Seabed Acoustic Mapping Revealing an Uncharted Habitat of Circular Depressions Along the Southeast Brazilian Outer Shelf
Initiatives such as the United Nations Decade of Ocean Science for Sustainable Development and Seabed 2030 promote seabed mapping worldwide. In Brazil, especially on the Espírito Santo Continental Shelf, high-resolution seabed mapping has revealed an unknown complex seascape. Circular depressions (C...
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2025-01-01
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| author | Ana Carolina Lavagnino Marcos Daniel Leite Tarcila Franco Pedro Smith Menandro Fernanda Vedoato Vieira Geandré Carlos Boni Alex Cardoso Bastos |
| author_facet | Ana Carolina Lavagnino Marcos Daniel Leite Tarcila Franco Pedro Smith Menandro Fernanda Vedoato Vieira Geandré Carlos Boni Alex Cardoso Bastos |
| author_sort | Ana Carolina Lavagnino |
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| description | Initiatives such as the United Nations Decade of Ocean Science for Sustainable Development and Seabed 2030 promote seabed mapping worldwide. In Brazil, especially on the Espírito Santo Continental Shelf, high-resolution seabed mapping has revealed an unknown complex seascape. Circular depressions (CDs) were mapped for the first time in the Costa das Algas Marine Protection Area. Herein, we aim to present the CD metrics characteristics and discuss their relationship with morphology and relevance as a habitat based on multibeam bathymetry and ground truthing. A total of 3660 depressions were mapped between 46 and 85 m in depth, reaching an area of 460 m<sup>2</sup> and 5 m relief. The continental shelf morphology was subdivided into three sectors based on morphology: inter-valleys, valley edges, and valley flanks, and eleven sites were selected for direct sampling/imaging at the CDs along the sectors. The direct sampling was carried out by scuba-diving with video images and sediment samples collected inside and outside the depressions. The deeper central parts of the circular depressions appear to function as a sink, presenting aggregations of rhodoliths or other carbonate fragments. In most inter-valley depressions, mounds were observed along the edges of the depression. We did not have any indication of gas seeps and no clear sedimentological or morphological control on their occurrence. We first hypothesize that their origin results from combined diachronous processes. The circular depressions mapped at high resolution could be related to sea level processes acting during the last glacial period and shelf exposure, i.e., relict features. The CDs are responsible for biomass aggregation and fish bioturbation, forming holes and rubble mounds, representing a modern process occurring on a centimetric scale. The data collected so far indicate that this fine-scale feature is an important habitat for different fish species. The modern maintenance of these structures could be due to low sedimentation regime areas shaped by biotic excavation. |
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| institution | Kabale University |
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| language | English |
| publishDate | 2025-01-01 |
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| series | Geosciences |
| spelling | doaj-art-ea057e02e4a943ee8c41ca729a65308c2025-01-24T13:34:07ZengMDPI AGGeosciences2076-32632025-01-01151710.3390/geosciences15010007Seabed Acoustic Mapping Revealing an Uncharted Habitat of Circular Depressions Along the Southeast Brazilian Outer ShelfAna Carolina Lavagnino0Marcos Daniel Leite1Tarcila Franco2Pedro Smith Menandro3Fernanda Vedoato Vieira4Geandré Carlos Boni5Alex Cardoso Bastos6Marine Geosciences Laboratory/LaboGeo, Programa de Pós-Graduação em Oceanografia Ambiental, Departamento de Oceanografia e Ecologia, Universidade Federal do Espírito Santo, Vitória 29075910, ES, BrazilCenter of Coastal and Ocean Mapping Joint Hydrographic Center/CCOM, University of New Hampshire, Durhan, NH 03824, USAMarine Geosciences Laboratory/LaboGeo, Programa de Pós-Graduação em Oceanografia Ambiental, Departamento de Oceanografia e Ecologia, Universidade Federal do Espírito Santo, Vitória 29075910, ES, BrazilSeascape Ecology and Mapping