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TitreSubmerged channels of the Eastern Brazilian Continental Shelf: can the slope value be used as potential surrogates of reef environments?
TéléchargerTéléchargement (publication entière)
AuteurAraújo, T C M; Camargo, J M R; Ferreira, B P; Maida, M
SourceProgram and abstracts: 2017 GeoHab Conference, Dartmouth, Nova Scotia, Canada; par Todd, B J; Brown, C J; Lacharité, M; Gazzola, V; McCormack, E; Commission géologique du Canada, Dossier public 8295, 2017 p. 35, https://doi.org/10.4095/305406 (Accès ouvert)
LiensGeoHab 2017
Année2017
ÉditeurRessources naturelles Canada
Réunion2017 GeoHab: Marine Geological and Biological Habitat Mapping; Dartmouth, NS; CA; mai 1-4, 2017
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.4095/305406
Mediaen ligne; numérique
Référence reliéeCette publication est contenue dans Todd, B J; Brown, C J; Lacharité, M; Gazzola, V; McCormack, E; (2017). Program and abstracts: 2017 GeoHab Conference, Dartmouth, Nova Scotia, Canada, Commission géologique du Canada, Dossier public 8295
Formatspdf
Sujetstechniques de cartographie; récifs; océanographie; milieux marins; organismes marins; écologie marine; gestion des ressources; marges continentales; plate-forme continentale; etudes de l'environnement; benthos; biote; chenaux; submersion; bassins versants; milieu côtièr; établissement de modèles; biologie; ressources halieutiques; géologie marine; géologie de l'environnement; géologie des dépôts meubles/géomorphologie
ProgrammeGéoscience de la gestion des océans, Géoscience en mer
Diffusé2017 09 26
Résumé(disponible en anglais seulement)
The Eastern Brazilian Continental Shelf (EBCS) is narrow, shallow and predominantly covered by biogenic sediments. Bathymetric surveys have revealed the common occurrence of submerged channels, related to the largest watersheds in the region and probably carved during periods of marine regression. With its break located between 40 and 80 metres deep, the EBCS was subjected to sub-aerial erosion for long periods, which justifies the occurrence of these erosive features related to continental drainage.
Based on a DEM with spatial resolution of 10 metres, the slope values of a section of the continental shelf of the state of Pernambuco were extracted. This initiative indicated an average slope value of 0.38°, consistent with that expected for a continental shelf. However, along the edges of three submerged channels the slope is more pronounced, with values generally between 3 and 45°. Therefore, in order to verify the characteristics of these steep reliefs, 03 video-transects were performed in two sectors of the Zieta Channel with a GoPRO 3 Black. Video-transects I and II were situated about 18 kilometres off the coast, while video-transect III was about 30 kilometres.
The data analysis involved the integration of the three parameters: substrate, geomorphology, and biota. The seascapes in each video-transect were defined such as: predominant, secondary or occasional. The record of combinations of substrate characteristics, geomorphology and biota occurrences also contributed to the definition of an associative pattern between the physical characteristics and the biological assemblages recorded.
Extreme values of slope (20-45°) are related to seascapes dominated by large rocky outcrops, cut by small channels and with relative structural complexity, as well as fish, sponges, algae and corals. On the other hand, values of slopes between 3 and 8°, composed seascapes dominated by small rocky outcrops, with irregular surface, usually covered by algae, and seascapes dominated by sub-outcrops, associated with rocky bottoms, sponges and corals. The flat reliefs (0-3°), related to the thalweg, harboured seascapes dominated by unconsolidated substrates, with bioturbation and occurrence of dense spots of algae of the genus Halimeda.
From these preliminary results, it can be suggested that the slope presented potential to be considered a surrogate for seascapes dominated by consolidated substrates and associated reef environments. This potential should be better investigated through new video surveys, contributing greatly to the consolidation of this relationship between slope, seascapes and benthic habitats, which, in turn, may guide the most appropriate design of Marine Protected Areas, as well as management measures of their fishing resources.
GEOSCAN ID305406