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<p>The Drake Passage (DP) is the most adverse region in the world due to strong hydrodynamics where it is difficult to navigate. So, there is therefore almost no data on bottom hydrographical and sediment studies in this region. This study compares, for the first time, the size of foraminiferal tests in seven stations: five stations (EB-1 to EB-5) at ~ 480&#xa0;m deep near the Bransfield Strait (BS), Antarctic Peninsula (AP) and two in a deeper area of ~ 3800&#xa0;m of the Drake Passage (DK-1 and DK-2). <i>Adercotryma glomeratum</i> (agglutinated benthic foraminifera) was chosen as it was the only abundant species in the surface sediment of the analyzed stations. In total, 861 specimens of <i>A. glomeratum</i> (from 100–140 specimens per station) were measured: 280 living (40 living specimens per station) and 581 dead specimens (60–100 dead specimens per station) were picked, stored in cardboard cell slides and individually measured along their longest axis using a digital camera (AxioCam SV6), coupled to a Zeiss Stemi SV6 stereomicroscope. The longest axis of the measured specimens had dimensions between ≈ 50–550&#xa0;µm, but the majority (81%) had dimensions between 100–200&#xa0;µm. The cluster analysis based on grain size, morphometric data, and depth shows that the largest sizes of living and dead organisms (300–550&#xa0;µm) only occur in fine-grained sediments at stations DK-1 and DK-2 (at about ~ 3800&#xa0;m); this is in calm bottom conditions (unlike what happens in the surface ocean). The average test size and standard deviation were lower at stations EB-1 to EB-5, with coarser-grained sediments and in a more unstable environment near the mainland (more influenced by glacial processes). Stable and calm hydrodynamic deep-sea environments, probably enable longer life cycles and more significant growth of the specimens at stations DK-1 and DK-2<i>.</i> The data obtained in this work suggest that the size of <i>A. glomeratum</i> (both living and dead) populations can be used as an indicator of the stability/instability of the bottom environment and as a proxy in environmental and paleoenvironmental reconstructions to trace the occurrence of environments exposed to disturbances or stable in deep-sea settings, such as that of the Southern Ocean.</p>

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Developing a palaeoceanographic proxy based on the dimensions of Adercotryma glomeratum: a case study in Drake Passage region (Antarctic Peninsula)

  • 期刊论文

  • 发表日期：

    2025年1月17日

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  • Camila Cunha Passos,
  • Maria Virginia Alves Martins,
  • Wânia Duleba

摘要

The Drake Passage (DP) is the most adverse region in the world due to strong hydrodynamics where it is difficult to navigate. So, there is therefore almost no data on bottom hydrographical and sediment studies in this region. This study compares, for the first time, the size of foraminiferal tests in seven stations: five stations (EB-1 to EB-5) at ~ 480 m deep near the Bransfield Strait (BS), Antarctic Peninsula (AP) and two in a deeper area of ~ 3800 m of the Drake Passage (DK-1 and DK-2). Adercotryma glomeratum (agglutinated benthic foraminifera) was chosen as it was the only abundant species in the surface sediment of the analyzed stations. In total, 861 specimens of A. glomeratum (from 100–140 specimens per station) were measured: 280 living (40 living specimens per station) and 581 dead specimens (60–100 dead specimens per station) were picked, stored in cardboard cell slides and individually measured along their longest axis using a digital camera (AxioCam SV6), coupled to a Zeiss Stemi SV6 stereomicroscope. The longest axis of the measured specimens had dimensions between ≈ 50–550 µm, but the majority (81%) had dimensions between 100–200 µm. The cluster analysis based on grain size, morphometric data, and depth shows that the largest sizes of living and dead organisms (300–550 µm) only occur in fine-grained sediments at stations DK-1 and DK-2 (at about ~ 3800 m); this is in calm bottom conditions (unlike what happens in the surface ocean). The average test size and standard deviation were lower at stations EB-1 to EB-5, with coarser-grained sediments and in a more unstable environment near the mainland (more influenced by glacial processes). Stable and calm hydrodynamic deep-sea environments, probably enable longer life cycles and more significant growth of the specimens at stations DK-1 and DK-2. The data obtained in this work suggest that the size of A. glomeratum (both living and dead) populations can be used as an indicator of the stability/instability of the bottom environment and as a proxy in environmental and paleoenvironmental reconstructions to trace the occurrence of environments exposed to disturbances or stable in deep-sea settings, such as that of the Southern Ocean.