Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems
Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems
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DOI：
10.5194/bg-12-7129-2015
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发表时间：
2015-01-01
期刊：
影响因子：
4.9
通讯作者：
Wickland, K. P.
中科院分区：
文献类型：
--
作者：
Vonk, J. E.;Tank, S. E.;Wickland, K. P.
北极是一个水资源丰富的地区，淡水系统覆盖了大约16%的北方永久冻土景观。永久冻土融化创造了新的淡水生态系统，同时改变了受融化影响的现有湖泊，溪流和河流。在这里，我们描述了目前的知识状态，关于冻土融化如何影响lentic（静止）和lotic（移动）系统，探索热岩溶（融化和丰富的冰冻土层的崩溃）和深化的活动层（每年融化和重新冻结的表层土壤层）的影响。在热岩溶中，我们进一步区分了热岩溶在低地地区和山坡上的影响。对于我们探索的几乎所有过程，解冻的影响因地区而异，在湖泊和河流系统之间也是如此。这种区域性的差异主要是由地面冰含量、地形、土壤类型和永久冻土覆盖率的差异造成的。总之，这些修改因素决定（一）在何种程度上表现为热岩溶冻土融化，（二）是否热岩溶导致塌陷或热岩溶湖泊的形成，以及（iii）的方式，其中成分输送到淡水系统被解冻改变。解冻使能的成分输送的差异可能是相当大的，这些修改因素决定了例如颗粒与溶解成分的输送之间以及无机与有机材料之间的平衡。受融化影响的沃茨成分的变化，再加上湖泊形态的变化，可以强烈影响热岩溶湖泊的物理和光学特性。受解冻影响的湖泊和溪流的生态也可能发生变化;这些系统具有独特的微生物群落，并在呼吸、初级生产和食物网结构方面表现出差异，这在很大程度上是由沉积物、溶解有机物和营养物质输送的差异驱动的。解冻的程度，使溶解与颗粒有机物的交付，再加上有机物的组成和受体系统的形态和分层特性将发挥重要作用，在确定有机物作为温室气体（CO2和CH 4）的释放之间的平衡，其埋藏在沉积物中，其下游损失。解冻对北方水生生态系统的影响程度正在增加，受解冻影响的湖泊和溪流的普遍性也在增加。因此，迫切需要量化永久冻土融化如何影响北极不同景观的水生生态系统，以及这种变化对进一步气候变暖的影响。
The Arctic is a water-rich region, with freshwater systems covering about 16% of the northern permafrost landscape. Permafrost thaw creates new freshwater ecosystems, while at the same time modifying the existing lakes, streams, and rivers that are impacted by thaw. Here, we describe the current state of knowledge regarding how permafrost thaw affects lentic (still) and lotic (moving) systems, exploring the effects of both thermokarst (thawing and collapse of ice-rich permafrost) and deepening of the active layer (the surface soil layer that thaws and refreezes each year). Within thermokarst, we further differentiate between the effects of thermokarst in lowland areas vs. that on hillslopes. For almost all of the processes that we explore, the effects of thaw vary regionally, and between lake and stream systems. Much of this regional variation is caused by differences in ground ice content, topography, soil type, and permafrost coverage. Together, these modifying factors determine (i) the degree to which permafrost thaw manifests as thermokarst, (ii) whether thermokarst leads to slumping or the formation of thermokarst lakes, and (iii) the manner in which constituent delivery to freshwater systems is altered by thaw. Differences in thaw-enabled constituent delivery can be considerable, with these modifying factors determining, for example, the balance between delivery of particulate vs. dissolved constituents, and inorganic vs. organic materials. Changes in the composition of thaw-impacted waters, coupled with changes in lake morphology, can strongly affect the physical and optical properties of thermokarst lakes. The ecology of thaw-impacted lakes and streams is also likely to change; these systems have unique microbiological communities, and show differences in respiration, primary production, and food web structure that are largely driven by differences in sediment, dissolved organic matter, and nutrient delivery. The degree to which thaw enables the delivery of dissolved vs. particulate organic matter, coupled with the composition of that organic matter and the morphology and stratification characteristics of recipient systems will play an important role in determining the balance between the release of organic matter as greenhouse gases (CO2 and CH4), its burial in sediments, and its loss downstream. The magnitude of thaw impacts on northern aquatic ecosystems is increasing, as is the prevalence of thaw-impacted lakes and streams. There is therefore an urgent need to quantify how permafrost thaw is affecting aquatic ecosystems across diverse Arctic landscapes, and the implications of this change for further climate warming.