Biogeochemistry of lakes in the Mackenzie Delta

长期目标是开发麦肯齐三角洲湖泊的一般生态系统模型，以便评估全球变化对主要河流泛滥平原造成的多重压力的影响[33-35][2]。该三角洲包含45,000个湖泊[16]，是北极圈主要河流三角洲中泛滥平原湖泊的代表[2]，这是世界上气候变化最快的地区[36]。由于热岩溶效应，环极地河流三角洲富含湖泊。这些系统很复杂[37-39]，代表着数千个湖泊[40]，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，因为热岩溶和河冰破裂效应高度依赖温度[41]，而且三角洲受到整个流域发生的过程的影响[2]。这项研究在过去6年中取得的重大进展包括：(1)水生自养生物、细菌和浮游动物；(2)水下光照；(3)对溶解有机碳(DOC)和水生细菌的光化学效应；(4)三角洲食物网中DOC的来源和去向；(5)麦肯齐三角洲对流入博福特海的河流营养盐通量的影响；(6)麦肯齐三角洲适合大型河流泛滥平原的生态模型；(7)关于三角洲湖泊对全球变化综合压力的反应的89项假说；以及(8)检测水位变化。未来5年将继续努力评估三角洲湖泊应对全球变化个别压力的力度和方向。具体目标包括评估：(1)通过水位动态范围建立三角洲水生栖息地模型；(2)湖泊洪水、土地/水比和三角洲景观变化；(3)过氧化氢的光化学产生和可生物降解的DOC；(4)水生细菌对洪水下降状况的响应；(5)对异养纳米鞭毛虫的食物网控制；以及(6)透明胞外聚合物颗粒的丰度和细菌定植。DG资金，连同所需的国家研究服务，将促进北极研究方面的2名博士和3名硕士学生以及5名外勤助理的培训和研究。

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 [33-35] resulting from global change [2]. The delta contains 45,000 lakes [16] and is representative of floodplain lakes among major river deltas of the circumpolar arctic [2], a region of the world where climate is changing more rapidly than anywhere else [36]. Circumpolar river deltas are lake-rich because of thermokarst effects [16]. These systems are complex [37-39] and represent thousands lakes [40] that function as critical aquatic habitat for fish, birds, and mammals. They are sensitive to global change because thermokarst and river-ice breakup effects are highly temperature dependent [41], and because deltas are affected by processes occurring throughout their drainage basin [2]. Significant advances in this research over the past 6 yr includes improved understanding of (1) aquatic autotrophs, bacteria, and zooplankton; (2) under-water irradiance; (3) photochemical effects on dissolved organic C (DOC) and aquatic bacteria; (4) sources and fates of DOC in delta foodwebs; (5) Mackenzie Delta effects on riverine nutrient fluxes to the Beaufort Sea; (6) Mackenzie Delta fit within ecological models of large river floodplains; (7) 89 hypotheses formulated on responses of delta lakes to combined stresses of global change; and (8) detection of 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) delta aquatic habitat modeling through dynamic range of water levels; (2) lake flooding, land/water ratios, and landscape changes in delta; (3) photochemical production of H2O2 and biolabile-DOC; (4) responses of aquatic bacteria to declining flooding regime; (5) foodweb controls on heterotrophic nanoflagellates; and (6) abundance and bacterial colonization of transparent exopolymer particles. DG funds, with requested NRS, will facilitate training and research of 2 PhD and 3 MSc students plus 5 field assistants in arctic-based research.