Pathways and mechanisms of offshore water intrusions on the Espírito Santo Basin shelf (18°S–22°S, Brazil)

Palóczy, André; Brink, Kenneth H.; Silveira, Ilson Carlos Almeida da; Arruda, Wilton Zumpichiatti; Martins, Renato Parkinson

doi:10.1002/2015jc011468

Cited by 23 publications

(5 citation statements)

References 64 publications

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“…Wave-dominated shelf, low sediment input, and a seasonal shelf upwelling [20,48] create favorable conditions for the development of extensive RBs. Upwelling along the DRS was also pointed out by many authors [49][50][51], which has been associated to the intrusion of the South Atlantic Central Water (SACW; [45]). Ovalle et al [52] and Palóczy et al [50] found that the temperature near the seabed was lower than 21 • C in many points along the ESCS, pointing out qualitative evidences of the influence of the SACW at this region.…”

Section: Discussionmentioning

confidence: 68%

“…Upwelling along the DRS was also pointed out by many authors [49][50][51], which has been associated to the intrusion of the South Atlantic Central Water (SACW; [45]). Ovalle et al [52] and Palóczy et al [50] found that the temperature near the seabed was lower than 21 • C in many points along the ESCS, pointing out qualitative evidences of the influence of the SACW at this region. This oceanographic circulation mechanism is probably one of the most important drivers, along with the sedimentation at this region, affecting the vitality of rhodoliths, at once contributing to the nutrient enrichment of the water and lowering its temperature.…”

Section: Discussionmentioning

confidence: 68%

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Structure of Rhodolith Beds and Surrounding Habitats at the Doce River Shelf (Brazil)

et al. 2020

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The world's largest rhodolith beds have been reported from the Brazilian continental shelf. Highly biodiverse beds are located in Southeast Brazil, but ecological aspects of these beds remain unknown. Despite their ecological importance, rhodolith beds (RBs) have recently been subjected to a severe threat, when more than 35 million cubic meters of mining residues slid down a mountainside on 5 November 2015, after a collapse of a gigantic dam upstream (the Mariana disaster), causing a huge impact on the Doce River. Our aim is to assess rhodolith beds and adjacent coralline formations on the Doce River Shelf (DRS) after the dam collapse. This paper describes the distribution, abundance, vitality, size and shape, as well as unmapped bryozoan rich sediment formations in this area, serving as baseline knowledge for environmental monitoring. Four distinct biogenic sea bottom habitats (bryozoan bottoms, rhodolith beds, carbonate concretions, and reefs) were recognized at different depth ranges with distribution indicated to be mostly related to the local sedimentary regime. Mud sediments dominated the seafloor up to 35 m depth. On the mid shelf, bryozoan bottoms were recorded from 35 to 45 m depth. Crustose coralline algae (CCA) occurring as rhodoliths and carbonate concretions extend over 1953 km 2 in the mid and outer shelf. Rhodolith beds predominate in these areas, totaling 1521 km 2 of sea bottom and were more abundant at depths between 45 and 65 m, occupying an extensive area south of the Doce River mouth. Northward, rhodolith beds are less abundant or absent likely due to the long-term deposition of fine sediments in this region. Carbonate concretions and reefs covered by CCA occupy sparse areas on the outer shelf (65-105 m depth). Differences in rhodolith features recorded, including coverage, density and size, may be related to the Doce River sedimentation and related factors (e.g., hydrodynamics, depth, and light). However, since there are no previous detailed studies on RBs along the DRS, we could not assess the impact of sedimentation of dam wastes on RBs' abundance and density. In any case, these are valuable results for the further monitoring of long-term effects. Considering that the growth of these rhodoliths is relatively slow, and that they are affected by the sedimentation from the Doce River, the implementation of a management and conservation plan for this area is necessary in order to preserve this ecosystem.

