Canadian Rivers Institute, University of New Brunswick, 100 Tucker Park Road, Saint John, NB, E2L 4L5, Canada.
Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA, 02543, USA.
Glob Chang Biol. 2017 Jan;23(1):331-340. doi: 10.1111/gcb.13370. Epub 2016 Jul 4.
Removal of biologically available nitrogen (N) by the microbially mediated processes denitrification and anaerobic ammonium oxidation (anammox) affects ecosystem N availability. Although few studies have examined temperature responses of denitrification and anammox, previous work suggests that denitrification could become more important than anammox in response to climate warming. To test this hypothesis, we determined whether temperature responses of denitrification and anammox differed in shelf and estuarine sediments from coastal Rhode Island over a seasonal cycle. The influence of temperature and organic C availability was further assessed in a 12-week laboratory microcosm experiment. Temperature responses, as characterized by thermal optima (T ) and apparent activation energy (E ), were determined by measuring potential rates of denitrification and anammox at 31 discrete temperatures ranging from 3 to 59 °C. With a few exceptions, T and E of denitrification and anammox did not differ in Rhode Island sediments over the seasonal cycle. In microcosm sediments, E was somewhat lower for anammox compared to denitrification across all treatments. However, T did not differ between processes, and neither E nor T changed with warming or carbon addition. Thus, the two processes behaved similarly in terms of temperature responses, and these responses were not influenced by warming. This led us to reject the hypothesis that anammox is more cold-adapted than denitrification in our study system. Overall, our study suggests that temperature responses of both processes can be accurately modeled for temperate regions in the future using a single set of parameters, which are likely not to change over the next century as a result of predicted climate warming. We further conclude that climate warming will not directly alter the partitioning of N flow through anammox and denitrification.
通过反硝化和厌氧氨氧化（anammox）等微生物介导的过程去除生物可利用氮（N）会影响生态系统 N 的可利用性。尽管很少有研究考察过反硝化和 anammox 的温度响应，但之前的研究表明，随着气候变暖，反硝化可能比 anammox 更为重要。为了验证这一假设，我们在罗德岛沿海的陆架和河口沉积物中，在一个季节性周期内，测定了反硝化和 anammox 的温度响应是否存在差异。在一个为期 12 周的实验室微宇宙实验中，进一步评估了温度和有机 C 可用性的影响。通过在 3 至 59°C 的 31 个离散温度下测量潜在的反硝化和 anammox 速率，确定了温度响应，其特征是热最佳温度（T）和表观活化能（E）。除了少数例外，罗德岛沉积物在整个季节周期内，反硝化和 anammox 的 T 和 E 没有差异。在微宇宙沉积物中，所有处理中，anammox 的 E 都比反硝化略低。然而，两个过程的 T 没有差异，E 和 T 都不会因增温或碳添加而改变。因此，这两个过程在温度响应方面表现相似，并且这些响应不受增温的影响。这使我们否定了在我们的研究系统中，anammox 比反硝化更适应寒冷的假设。总的来说，我们的研究表明，在未来，使用一组单一的参数就可以准确地模拟温带地区这两个过程的温度响应，而这些参数在未来一个世纪内不会因预测的气候变暖而发生变化。我们进一步得出结论，气候变暖不会直接改变通过 anammox 和反硝化的 N 流的分配。
