Long-term decline in krill stock and increase in salps within the Southern Ocean
Long-term decline in krill stock and increase in salps within the Southern Ocean
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DOI：
10.1038/nature02996
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发表时间：
2004-11-04
期刊：
影响因子：
64.8
通讯作者：
Rothery, P
中科院分区：
文献类型：
--
作者：
Atkinson, A;Siegel, V;Rothery, P
南极磷虾（Euphausia superba）和海鞘（主要是Salpa thompsoni）是南大洋的主要食草动物（1-4），磷虾支持商业渔业（5）。它们的密度分布（1，3，4，6）在1926 - 1951年期间被描述，而最近的局部研究（7-10）表明短期的变化。为了研究更大尺度上的时空变化，我们结合了1926年至2003年所有可用的科学净抽样数据。该数据库显示，西南大西洋的生产部门包含超过50%的南大洋磷虾种群，但自20世纪70年代以来，它们的密度已经下降。在空间上，在其栖息地，夏季磷虾密度与叶绿素浓度呈正相关。从时间上看，在西南大西洋，夏季磷虾密度与前一个冬天的海冰范围呈正相关。因此，夏季食物和冬季海冰的范围是在西南大西洋观察到的高磷虾密度的关键因素。磷虾需要这个区域夏季浮游植物的大量繁殖，在那里，冬季广泛的海冰意味着冰藻提供了丰富的冬季食物，促进了幼虫的招募（7-11）并补充了种群。相比之下，海鞘占据了南大洋广泛的低生产力区域，比磷虾更能忍受温暖的海水（2- 4，12）。随着磷虾密度在上个世纪的下降，海鞘在其活动范围的南部似乎有所增加。这些变化对南大洋食物网产生了深远的影响（10、13）。
Antarctic krill ( Euphausia superba) and salps ( mainly Salpa thompsoni) are major grazers in the Southern Ocean(1-4), and krill support commercial fisheries(5). Their density distributions(1,3,4,6) have been described in the period 1926 - 51, while recent localized studies(7-10) suggest short-term changes. To examine spatial and temporal changes over larger scales, we have combined all available scientific net sampling data from 1926 to 2003. This database shows that the productive southwest Atlantic sector contains > 50% of Southern Ocean krill stocks, but here their density has declined since the 1970s. Spatially, within their habitat, summer krill density correlates positively with chlorophyll concentrations. Temporally, within the southwest Atlantic, summer krill densities correlate positively with sea-ice extent the previous winter. Summer food and the extent of winter sea ice are thus key factors in the high krill densities observed in the southwest Atlantic Ocean. Krill need the summer phytoplankton blooms of this sector, where winters of extensive sea ice mean plentiful winter food from ice algae, promoting larval recruitment(7-11) and replenishing the stock. Salps, by contrast, occupy the extensive lower-productivity regions of the Southern Ocean and tolerate warmer water than krill(2-4,12). As krill densities decreased last century, salps appear to have increased in the southern part of their range. These changes have had profound effects within the Southern Ocean food web(10,13).