Research Division Marine Biogeochemistry, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany ; Institute for General Microbiology, Christian-Albrechts-University, Kiel, Germany.
PLoS One. 2013 Aug 21;8(8):e68661. doi: 10.1371/journal.pone.0068661. eCollection 2013.
In Eastern Boundary Upwelling Systems nutrient-rich waters are transported to the ocean surface, fuelling high photoautotrophic primary production. Subsequent heterotrophic decomposition of the produced biomass increases the oxygen-depletion at intermediate water depths, which can result in the formation of oxygen minimum zones (OMZ). OMZs can sporadically accumulate hydrogen sulfide (H2S), which is toxic to most multicellular organisms and has been implicated in massive fish kills. During a cruise to the OMZ off Peru in January 2009 we found a sulfidic plume in continental shelf waters, covering an area >5500 km(2), which contained ∼2.2×10(4) tons of H2S. This was the first time that H2S was measured in the Peruvian OMZ and with ∼440 km(3) the largest plume ever reported for oceanic waters. We assessed the phylogenetic and functional diversity of the inhabiting microbial community by high-throughput sequencing of DNA and RNA, while its metabolic activity was determined with rate measurements of carbon fixation and nitrogen transformation processes. The waters were dominated by several distinct γ-, δ- and ε-proteobacterial taxa associated with either sulfur oxidation or sulfate reduction. Our results suggest that these chemolithoautotrophic bacteria utilized several oxidants (oxygen, nitrate, nitrite, nitric oxide and nitrous oxide) to detoxify the sulfidic waters well below the oxic surface. The chemolithoautotrophic activity at our sampling site led to high rates of dark carbon fixation. Assuming that these chemolithoautotrophic rates were maintained throughout the sulfidic waters, they could be representing as much as ∼30% of the photoautotrophic carbon fixation. Postulated changes such as eutrophication and global warming, which lead to an expansion and intensification of OMZs, might also increase the frequency of sulfidic waters. We suggest that the chemolithoautotrophically fixed carbon may be involved in a negative feedback loop that could fuel further sulfate reduction and potentially stabilize the sulfidic OMZ waters.
在东边界上升流系统中，富营养水被输送到海洋表面，为高光合作用初级生产力提供燃料。随后，产生的生物量的异养分解会增加中层水的缺氧程度，从而导致形成氧最小区 (OMZ)。OMZ 会偶尔积累硫化氢 (H2S)，这对大多数多细胞生物都是有毒的，并且与大规模鱼类死亡有关。在 2009 年 1 月对秘鲁 OMZ 的一次巡航中，我们在大陆架水域发现了一个含有约 2.2×10(4)吨 H2S 的硫化物羽流，覆盖面积超过 5500 平方公里。这是首次在秘鲁 OMZ 中测量到 H2S，而羽流的体积约为 440 立方公里，是迄今为止报告的海洋水域中最大的羽流。我们通过高通量 DNA 和 RNA 测序评估了栖息微生物群落的系统发育和功能多样性，同时通过测定碳固定和氮转化过程的速率来确定其代谢活性。这些水域主要由几种不同的γ-、δ-和 ε-变形菌门分类群主导，它们与硫氧化或硫酸盐还原有关。我们的研究结果表明，这些化能自养细菌利用几种氧化剂（氧气、硝酸盐、亚硝酸盐、一氧化氮和氧化亚氮）来解毒远低于有氧表面的硫化物水。在我们的采样点，化能自养活性导致了高的黑暗碳固定速率。假设这些化能自养率在整个硫化物水域中保持不变，它们可能代表了高达 30%的光自养碳固定。假设的变化，如富营养化和全球变暖，导致 OMZ 的扩张和加剧，也可能增加硫化物水的频率。我们认为，化能自养固定的碳可能参与负反馈循环，从而为进一步的硫酸盐还原提供燃料，并有可能稳定硫化物 OMZ 水域。
