Biogeochemistry of lakes in the Mackenzie delta

长期目标是为麦肯齐三角洲的湖泊开发一个通用的生态系统模型，以便于评估全球变化[1]对主要河流洪泛区[28-30]造成的多重压力的影响。该三角洲包含45，000个湖泊[11]，是环北极地区主要河流三角洲中洪泛平原湖泊的代表[1]，该地区的气候变化比其他任何地方都快[31]。由于热岩溶效应，环极河流三角洲湖泊丰富[11]。这些系统是复杂的[32-34]，代表了数千个湖泊[35]，这些湖泊是鱼类，鸟类和哺乳动物的重要水生栖息地。它们对全球变化敏感，因为热岩溶和河冰堵塞高度依赖于温度[36]，而且三角洲受到整个流域发生的过程的影响[1]。在过去的5年里，该研究取得了重大进展，包括：（1）水生自养生物，水下光，细菌和浮游动物;（2）水类型对紫外辐射的透明度;（3）溶解有机碳（DOC）和水生细菌的光化学效应;（4）麦肯齐三角洲对流向博福特海的河流营养盐通量的影响;（5）麦肯齐三角洲在大型河流洪泛区生态模型中的拟合;（6）三角洲湖泊对全球变化综合应力响应的89个假设的制定;（7）水位动态显著变化的检测。今后5年将继续努力评估三角洲湖泊对全球变化的个别压力的反应的强度和方向。具体目标包括评估（1）三角洲食物网中DOC的来源和归宿;（2）透明外聚合物颗粒的丰度和细菌定殖;（3）食物网对异养纳米鞭毛虫的控制;（4）H2 O2和生物不稳定性DOC的光化学产生;（5）水生细菌对洪水下降的响应;（6）利用即将到来的IPY，研究三角洲对博福特海营养盐通量的影响。DG资金，与要求NRS，将促进培训和研究2博士和3硕士生加5实地助理在北极为基础的研究。

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.