Krill-copepod interactions at South Georgia, Antarctica, I. Omnivory by Euphausia superba
Krill-copepod interactions at South Georgia, Antarctica, I. Omnivory by Euphausia superba
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DOI：
10.3354/meps160063
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发表时间：
1997-01-01
影响因子：
2.5
通讯作者：
Snyder, R
中科院分区：
文献类型：
--
作者：
Atkinson, A;Snyder, R
在1995/1996年夏季，对南格鲁吉亚附近的南极磷虾幼虾的摄食进行了研究。肠道荧光的结果进行了比较，从孵化在天然海水和海水丰富的浮游植物和浮游动物。在天然海水中，食物浓度通常较低（中位数为56 mg Cm（-3）），磷虾碳d（-1）的中位数比率为0.68%。浮游植物占主导地位的碳在自然孵化水，但甲藻，纤毛虫和小哲水蚤桡足类占主导地位的碳摄入量的磷虾。在自然和丰富的水，最大的清除率为1至3毫米的哲水蚤桡足类。比这更大的桡足类（例如，晚期桡足类阶段的尖哲水蚤和Rhincalanus gigas）被清除得更慢，尽管在富集孵育中占主导地位的碳。长蝽属比类似大小的哲水蚤清除得更慢，尽管它们的丰度更高，对可用碳的贡献也相似。这些趋势可能反映了磷虾和桡足类之间的检测/逃逸相互作用。在强化食物的情况下，桡足类占磷虾食物的主导地位，磷虾的摄食量超过体碳d（-1）的10%，即使食物浓度接近1 g C m（-3），摄食量也没有达到稳定水平。这表明磷虾可以在定期遇到浮游动物层或斑块时快速进食。肠道荧光显示肠道通过时间为3.7至6.3小时，藻类碳比率为0.43%d（-1），因此支持来自孵育的低藻类碳比率。公布的平均磷虾生物量南格鲁吉亚，夏季8.3克干质量m（-2）的声学值相结合，以估计磷虾去除每日0.2%的浮游植物常备库存，0.6%的原生动物和1.6%的小哲水蚤桡足类。这种对桡足类的影响比以前对南极端足类和毛颚类的估计要高得多。南极桡足类的世代时间长，意味着磷虾在我们的研究中可能是小型桡足类的重要捕食者。
Feeding by juvenile Antarctic krill Euphausia superba near South Georgia was assessed during the austral summer of 1995/1996. Gut fluorescence results were compared with those from incubations in natural seawater and seawater enriched with phytoplankton and zooplankton. In natural seawater, with typically low food concentrations (median 56 mg C m(-3)) the median ration was 0.68 % of krill carbon d(-1). Phytoplankton dominated carbon in the natural incubation water but dinoflagellates, ciliates and small calanoid copepods dominated the carbon intake of krill. In both natural and enriched water, maximum clearance rates were on 1 to 3 mm calanoid copepods. Copepods larger than this (e.g. late copepodite stages of Calanoides acutus and Rhincalanus gigas) were cleared more slowly despite dominating the carbon in the enriched incubations. Oithona spp. were cleared more slowly than calanoids of similar size, despite their greater abundance and their similar contributions to available carbon. These trends could reflect detection/escape interactions between krill and copepods. With enriched food, copepods dominated krill diet, krill rations exceeded 10 % of body carbon d(-1) and rations did not appear to reach a plateau even at food concentrations of similar to 1 g C m(-3). This suggests that krill could feed rapidly during periodic encounters with layers or patches of zooplankton. Gut fluorescence revealed gut passage times of 3.7 to 6.3 h and an algal carbon ration of 0.43 % d(-1), thus supporting the low algal carbon rations derived from the incubations. Published acoustic values of mean krill biomass north of South Georgia that summer of 8.3 g dry mass m(-2) were combined with their clearance rates to give estimates of krill removing daily 0.2% of phytoplankton standing stocks, 0.6% of protozoans and 1.6% of small calanoid copepods. This impact on copepods is much higher than previous estimates from Antarctic amphipods and chaetognaths. The long generation times of Antarctic copepods mean that krill were potentially important predators of small copepods during our study.