Robinson Colin Michael, Hansen Lee D, Xue Xia, Adams Byron J
Department of Biology, Brigham Young University, Provo, UT 84602, USA.
Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
Biology (Basel). 2023 Jan 10;12(1):109. doi: 10.3390/biology12010109.
Because of climate change, the McMurdo Dry Valleys of Antarctica (MCM) have experienced an increase in the frequency and magnitude of summer pulse warming and surface ice and snow melting events. In response to these environmental changes, some nematode species in the MCM have experienced steady population declines over the last three decades, but , a mesophilic nematode species, has responded with a steady increase in range and abundance. To determine how responds to increasing temperatures, we measured metabolic heat and CO production rates and calculated O consumption rates as a function of temperature at 5 °C intervals from 5 to 50 °C. Heat, CO production, and O consumption rates increase approximately exponentially up to 40 °C, a temperature never experienced in their polar habitat. Metabolic rates decline rapidly above 40 °C and are irreversibly lost at 50 °C due to thermal stress and mortality. , a much more widespread nematode that is found in more temperate environments reaches peak metabolic heat rate at just 27 °C, above which it experiences high mortality due to thermal stress. At temperatures from 10 to 40 °C, produces about 6 times more CO than the O it consumes, a respiratory quotient indicative of either acetogenesis or de novo lipogenesis. No potential acetogenic microbes were identified in the microbiome, suggesting that is producing increased CO as a byproduct of de novo lipogenesis. This phenomenon, in conjunction with increased summer temperatures in their polar habitat, will likely lead to increased demand for carbon and subsequent increases in CO production, population abundance, and range expansion. If such changes are not concomitant with increased carbon inputs, we predict the MCM soil ecosystems will experience dramatic declines in functional and taxonomic diversity.
由于气候变化，南极洲的麦克默多干谷（MCM）夏季脉冲变暖以及地表冰雪融化事件的频率和强度都有所增加。针对这些环境变化，在过去三十年里，MCM中的一些线虫物种数量持续下降，但嗜温线虫物种的分布范围和数量却稳步增加。为了确定该物种如何应对温度升高，我们测量了代谢热和二氧化碳产生率，并计算了在5至50°C范围内每隔5°C的氧气消耗率。在高达40°C时，热、二氧化碳产生和氧气消耗率大致呈指数增长，而这一温度在它们的极地栖息地从未出现过。在40°C以上，代谢率迅速下降，在50°C时由于热应激和死亡而不可逆转地丧失。在更温和环境中分布更为广泛的另一种线虫，在仅27°C时就达到了代谢热率峰值，高于此温度，它会因热应激而出现高死亡率。在10至40°C的温度范围内，该物种产生的二氧化碳比消耗的氧气多约6倍，这一呼吸商表明存在产乙酸或从头合成脂肪的情况。在该物种的微生物群落中未发现潜在的产乙酸微生物，这表明该物种产生的二氧化碳增加是从头合成脂肪的副产品。这种现象，再加上其极地栖息地夏季温度升高，可能会导致对碳的需求增加，进而导致二氧化碳产生量、种群数量和分布范围扩大。如果这些变化没有伴随着碳输入的增加，我们预测MCM土壤生态系统的功能和分类多样性将大幅下降。
