School of Environment and Sustainability, University of Saskatchewan, Saskatoon, SK, Canada.
Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden.
Glob Chang Biol. 2018 Aug;24(8):3692-3714. doi: 10.1111/gcb.14129. Epub 2018 Apr 18.
Northern ecosystems are experiencing some of the most dramatic impacts of global change on Earth. Rising temperatures, hydrological intensification, changes in atmospheric acid deposition and associated acidification recovery, and changes in vegetative cover are resulting in fundamental changes in terrestrial-aquatic biogeochemical linkages. The effects of global change are readily observed in alterations in the supply of dissolved organic matter (DOM)-the messenger between terrestrial and lake ecosystems-with potentially profound effects on the structure and function of lakes. Northern terrestrial ecosystems contain substantial stores of organic matter and filter or funnel DOM, affecting the timing and magnitude of DOM delivery to surface waters. This terrestrial DOM is processed in streams, rivers, and lakes, ultimately shifting its composition, stoichiometry, and bioavailability. Here, we explore the potential consequences of these global change-driven effects for lake food webs at northern latitudes. Notably, we provide evidence that increased allochthonous DOM supply to lakes is overwhelming increased autochthonous DOM supply that potentially results from earlier ice-out and a longer growing season. Furthermore, we assess the potential implications of this shift for the nutritional quality of autotrophs in terms of their stoichiometry, fatty acid composition, toxin production, and methylmercury concentration, and therefore, contaminant transfer through the food web. We conclude that global change in northern regions leads not only to reduced primary productivity but also to nutritionally poorer lake food webs, with discernible consequences for the trophic web to fish and humans.
北方生态系统正在经历地球上海洋变化最剧烈的影响。气温升高、水文强化、大气酸沉降及其相关酸化恢复的变化以及植被覆盖的变化，导致陆地-水域生物地球化学联系发生根本变化。全球变化的影响在溶解有机物质（DOM）供应的改变中显而易见，而 DOM 是陆地和湖泊生态系统之间的信使，这可能对湖泊的结构和功能产生深远影响。北方陆地生态系统含有大量的有机物质，并过滤或引导 DOM，从而影响 DOM 向地表水域输送的时间和规模。这种陆地 DOM 在溪流、河流和湖泊中进行处理，最终改变其组成、化学计量和生物利用度。在这里，我们探讨了这些由全球变化驱动的影响对北方高纬度地区湖泊食物网的潜在后果。值得注意的是，我们提供的证据表明，湖泊中增加的异源 DOM 供应超过了可能由于冰融化更早和生长季节更长而导致的增加的同源 DOM 供应。此外，我们还评估了这种变化对自养生物的营养质量的潜在影响，包括其化学计量、脂肪酸组成、毒素产生和甲基汞浓度，因此，通过食物网进行污染物转移。我们的结论是，北方地区的全球变化不仅导致初级生产力降低，而且还导致营养较差的湖泊食物网，这对食物链中的鱼类和人类产生了明显的后果。
