Morfologia de recifes submersos na plataforma de Abrolhos (Brasil): da resposta à variação do nível do mar, à heterogeneidade do habitat
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Data
2025-06-25
Autores
Vieira, Fernanda Vedoato
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Universidade Federal do Espírito Santo
Resumo
Submarine geomorphology directly controls the configuration of the marine landscape and benthic habitats and is primarily influenced by eustatic sea-level fluctuations, sedimentation rates, and accommodation space. During the last deglaciation, variations in sea-level rise rates resulted in periods of relative stabilization (stillstands) and rapid acceleration, shaping distinct geomorphological features on the continental shelf.Reefs play a central role in marine ecosystems and are regarded as priority areas for the establishment of marine protected areas, being fundamental to marine spatial planning. In addition, they act as sensitive indicators of the impacts of climate change. Submerged reefs, in turn, are products of oceanographic conditions and short- and long-term sea-level variations, reflecting in their position, morphology, and extent the history of environmental and ecological changes.The Abrolhos Continental Shelf hosts the largest reef province in the South Atlantic and represents the main study area for reef evolution on the Brazilian continental shelf. However, studies on submerged reefs along this platform remain incipient. Nevertheless, understanding the extent, evolution, and connectivity between these submerged reefs and the emergent reefs is essential to fill knowledge gaps regarding the genesis, evolution, morphology, and spatial distribution of the largest reef complex in the South Atlantic. The use of high-resolution multibeam bathymetry, combined with geomorphological analysis methods, constitutes the scope of this research, aiming to elucidate the processes of formation, evolution, and drowning of both previously known and still poorly mapped reefs on the Abrolhos Shelf.Based on morphological data, two main groups of submerged reefs were identified in the southern portion of the Abrolhos Shelf, between depths of 14 and 35 meters. These groups are associated with different seabed features, including linear forms (longitudinal and transverse), sedimentary banks, and incised valleys, indicating a diversity of geomorphological processes and distinct origins. In contrast, in the northern portion of the Abrolhos Shelf, high resolution acoustic mapping revealed more than 34,000 reef structures, ranging from pinnacles to banks, evidencing significant morphological heterogeneity. Finally, the areas were compared in terms of morphological aspects and correlated with post–Last Glacial Maximum eustatic events and the presence of remnant Pleistocene structures.Thus, the Abrolhos Continental Shelf preserves unique features that record paleoenvironmental changes, functioning as geological archives of deglacial pulses and sea-level variations. The interaction between eustasy, pre-existing topography, and sedimentation has shaped the present-day geodiversity, highlighting the importance of submerged reefs in understanding the evolution of the largest reef complex in the South Atlantic.
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Palavras-chave
Abrolhos , Multifeixe , Geomorfologia , Geodiversidade , Variação do nível do mar