Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland.
Biology Department, Canadian Rivers Institute, University of New Brunswick, Fredericton, NB, Canada.
Glob Chang Biol. 2021 Jan;27(2):282-296. doi: 10.1111/gcb.15387. Epub 2020 Oct 30.
Climate change in the Arctic is outpacing the global average and land-use is intensifying due to exploitation of previously inaccessible or unprofitable natural resources. A comprehensive understanding of how the joint effects of changing climate and productivity modify lake food web structure, biomass, trophic pyramid shape and abundance of physiologically essential biomolecules (omega-3 fatty acids) in the biotic community is lacking. We conducted a space-for-time study in 20 subarctic lakes spanning a climatic (+3.2°C and precipitation: +30%) and chemical (dissolved organic carbon: +10 mg/L, total phosphorus: +45 µg/L and total nitrogen: +1,000 µg/L) gradient to test how temperature and productivity jointly affect the structure, biomass and community fatty acid content (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) of whole food webs. Increasing temperature and productivity shifted lake communities towards dominance of warmer, murky-water-adapted taxa, with a general increase in the biomass of primary producers, and secondary and tertiary consumers, while primary invertebrate consumers did not show equally clear trends. This process altered various trophic pyramid structures towards an hour glass shape in the warmest and most productive lakes. Increasing temperature and productivity had negative fatty acid content trends (mg EPA + DHA/g dry weight) in primary producers and primary consumers, but not in secondary nor tertiary fish consumers. The massive biomass increment of fish led to increasing areal fatty acid content (kg EPA + DHA/ha) towards increasingly warmer, more productive lakes, but there were no significant trends in other trophic levels. Increasing temperature and productivity are shifting subarctic lake communities towards systems characterized by increasing dominance of cyanobacteria and cyprinid fish, although decreasing quality in terms of EPA + DHA content was observed only in phytoplankton, zooplankton and profundal benthos.
北极的气候变化速度超过了全球平均水平，由于以前无法进入或无利可图的自然资源的开发，土地利用也在加剧。对于气候变化和生产力变化如何共同改变湖泊食物网结构、生物量、营养金字塔形状以及生物群落中生理必需生物分子（ω-3 脂肪酸）的丰度，人们还缺乏全面的了解。我们在 20 个亚北极湖泊中进行了时空研究，这些湖泊跨越了气候（+3.2°C 和降水：+30%）和化学（溶解有机碳：+10mg/L，总磷：+45µg/L，总氮：+1000µg/L）梯度，以测试温度和生产力如何共同影响整个食物网的结构、生物量和群落脂肪酸含量（二十碳五烯酸 [EPA]和二十二碳六烯酸 [DHA]）。温度和生产力的升高使湖泊群落向温暖、浑浊水适应的类群主导地位转变，初级生产者、二级和三级消费者的生物量普遍增加，而初级无脊椎动物消费者则没有表现出同样明显的趋势。这一过程改变了各种营养金字塔结构，在最温暖和生产力最高的湖泊中形成沙漏形状。温度和生产力的升高导致初级生产者和初级消费者的脂肪酸含量呈负趋势（mg EPA+DHA/g 干重），但在二级和三级鱼类消费者中则没有。鱼类的大量生物量增加导致越来越温暖、生产力越来越高的湖泊中，面积脂肪酸含量（kg EPA+DHA/ha）增加，但其他营养水平没有明显趋势。温度和生产力的升高正在使亚北极湖泊群落向蓝藻和鲤科鱼类占主导地位的系统转变，尽管仅在浮游植物、浮游动物和深底栖生物中观察到 EPA+DHA 含量下降。
