Micronekton of the Cariaco Basin: Adaptation to a Severe Oxygen Minimum

委内瑞拉沿海沃茨的Cariaco盆地的最低含氧量区是世界上最严重的含氧量区之一。 与海洋中大多数严重含氧极小区一样，这是高生产力时期加上利用溶解氧使下沉有机物微生物降解以及较深沃茨循环受限的结果。 Cariaco盆地（140米）的浅岩床严重限制了与南极洲其他地区的交流。 在大约250米的深度以下，盆地是缺氧的，硫化氢，一种代谢毒物，在400米以下的深度以高浓度存在。 毫不奇怪，这些沃茨的鱼类和无脊椎动物主要存在于200米以上的含氧沃茨。 该项目涉及的垂直分布，丰度和物种组成的Cariaco盆地鱼类和无脊椎动物群落的特性。 不仅这个群落的身份不明，而且它们与氧气最低限度的关系也没有描述。 1973年的一项经典的Cariaco盆地研究报告了一种小鱼，即小鳕鱼Bregmaceros cantori的存在，这种小鱼能够迁移到含硫沃茨的氧气最低值，作为其正常昼夜模式的一部分，并在白天在那里停留长达12小时。 研究人员还将研究这种鱼是如何实现这一非凡壮举的。 将与委内瑞拉科学家合作，在CARIACO时间序列船R/V Hermano Gines上用离散网拖对Cariaco社区进行采样。 耐受硫化物或解毒硫化物的鳕鱼和其他种类的鱼类的组织中的能力将使用一套新的技术，包括代谢酶的测量，确定硫化物的存在下，在白天捕获的鱼的组织中，硫化物的耐受性的重要呼吸蛋白，硫化物解毒鳃，肝脏，血液和肌肉，和线粒体呼吸的硫化物的存在下进行检查。 小鳕鱼是否使用有氧或厌氧策略存活将根据白天捕获的鱼中厌氧终产物的积累、酶活性和可能的循环适应以允许在鱼鳔中保留氧气来评估。 除了国际科学合作，该项目还将涉及来自美国和委内瑞拉的研究生的培训。

The oxygen minimum zone of the Cariaco Basin in the coastal waters of Venezuela is one of the most severe in the world. Like most zones of severe oxygen minima in the oceans, it is the result of periods of high productivity coupled with microbial degradation of the sinking organic matter with utilization of the dissolved oxygen, and restricted circulation of its deeper waters. The shallow sill of the Cariaco basin (140 m) severely restricts exchange with the rest of the Atlantic.Ocean. Below a depth of approximately 250 m the basin is anoxic, and hydrogen sulfide, a metabolic poison, is present at depths below 400 m in high concentrations. Not surprisingly, the fish and invertebrates of these waters principally exist in the oxygenated waters of the upper 200 m. This project involves the characterization of the vertical distribution, abundance, and species composition of the Cariaco Basin fish and invertebrate communities. Not only is the identity of much of this community unknown, but their relationship to the oxygen minimum is undescribed. A classic Cariaco Basin study from 1973 reported the presence of a small fish, the codlet, Bregmaceros cantori, that had the ability to migrate into the sulfide laden waters of the oxygen minimum as part of its normal diel pattern, and resided there during the day for up to 12 h. The investigators will also study how this fish achieves this remarkable feat. The Cariaco community will be sampled with discrete net tows aboard the CARIACO time-series vessel, the R/V Hermano Gines, in collaboration with Venezuelan scientists. The ability to tolerate sulfide or detoxify sulfide in the tissues of the codlet and the other species of fishes will be examined using a suite of novel techniques including metabolic enzyme measurements, determining presence of sulfides in tissues of fish caught during the day, tolerance of sulfide by important respiratory proteins, sulfide detoxification by gill, liver, blood, and muscle, and mitochondrial respiration in the presence of sulfide. Whether the codlet survives using an aerobic or anaerobic strategy will be evaluated based on the accumulation of anaerobic end products in fish captured during the day, enzyme activities, and possibly circulatory adaptations to allow retention of oxygen in the swimbladder. In addition to the international scientific collaboration the project will also involve the training of graduate students from the US and Venezuela.