Burdwood Bank Research Articles

Notes on reproduction in the deep-sea cup coral Balanophyllia malouinensis (Squires 1961) from the Southern Ocean

Deep-sea scleractinian cup corals are prominent members of Southern Ocean megabenthic communities, though little is known about their life history. This study used paraffin histology and scanning electron microscopy to characterize the reproduction of the scleractinian coral Balanophyllia malouinensis (Squires, 1961) from Burdwood Bank in the Drake Passage. Samples were taken in April and May via otter trawls, Blake trawls, and dredges on three separate cruises: one on the RV Lawrence M. Gould in 2006, and two on the RV Nathaniel B. Palmer in 2008 and 2011. B. malouinensis is gonochoric with rare hermaphroditism. All four spermatocyst stages were seen simultaneously in males; similarly, most females contained oocytes at varying stages of development, though seasonality or periodicity could not be determined without a wider range of sample dates. Average fecundity was 241 ± 184 oocytes/individual (n = 38) and not correlated to cup size. Maturing larvae were found in the mesenteries and coelenteron of females, indicating B. malouinensis broods its larvae. This study was the first to characterize the reproduction of a deep-sea Balanophyllia species and adds to a small but growing body of work seeking to understand the unique benthic communities of Burdwood Bank.

Pyramidellidae (Gastropoda: Heterobranchia) from the End of the World

Current knowledge on the pyramidellids from the southern tip of South America appears restricted to a couple of species described in the beginning of the 20th century and a few taxa subsequently reported from this area, including some species recognized as new, but never formally described. This study fills this gap in the knowledge by performing the first revision on the diversity of Pyramidellidae occurring in the Magellanic Province. The material for this study arises from extant collections made along the Atlantic and Pacific coasts of Patagonia, the Beagle Channel, the Magellan Strait and in Burdwood Bank; this information was supplied with specimens from museum collections. As part of this study, eight pyramidellid species, belonging to the genera Turbonilla, Fargoa, Menestho and Brachystomia are recognized from the Magellanic Province, including five species new to science: Turbonilla deseadensis n. sp., Menestho beaglensis n. sp., M. patagonica n. sp., Brachystomia conica n. sp. and B. tenuilirata n. sp. The distinctive characters of Menestho, a genus frequently misunderstood in the past, are also discussed. The presence of Menestho and Brachystomia are here documented for the first time for the southern tip of South America. In addition, a neotype for Turbonilla strebeliStrebel, 1905 (nonVerrill, 1880) is here designated.

Bryozoan assemblages on gastropod shells occupied by the hermit crab Pagurus comptus

Bryozoans are common on gastropod shells inhabited by the hermit crab Pagurus comptus in the southern southwest Atlantic. The aim of this study was to test whether bryozoan biodiversity was higher on larger and more complexly sculptured gastropod shells, as well as to analyze spatial and bathymetric changes in bryozoan assemblages. Forty-four bryozoan species were recorded on 59 gastropod (morpho) species. Larger shells tended to host a higher number of bryozoan species than smaller ones. Bryozoan species richness differed significantly among gastropods with different shell ornamentation, but richness did not increase along a predicted qualitative scale of increasing ornamentation complexity. Almost smooth but large shells had a much higher bryozoan richness than expected, and small shells with prominent ornamentation had unexpectedly the lowest richness, suggesting that shell size may be more important than ornamentation in determining bryozoan richness. Most of the shells hosted two bryozoan species, although up to 11 species per shell were observed. Maximum bryozoan richness occurred between 99 and 137 m. Bryozoan species richness on gastropod shells occupied by P. comptus was higher in the Burdwood Bank than around Tierra del Fuego and Isla de los Estados. Epibiont assemblage composition and species richness differed among the six most abundant gastropods (Trophon ohlini, Pareuthria atrata, Cerithiopsis caelatum, Fuegotrophon pallidus, P. fuscata, Argeneuthria cerealis). The two most abundant bryozoans, Burdwoodipora paguricola and Odontoporella adpressa, do not overlap in their occupation of shell surfaces. This is the first study analyzing the relationships among bryozoans, gastropod shells, and hermit crabs in subantarctic waters.

