The impact of dissolved organic matter photochemistry on the carbon and nutrient cycling in arctic and subarctic marine ecosystems

溶解有机物光化学对北极和亚北极海洋生态系统碳和养分循环的影响

• 批准号: 250966-2007
• 负责人: Xie, Huixiang
• 金额: $ 1.54万
• 依托单位: Université du Québec à Rimouski
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2008
• 资助国家: 加拿大
• 起止时间: 2008-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=394835
• 关键词: impact; dissolved; organic; matter; photochemistry

The Arctic Ocean receives the largest input of terrestrially derived dissolved organic matter (DOM) on a per unit volume basis. Currently, little is known of the processes controlling the transformation and fate of this DOM pool. Mid- and low-latitude studies suggest that sunlight-initiated photochemistry in the surface ocean likely play an important role in processing terrestrial dissolved organic carbon (DOC) by directly oxidizing DOM to small inorganic carbon molecules (e.g., CO2 and CO) and by labilizing biologically refractory DOM to bacterial metabolic attack. Phototransformation of DOM may also affect the nitrogen cycling by directly converting biologically resistant dissolved organic nitrogen (DON) to bioavailable inorganic nitrogen (e.g., ammonium, nitrite) and/or through enhancing bacterial demand for inorganic nutrients. The impact of photochemistry on terrestrial DOM cycling in Arctic and subarctic oceans has been assumed to be insignificant due to low solar angles and extensive seasonal and year-round ice cover. However, this may change as a consequence of climate warming and stratospheric ozone reduction that are possible already occurring over the high northern latitudes. Climate warming reduces ice cover extent and ice thickness while stratospheric ozone reduction increases the ultraviolet radiation reaching the sea surface; the combination of the two hence augments the solar radiation penetrating into the water column. By conducting three field surveys in Arctic (Mackenzie Shelf and Lena Delta) and subarcitc (Hudson Bay) seas, this proposed research is aimed at (1) quantitatively evaluating the impacts of photochemistry on the fate of terrestrial DOC and on inorganic nitrogen cycling in Arctic and subarctic marine ecosystems, and (2) predicting how climate warming and stratospheric ozone reduction over these regions affect these impacts.

按单位体积计算，北冰洋接收的陆源溶解有机质（DOM）输入量最大。目前，对控制这个DOM池的转换和命运的过程知之甚少。中低纬度研究表明，海洋表面阳光引发的光化学可能通过直接将DOM氧化成小的无机碳分子（如CO2和CO）以及通过稳定生物难降解的DOM以抵抗细菌代谢攻击，在处理陆地溶解有机碳（DOC）过程中发挥重要作用。DOM的光转化也可能通过直接将具有生物抗性的溶解有机氮（DON）转化为生物可利用的无机氮（如铵、亚硝酸盐）和/或通过增加细菌对无机营养物质的需求来影响氮循环。光化学对北极和亚北极海洋陆地DOM循环的影响一直被认为是微不足道的，因为太阳角度较低，并且广泛的季节性和全年冰盖。然而，由于气候变暖和平流层臭氧减少，这种情况可能会发生变化，这种情况可能已经在北半球高纬度地区发生。气候变暖减少了海冰覆盖范围和冰层厚度，而平流层臭氧的减少增加了到达海面的紫外线辐射；因此，两者的结合增加了穿透水柱的太阳辐射。本研究通过在北极（麦肯齐陆架和勒拿三角洲）和亚北极（哈德逊湾）海域进行3次野外调查，旨在(1)定量评估光化学对北极和亚北极海洋生态系统陆相DOC命运和无机氮循环的影响，(2)预测这些地区气候变暖和平流层臭氧减少如何影响这些影响。