Department of Marine Biology and Oceanography, Institut de Ciències del Mar, CSIC Barcelona, Spain ; Département des Sciences Biologiques, Université du Québéc à Montréal Montréal, QC, Canada.
Front Microbiol. 2013 May 23;4:131. doi: 10.3389/fmicb.2013.00131. eCollection 2013.
Heterotrophic bacterioplankton are main consumers of dissolved organic matter (OM) in aquatic ecosystems, including the sunlit upper layers of the ocean and freshwater bodies. Their well-known sensitivity to ultraviolet radiation (UVR), together with some recently discovered mechanisms bacteria have evolved to benefit from photosynthetically available radiation (PAR), suggest that natural sunlight plays a relevant, yet difficult to predict role in modulating bacterial biogeochemical functions in aquatic ecosystems. Three decades of experimental work assessing the effects of sunlight on natural bacterial heterotrophic activity reveal responses ranging from high stimulation to total inhibition. In this review, we compile the existing studies on the topic and discuss the potential causes underlying these contrasting results, with special emphasis on the largely overlooked influences of the community composition and the previous light exposure conditions, as well as the different temporal and spatial scales at which exposure to solar radiation fluctuates. These intricate sunlight-bacteria interactions have implications for our understanding of carbon fluxes in aquatic systems, yet further research is necessary before we can accurately evaluate or predict the consequences of increasing surface UVR levels associated with global change.
异养浮游细菌是水生生态系统中溶解有机物 (OM) 的主要消费者，包括海洋的阳光上层和淡水体。它们对紫外线辐射 (UVR) 的众所周知的敏感性，以及一些最近发现的细菌为了从光合可用辐射 (PAR) 中受益而进化出的机制，表明自然阳光在调节水生生态系统中细菌生物地球化学功能方面起着相关但难以预测的作用。三十年来，评估阳光对自然细菌异养活性影响的实验工作揭示了从高度刺激到完全抑制的反应。在这篇综述中，我们汇编了关于该主题的现有研究，并讨论了导致这些对比结果的潜在原因，特别强调了群落组成和先前光照条件的影响，以及太阳辐射波动的不同时间和空间尺度，这些复杂的阳光-细菌相互作用对我们理解水生系统中的碳通量有影响，但在我们能够准确评估或预测与全球变化相关的地表 UVR 水平增加的后果之前，还需要进一步的研究。
