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Characterisation of the nematode community of a low-activity cold seep in the recently ice-shelf free Larsen B area, Eastern Antarctic Peninsula.

Hauquier F, Ingels J, Gutt J, Raes M, Vanreusel A - PLoS ONE (2011)

Bottom Line: The nematode community at the Larsen B seep site differed significantly from other Antarctic sites in terms of dominant genera, diversity and abundance.The recent ice-shelf collapse and enhanced food input from surface phytoplankton blooms were responsible for the shift from oligotrophic pre-collapse conditions to a phytodetritus-based community with high densities and low diversity.The parthenogenetic reproduction of the highly dominant Halomonhystera species is rather unusual for marine nematodes and may be responsible for the successful colonisation by this single species.

View Article: PubMed Central - PubMed

Affiliation: Marine Biology Section, Ghent University, Ghent, Belgium. freija.hauquier@ugent.be

ABSTRACT

Background: Recent climate-induced ice-shelf disintegration in the Larsen A (1995) and B (2002) areas along the Eastern Antarctic Peninsula formed a unique opportunity to assess sub-ice-shelf benthic community structure and led to the discovery of unexplored habitats, including a low-activity methane seep beneath the former Larsen B ice shelf. Since both limited particle sedimentation under previously permanent ice coverage and reduced cold-seep activity are likely to influence benthic meiofauna communities, we characterised the nematode assemblage of this low-activity cold seep and compared it with other, now seasonally ice-free, Larsen A and B stations and other Antarctic shelf areas (Weddell Sea and Drake Passage), as well as cold-seep ecosystems world-wide.

Principal findings: The nematode community at the Larsen B seep site differed significantly from other Antarctic sites in terms of dominant genera, diversity and abundance. Densities in the seep samples were high (>2000 individuals per 10 cm(2)) and showed below-surface maxima at a sediment depth of 2-3 cm in three out of four replicates. All samples were dominated by one species of the family Monhysteridae, which was identified as a Halomonhystera species that comprised between 80 and 86% of the total community. The combination of high densities, deeper density maxima and dominance of one species is shared by many cold-seep ecosystems world-wide and suggested a possible dependence upon a chemosynthetic food source. Yet stable (13)C isotopic signals (ranging between -21.97±0.86‰ and -24.85±1.89‰) were indicative of a phytoplankton-derived food source.

Conclusion: The recent ice-shelf collapse and enhanced food input from surface phytoplankton blooms were responsible for the shift from oligotrophic pre-collapse conditions to a phytodetritus-based community with high densities and low diversity. The parthenogenetic reproduction of the highly dominant Halomonhystera species is rather unusual for marine nematodes and may be responsible for the successful colonisation by this single species.

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Vertical profiles of nematode densities, Halomonhystera densities and CPE concentration per sediment layer.Scale bars have been made uniform for comparison. White arrows indicate the position of the sulphidic layer as observed upon sampling [28].
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pone-0022240-g002: Vertical profiles of nematode densities, Halomonhystera densities and CPE concentration per sediment layer.Scale bars have been made uniform for comparison. White arrows indicate the position of the sulphidic layer as observed upon sampling [28].

Mentions: At Larsen B_Seep, some sediment cores exhibited a clear sulphidic layer between 3 and 10 cm sediment depth (see Table 1; Fig 2), characterised by a typical sulphide smell and dark blue-grey colour ([28]; personal observations). Empty shells of the cold-seep clam Calyptogena, also observed by [9], were still present at the time of sampling [21], [28].


Characterisation of the nematode community of a low-activity cold seep in the recently ice-shelf free Larsen B area, Eastern Antarctic Peninsula.

Hauquier F, Ingels J, Gutt J, Raes M, Vanreusel A - PLoS ONE (2011)

Vertical profiles of nematode densities, Halomonhystera densities and CPE concentration per sediment layer.Scale bars have been made uniform for comparison. White arrows indicate the position of the sulphidic layer as observed upon sampling [28].
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3140504&req=5

pone-0022240-g002: Vertical profiles of nematode densities, Halomonhystera densities and CPE concentration per sediment layer.Scale bars have been made uniform for comparison. White arrows indicate the position of the sulphidic layer as observed upon sampling [28].
Mentions: At Larsen B_Seep, some sediment cores exhibited a clear sulphidic layer between 3 and 10 cm sediment depth (see Table 1; Fig 2), characterised by a typical sulphide smell and dark blue-grey colour ([28]; personal observations). Empty shells of the cold-seep clam Calyptogena, also observed by [9], were still present at the time of sampling [21], [28].

Bottom Line: The nematode community at the Larsen B seep site differed significantly from other Antarctic sites in terms of dominant genera, diversity and abundance.The recent ice-shelf collapse and enhanced food input from surface phytoplankton blooms were responsible for the shift from oligotrophic pre-collapse conditions to a phytodetritus-based community with high densities and low diversity.The parthenogenetic reproduction of the highly dominant Halomonhystera species is rather unusual for marine nematodes and may be responsible for the successful colonisation by this single species.

View Article: PubMed Central - PubMed

Affiliation: Marine Biology Section, Ghent University, Ghent, Belgium. freija.hauquier@ugent.be

ABSTRACT

Background: Recent climate-induced ice-shelf disintegration in the Larsen A (1995) and B (2002) areas along the Eastern Antarctic Peninsula formed a unique opportunity to assess sub-ice-shelf benthic community structure and led to the discovery of unexplored habitats, including a low-activity methane seep beneath the former Larsen B ice shelf. Since both limited particle sedimentation under previously permanent ice coverage and reduced cold-seep activity are likely to influence benthic meiofauna communities, we characterised the nematode assemblage of this low-activity cold seep and compared it with other, now seasonally ice-free, Larsen A and B stations and other Antarctic shelf areas (Weddell Sea and Drake Passage), as well as cold-seep ecosystems world-wide.

Principal findings: The nematode community at the Larsen B seep site differed significantly from other Antarctic sites in terms of dominant genera, diversity and abundance. Densities in the seep samples were high (>2000 individuals per 10 cm(2)) and showed below-surface maxima at a sediment depth of 2-3 cm in three out of four replicates. All samples were dominated by one species of the family Monhysteridae, which was identified as a Halomonhystera species that comprised between 80 and 86% of the total community. The combination of high densities, deeper density maxima and dominance of one species is shared by many cold-seep ecosystems world-wide and suggested a possible dependence upon a chemosynthetic food source. Yet stable (13)C isotopic signals (ranging between -21.97±0.86‰ and -24.85±1.89‰) were indicative of a phytoplankton-derived food source.

Conclusion: The recent ice-shelf collapse and enhanced food input from surface phytoplankton blooms were responsible for the shift from oligotrophic pre-collapse conditions to a phytodetritus-based community with high densities and low diversity. The parthenogenetic reproduction of the highly dominant Halomonhystera species is rather unusual for marine nematodes and may be responsible for the successful colonisation by this single species.

Show MeSH
Related in: MedlinePlus