankton carbon supply. Our work reveals that an accentuated in situ P limitation may promote reductions both in carbon uptake and fluxes between trophic levels in microbial plankton communities under global-change conditions. We show that considering long-term series can aid in identifying major local environmental drivers (i.e. temperature and nutrients in our case), easing the design of future global-change studies, but also that the abiotic environment to which microbial plankton communities are acclimated should be taken into account to avoid biased predictions concerning the effects of multiple interacting global-change drivers on marine ecosystems.
多种驱动因素正在威胁微生物食物网和营养相互作用的功能。我们对温度、CO2、养分输入和太阳紫外线辐射 (UVR) 可用性如何相互作用以改变生态系统功能的理解还很匮乏，因为研究主要集中在单一和双重相互作用上。此外，尽管在海洋生态系统中普遍存在，但原位养分限制程度在这些相互作用的结果中可能发挥的作用在很大程度上被忽视了。我们通过结合遥感分析和一个从地中海和大西洋暴露于温度、养分、CO2 和 UVR 相互作用的自然微生物群落的崩溃实验设计来解决这些不确定性。在十年的时间尺度上，我们发现更强烈和频繁（并且持续时间更长）的撒哈拉尘埃输入（和海洋热浪）仅与减少浮游植物生物量生产有关。当微生物群落同时暴露于未来的温度、CO2、养分和 UVR 条件下（即长期尺度上研究的驱动因素）时，我们发现从净自养（初级生产：呼吸 (PP:R) 比>1）向代谢平衡（PP:R 比~1）甚至净异养（PP:R 比<1）的转变，因为限制程度越高（即大西洋）。这种代谢平衡的变化与浮游植物-细菌相互作用的减弱有关（即细菌的碳需求超过了浮游植物的碳供应）。我们的工作表明，在全球变化条件下，原位 P 限制的加剧可能会减少微生物浮游生物群落中碳的吸收和营养水平之间的通量。我们表明，考虑长期系列可以帮助确定主要的本地环境驱动因素（在我们的案例中即温度和养分），从而简化未来全球变化研究的设计，但也应考虑微生物浮游生物群落适应的非生物环境，以避免对多种相互作用的全球变化驱动因素对海洋生态系统的影响产生有偏差的预测。
