The Roles of Suspension-Feeding and Flux-Feeding Zooplankton as Gatekeepers of Particle Flux Into the Mesopelagic Ocean in the Northeast Pacific
The Roles of Suspension-Feeding and Flux-Feeding Zooplankton as Gatekeepers of Particle Flux Into the Mesopelagic Ocean in the Northeast Pacific
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DOI：
10.3389/fmars.2019.00397
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发表时间：
2019-07
影响因子：
3.7
通讯作者：
M. Stukel;M. Ohman;T. Kelly;Tristan Biard
中科院分区：
文献类型：
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作者：
M. Stukel;M. Ohman;T. Kelly;Tristan Biard
浮游动物是海洋阴阳魔界中下沉颗粒的重要消费者。然而，不同类群的影响取决于它们的摄食方式。与典型的悬浮摄食浮游动物相比，通量摄食类群优先消耗快速下沉的颗粒，否则这些颗粒会渗透到深海。要量化的潜在影响的两个通量喂养浮游动物类群（Aulosphaeridae [Rhizaria]，和Limacina helicina [euthecosome pteropod]）和总悬浮液喂养浮游动物社区，我们测量了这些生物的深度分层丰度在六个巡航在加州当前生态系统。利用异速生长的比例关系，我们计算了通量馈线和悬浮馈线拦截的碳通量的百分比。这些估计进行了比较，使用漂流沉积物陷阱和238 U-234 Th不平衡的碳通量衰减的直接测量。我们发现，在浅暮光区的碳通量衰减通常在500 - 1000 μmol有机碳通量范围内，平均每10米垂直深度箱。这相当于约6 - 10%的碳通量矿化/ 10 m。在这项研究中考虑的两个通量喂养类群可以占相当大的比例，这个通量附近的透光层的基础。在其最大丰度深度（~100 m）处，Aulosphaeridae的平均通量衰减为0.69% / 10 m（中位数= 0.21%/10 m，四分位距= 0.04 - 0.81%），相当于该深度范围内总通量衰减的~ 10%。当原生生物最丰富时，管壳虫科的通量衰减最大，达到4.2% / 10 m。L.螺旋藻对碳通量的平均截留率为0.45 - 1.6%，略高于管球藻。相比之下，悬浮液喂养浮游动物在中层（包括桡足类，磷虾类，apperitularians，介形类）的综合清除率为2-81 L m-3 d-1（平均19.6 L m-3 d-1）。这意味着对缓慢沉降的颗粒有很大影响，但对可能快速沉降的粪便颗粒的影响可以忽略不计，粪便颗粒构成了沉积物收集器中收集的大部分物质。我们的研究结果强调，需要更多的研究重点放在许多类群，可能作为通量饲养在海洋曙暮光区。
Zooplankton are important consumers of sinking particles in the ocean’s twilight zone. However, the impact of different taxa depends on their feeding mode. In contrast to typical suspension-feeding zooplankton, flux-feeding taxa preferentially consume rapidly-sinking particles that would otherwise penetrate into the deep ocean. To quantify the potential impact of two flux-feeding zooplankton taxa (Aulosphaeridae [Rhizaria], and Limacina helicina [euthecosome pteropod]) and the total suspension-feeding zooplankton community, we measured depth-stratified abundances of these organisms during six cruises in the California Current Ecosystem. Using allometric-scaling relationships, we computed the percentage of carbon flux intercepted by flux feeders and suspension feeders. These estimates were compared to direct measurements of carbon flux attenuation made using drifting sediment traps and 238U-234Th disequilibrium. We found that carbon flux attenuation in the shallow twilight zone typically ranged from 500 – 1000 µmol organic C flux remineralized per 10-m vertical depth bin. This equated to approximately 6 – 10% of carbon flux remineralized / 10 m. The two flux-feeding taxa considered in this study could account for a substantial proportion of this flux near the base of the euphotic zone. The mean flux attenuation attributable to Aulosphaeridae was 0.69% / 10 m (median = 0.21%/10 m, interquartile range = 0.04 – 0.81%) at their depth of maximum abundance (~100 m), which would equate to ~ 10% of total flux attenuation in this depth range. The maximum flux attenuation attributable to Aulosphaeridae reached 4.2% / 10 m when these protists were most abundant. L. helicina, meanwhile, could intercept 0.45 – 1.6% of carbon flux / 10 m, which was slightly greater (on average) than the Aulosphaeridae. In contrast, suspension-feeding zooplankton in the mesopelagic (including copepods, euphausiids, appendicularians, and ostracods) had combined clearance rates of 2–81 L m-3 d-1 (mean of 19.6 L m-3 d-1). This implies a substantial impact on slowly sinking particles, but a negligible impact on the presumably rapidly-sinking fecal pellets that comprised the majority of the material collected in sediment traps. Our results highlight the need for a greater research focus on the many taxa that potentially act as flux feeders in the oceanic twilight zone.