Flow increases tolerance of heat and hypoxia of an aquatic insect

Recent experiments support the idea that upper thermal limits of aquatic insects arise, at least in part, from a lack of sufficient oxygen: rising temperatures typically stimulate metabolic demand for oxygen more than they increase rates of oxygen supply from the environment. Consequently, factors influencing oxygen supply, like water flow, should also affect thermal and hypoxia tolerance. We tested this hypothesis by measuring the effects of experimentally manipulated flows on the heat and hypoxia tolerance of aquatic nymphs of the giant salmonfly (Plecoptera: Pteronarcys californica), a common stonefly in western North America. As predicted, stoneflies in flowing water (10 cm s-1) tolerated water that was ~4 ºC warmer and that contained ~15% less oxygen than did those in standing water. Our results imply that the impacts of climate change on streamflow, such as changes in patterns of precipitation, and decreased snowpack, will magnify the threats to aquatic insects from warmer water t...近期多项实验佐证了下述假说：水生昆虫的高温耐受上限，至少部分源于氧气供给不足——温度升高通常会提升机体的氧气代谢需求，但其对环境氧气供给速率的提升幅度却相对有限。因此，诸如水流这类影响氧气供给的因素，同样会对生物的耐热性与低氧耐受能力产生影响。我们通过测定人工调控水流对巨鲑蝇（Plecoptera: Pteronarcys californica）水生若虫的耐热性与低氧耐受能力的影响，验证了该假说；该物种是北美西部常见的石蝇。正如实验预期，相较于静水环境中的个体，流速为10 cm·s⁻¹的流水中的石蝇可耐受高约4℃、溶氧含量低约15%的水体。本研究结果表明，气候变化对溪流径流的诸多影响——例如降水格局改变与积雪量减少——将会进一步放大水体升温对水生昆虫构成的生存威胁……