Research ArticleMarine Ecology

Climate change and glacier retreat drive shifts in an Antarctic benthic ecosystem

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Science Advances  13 Nov 2015:
Vol. 1, no. 10, e1500050
DOI: 10.1126/sciadv.1500050
  • Fig. 1 Map of Potter Cove.

    Picture of 2010 showing glacier retreat since 1995 and the gradient of sediment influence in different areas of the cove, represented by the color gradient. Rectangles are sampling stations with their depth sampling profiles, 15, 20, 25, and 30 m. The Inner Station (I) is most exposed to sediments carried by (a) Potter and (b) Matías creeks. M, Middle Station; O, Outer Station. Inner and Middle stations are located in the inner cove (c), sheltered from the entrance of big icebergs by a sill at 26- to 28-m depth (d; red dashed line). Outer Station is in the outer cove (e). (c) PO3 sediment core location (bathymetry of Potter Cove shown in fig. S1).

  • Fig. 2 Species coverage and sediments at Potter Cove.

    Percentage cover of the different taxa at the Inner Station and at 25- to 30-m depth of the Middle Station, the areas that showed marked shifts in benthic communities at Potter Cove (see details for all the stations and depths in fig. S2). At the Inner Station, trends of decreasing abundance in ascidians and increased pennatulids, sponges, and mobile taxa are visible. Note that at 30-m depth, there are less taxa present in 1998 than in 1994 or 2010. The Middle Station exhibited a shift from macroalgal to zoobenthic dominance, particularly pennatulids, sponges, and ascidians. In 1998, only transects at 20- and 30-m depths were sampled. The lower part of the graph shows mass accumulation rates of bulk sediments (MARBS), total suspended particulate matter (SPM), and percentage of organic matter (OM) in the time lapse of the benthic surveys. MARBS and SPM peaked between 1994 and 1998 (gray shadow bar, which could be a threshold for this ecosystem), and the MARBS values were also the highest registered during the last century (see fig. S3).

  • Fig. 3 Shifts of benthic assemblages at Potter Cove between 1994 and 2010.

    nMDS ordination of relationships among stations, depths, and year, showing high similarity between the Outer Station and the shallower depths (15 to 20 m) of the Middle Station across years. In contrast, the Inner Station and deeper areas of the Middle Station (25 to 30 m) showed a marked change. Analyses were performed using Bray-Curtis similarity index.

  • Fig. 4 Community shifts: Conceptual and mathematical models of ecosystem dynamics under environmental changes.

    (A to C) The plots represent (A) a linear response to a gradual environmental shift with two different communities at both extremes of environmental conditions; (B) a sudden change between states, under which communities can absorb changes in environmental factors until a threshold limit pushes the system from one state to the other; and (C) thresholds with hysteresis occur when different communities can be present under the same environmental conditions. C1, community 1; C2, community 2. (D to F) Benthic shifts and three possible processes showing diversity variation with time. (D) Classical succession: Community 1 is characteristic of early successional stages, and community 2 represents mature stages. (E) Gradual replacement between communities (for example, in an ecosystem displacement process). (F) Sudden change between communities due to a nonlinear response to environmental conditions. (G) A simple simulation of a multispecies spatial competition model under sedimentation based on Levins competition model.

  • Table 1 ANOSIM and SIMPER analyses.

    (A) ANOSIM pairwise analysis among years within each Station and depth. Note that 15- and 25-m depths of 1998 were compared with 20 m and 20 and 30 m of 1994 and 2010, respectively. (B) SIMPER analysis showing the degree of dissimilarity among years and the relevant taxa. See tables S1 and S2 for overall comparisons of ANOSIM and SIMPER analyses.

    A
    StationInnerMiddleOuter
    Depth (m)152025301520253015202530
    1994–19980.090.24*0.55*/0.16*0.15*0.030.050.04/0.26*0.13*0.100.17*0.17*/0.26*0.17*
    1994–20100.24*0.41*0.39*0.46*0.070.010.52*0.38*0.070.070.020.08
    1998–20100.15*0.19*0.31*/0.40*0.40*0.100.73*0.39*/0.73*0.73*0.080.080.18*/0.070.07
    Global R: 0.40*Global R: 0.28*Global R: 0.21*
    B
    StationInnerMiddleOuter
    Depth (m)152025301520253015202530
    1994–199862,7879,5689,7665,763,6275,9669,6184,7982,6774,3260,2765,9166,4157,7161,45
    PenAscAscAscAscAlgAlgAlgAlgAlgAlgAlgAlgAlgAlg
    BivPenPenPolPolAstBivPolAscAscBivBivOphOphAsc
    AstBivBivPorPorPolAscAscAstPolAstBivAscOph
    PenNemAscAstAstPen
    BivalveEch
    1994–201063,5779,4675,6778,451,9844,8793,6681,5357,1358,5158,7870,96
    OphAscAscAscAlgAlgAlgPenAlgAlgAlgAlg
    PenPenaPenPorAstPenAscAstAstOphAsc
    BivOphOphPenBivBivAlgAstOph
    AstBivPorActAscEchOph
    BivOphPorBiv
    Ech
    1998–201066,4666,6170,4185,1981,8668,6270,8586,0882,9192,253,7355,5961,3652,7950,86
    PenPenPenAscPorAlgAlgAlgAlgAlgAlgAlgAlgAlgAlg
    OphOphAscPenAscAscAstPenAscPenBivBivOphOphAsc
    BivBivOphPolPenBivBivBivPenAscAstAstBivAscOph
    AstAscBivPorPolPoliAscBivPolAstAst
    AstOphActPorPolBiv
    IsoEchAstPorAst

    * Statistical differences of R values.

    Supplementary Materials

    • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/10/e1500050/DC1

      Fig. S1. Bathymetry of Potter Cove.

      Fig. S2. Coverage of the different taxa at each of the stations, depths, and dates sampled at Potter Cove.

      Fig. S3. 210Pb profile and mass accumulation rates of bulk sediments (MARBS) for Potter Cove.

      Fig. S4. Benthic assemblages in 1994 and 2010.

      Table S1. Overall pairwise comparison of ANOSIM analyses among stations, depths, and dates.

      Table S2. SIMPER analyses among depths and dates within each station.

    • Supplementary Materials

      This PDF file includes:

      • Fig. S1. Bathymetry of Potter Cove.
      • Fig. S2. Coverage of the different taxa at each of the stations, depths, and dates sampled at Potter Cove.
      • Fig. S3. 210Pb profile and mass accumulation rates of bulk sediments (MARBS) for Potter Cove.
      • Fig. S4. Benthic assemblages in 1994 and 2010.
      • Table S1. Overall pairwise comparison of ANOSIM analyses among stations, depths, and dates.
      • Table S2. SIMPER analyses among depths and dates within each station.

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