Anthropogenic Microfibers are Highly Abundant at the Burdwood Bank Seamount, a Protected Sub-Antarctic Environment in the Southwestern Atlantic Ocean

Anthropogenic Microfibers are Highly Abundant at the Burdwood Bank Seamount, a Protected Sub-Antarctic Environment in the Southwestern Atlantic Ocean

Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54ºS-56ºS).

In this study we provide an updated checklist of benthic Cnidaria from SW Atlantic Ocean that comprised the Marine Protected Areas Namuncurá I and II, located at Burdwood bank, and other neighbouring locations. A total of 88 taxa was recorded: 36 hydrozoans and 52 anthozoans from which 32 were octocorals, 10 scleractinian corals, 8 sea anemones and 2 zoanthids. Burdwood bank presented the highest richness considering that 87% of the recorded species inhabit this plateau or its slope. Besides some common species widely distributed in the studied sub-areas, at least 24 species represent new distributional records while few were exclusively recorded at Burdwood bank. The inventory here provided will help to identify key habitat-forming species in a complex habitat where marine animal forests and vulnerable marine ecosystems were previously detected. It will be also a very valuable tool for the management and monitoring of the sub-areas under protection.

Trophic structure of southern marine ecosystems: a comparative isotopic analysis from the Beagle Channel to the oceanic Burdwood Bank area under a wasp-waist assumption

Understanding the structure and functioning of marine ecosystems has become a critical issue to assess the potential short- and long-term effects of natural and anthropogenic impacts and to determine the knowledge needed to conduct appropriate conservation actions. This goal can be achieved in part by acquiring more detailed food web information and evaluating the processes that shape food web structure and dynamics. Our main objective was to identify large-scale patterns in the organization of pelagic food webs that can be linked to a wasp-waist (WW) structure, proposed for the southwestern South Atlantic Ocean. We evaluated 3 sub-Antarctic marine areas in a regional context: the Beagle Channel (BC), the Atlantic coast of Tierra del Fuego (CA) and the oceanic Burdwood Bank area (BB). We used carbon and nitrogen isotopic information of all functional trophic groups, ranging from primary producers to top predators, and analyzed them through stable isotope-based Bayesian analyses. We found that BC and BB have a more pronounced WWstructure compared to CA. We identified species at mid to low trophic positions that play a key role in the trophodynamics of each marine area (e.g. Fuegian spratSprattus fuegensis, longtail southern codPatagonotothen ramsayiand squat lobsterMunida gregaria) and considered them as the most plausible WW species. The identification of the most influential species within food webs has become a crucial task for conservation purposes in local and regional contexts to maintain ecosystem integrity and the supply of ecosystem services for the southwestern South Atlantic Ocean.

Habitat preferences, foraging behaviour and bycatch risk among breeding sooty shearwaters Ardenna grisea in the Southwest Atlantic

Pelagic seabirds are important components of many marine ecosystems. The most abundant species are medium/small sized petrels (<1100 g), yet the sub-mesoscale (<10 km) distribution, habitat use and foraging behaviour of this group are not well understood. Sooty shearwaters Ardenna grisea are among the world’s most numerous pelagic seabirds. The majority inhabit the Pacific, where they have declined, partly due to bycatch and other anthropogenic impacts, but they are increasing in the Atlantic. To evaluate the sub-mesoscale habitat preferences (i.e. the disproportionality between habitat use and availability), diving behaviour and bycatch risk of Atlantic breeders, we tracked sooty shearwaters from the Falkland Islands during late incubation and early chick-rearing with GPS loggers (n = 20), geolocators (n = 10) and time-depth recorders (n = 10). These birds foraged exclusively in neritic and shelf-break waters, principally over the Burdwood Bank, ~350 km from their colony. Like New Zealand breeders, they dived mostly during daylight, especially at dawn and dusk, consistent with the exploitation of vertically migrating prey. However, Falkland birds made shorter foraging trips, shallower dives, and did not forage in oceanic waters. Their overlap with fisheries was low, and they foraged at shallower depths than those targeted by trawlers, the most frequent fishing vessels encountered, indicating that bycatch risk was low during late incubation/early chick-rearing. Although our results should be treated with caution, they indicate that Atlantic and Pacific sooty shearwaters may experience markedly differing pressures at sea. Comparative study between these populations, e.g. combining biologging and demography, is therefore warranted.

