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首页> 外文期刊>Marine ecology >Diversity of bathyal macrofauna on the northeastern Pacific margin: the influence of methane seeps and oxygen minimum zones
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Diversity of bathyal macrofauna on the northeastern Pacific margin: the influence of methane seeps and oxygen minimum zones

机译：东北太平洋边缘的海底大型动物区系的多样性：甲烷渗漏和最小含氧区的影响

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摘要

The upper continental slope in the northeastern Pacific Ocean is intercepted by a deep oxygen minimum zone (OMZ; 650-1100 m) and punctuated by conduits of methane seepage. We examined the effects of these two dominant sources of heterogeneity on the density, composition and diversity of heterotrophic macrofauna off Hydrate Ridge, Oregon (OR; 800 m water depth), where the seeps co-occur within an OMZ, and off the Eel River, Northern California (CA; 500 m), where seeps are overlain by better oxygenated waters. We hypothesized that seeps (containing clam beds and microbial mats) should contribute a suite of distinct species to the regional margin species pool but that OMZ-associated hypoxia would dampen seep-related heterogeneity. Macrofaunal densities were highest (23,000-33,510 ind·m~(-2)) in the CA seep sediments and in the OR near-seep samples, intermediate in the OR seep, CA near seep and CA and OR 500-m margin sediments (10,054-19,777 ind·m~(-2)), and lowest in the CA and OR OMZ habitats at 800 m (4269-7847 ind·m~(-2)). Annelids constituted over 50% of the taxa in all but the CA clam bed and OR microbial mat sediments, where mollusks were abundant. Approximately 50% of seep species appeared to be habitat endemic; species present in microbial mats largely formed a subset of those present in the clam beds. Dorvilleid and ampharetid polychaetes were dominant in the seep sediments; non-seep margin sediments at 500 and 800 m were populated heavily by branchiate polychaetes including cossurids and paraonids. Alpha diversity (Es[20] calculated per core) was lowest and rank 1 dominance was highest in the CA and OR microbial mat habitats. Pooled analyses of Es[100] revealed highest species richness in the CA clam bed and near-seep habitats (30.3 and 29.6, respectively), and lowest species richness in the OR microbial mat and near-seep habitats (16.5 and 17.9, respectively). Non-seep sediments (500 and 800 m) off both CA and OR were more homogeneous (55-57% within-habitat similarity) than clam bed and microbial mat sediments (only 32-37% within-habitat similarity). CA sediment macrofauna generally exhibit higher alpha diversity, and as habitats are combined, a higher rate of increase in the slope of the species accumulation curves than do OR margin macrofauna. Methane seeps in the NE Pacific introduce significant heterogeneity that increases margin biodiversity at multiple spatial scales. However, our hypothesis that the OMZ would lessen the seep contributions to diversity was not supported. The better oxygenated CA seeps at 500 m shared more of the background margin fauna (at 500 m) than did the OR seeps at 800 m (with OMZ fauna at 800 m). Geographical differences in the fluxes of methane-rich fluids and the increased reliance on chemosynthetic food sources with increased depth could explain these results.
机译：东北太平洋的上大陆斜坡被一个最小的氧气最低带（OMZ； 650-1100 m）拦截，并被甲烷渗透的管道所打断。我们研究了这两个主要的异质性源对俄勒冈州水合物山脊（OR；水深800 m）附近的异养大型动物的密度，组成和多样性的影响，那里的渗漏在OMZ内同时发生，而在鳗鱼河附近加利福尼亚北部（CA; 500 m），那里的渗水被更好的含氧水覆盖。我们假设渗水（包含蛤beds床和微生物垫）应为区域边缘物种库贡献一套独特的物种，但是与OMZ相关的缺氧会抑制渗水相关的异质性。 CA渗流沉积物和OR近深样品中大型动物的密度最高（23,000-33,510 ind·m〜（-2）），OR渗流，CA渗流附近以及CA和OR-500m边缘沉积物的中间值最高（ 10,054-19,777 ind·m〜（-2）），在CA和OR OMZ生境中最低，为800 m（4269-7847 ind·m〜（-2））。在软体动物丰富的CA蛤层和OR微生物垫沉积物以外的所有种类中，Annilids构成了超过50％的分类单元。大约50％的渗透物种似乎是栖息地特有的；微生物垫中存在的物种在很大程度上构成了蛤beds床中存在的物种的子集。 Dorvilleid和ampharetid多毛类在渗流沉积物中占优势。 500 m和800 m处的非深部边缘沉积物大量分布着分支状多毛类动物，包括共生类和副类动物。在CA和OR微生物垫生境中，α多样性（每个核心计算的Es [20]）最低，而1级优势最高。对Es [100]的汇总分析显示，CA蛤层和近距离生境中的物种丰富度最高（分别为30.3和29.6），而OR微生物垫和近距离生境中的物种丰富度最低（分别为16.5和17.9） 。与蛤床和微生物垫沉积物（仅32-37％的栖息地内相似性）相比，CA和OR处的非深部沉积物（500和800 m）均较均匀（栖息地内相似度为55-57％）。 CA沉积物大型动物通常表现出更高的α多样性，并且随着栖息地的组合，物种积累曲线的斜率比OR边缘大型动物具有更高的增长率。北太平洋东北部的甲烷渗流引入了明显的异质性，从而在多个空间尺度上增加了边缘生物多样性。但是，我们的假设是，OMZ会减少对多样性的渗透贡献。与800 m处的OR渗漏（800 m处的OMZ动物）相比，500 m处更好的含氧CA渗漏共享更多的背景边缘动物（在500 m处）。富含甲烷的流体通量的地理差异以及对化学合成食物来源的依赖随着深度的增加而增加，可以解释这些结果。

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