The organisms that inhabit Oxygen Minimum Zones (OMZ) have specialized adaptations that allow them to survive within a very narrow range of environmental conditions. Consequently, even small environmental perturbations can result in local species distribution shifts that alter ecosystem trophodynamics. Here, we examined the effect of changing sea water temperatures and oxygen levels on the physiological performance and metabolic traits of the species forming marine demersal communities along the OMZ margins in the Costa Rican Pacific. The strong temperature and oxygen gradients along this OMZ margin provide a “natural experiment” to explore the effects of warming and hypoxia on marine demersal communities. We identified two distinct marine fauna communities separated by an environmental oxygen partial pressure threshold of 0.003–0.009 atm. The community inhabiting cooler waters with less oxygen was comprised of species with very low oxygen demands, while the second community inhabiting warmer waters with more oxygen was comprised by a higher diversity of species with higher oxygen demands. We also compared the community composition across different El Niño Southern Oscillation phases. During “neutral” and El Niño conditions, with relatively warmer temperatures and higher oxygen levels, species’ average oxygen demand was higher, and species stayed at greater depths than during the cooler, low oxygen, La Niña phases. Our findings suggest that the effects of environmental temperature and oxygen levels on the structure of demersal communities within OMZs can be predicted by understanding species’ oxygen demand. This study highlights the vulnerability of demersal ecosystem structures surrounding the Costa Rican OMZ to deoxygenation and warming under climate change.

居住在氧气最低区 (OMZ) 的生物具有特殊的适应性，使它们能够在非常狭窄的环境条件范围内生存。因此，即使是很小的环境扰动也可能导致改变生态系统营养动力学的当地物种分布变化。在这里，我们研究了海水温度和氧气水平变化对哥斯达黎加太平洋沿岸 OMZ 边缘形成海洋底层群落的物种的生理性能和代谢特征的影响。沿着 OMZ 边缘的强烈温度和氧气梯度提供了一个“自然实验”来探索变暖和缺氧对海洋底层群落的影响。我们确定了两个不同的海洋动物群落，环境氧分压阈值为 0.003-0.009 atm。居住在氧气较少的较冷水域的群落由氧气需求量非常低的物种组成，而居住在氧气较多的温暖水域的第二个群落则由具有较高氧气需求的物种多样性组成。我们还比较了厄尔尼诺南方涛动不同阶段的群落组成。在“中性”和厄尔尼诺条件下，温度相对较高，氧气含量较高，物种的平均需氧量较高，物种停留在较冷、低氧、拉尼娜阶段更深的地方。我们的研究结果表明，环境温度和氧气水平对 OMZ 内底层群落结构的影响可以通过了解物种的需氧量来预测。