Institute for Marine Resources and Ecosystem Studies, Texel, The Netherlands.
PLoS One. 2012;7(2):e31775. doi: 10.1371/journal.pone.0031775. Epub 2012 Feb 23.
The association of Antarctic krill Euphausia superba with the under-ice habitat was investigated in the Lazarev Sea (Southern Ocean) during austral summer, autumn and winter. Data were obtained using novel Surface and Under Ice Trawls (SUIT), which sampled the 0-2 m surface layer both under sea ice and in open water. Average surface layer densities ranged between 0.8 individuals m(-2) in summer and autumn, and 2.7 individuals m(-2) in winter. In summer, under-ice densities of Antarctic krill were significantly higher than in open waters. In autumn, the opposite pattern was observed. Under winter sea ice, densities were often low, but repeatedly far exceeded summer and autumn maxima. Statistical models showed that during summer high densities of Antarctic krill in the 0-2 m layer were associated with high ice coverage and shallow mixed layer depths, among other factors. In autumn and winter, density was related to hydrographical parameters. Average under-ice densities from the 0-2 m layer were higher than corresponding values from the 0-200 m layer collected with Rectangular Midwater Trawls (RMT) in summer. In winter, under-ice densities far surpassed maximum 0-200 m densities on several occasions. This indicates that the importance of the ice-water interface layer may be under-estimated by the pelagic nets and sonars commonly used to estimate the population size of Antarctic krill for management purposes, due to their limited ability to sample this habitat. Our results provide evidence for an almost year-round association of Antarctic krill with the under-ice habitat, hundreds of kilometres into the ice-covered area of the Lazarev Sea. Local concentrations of postlarval Antarctic krill under winter sea ice suggest that sea ice biota are important for their winter survival. These findings emphasise the susceptibility of an ecological key species to changing sea ice habitats, suggesting potential ramifications on Antarctic ecosystems induced by climate change.
在南极夏季、秋季和冬季，对拉扎列夫海（南大洋）的南极磷虾（Euphausia superba）与冰下栖息地的关联进行了调查。使用新型的表面和冰下拖网（SUIT）获得了数据，该拖网在海冰下和开阔水域中均采集了 0-2 米的表层。平均表层密度在夏季和秋季为 0.8 个个体/平方米，冬季为 2.7 个个体/平方米。在夏季，冰下南极磷虾的密度明显高于开阔水域。在秋季，相反的模式观察到。在冬季海冰下，密度通常较低，但多次远远超过夏季和秋季的最大值。统计模型表明，在夏季，0-2 米层中南极磷虾的高密度与高冰覆盖率和浅层混合层深度等因素有关。在秋季和冬季，密度与水文学参数有关。夏季，0-2 米层的冰下平均密度高于用矩形中层拖网（RMT）在 0-200 米层中收集的相应值。在冬季，几次出现冰下密度远远超过最大的 0-200 米密度。这表明，由于其有限的采样此栖息地的能力，用于管理目的估计南极磷虾种群规模的浮游网和声纳可能低估了冰-水界面层的重要性。我们的结果为南极磷虾几乎全年与拉扎列夫海冰覆盖区数百公里范围内的冰下栖息地有关提供了证据。冬季海冰下幼虾的局部集中表明，海冰生物群对其冬季生存很重要。这些发现强调了一个生态关键物种对不断变化的海冰栖息地的敏感性，表明气候变化对南极生态系统的潜在影响。
