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[28-30]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泛洪平原湖泊的代表，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。这些系统非常复杂[32-34]，代表了数千个湖泊，它们是鱼类、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5年中，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)水型对紫外线的透明度；(3)光化学对溶解有机C （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89个三角洲湖泊对全球变化综合压力响应的假设；&(7)探测水位状态的显著变化。未来5年将继续努力评估三角洲湖泊对全球变化个别压力的反应强度和方向。具体目标包括评估(1)三角洲食物网中DOC的来源和命运；(2)透明聚合物颗粒的丰度和细菌定植；(3)异养型纳米鞭毛虫的食物网控制；(4)光化学生成H2O2和生物相容性doc；(5)水生细菌对洪水消长的响应；&(6)三角洲效应对波弗特海年度营养通量的影响，以利用即将到来的国际淡水年。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 [28-30] resulting from global change [1]. The delta contains 45,000 lakes [11] 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 [31]. Circumpolar river deltas are lake-rich because of thermokarst effects [11]. These systems are complex [32-34] and represent thousands lakes [35] 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 [36], and because deltas are affected by processes occurring throughout the drainage basin [1]. Significant advances in this research over the past 5 yr includes improved understanding of (1) aquatic autotrophs, underwater light, bacteria, & zooplankton; (2) transparency of water-types to UV-radiation; (3) photochemical effects on dissolved organic C (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; (6) formulation of 89 hypotheses on responses of delta lakes to combined stresses of global change; & (7) detection of significant changes in water level regime. Next 5 years will involve continuing efforts to assess the strength and direction of delta lake responses to individual stresses of global change. Specific goals include assessing (1) sources and fates of DOC in delta foodwebs; (2) abundance & bacterial colonization of transparent exopolymer particles; (3) foodweb controls on heterotrophic nanoflagellates; (4) photochemical production of H2O2 and biolabile-DOC; (5) responses of aquatic bacteria to declining flooding regime; & (6) delta effect on annual nutrient fluxes to Beaufort Sea, to capitalize on upcoming IPY. DG funds, with requested NRS, will facilitate training & research of 2 PhD & 3 MSc students plus 5 field assistants in arctic-based research.