Patterns of Life on the Southern Mid-Atlantic Ridge: Compiling What is Known and Addressing Future Research

Perez, J. A.; Alves, Elana dos Santos; Clark, Malcolm R.; Bergstad, Odd Aksel; Gebruk, Andrey; Cardoso, Irene A.; Rogacheva, Antonina

doi:10.5670/oceanog.2012.102

Cited by 29 publications

(25 citation statements)

References 31 publications

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“…Therefore, crusts from depths deeper than 800 m, which would less likely Knowledge of the export and remineralization of organic matter in the water column, an important source of dissolved metals to crusts, is scarce for waters over RGR [14]. The RGR is considered to be below the oligotrophic surface waters of the South Atlantic Subtropical regime, with relatively low primary productivity and phytoplankton biomass [119]. However, the global map of annual net primary production shows that the RGR is actually under the surface water of intermediate primary productivity, higher than in the Pacific PCZ but lower than the Northeast Atlantic, and much lower than in the central-east equatorial Pacific for example [120].…”

Section: Resource Considerationsmentioning

confidence: 99%

Genesis and Evolution of Ferromanganese Crusts from the Summit of Rio Grande Rise, Southwest Atlantic Ocean

et al. 2020

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The Rio Grande Rise (RGR) is a large elevation in the Atlantic Ocean and known to host potential mineral resources of ferromanganese crusts (Fe–Mn), but no investigation into their general characteristics have been made in detail. Here, we investigate the chemical and mineralogical composition, growth rates and ages of initiation, and phosphatization of relatively shallow-water (650–825 m) Fe–Mn crusts dredged from the summit of RGR by using computed tomography, X-ray diffraction, 87Sr/86Sr ratios, U–Th isotopes, and various analytical techniques to determine their chemical composition. Fe–Mn crusts from RGR have two distinct generations. The older one has an estimated age of initiation around 48–55 Ma and was extensively affected by post-depositional processes under suboxic conditions resulting in phosphatization during the Miocene (from 20 to 6.8 Ma). As a result, the older generation shows characteristics of diagenetic Fe–Mn deposits, such as low Fe/Mn ratios (mean 0.52), high Mn, Ni, and Li contents and the presence of a 10 Å phyllomanganate, combined with the highest P content among crusts (up to 7.7 wt %). The younger generation is typical of hydrogenetic crusts formed under oxic conditions, with a mean Fe/Mn ratio of 0.75 and mean Co content of 0.66 wt %, and has the highest mean contents of Bi, Nb, Ni, Te, Rh, Ru, and Pt among crusts formed elsewhere. The regeneration of nutrients from local biological productivity in the water column is the main source of metals to crusts, providing mainly metals that regenerate rapidly in the water column and are made available at relatively shallow water depths (Ni, As, V, and Cd), at the expense of metals of slower regeneration (Si and Cu). Additionally, important contributions of nutrients may derive from various water masses, especially the South Atlantic Mode Water and Antarctic Intermediate Water (AAIW). Bulk Fe–Mn crusts from the summit of RGR plateau are generally depleted in metals considered of greatest economic interest in crusts like Co, REE, Mo, Te, and Zr, but are the most enriched in the critical metals Ni and Li compared to other crusts. Further investigations are warranted on Fe–Mn crusts from deeper-water depths along the RGR plateau and surrounding areas, which would less likely be affected by phosphatization.

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Section: Resource Considerationsmentioning

confidence: 99%

Genesis and Evolution of Ferromanganese Crusts from the Summit of Rio Grande Rise, Southwest Atlantic Ocean

et al. 2020

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“…(2008). and 98 Part B (2013), Bergstad et al, 2008;Vecchione et al, 2010;Priede et al, 2013), as well as studies of the Mid-Atlantic Ridge in the South Atlantic (Perez et al, 2012).…”

Section: Ridges and Plateausmentioning

confidence: 99%

Biological Communities on Seamounts and Other Submarine Features Potentially Threatened by Disturbance

