Limits...
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.

Show MeSH

Related in: MedlinePlus

nMDS plot.The plot is based on Bray-Curtis similarities of the Larsen replicates ([3]; this study) and the reference data of the Weddell Sea [26] and Drake Passage [24]. Data have been standardised and square-root transformed prior to analysis. The stress value in the upper right corner indicates the goodness-of-fit of the MDS plot.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3140504&req=5

pone-0022240-g005: nMDS plot.The plot is based on Bray-Curtis similarities of the Larsen replicates ([3]; this study) and the reference data of the Weddell Sea [26] and Drake Passage [24]. Data have been standardised and square-root transformed prior to analysis. The stress value in the upper right corner indicates the goodness-of-fit of the MDS plot.

Mentions: Meiofauna in general and the nematode community at B_Seep were depauperated compared to other Antarctic areas (see Table 7 for an overview of the average diversity values for the different areas). Low diversity at B_Seep in terms of H'loge and EG was attributed the absolute dominance of one Halomonhystera species (80–86%), family Monhysteridae. The same species was also found in the other Larsen stations, although with lower relative abundances (9–58%; [3]). Figure 5 shows the nMDS plot based on genera composition data, including all Larsen stations as well as other shelf stations from the Weddell Sea and Drake Passage known from literature. The high contribution of Monhysteridae to total nematode densities at B_Seep was the main factor (as revealed by SIMPER analysis) explaining on one hand the higher similarity with B_West and B_North (41.11% and 43.45%, respectively), and on the other hand the larger differences in community composition with B_South (dissimilarity of 78,22%), A_South (dissimilarity of 68.91%) and other Weddell Sea regions (dissimilarity of 75.09% with Drake Passage average and 79.42% Weddell Sea average) [24], [26], where the genus Halomonhystera and the family Monhysteridae are rather sparse. Overall, nematode community structure was significantly different between different shelf regions, based on the one-way ANOSIM analyses (overall R = 0.97 and p = 0.001 for 7 groups (5 Larsen stations + Weddell Sea + DP); R between 0.904 and 1 for all pairwise comparisons; higher R values indicate higher dissimilarity between sites).


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)

nMDS plot.The plot is based on Bray-Curtis similarities of the Larsen replicates ([3]; this study) and the reference data of the Weddell Sea [26] and Drake Passage [24]. Data have been standardised and square-root transformed prior to analysis. The stress value in the upper right corner indicates the goodness-of-fit of the MDS plot.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0022240-g005: nMDS plot.The plot is based on Bray-Curtis similarities of the Larsen replicates ([3]; this study) and the reference data of the Weddell Sea [26] and Drake Passage [24]. Data have been standardised and square-root transformed prior to analysis. The stress value in the upper right corner indicates the goodness-of-fit of the MDS plot.
Mentions: Meiofauna in general and the nematode community at B_Seep were depauperated compared to other Antarctic areas (see Table 7 for an overview of the average diversity values for the different areas). Low diversity at B_Seep in terms of H'loge and EG was attributed the absolute dominance of one Halomonhystera species (80–86%), family Monhysteridae. The same species was also found in the other Larsen stations, although with lower relative abundances (9–58%; [3]). Figure 5 shows the nMDS plot based on genera composition data, including all Larsen stations as well as other shelf stations from the Weddell Sea and Drake Passage known from literature. The high contribution of Monhysteridae to total nematode densities at B_Seep was the main factor (as revealed by SIMPER analysis) explaining on one hand the higher similarity with B_West and B_North (41.11% and 43.45%, respectively), and on the other hand the larger differences in community composition with B_South (dissimilarity of 78,22%), A_South (dissimilarity of 68.91%) and other Weddell Sea regions (dissimilarity of 75.09% with Drake Passage average and 79.42% Weddell Sea average) [24], [26], where the genus Halomonhystera and the family Monhysteridae are rather sparse. Overall, nematode community structure was significantly different between different shelf regions, based on the one-way ANOSIM analyses (overall R = 0.97 and p = 0.001 for 7 groups (5 Larsen stations + Weddell Sea + DP); R between 0.904 and 1 for all pairwise comparisons; higher R values indicate higher dissimilarity between sites).

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