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The association of Antarctic krill Euphausia superba with the under-ice habitat.

Flores H, van Franeker JA, Siegel V, Haraldsson M, Strass V, Meesters EH, Bathmann U, Wolff WJ - PLoS ONE (2012)

Bottom Line: In summer, under-ice densities of Antarctic krill were significantly higher than in open waters.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.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.

View Article: PubMed Central - PubMed

Affiliation: Institute for Marine Resources and Ecosystem Studies, Texel, The Netherlands. hauke.flores@awi.de

ABSTRACT
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.

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Euphausia superba.Day/night comparisons of the surface layer density of (A) postlarval krill at three locations in summer (2007/2008), (B) postlarval krill, and (C) furcilia larvae at two locations in winter (2006). Scaling of y-axis differs. Denotations above bars are location codes. d = daytime, night = night-time; ice = under-ice, ow = open water SUIT hauls.
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pone-0031775-g003: Euphausia superba.Day/night comparisons of the surface layer density of (A) postlarval krill at three locations in summer (2007/2008), (B) postlarval krill, and (C) furcilia larvae at two locations in winter (2006). Scaling of y-axis differs. Denotations above bars are location codes. d = daytime, night = night-time; ice = under-ice, ow = open water SUIT hauls.

Mentions: A diel pattern in the surface density of postlarval Antarctic krill was apparent from the five day/night comparative locations that yielded a sufficient number of animals in summer and winter. In summer, densities of postlarval Antarctic krill were higher at day than at night, both under ice and in open water (Figure 3 A). In winter, a much more pronounced opposite pattern was recorded. The under-ice density at night was up to two orders of magnitude above daytime values (Figure 3 B).


The association of Antarctic krill Euphausia superba with the under-ice habitat.

Flores H, van Franeker JA, Siegel V, Haraldsson M, Strass V, Meesters EH, Bathmann U, Wolff WJ - PLoS ONE (2012)

Euphausia superba.Day/night comparisons of the surface layer density of (A) postlarval krill at three locations in summer (2007/2008), (B) postlarval krill, and (C) furcilia larvae at two locations in winter (2006). Scaling of y-axis differs. Denotations above bars are location codes. d = daytime, night = night-time; ice = under-ice, ow = open water SUIT hauls.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3285626&req=5

pone-0031775-g003: Euphausia superba.Day/night comparisons of the surface layer density of (A) postlarval krill at three locations in summer (2007/2008), (B) postlarval krill, and (C) furcilia larvae at two locations in winter (2006). Scaling of y-axis differs. Denotations above bars are location codes. d = daytime, night = night-time; ice = under-ice, ow = open water SUIT hauls.
Mentions: A diel pattern in the surface density of postlarval Antarctic krill was apparent from the five day/night comparative locations that yielded a sufficient number of animals in summer and winter. In summer, densities of postlarval Antarctic krill were higher at day than at night, both under ice and in open water (Figure 3 A). In winter, a much more pronounced opposite pattern was recorded. The under-ice density at night was up to two orders of magnitude above daytime values (Figure 3 B).

Bottom Line: In summer, under-ice densities of Antarctic krill were significantly higher than in open waters.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.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.

View Article: PubMed Central - PubMed

Affiliation: Institute for Marine Resources and Ecosystem Studies, Texel, The Netherlands. hauke.flores@awi.de

ABSTRACT
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.

Show MeSH