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Section: Discussionmentioning

confidence: 68%

Section: Discussionmentioning

confidence: 68%

Structure of Rhodolith Beds and Surrounding Habitats at the Doce River Shelf (Brazil)

et al. 2020

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“…SES is influenced by coastal upwelling during the summer months. Sea surface temperatures range from 24 to 288C, but during deep-water intrusion, bottom temperature can descend to 16.58C on the shelf (Paloczy et al 2016). Chlorophyll a measured during two years in an area situated 40 km north of studied sites at SES ranges from 0.11 to 1.55 lg/l (average 0.47 lg/l) (Costa et al 2014).…”

Section: Introductionmentioning

confidence: 95%

Burial Rate Determines Holocene Rhodolith Development on the Brazilian Shelf

Brasileiro

Braga

Amado‐Filho

et al. 2018

Palaios

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The structure and composition of rhodoliths in two regions of the Brazilian shelf, Abrolhos Continental Shelf (ACS) and South Esp´ırito Santo State (SES) were examined and compared. Rhodoliths were sampled at depth ranges of 10-20 m and 50-60 m in SES, and 20-30 m and 50-75 m in ACS. Rhodoliths in SES are algal boundstones, built mainly of melobesioid corallines, with subordinate bryozoans and encrusting foraminifers. They show high porosity and the sediment infill of borings and voids contains a relatively high amount of siliciclastics (up to 8%). Rhodoliths from ACS are formed by a structureless carbonate mass covered by a thin veneer of encrusting coralline algae. The massive interior was produced by multiphase boring and infilling of an original boundstone. The infillings consist of a micritic matrix with bioclasts and low amounts of siliciclastic grains. Coralline assemblages are reduced to fragments of thin crusts. Rhodoliths from shallow depths are small (, 8 cm) whereas rhodoliths from the deeper zone have a wide size range (1 to 17 cm). The innermost parts of deeper rhodoliths in ACS yield radiocarbon ages of ~ 7,000 years BP (75 m) and ~ 2,000 years BP (65 m). Rhodoliths from the deep zone in SES are younger (less than 700 years BP). Siliciclastic sediment influx reaching rhodolith beds promotes burial of rhodoliths, determining the small size of shallow SES rhodoliths and the relatively young ages of the deeper ones. Scarce siliciclastic influx at the ACS rhodolith beds favors long residence times of rhodoliths on the seafloor, resulting in a thorough destruction of the original coralline/invertebrate boundstone by bioerosion.Despite the increasing knowledge about Brazilian rhodoliths in the last decade, little is known about their inner arrangement and composition (Leal et al. 2012; Tamega et al. 2014; Vale et al. 2018). The taxonomic composition, morphology, inner structure, and interactions of coralline algae with other encrusting groups (such as bryozoans, corals, and serpulids) are relevant for understanding the factors that control long-term development of rhodoliths (Adey and MacIntyre 1973; Aguirre et al. 2012) and to reconstruct the paleoenvironments in which they grew (Bosence 1983a;

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“…Among such relict features, IVs reach up to 600 m widths and extend along 15 km of the cross-shelf gradient, between the 30 m isobath and the shelf break at 70–80 m depth, well within the RB megahabitat ( Fig 1 ) [ 12 , 30 , 31 ]. Shelf waters encompass the interface between hyposaline and turbid Coastal Water nearshore, Tropical Water in the neritic zone, and the south-flowing, warm and oligotrophic Brazil Current along the continental slope, with seasonal upwelling of colder South Atlantic Central Water [ 31 – 33 ]. Sampling sites are located within a multiple-use Marine Protected Area (MPA), the Costa das Algas Environmental Protection Area, and in the vicinity of a no-take MPA, the Santa Cruz Wildlife Refuge ( Fig 1 ).…”

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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Pathways and mechanisms of offshore water intrusions on the Espírito Santo Basin shelf (18°S–22°S, Brazil)

Cited by 23 publications

References 64 publications

Structure of Rhodolith Beds and Surrounding Habitats at the Doce River Shelf (Brazil)

Structure of Rhodolith Beds and Surrounding Habitats at the Doce River Shelf (Brazil)

Burial Rate Determines Holocene Rhodolith Development on the Brazilian Shelf

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

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