美國研究人員4月11日公布報告稱,，由于氣候變暖導致南極企鵝主要食物之一磷蝦的密度下降，在南極半島和鄰近的斯科舍海,，阿德利企鵝和帽帶企鵝數(shù)量近年來急劇減少,。
美國國家海洋和大氣管理局海鳥專家韋恩·特里維爾皮斯等人在新一期美國《國家科學院院刊》（PNAS）上報告說,，他們分析南極半島和鄰近的斯科舍海地區(qū)的實地數(shù)據(jù)后發(fā)現(xiàn)，在20世紀30年代到70年代之間,，有利的氣候條件以及其他南極動物對磷蝦捕食量的減少導致南極地區(qū)企鵝數(shù)量增加,；然而，此后不斷上升的溫度和來自海洋哺乳動物的競爭加劇可能讓上述地區(qū)的磷蝦密度下降了至多80%,。阿德利企鵝和帽帶企鵝種群的衰退與磷蝦的減少處于同一時期,，而幼年企鵝可能對食物短缺最為敏感。
報告說,，南極半島和斯科舍海的平均溫度自20世紀中葉以來上升了5到6攝氏度,，而全球平均氣溫在20世紀上升了不到0.74攝氏度。
磷蝦主要以南極冰藻等浮游植物為食,，是南極食物鏈的重要基礎(chǔ),，為包括企鵝在內(nèi)的諸多南極動物提供食物來源。由于南極磷蝦資源豐富,，它也被譽為“世界未來的食品庫”,。不過，在過去數(shù)十年中,，由于全球氣溫變暖的影響，南極一些地區(qū)冬季海冰形成時間延后,，覆蓋面積也縮小,，而春季融化時間卻向前推移，影響了冰藻的繁殖,，進而導致磷蝦密度減少,。
研究人員此前曾推測，由于阿德利企鵝喜歡冰,，而帽帶企鵝不喜歡冰,，全球變暖可能導致阿德利企鵝數(shù)量減少、帽帶企鵝數(shù)量增加,，但這項研究結(jié)果卻與之大相徑庭,。
研究人員警告說，今后人類捕撈磷蝦的作業(yè)難度可能會有所增加,；另外,，如果磷蝦的密度繼續(xù)減少，阿德利企鵝和帽帶企鵝種群都可能隨之衰退,。（生物谷Bioon.com）
生物谷推薦原文出處：
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.
