美国研究人员4月11日公布报告称，由于气候变暖导致南极企鹅主要食物之一磷虾的密度下降，在南极半岛和邻近的斯科舍海，阿德利企鹅和帽带企鹅数量近年来急剧减少。
美国国家海洋和大气管理局海鸟专家韦恩·特里维尔皮斯等人在新一期美国《国家科学院院刊》（PNAS）上报告说，他们分析南极半岛和邻近的斯科舍海地区的实地数据后发现，在20世纪30年代到70年代之间，有利的气候条件以及其他南极动物对磷虾捕食量的减少导致南极地区企鹅数量增加；然而，此后不断上升的温度和来自海洋哺乳动物的竞争加剧可能让上述地区的磷虾密度下降了至多80%。阿德利企鹅和帽带企鹅种群的衰退与磷虾的减少处于同一时期，而幼年企鹅可能对食物短缺最为敏感。
报告说，南极半岛和斯科舍海的平均温度自20世纪中叶以来上升了5到6摄氏度，而全球平均气温在20世纪上升了不到0.74摄氏度。
磷虾主要以南极冰藻等浮游植物为食，是南极食物链的重要基础，为包括企鹅在内的诸多南极动物提供食物来源。由于南极磷虾资源丰富，它也被誉为“世界未来的食品库”。不过，在过去数十年中，由于全球气温变暖的影响，南极一些地区冬季海冰形成时间延后，覆盖面积也缩小，而春季融化时间却向前推移，影响了冰藻的繁殖，进而导致磷虾密度减少。
研究人员此前曾推测，由于阿德利企鹅喜欢冰，而帽带企鹅不喜欢冰，全球变暖可能导致阿德利企鹅数量减少、帽带企鹅数量增加，但这项研究结果却与之大相径庭。
研究人员警告说，今后人类捕捞磷虾的作业难度可能会有所增加；另外，如果磷虾的密度继续减少，阿德利企鹅和帽带企鹅种群都可能随之衰退。（生物谷Bioon.com）
生物谷推荐原文出处：
PNAS doi: 10.1073/pnas.1016560108
Variability in krill biomass links harvesting and climate warming to penguin population changes in Antarctica
Wayne Z. Trivelpiecea,1, Jefferson T. Hinkea,b, Aileen K. Millera, Christian S. Reissa, Susan G. Trivelpiecea, and George M. Wattersa
Abstract
The West Antarctic Peninsula (WAP) and adjacent Scotia Sea support abundant wildlife populations, many of which were nearly extirpated by humans. This region is also among the fastest-warming areas on the planet, with 5–6 °C increases in mean winter air temperatures and associated decreases in winter sea-ice cover. These biological and physical perturbations have affected the ecosystem profoundly. One hypothesis guiding ecological interpretations of changes in top predator populations in this region, the “sea-ice hypothesis,” proposes that reductions in winter sea ice have led directly to declines in “ice-loving” species by decreasing their winter habitat, while populations of “ice-avoiding” species have increased. However, 30 y of field studies and recent surveys of penguins throughout the WAP and Scotia Sea demonstrate this mechanism is not controlling penguin populations; populations of both ice-loving Adélie and ice-avoiding chinstrap penguins have declined significantly. We argue in favor of an alternative, more robust hypothesis that attributes both increases and decreases in penguin populations to changes in the abundance of their main prey, Antarctic krill. Unlike many other predators in this region, Adélie and chinstrap penguins were never directly harvested by man; thus, their population trajectories track the impacts of biological and environmental changes in this ecosystem. Linking trends in penguin abundance with trends in krill biomass explains why populations of Adélie and chinstrap penguins increased after competitors (fur seals, baleen whales, and some fishes) were nearly extirpated in the 19th to mid-20th centuries and currently are decreasing in response to climate change.
