Ocean Biogeochemistry and Ecosystems Research Group, National Oceanography Centre, Southampton SO14 3ZH, United Kingdom.
Proc Natl Acad Sci U S A. 2012 Apr 10;109(15):5756-60. doi: 10.1073/pnas.1118179109. Epub 2012 Mar 26.
Oligotrophic subtropical gyres are the largest oceanic ecosystems, covering >40% of the Earth's surface. Unicellular cyanobacteria and the smallest algae (plastidic protists) dominate CO(2) fixation in these ecosystems, competing for dissolved inorganic nutrients. Here we present direct evidence from the surface mixed layer of the subtropical gyres and adjacent equatorial and temperate regions of the Atlantic Ocean, collected on three Atlantic Meridional Transect cruises on consecutive years, that bacterioplankton are fed on by plastidic and aplastidic protists at comparable rates. Rates of bacterivory were similar in the light and dark. Furthermore, because of their higher abundance, it is the plastidic protists, rather than the aplastidic forms, that control bacterivory in these waters. These findings change our basic understanding of food web function in the open ocean, because plastidic protists should now be considered as the main bacterivores as well as the main CO(2) fixers in the oligotrophic gyres.
贫营养亚热带回旋流是最大的海洋生态系统，覆盖了地球表面的>40%。在这些生态系统中，单细胞蓝细菌和最小的藻类（质体原生生物）占主导地位，它们通过竞争溶解无机养分来固定 CO(2)。在这里，我们提供了直接证据，这些证据来自于大西洋亚热带回旋流及其相邻的赤道和温带地区的表层混合层，这些样本是在连续三年的三次大西洋子午剖面考察中收集的，表明质体和无质体原生生物以相当的速率被细菌吞噬。在有光和无光的情况下，细菌的吞噬率是相似的。此外，由于它们的丰度更高，控制这些水域中细菌吞噬的是质体原生生物，而不是无质体形式。这些发现改变了我们对开阔海洋食物网功能的基本认识，因为现在应该将质体原生生物视为贫营养回旋流中的主要细菌吞噬者和主要 CO(2)固定者。