Structure and distribution of fish assemblages at Burdwood Bank, the first Sub-Antarctic Marine Protected Area “Namuncurá” in Argentina (Southwestern Atlantic Ocean)

The first non-coastal Sub-Antarctic Marine Protected Area (Namuncura) in Argentina was created in 2013, at Burdwood Bank (MPAN-BB), an undersea plateau located about 200 km south from Malvinas/Falkland Islands, SW Atlantic Ocean. The main contribution of this work was to explore fish species composition and the structure of fish assemblages in three different zones of the MPAN-BB with different conservation strategies and different surrounding areas. Twenty-two fishing trawls were performed using a demersal bottom trawl pilot net at depths between 71 and 608 m. A total of 667 fish belonging to 30 species were collected in the surveyed area. The richest family in terms of species number was Nototheniidae (seven species), followed by Macrouridae, Myxinidae and Zoarcidae (four species each), then Moridae and Arhynchobatidae (three species each), and finally Muraenolepididae and Psychrolutidae (two species each). The remaining families were represented by a single species. Three significantly different fish assemblages were detected. These distinct assemblages were largely circumscribed at the plateau, the shelf-break slope, and the area west of the BB. The results showed that fish diversity in the MPAN-BB is relatively high constituting ~ 10% of the fish composition reported for the Atlantic sector of the Magellanic Province. The present data suggest that fishes are an important component of the benthic community planned to be protected by the implementation of the MPAN-BB. These findings have important implications for habitat preservation and threatened species conservation.

Biodiversity of Isopoda and Cumacea (Peracarida, Crustacea) from the Marine Protected Area Namuncurá-Burdwood Bank, South-West Atlantic

Burdwood Bank is a shallow seamount located south of the Malvinas (Falkland) Islands and east of Tierra del Fuego. In 2013, the area down to 200 m depth of this bank was declared the first open-sea (non-coastal) Marine Protected Area (MPA) in Argentina, and named “Namuncurá” (MPAN-BB). The present study aimed to evaluate the biodiversity of the isopods and cumaceans from the MPAN-BB. The studied material was collected on board the Argentine RV Puerto Deseado during the Campaña Antártica de Verano 2013. Three stations from the MPAN-BB, respectively, located in the core, buffer, and transition sectors, were sampled. A total of 17,076 specimens were sorted and 70 taxa distributed in 22 families were identified. Thirty-five new records of distribution and eight species most probably new to science are herein reported. Paramunnidae and Diastylidae were the most abundant and diverse families among isopods and cumaceans, respectively. Our records, together with those obtained from the literature, make a total of 55 nominal species so far known from Burdwood Bank. Except for one nominal species, which had been reported from the Puerto Rico Trench and the Argentine Basin, all the remaining species had also been recorded from other localities within the Magellan Region. In contrast, only nine out of the 55 nominal species had also been reported from the Antarctic Peninsula and/or Scotia Arc. This indicates that the isopods and cumaceans from Burdwood Bank are typically Magellanic, and there is little correspondence between this fauna and that from the Antarctic Peninsula and Scotia Arc.

Spatial gradients of spring zooplankton assemblages at the open ocean sub-Antarctic Namuncurá Marine Protected Area/Burdwood Bank, SW Atlantic Ocean