2017

The First Global Integrated Marine Assessment

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Seamounts are predominantly submerged volcanoes, mostly extinct, rising hundreds to thousands of metres above the surrounding seafloor. Some also arise through tectonic uplift. The conventional geological definition includes only features greater than 1000 m in height, with the term "knoll" often used to refer to features 100-1000 m in height (Yesson et al., 2011). However, seamounts and knolls do not appear to differ much ecologically, and human activity, such as fishing, focuses on both. We therefore include here all such features with heights > 100 m. Only 6.5 per cent of the deep seafloor has been mapped, so the global number of seamounts must be estimated, usually from a combination of satellite altimetry and multibeam data as well as extrapolation based on size-frequency relationships of seamounts for smaller features. Estimates have varied widely as a result of differences in methodologies as well as changes in the resolution of data. Yesson et al. (2011) identified 33,452 seamount and guyot features > 1000 m in height and 138,412 knolls (100-1000 m), whereas Harris et al. (2014) identified 10,234 seamount and guyot features, based on a stricter definition that restricted seamounts to conical forms. Estimates of total abundance range to >100,000 seamounts and to 25 million for features > 100 m in height (Smith 1991; Wessel et al., 2010). At least half are in the Pacific, with progressively fewer in the Atlantic, Indian, Southern, and Arctic Oceans. Identified seamounts cover approximately 4.7 per cent of the ocean floor, with identified knolls covering an additional 16.3 per cent, in total an area approximately the size of Africa and Asia combined, about threefold larger than all continental shelf areas in the world's oceans (Etnoyer et al., 2010; Yesson et al., 2011). Seamounts can influence local ocean circulation, amplifying and rectifying flows, including tidal currents, particularly near seamount summits, enhancing vertical mixing, and creating retention cells known as Taylor columns or cones over some seamounts. These effects depend on many factors, including the size (height and diameter) of the seamount relative to the water depth, its latitude, and the character of the flow around the seamount (White et al., 2007).

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“…This research focused on the north Atlantic until late 2009, when a first exploratory cruise began sampling the southern MAR between the Canary Islands and Cape Town (see Figure 1), a relatively poorly known area of the deep sea (Perez et al 2012). Collections from this voyage included over 7000 fish specimens (Kobyliansky et al 2010), plus benthic and pelagic invertebrates; the latter included 262 paralarval and juvenile cephalopods.…”

Section: Introductionmentioning

confidence: 99%

Cranchiids of the South Atlantic Mid-Oceanic Ridge: results from the first southern MAR-ECO expedition

Bolstad¹,

Perez²,

Strugnell³

et al. 2014

Journal of Natural History

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Cranchiids were the most diverse squid family collected during the first southern MAR-ECO expedition in late 2009, with nine taxa identified to species. A total of 45 young specimens were collected (mantle length 7.4-59.2 mm), allowing a survey of early ontogenetic tentacular morphology in cranchiids using scanning electron micrographs. Paralarval tentacular sucker morphology appeared similar among species within the same subfamily: in the Cranchiinae, the paralarval suckers possess relatively large, narrowly polygonal or ovoid-faced pegs in the innermost ring around the aperture, and the infundibular ring lacks the dentition observed in most taoniin genera. Hook development in Galiteuthis armata appears to vary widely among small individuals. Tissue samples were also collected from five genera (Cranchia, Galiteuthis, Helicocranchia, Leachia and Teuthowenia); phylogenetic trees (maximum-likelihood and Bayesian methods) built using these cytochrome oxidase subunit I sequences and others available from GenBank show some support for the subfamilies Cranchiinae and Taoniinae, and that within the latter, the hooked taxa group together. It is hoped that reporting this opportunistic systematic and genetic information may be of eventual assistance in helping to resolve this most problematic of squid families.

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Patterns of Life on the Southern Mid-Atlantic Ridge: Compiling What is Known and Addressing Future Research

Cited by 29 publications

References 31 publications

Genesis and Evolution of Ferromanganese Crusts from the Summit of Rio Grande Rise, Southwest Atlantic Ocean

Genesis and Evolution of Ferromanganese Crusts from the Summit of Rio Grande Rise, Southwest Atlantic Ocean

Biological Communities on Seamounts and Other Submarine Features Potentially Threatened by Disturbance

Cranchiids of the South Atlantic Mid-Oceanic Ridge: results from the first southern MAR-ECO expedition

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