Sedimentological and morphological evidences of Meltwater Pulse 1B in the Southwestern Atlantic Margin

Bastos, Alex Cardoso; D’Agostini, Danielle P.; Silva, Alex E.; Menandro, Pedro S.; Vieira, Fernanda V.; Boni, Geandré C.; Quaresma, Valéria da Silva

doi:10.1016/j.margeo.2022.106850

Cited by 5 publications

(2 citation statements)

References 42 publications

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“…These processes were responsible to shape the seafloor and, in the case of mesophotic habitats and mesophotic reefs, most of shelf morphology reflects features formed during sealevel fall and lowstand, which drowned during the deglaciation process. The development of mesophotic reefs, for instance, is related to submarine morphology resembling features such as drowned reefs (Harris and Davies, 1989;Bridge et al, 2011;Abbey et al, 2013), paleoshorelines (Brooke et al, 2014;Pretorius et al, 2016), hard grounds/terraces (Khanna et al, 2017), cemented dunes and barriers (Brooke et al, 2014;Passos et al, 2019), and incised valleys (Bastos et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

Geomorphological significance of shelf-incised valleys as mesophotic habitats

Oliveira

Lavagnino

Rocha

et al. 2023

Front. Remote Sens.

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Geomorphology provides the core attributes for outlining marine seascapes, once the structural complexity of the seafloor mediates several oceanographic processes and ecosystem services, and is positively associated with biodiversity. Shelf-incised valleys and other prominent meso-scale structures such as reefs and sinkholes have a great potential for the discrimination of benthic habitat groups. Here, we investigate shelf-incised valleys as a mesophotic habitat, by focusing on their geomorphological control in defining distinct habitats in comparison with the flat surrounding area. The study was based on the integration of high-resolution bathymetry data (multibeam echosounder), video imaging, and physical-chemical parameters of the water column. Habitat mapping was conducted using object-based image analysis segmentation and clustering. Principal Component Analysis was used to assess the variables associated with habitat distribution at each morphological region of the valleys. Bathymetric data revealed the presence of 5 shelf-incised valleys and 5 seabed classes were defined as carbonate crusts, Rhodoliths (3 distinct classes) and unconsolidated sediments. A comprehensive habitat map with 17 classes was produced, and 13 are associated with valley´s relief. Extensive rhodolith beds were mapped in the valley flanks/bottom and in the flat areas. Shelf-incised valleys are prominent morphological features that add complexity to the seascape, contrasting with the flat relief that dominates the seascape. The seabed footage obtained in the valleys revealed that their heterogeneous, complex and irregular topography harbors a great diversity of epibionts, such as scleractinian corals, coralline algae, sponges and bryozoans. Most of the variability in the dataset is correlated with salinity, temperature and carbonate sediments, which seem to be the most influential variables over the biological assemblage, together with water depth and seabed slope. Shelf-incised valleys, similarly to submarine canyons, can define a complex mesophotic habitat and sustain distinct biodiversity, and even form mesophotic reefs. These features are the legacy of Quaternary sea-level changes and should be further investigated as important mesophotic habitats.

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Section: Discussionmentioning

confidence: 99%

Geomorphological significance of shelf-incised valleys as mesophotic habitats

Oliveira

Lavagnino

Rocha

et al. 2023

Front. Remote Sens.

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“…We sampled (April 29-May 04, 2021) the walls and channels of two IVs and two adjacent RB sites ( Fig 1 , Table 1 ) that had been previously covered by a regional survey with multibeam echosounders [ 12 , 34 , 35 ] ( Fig 1 ). A mooring system (SeaGuardII ® , Aandreaa) was deployed ~1 m above the bottom in sites RB1 and IV1 for measurements of dissolved oxygen (DO), turbidity, pH, chlorophyll a (chl-a), colored dissolved organic matter (CDOM), photosynthetically active radiation (PAR), temperature (T), density and salinity (S).…”

Section: Methodsmentioning

confidence: 99%

Incised valleys drive distinctive oceanographic processes and biological assemblages within rhodolith beds

Castro,

Vargens,

Carlos-Júnior

et al. 2023

PLoS ONE

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Continental shelves encompass gently sloped seascapes that are highly productive and intensively exploited for natural resources. Islands, reefs and other emergent or quasi-emergent features punctuate these shallow (<100 m) seascapes and are well known drivers of increased biomass and biodiversity, as well as predictors of fishing and other human uses. On the other hand, relict mesoscale geomorphological features that do not represent navigation hazards, such as incised valleys (IVs), remain poorly charted. Consequently, their role in biophysical processes remains poorly assessed and sampled. Incised valleys are common within rhodolith beds (RBs), the most extensive benthic habitat along the tropical and subtropical portions of the mid and outer Brazilian shelf. Here, we report on a multi-proxy assessment carried out in a tropical-subtropical transition region (~20°S) off Eastern Brazil, contrasting physicochemical and biological variables in IVs and adjacent RBs. Valleys interfere in near bottom circulation and function as conduits for water and propagules from the slope up to the mid shelf. In addition, they provide a stable and structurally complex habitat for black corals and gorgonians that usually occur in deeper water, contrasting sharply with the algae-dominated RB. Fish richness, abundance and biomass were also higher in the IVs, with small planktivores and large-bodied, commercially important species (e.g. groupers, snappers and grunts) presenting smaller abundances or being absent from RBs. Overall, IVs are unique and vulnerable habitats that sustain diverse assemblages and important ecosystem processes. As new IVs are detected by remote sensing or bathymetric surveys, they can be incorporated into regional marine management plans as conservation targets and priority sites for detailed in situ surveys.

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