Department of Oceanography, School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i at Mānoa, Honolulu, HI 96822, USA.
Daniel K. Inouye Center for Microbial Oceanography: Research and Education, School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i at Mānoa, Honolulu, HI 96822, USA.
Proc Biol Sci. 2023 Jan 25;290(1991):20222021. doi: 10.1098/rspb.2022.2021.
A large fraction of marine primary production is performed by diverse small protists, and many of these phytoplankton are phagotrophic mixotrophs that vary widely in their capacity to consume bacterial prey. Prior analyses suggest that mixotrophic protists as a group vary in importance across ocean environments, but the mechanisms leading to broad functional diversity among mixotrophs, and the biogeochemical consequences of this, are less clear. Here we use isolates from seven major taxa to demonstrate a tradeoff between phototrophic performance (growth in the absence of prey) and phagotrophic performance (clearance rate when consuming ). We then show that trophic strategy along the autotrophy-mixotrophy spectrum correlates strongly with global niche differences, across depths and across gradients of stratification and chlorophyll . A model of competition shows that community shifts can be explained by greater fitness of faster-grazing mixotrophs when nutrients are scarce and light is plentiful. Our results illustrate how basic physiological constraints and principles of resource competition can organize complexity in the surface ocean ecosystem.
海洋初级生产力的很大一部分是由多种多样的小型原生生物完成的，其中许多浮游植物是吞噬性混合营养体，它们消耗细菌猎物的能力差异很大。先前的分析表明，混合营养体作为一个群体，在海洋环境中的重要性各不相同，但导致混合营养体功能广泛多样性的机制以及由此产生的生物地球化学后果尚不明确。在这里，我们使用来自七个主要类群的分离物来证明在光合性能（无猎物生长）和吞噬性能（消耗时的清除率）之间存在权衡。然后，我们表明，沿着自养-混合营养谱的营养策略与全球生态位差异强烈相关，这些差异跨越了深度以及分层和叶绿素的梯度。竞争模型表明，当营养物质稀缺且光照充足时，具有更高适应性的摄食混合营养体可以解释群落的变化。我们的研究结果说明了基本生理限制和资源竞争原则如何在海洋表面生态系统的复杂性中发挥作用。
