Degradation of copepod faecal pellets in the upper layer: role of microbial community and Calanus finmarchicus
Degradation of copepod faecal pellets in the upper layer: role of microbial community and Calanus finmarchicus
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DOI：
10.3354/meps09808
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发表时间：
2012-08
影响因子：
2.5
通讯作者：
C. Svensen;C. W. Riser;M. Reigstad;Lena Seuthe
中科院分区：
文献类型：
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作者：
C. Svensen;C. W. Riser;M. Reigstad;Lena Seuthe
桡足类粪便颗粒（FP）被认为是垂直碳通量的重要贡献者，但比较FP生产与FP出口使用沉积物捕集器的调查得出结论，垂直出口不是他们唯一的命运。FP在60米以上的深度发生了很大程度的降解，即使在快速下沉的大型FP中，也只有一小部分到达了200米以上的沉积物捕集器。桡足类FP的保留机制仍不清楚。为了研究浮游生物群落的小隔室（<180 μm）与较大的滤食性桡足类对大的、快速下沉的FP的降解的相对重要性，我们将芬兰哲水蚤（Calanus finmarchicus（Gunnerus））产生的FP培养在180 μ m过滤的叶绿素a最大值的水中。从一系列实验中，我们发现大FP的降解是时间依赖性的，因为在孵育20或48小时后没有明显的降解，但在72小时后FP体积减少了32%。我们还发现，大型滤食性桡足类可能会促进降解过程，因为在5 ℃下孵育48 h后，FP降解率从0增加到75%。finmarchicus。我们的结论是，纤毛虫和甲藻能够降解大型桡足类FP，但这个过程太慢，无法解释观察到的大FP的保留在上200米的水柱由于快速下沉的大颗粒。而不是寻找单因素的通量调节过程的解释，我们强调的重要性，调查在相关的时间范围内的综合影响，以了解自然系统中的碳通量调节的复杂性。
Copepod faecal pellets (FP) are considered important contributors to vertical carbon flux, but investigations comparing FP production with FP export using sediment traps conclude that vertical export is not their only fate. FP are degraded to a large extent in the upper 60 m, and even among large, fast-sinking FP, only a fraction reaches sediment traps deeper than 200 m. Retention mechanisms for copepod FP are still not well understood. In order to investigate the relative importance of the small (<180 μm) compartment of the plankton community versus larger filter-feeding copepods for degradation of large, fast-sinking FP, we incubated FP produced by Calanus finmarchicus (Gunnerus) in 180 μm-filtered water from the chlorophyll a maximum. From a series of experiments, we found that the degradation of large FP is time-dependent, as no degradation was apparent after 20 or 48 h of incubation, but after 72 h FP volume was reduced by 32%. We also found that large filter-feeding copepods may facilitate the degradation process, since FP degradation increased from 0 to 75% after 48 h of incubation in the presence of 5 C. finmarchicus. We conclude that ciliates and dinoflagellates are able to degrade large copepod FP, but that this process is too slow to explain observed retention of large FP in the upper 200 m of the water column due to fast sinking of large particles. Rather than looking for single-factor explanations for flux-regulating processes, we stress the importance of investigating combined effects in relevant time frames to understand the complexity of carbon flux regulation in natural systems.