Using bomb calorimetry to assess thermal and seasonal energetics

许多越冬的外温动物被“困”在池塘的冰层下过冬。 在低温潜水的早期阶段，它们的代谢率因低温而降低。 随着冬季的进行，池塘中的居民和腐烂的植被的氧气消耗有效地“超过”通过光合作用更新的氧气量，从而降低了氧气水平（即，缺氧）。 越冬动物被置于一个不稳定的情况下，它不仅要科普日益减少的氧气，而且还与有限的能量储存供应（主要是脂肪和碳水化合物）。 在实验室中，这些动物在冬季开始时燃烧脂肪储存，随着寒冷、缺氧暴露的进展，它们转向碳水化合物储存，大概是为了春季活动而节省脂肪储存。 这些关系如何以及是否在该领域表现出来尚不清楚。 越冬往往伴随着大量的冬季杀死在春天，大量的水生外温动物（主要是两栖动物和鱼类）屈服于寒冷和缺氧的环境。 那些在这些条件下生存下来的两栖动物可能耗尽了能量储存;然而，许多两栖动物必须在从越冬状态中出现后立即进行昂贵的春季繁殖行为。 我们建议评估两栖动物的能量储存在其每年的周期的各个阶段，以确定是否在越冬环境的质量变化（在温度和氧气方面）修改冬眠后的能量储存。 全球气候变化预示着冬季会逐渐变暖，但高温并不一定会导致两栖动物的生存增加。 温度升高可能会导致能量“浪费”，因为新陈代谢增加。 弹式热量计可以直接测量总能量含量，并了解动物拥有多少脂肪或糖原储存，从而预测越冬生存和繁殖适应性。 弹式量热计是将实验室技术带到野外站的成本效益高的手段，因为它几乎不需要技术和人员支持，但却能产生有生理和生态意义的结果。

Many overwintering ectotherms pass the winter 'trapped' beneath the ice-cover of ponds.  During the early stages of their cold submergence, their metabolic rate is lowered by the cold temperatures.  As winter proceeds, the oxygen consumption of the residents in the pond and decaying vegetation effectively 'outpaces' the amount of oxygen renewed through photosynthesis, thus reducing the oxygen levels (i.e., become hypoxic).  The overwintering animal is placed in a precarious situation where it must not only cope with the dwindling oxygen, but also with a finite supply of energy stores (primarily fats and carbohydrates).  In the laboratory, these animals burn fat stores at the beginning of winter and turn to carbohydrate stores as cold, hypoxic exposure progresses, presumably sparing fat stores for spring activities.  How and whether these relationships manifest in the field is unknown.  Overwintering is accompanied quite often by large winterkill in the spring, where high numbers of aquatic ectotherms (mainly amphibians and fish) succumb to the combined cold and hypoxic environments.  Those that survive these conditions are presumably depleted of energy stores; yet, many amphibians must engage immediately in costly spring reproductive behaviours upon emergence from their overwintering state.  We propose to assess the energy stores of amphibians at various stages of their yearly cycle in order to ascertain whether variations in the quality of the overwintering environment (in terms of temperature and oxygen) modify post-hibernation energy stores.  Global climate change predicts progressively warmer winters, yet it is not necessarily the case that high temperatures will lead to increased survival for amphibians.  Warmer temperatures may lead to energy 'wasting' as a result of the increased metabolism.  A bomb calorimeter can directly measure the total energy content and give insight into how much fat or glycogen stores animals possess, and thus allow predictions of overwintering survival and reproductive fitness.  A bomb calorimeter is cost effective means of bringing laboratory techniques to a field station since it requires little technical and personnel support yet yields physiologically and ecologically meaningful results.