- U. Bathmann (2)
- A.P. Florentino De Souza Silva (1)
- H. Flores (1)
- J.A. Franeker van (2)
- M. Haraldsson (1)
- B.P.V. Hunt (1)
- S. Kruse (1)
- H.W.G. Meesters (2)
- E.A. Pakhomov (1)
- A.P. Putte van de (1)
- V. Siegel (2)
- V. Strass (2)
- W.J. Wolff (1)
Seasonal changes in the vertical distribution and community structure of Antarctic macrozooplankton and mikronekton
Flores, H. ; Hunt, B.P.V. ; Kruse, S. ; Pakhomov, E.A. ; Siegel, V. ; Franeker, J.A. van; Strass, V. ; Putte, A.P. van de; Meesters, H.W.G. ; Bathmann, U. - \ 2014
Deep Sea Research Part I: Oceanographic Research Papers 84 (2014). - ISSN 0967-0637 - p. 127 - 141.
chaetognath eukrohnia-hamata - larval euphausia-superba - northern weddell sea - southern-ocean - scotia sea - maud-rise - ice-edge - pack-ice - zooplankton community - limacina-helicina
The macrozooplankton and micronekton community of the Lazarev Sea (Southern Ocean) was investigated at 3 depth layers during austral summer, autumn and winter: (1) the surface layer (0-2 m); (2) the epipelagic layer (0-200 m); and (3) the deep layer (0-3000 m). Altogether, 132 species were identified. Species composition changed with depth from a euphausiid-dominated community in the surface layer, via a siphonophore-dominated community in the epipelagic layer, to a chaetognath-dominated community in the deep layer. The surface layer community predominantly changed along gradients of surface water temperature and sea ice parameters, whereas the epipelagic community mainly changed along hydrographical gradients. Although representing only 1% of the depth range of the epipelagic layer, mean per-area macrofauna densities in the surface layer ranged at 8% of corresponding epipelagic densities in summer, 6% in autumn, and 24% in winter. Seasonal shifts of these proportional densities in abundant species indicated different strategies in the use of the surface layer, including both hibernal downward and hibernal upward shift in the vertical distribution, as well as year-round surface layer use by Antarctic krill. These findings imply that the surface layer, especially when it is ice-covered, is an important functional node of the pelagic ecosystem that has been underestimated by conventional depth-integrated sampling in the past. The exposure of this key habitat to climate-driven forces most likely adds to the known susceptibility of Antarctic pelagic ecosystems to temperature rise and changing sea ice conditions. (C) 2013 Elsevier Ltd. All rights reserved.
The Association of Antarctic Krill Euphausia superba with the Under-Ice Habitat
Florentino De Souza Silva, A.P. ; Franeker, J.A. van; Siegel, V. ; Haraldsson, M. ; Strass, V. ; Meesters, H.W.G. ; Bathmann, U. ; Wolff, W.J. - \ 2012
PLoS ONE 7 (2012)2. - ISSN 1932-6203 - 11 p.
northern weddell sea - southern-ocean - pack-ice - community structure - lazarev sea - trophic relationships - population-dynamics - foraging behavior - elephant island - energy budgets
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