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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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Overview of the stations.The stations sampled during the ANT-XXIII/8 Polarstern campaign are indicated on the inserted map B. Larsen B_Seep is indicated in red (adapted from [75]). The reference stations used for comparison are indicated on map A: two areas in the Drake Passage (Southern Scotia Arc (SSA) & Northern Scotia Arc (NSA) indicated in blue; [24]), two locations at the eastern Weddell Sea (Halley Bay (HB) & Kapp Norvegia (KN) indicated in green; [26]).
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pone-0022240-g001: Overview of the stations.The stations sampled during the ANT-XXIII/8 Polarstern campaign are indicated on the inserted map B. Larsen B_Seep is indicated in red (adapted from [75]). The reference stations used for comparison are indicated on map A: two areas in the Drake Passage (Southern Scotia Arc (SSA) & Northern Scotia Arc (NSA) indicated in blue; [24]), two locations at the eastern Weddell Sea (Halley Bay (HB) & Kapp Norvegia (KN) indicated in green; [26]).

Mentions: Sampling was conducted at the Antarctic Peninsula during the ANT-XXIII/8 Polarstern campaign in 2006–2007 in the framework of the Belgian Science Policy project BIANZO II (BIodiversity of three representative groups of the ANtarctic ZOobenthos: coping with change). Special attention was given to the Larsen A and B areas at the eastern side of the Peninsula, which were covered with a permanent ice shelf until 1995–2002. Larsen A lies to the north of Larsen B and both areas are separated by a narrow land/ice strip. A total of five stations was sampled for meiofauna analyses: Larsen B_South, Larsen B_Seep, Larsen B_West, Larsen B_North and Larsen A_South (Fig 1). The different stations have been free of ice cover for different periods of time (see [3]). Larsen B_South was always situated very close to the ice shelf edge, and hence subject to conditions of the open Weddell Sea, whereas the other stations have only been exposed since 2002 or later (Larsen B collapse). Larsen B_Seep is analysed in this study and was selected because of possible cold-seep activity [9], [21]. The other four stations were analysed by [3] and serve as a reference throughout this study. The Larsen B seep area lies more centrally compared to the other Larsen stations, at a depth of approximately 820 m, whereas depth ranges between 229 m and 427 m for the other stations. This difference in depth is attributed to its location within a trough formed by two glaciers [21].


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)

Overview of the stations.The stations sampled during the ANT-XXIII/8 Polarstern campaign are indicated on the inserted map B. Larsen B_Seep is indicated in red (adapted from [75]). The reference stations used for comparison are indicated on map A: two areas in the Drake Passage (Southern Scotia Arc (SSA) & Northern Scotia Arc (NSA) indicated in blue; [24]), two locations at the eastern Weddell Sea (Halley Bay (HB) & Kapp Norvegia (KN) indicated in green; [26]).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0022240-g001: Overview of the stations.The stations sampled during the ANT-XXIII/8 Polarstern campaign are indicated on the inserted map B. Larsen B_Seep is indicated in red (adapted from [75]). The reference stations used for comparison are indicated on map A: two areas in the Drake Passage (Southern Scotia Arc (SSA) & Northern Scotia Arc (NSA) indicated in blue; [24]), two locations at the eastern Weddell Sea (Halley Bay (HB) & Kapp Norvegia (KN) indicated in green; [26]).
Mentions: Sampling was conducted at the Antarctic Peninsula during the ANT-XXIII/8 Polarstern campaign in 2006–2007 in the framework of the Belgian Science Policy project BIANZO II (BIodiversity of three representative groups of the ANtarctic ZOobenthos: coping with change). Special attention was given to the Larsen A and B areas at the eastern side of the Peninsula, which were covered with a permanent ice shelf until 1995–2002. Larsen A lies to the north of Larsen B and both areas are separated by a narrow land/ice strip. A total of five stations was sampled for meiofauna analyses: Larsen B_South, Larsen B_Seep, Larsen B_West, Larsen B_North and Larsen A_South (Fig 1). The different stations have been free of ice cover for different periods of time (see [3]). Larsen B_South was always situated very close to the ice shelf edge, and hence subject to conditions of the open Weddell Sea, whereas the other stations have only been exposed since 2002 or later (Larsen B collapse). Larsen B_Seep is analysed in this study and was selected because of possible cold-seep activity [9], [21]. The other four stations were analysed by [3] and serve as a reference throughout this study. The Larsen B seep area lies more centrally compared to the other Larsen stations, at a depth of approximately 820 m, whereas depth ranges between 229 m and 427 m for the other stations. This difference in depth is attributed to its location within a trough formed by two glaciers [21].

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