Trophic cascades in the western Ross Sea, Antarctica: revisited
Trophic cascades in the western Ross Sea, Antarctica: revisited
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DOI：
10.3354/meps11394
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发表时间：
2015-08-27
影响因子：
2.5
通讯作者：
Veloz, Sam
中科院分区：
文献类型：
--
作者：
Ainley, David G.;Ballard, Grant;Veloz, Sam
我们研究了南极罗斯海中掠食者对猎物可获得性的影响，评估了阿德利企鹅的觅食旅行持续时间(FTD)增加的原因，以及随着企鹅觅食区域觅食企鹅和竞争鲸目动物数量的增加，从磷虾到鱼类的饮食变化的原因。为了研究企鹅随季节变化的FTD与觅食种群大小的关系-之前间接进行了调查-我们使用生物测井来确定企鹅的三维觅食量，而自动滑翔机则量化了潜在猎物的深度、丰度和分布。随着觅食的企鹅和鲸目动物数量的增加，企鹅在觅食旅行中花费的时间更多，旅行的地方更远、更深，它们的食物包括更多的鱼，因为磷虾的平均最大深度从45米增加到65米，小鱼的食物深度也增加了，但只从51米增加到57米。由于需要在更深的地方觅食，以增加对猎物的重叠，企鹅消耗了更多的能量密集型鱼类。磷虾的深度与叶绿素(磷虾食物的代用品)呈负相关，表明两者之间存在分离，磷虾避免捕食相对于食物获取具有压倒性的重要性。结果支持以下假设：(1)捕食者将食草动物从罗斯海表层水域移走，控制它们的垂直分布；(2)食物网具有‘黄蜂-腰部’结构，其中中上层营养层受到自上而下的控制，而藻类吨的生产和积累受到自下而上的调节，在很大程度上与食草动物的控制无关。罗斯海模型需要修改，以反映这种食物网络结构。
We investigated mesopredator effects on prey availability in the Ross Sea, Antarctica, assessing the reasons why Adelie penguin Pygoscelis adeliae foraging trip duration (FTD) increases and diet changes from krill to fish as numbers of foraging penguins and competing cetaceans increase in the penguins' foraging area. To investigate penguins' seasonally changing FTD as a function of foraging population size-previously investigated indirectly-we used bio-logging to determine the penguins' 3-dimensional foraging volume, while an autonomous glider quantified the depth, abundance, and distribution of potential prey. As numbers of foraging penguins and cetaceans increased, penguins spent more time on foraging trips, traveling farther and deeper, and their diet included more fish, as average maximum depth of krill increased from 45 to 65 m, and that of small fish also deepened, but only from 51 to 57 m. With a need to forage at greater depths for in creasingly over lapping prey, the penguins consumed more of the energy-dense fish. Krill depth was negatively correlated with chlorophyll (a proxy for krill food), indicating an uncoupling between the two and the overwhelming importance of predation avoidance by the krill relative to food acquisition. Results support the hypotheses that (1) predators remove the grazers from Ross Sea surface waters, controlling their vertical distributions; and (2) the food web has a 'wasp-waist' structure, in which middle-and upper-trophic levels are controlled top-down, whereas phytoplank ton production and accumulation are regulated bottom-up, largely independent of grazer control. Ross Sea models need revision to reflect this food web structure.