Lab, Department of Oceanography, Dalhousie University, Halifax, NS B3H 4R2, CanadaMarine Geosciences Laboratory/LaboGeo, Programa de Pós-Graduação em Oceanografia Ambiental, Departamento de Oceanografia e Ecologia, Universidade Federal do Espírito Santo, Vitória 29075910, ES, BrazilMarine Geosciences Laboratory/LaboGeo, Programa de Pós-Graduação em Oceanografia Ambiental, Departamento de Oceanografia e Ecologia, Universidade Federal do Espírito Santo, Vitória 29075910, ES, BrazilMarine Geosciences Laboratory/LaboGeo, Programa de Pós-Graduação em Oceanografia Ambiental, Departamento de Oceanografia e Ecologia, Universidade Federal do Espírito Santo, Vitória 29075910, ES, BrazilInitiatives such as the United Nations Decade of Ocean Science for Sustainable Development and Seabed 2030 promote seabed mapping worldwide. In Brazil, especially on the Espírito Santo Continental Shelf, high-resolution seabed mapping has revealed an unknown complex seascape. Circular depressions (CDs) were mapped for the first time in the Costa das Algas Marine Protection Area. Herein, we aim to present the CD metrics characteristics and discuss their relationship with morphology and relevance as a habitat based on multibeam bathymetry and ground truthing. A total of 3660 depressions were mapped between 46 and 85 m in depth, reaching an area of 460 m<sup>2</sup> and 5 m relief. The continental shelf morphology was subdivided into three sectors based on morphology: inter-valleys, valley edges, and valley flanks, and eleven sites were selected for direct sampling/imaging at the CDs along the sectors. The direct sampling was carried out by scuba-diving with video images and sediment samples collected inside and outside the depressions. The deeper central parts of the circular depressions appear to function as a sink, presenting aggregations of rhodoliths or other carbonate fragments. In most inter-valley depressions, mounds were observed along the edges of the depression. We did not have any indication of gas seeps and no clear sedimentological or morphological control on their occurrence. We first hypothesize that their origin results from combined diachronous processes. The circular depressions mapped at high resolution could be related to sea level processes acting during the last glacial period and shelf exposure, i.e., relict features. The CDs are responsible for biomass aggregation and fish bioturbation, forming holes and rubble mounds, representing a modern process occurring on a centimetric scale. The data collected so far indicate that this fine-scale feature is an important habitat for different fish species. The modern maintenance of these structures could be due to low sedimentation regime areas shaped by biotic excavation.https://www.mdpi.com/2076-3263/15/1/7seabed habitat mappingseafloor circular depressionhigh-resolution acoustic data |
| spellingShingle | Ana Carolina Lavagnino Marcos Daniel Leite Tarcila Franco Pedro Smith Menandro Fernanda Vedoato Vieira Geandré Carlos Boni Alex Cardoso Bastos Seabed Acoustic Mapping Revealing an Uncharted Habitat of Circular Depressions Along the Southeast Brazilian Outer Shelf Geosciences seabed habitat mapping seafloor circular depression high-resolution acoustic data |
| title | Seabed Acoustic Mapping Revealing an Uncharted Habitat of Circular Depressions Along the Southeast Brazilian Outer Shelf |
| title_full | Seabed Acoustic Mapping Revealing an Uncharted Habitat of Circular Depressions Along the Southeast Brazilian Outer Shelf |
| title_fullStr | Seabed Acoustic Mapping Revealing an Uncharted Habitat of Circular Depressions Along the Southeast Brazilian Outer Shelf |
| title_full_unstemmed | Seabed Acoustic Mapping Revealing an Uncharted Habitat of Circular Depressions Along the Southeast Brazilian Outer Shelf |
| title_short | Seabed Acoustic Mapping Revealing an Uncharted Habitat of Circular Depressions Along the Southeast Brazilian Outer Shelf |
| title_sort | seabed acoustic mapping revealing an uncharted habitat of circular depressions along the southeast brazilian outer shelf |
| topic | seabed habitat mapping seafloor circular depression high-resolution acoustic data |
| url | https://www.mdpi.com/2076-3263/15/1/7 |
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