Biogeochemistry of lakes in the Mackenzie Delta

长期目标是为麦肯齐三角洲的湖泊建立一个通用的生态系统模型，以促进评估全球变化对主要河流洪泛平原造成的多重压力[36-38]的影响。该三角洲包含45000个湖泊，是环极北极地区主要河流三角洲中洪泛平原湖泊的代表，该地区的气候变化比世界上任何其他地区都要快。由于热岩溶作用，环极河三角洲湖泊丰富。这些系统是复杂的[39-41]，由数千个湖泊组成，这些湖泊是鱼类、鸟类和哺乳动物的重要水生栖息地。它们对全球变化很敏感，因为热岩溶和河冰堵塞高度依赖于温度，而且三角洲受到整个流域发生的过程的影响。在过去的4年里，这项研究取得了重大进展，包括提高了对以下方面的认识：(1)水生自养生物、水下光、细菌和浮游动物；(2)水类型（有色（CDOC）和非有色（NCDOC）溶解有机碳的混合物）对紫外线辐射的透明度；(3)光化学对DOC和水生细菌的影响；(4)麦肯齐三角洲对流入波弗特海的河流养分通量的影响；(5)麦肯齐三角洲符合大河漫滩生态模型；(6)提出了三角洲湖泊对全球变化综合压力响应的89个假设。未来5年将继续努力评估三角洲湖泊生态系统对全球变化个别压力的反应强度和方向。具体目标包括：(1)通过同位素模拟评估三角洲食物网中溶解有机碳的来源和去向；(2)三角洲湖泊浮游生物异养型纳米鞭毛虫（HNAN）的食物网调控；(3)三角洲湖泊H2O2光化学生成和生物相容性doc；(4)三角洲湖泊水体细菌对光化学效应和高pH值的响应；(5)进一步研究三角洲对河流向波弗特流出的影响，这需要独立但合作的IPY调查。DG基金将与NRS合作，为2名博士和3名硕士学生以及5名北极研究现场助理提供培训和研究。

The long-term goal is to develop a general ecosystem model for lakes in the Mackenzie Delta to facilitate assessing the effects of multiple stresses on major river floodplains [36-38] resulting from global change [1]. The delta contains 45,000 lakes [6] and is representative of floodplain lakes among major river deltas of the circumpolar arctic [1], a region of the world where climate is changing more rapidly than anywhere else [24]. Circumpolar river deltas are lake-rich because of thermokarst effects [6]. These systems are complex [39-41] and represent thousands lakes [42] that function as critical aquatic habitat for fish, birds, and mammals. They are sensitive to global change because thermokarst and jamming of river-ice are highly temperature dependent [26], and because deltas are affected by processes occurring throughout the drainage basin [1]. Significant advances in this research over the past 4 yr includes improved understanding of (1) aquatic autotrophs, underwater light, bacteria, & zooplankton; (2) transparency of water-types (mixtures of colored (CDOC) & non-colored (NCDOC) dissolved organic carbon) to UV-radiation; (3) photochemical effects on DOC & aquatic bacteria; (4) Mackenzie Delta effects on riverine nutrient fluxes to the Beaufort Sea; (5) Mackenzie Delta fit within ecological models of large river floodplains; and (6) formulation of 89 hypotheses on responses of delta lakes to combined stresses of global change. Next 5 years will involve continuing efforts to assess the strength and direction of ecosystem responses in delta lakes to individual stresses of global change. Specific goals include assessing (1) sources and fates of dissolved organic carbon in delta foodwebs via isotopic modeling; (2) foodweb controls on plankton heterotrophic nanoflagellates (HNAN) in delta lakes; (3) photochemical production of H2O2 and biolabile-DOC in delta lakes; (4) responses of aquatic bacteria to photochemical effects and high pH in delta lakes; and (5) further work on delta effects on river outflow to the Beaufort, needed for independent but collaborative IPY investigations. DG funds, with requested NRS, will facilitate training & research of 2 PhD & 3 MSc students plus 5 field assistants in arctic-based research.