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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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Pigment concentrations of the five Larsen A and B stations.Concentrations are given both for the entire sediment column and the upper cm separately (in µg/g). Bars represent standard errors.
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pone-0022240-g003: Pigment concentrations of the five Larsen A and B stations.Concentrations are given both for the entire sediment column and the upper cm separately (in µg/g). Bars represent standard errors.

Mentions: In general, meiofaunal standing stock and distribution in the sediment is to a large extent determined by the amount of utilisable organic matter in the sediments [40]–[42], which in turn is controlled by sedimentation rate, degradation in the water column, and other benthic processes. Higher CPE concentrations in the sediment, especially chlorophyll a (as a measure of freshness of the organic matter), are indicative of a higher primary production in the euphotic zone, in combination with a shallower water depth. Because pigment concentrations and hence food availability tend to decrease with increasing water depth and distance to the coast [26], [42]–[44], meiofaunal densities often decline when moving from the shallows towards the deeper abyss [31], [40], [42]–[45]. At Larsen B_Seep, total phytopigment concentrations were the highest for the whole Larsen region studied so far (Fig 3), which was also observed by [23] during the same ANT-XXIII/8 campaign (data provided by Isla & Sañé Schepisi). Enhanced CPE concentrations at B_Seep relative to adjacent, even shallow, stations can partly be explained by its location within a trough formed by two glaciers. This trough may act as a trap accumulating food deposition from the surface waters [23], [44].


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)

Pigment concentrations of the five Larsen A and B stations.Concentrations are given both for the entire sediment column and the upper cm separately (in µg/g). Bars represent standard errors.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0022240-g003: Pigment concentrations of the five Larsen A and B stations.Concentrations are given both for the entire sediment column and the upper cm separately (in µg/g). Bars represent standard errors.
Mentions: In general, meiofaunal standing stock and distribution in the sediment is to a large extent determined by the amount of utilisable organic matter in the sediments [40]–[42], which in turn is controlled by sedimentation rate, degradation in the water column, and other benthic processes. Higher CPE concentrations in the sediment, especially chlorophyll a (as a measure of freshness of the organic matter), are indicative of a higher primary production in the euphotic zone, in combination with a shallower water depth. Because pigment concentrations and hence food availability tend to decrease with increasing water depth and distance to the coast [26], [42]–[44], meiofaunal densities often decline when moving from the shallows towards the deeper abyss [31], [40], [42]–[45]. At Larsen B_Seep, total phytopigment concentrations were the highest for the whole Larsen region studied so far (Fig 3), which was also observed by [23] during the same ANT-XXIII/8 campaign (data provided by Isla & Sañé Schepisi). Enhanced CPE concentrations at B_Seep relative to adjacent, even shallow, stations can partly be explained by its location within a trough formed by two glaciers. This trough may act as a trap accumulating food deposition from the surface waters [23], [44].

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