Data from: A year in hypoxia: epibenthic community responses to severe oxygen deficit at a subsea observatory in a coastal inlet

Changes in ocean ventilation driven by climate change result in loss of oxygen in the open ocean that, in turn, affects coastal areas in upwelling zones such as the northeast Pacific. Saanich Inlet, on the west coast of Canada, is a natural seasonally hypoxic fjord where certain continental shelf species occur in extreme hypoxia. One study site on the VENUS cabled subsea network is located in the hypoxic zone at 104 m depth. Photographs of the same 5 m2 area were taken with a remotely-controlled still camera every 2/3 days between October 6th 2009 and October 18th 2010 and examined for community composition, species behaviour and microbial mat features. Instruments located on a near-by platform provided high-resolution measurements of environmental variables. We applied multivariate ordination methods and a principal coordinate analysis of neighbour matrices to determine temporal structures in our dataset. Responses to seasonal hypoxia (0.1–1.27 ml/l) and its high variability on short time-scale (hours) varied among species, and their life stages. During extreme hypoxia, microbial mats developed then disappeared as a hippolytid shrimp, Spirontocaris sica, appeared in high densities (200 m22) despite oxygen below 0.2 ml/l. The slender sole Lyopsetta exilis was abundant in severe hypoxia and diminished as oxygen increased in the summer. This planktivore may be responding to changes in the depth of the diurnal migration of zooplankton. While the squat lobster Munida quadrispina was common at all times, juveniles disappeared in fluctuating conditions. Despite low oxygen conditions, animal densities were high indicating that the risk from hypoxia is balanced by factors such as food availability and escape from less tolerant predators. As hypoxia increases on the continental shelf, we expect benthic communities to become dominated by low diversity, hypoxia-tolerant species of low commercial significance.

气候变化驱动的海洋通风（ocean ventilation）变化导致开阔大洋缺氧，进而影响东北太平洋等上升流区域的近岸海域。加拿大西海岸的萨尼奇湾（Saanich Inlet）是一处季节性自然低氧（hypoxic）峡湾（fjord），部分大陆架物种可在极端低氧环境中存活。VENUS有线海底观测网络（VENUS cabled subsea network）的一处研究站位设于104米水深的低氧区域内。2009年10月6日至2010年10月18日期间，研究人员每2/3天使用遥控静态相机（remotely-controlled still camera）对同一5平方米区域进行拍摄，以此分析群落组成、物种行为及微生物垫（microbial mat）特征。邻近平台搭载的仪器可对环境变量开展高分辨率监测。本研究采用多元排序方法（multivariate ordination methods）与邻域矩阵主坐标分析（principal coordinate analysis of neighbour matrices），以解析数据集的时间结构特征。不同物种及其生活史阶段对季节性低氧（0.1~1.27 ml/L）及其短时尺度（小时级）高变异性的响应存在显著差异。在极端低氧条件下，微生物垫先发育后消失，此时藻虾科（Hippolytidae）的*Spirontocaris sica*种群密度可达200个/平方米，尽管水体溶解氧浓度低于0.2 ml/L。细菱鲽*Lyopsetta exilis*在严重低氧环境中种群数量丰富，随夏季溶解氧浓度升高而逐渐缩减。这种浮游食性（planktivore）鱼类可能响应了浮游动物昼夜迁移深度的变化。尽管铠甲虾（squat lobster）*Munida quadrispina*在各观测时段均较为常见，但其幼体在环境波动条件下会消失。尽管存在低氧环境，该区域动物密度仍维持在较高水平，这表明低氧带来的生存压力可被食物可获得性、躲避耐受性更低的捕食者等因素抵消。随着大陆架低氧现象加剧，预计底栖生物群落（benthic communities）将逐渐由多样性低、耐低氧且经济价值较低的物种主导。