Abstract The sub-Antarctic Namuncura Marine Protected Area at Burdwood Bank (NMPA/BB) is an area of favorable conditions for the development of planktonic organisms and the sustenance of numerous species of ecological importance. The current study aimed to evaluate the spatial distribution of the abundance, biomass, community structure, and functional diversity of the mesozooplankton from the NMPA/BB during spring 2014. We also assessed the potential of zooplankton as prey for upper trophic levels, in particular the larvae of the Fuegian sprat (Sprattus fuegensis), a key species in the food web of the NMPA/BB. A total of 26 zooplankton taxa were identified. Nauplii and copepods evidenced the highest abundances, with the latter representing the dominant group in terms of biomass. Copepods showed a strong eastward gradient in their abundance, biomass, and diversity. This spatial structure in the community composition seems to be modulated by a west-to-east decreasing trend in the size of available preys, with nano- and picoplankton playing a major role in the eastern part of the NMPA/BB. Such pattern would be, in turn, a consequence of productivity gradients along hydrographic features. The high abundance of nauplii and copepods suggests that spring is an appropriate time for their reproduction and, given their size structure, they represent an adequate food source for Fuegian sprat larvae. This would be enhanced by anticyclonic cells present in the NMPA/BB, which can gather and retain sprat larvae along with their zooplanktonic preys. The results of our study, which is the first comprehensive approach addressing the zooplanktonic indicators of the NMPA/BB, serve as a baseline for future ecosystem-based policies aiming to manage and protect the natural marine resources sheltered here.

Microbial plankton configuration in the epipelagic realm from the Beagle Channel to the Burdwood Bank, a Marine Protected Area in Sub-Antarctic waters.

Marine microbial plankton hold high structural and functional diversity, however, high-resolution data are lacking in a large part of the Global Ocean, such as in subpolar areas of the SW Atlantic. The Burdwood Bank (BB) is a submerged plateau (average depth 100 m) that constitutes the westernmost segment of the North Scotia Ridge (54°–55°S; 56°–62°W). The BB hosts rich benthic biodiversity in low chlorophyll waters of the southern Patagonian Shelf, Argentina, declared Namuncurá Marine Protected Area (NMPA) in 2013. So far, the pelagic microorganisms above the bank have not been described. During austral summer 2016, we assessed the microbial plankton (0.2–200 μm cell size) biomass and their taxonomical and functional diversity along a longitudinal transect (54.2–55.3°S, 58–68°W) from the Beagle Channel (BC) to the BB, characterized by contrasting hydrography. Results displayed a marked zonation in the composition and structure of the microbial communities. The biomass of phytoplankton >5 μm was 28 times higher in the BC, attributed mainly to large diatom blooms, than in oceanic waters above the BB, where the small coccolithophore Emiliania huxleyi and flagellates <10 μm dominated. In turn, the biomass of microheterotrophs above the BB doubled the biomass in the BC due to large ciliates. Notably, toxic phytoplankton species and their phycotoxins were detected, in particular high abundance of Dinophysis acuminata and pectenotoxins above the bank, highlighting their presence in open subpolar regions. Picophytoplankton (<2 μm), including Synechococcus and picoeukaryotes, were remarkably important above the BB, both at surface and deep waters (up to 150 m). Their biomass surpassed by 5 times that of phytoplankton > 5 μm, emphasizing the importance of small-sized phytoplankton in low chlorophyll waters. The homogeneous water column and high retention above the bank seem to favor the development of abundant picophytoplankton and microzooplankton communities. Overall, our findings unfold the plankton configuration in the Southern Patagonian Shelf, ascribed as a sink for anthropogenic CO2, and highlight the diverse ecological traits that microorganisms develop to adjust their yield to changing conditions.

The Subantarctic Front as a sedimentary conveyor belt for tsunamigenic submarine landslides

The Subantarctic Front (SAF), one of the three main jets of the Antarctic Circumpolar Current (ACC), flows through a narrow gap in the North Scotia Ridge and then north-westward across the continental slope of Burdwood Bank, ~150 km south of the Falkland Islands. There, the SAF flows across a fold-and-thrust belt caused by oblique convergence at the active plate boundary between the Scotia Plate and South American Plate. We here use regional 2D and 3D seismic reflection data to show the interaction of the associated bottom currents with the active margin, particularly to understand the causes and consequences of a number of large submarine landslides located in the adjacent foredeep. Kinematic indicators from the landslide deposits show that they are derived from a single point source located in an embayment on the northern slope of Burdwood Bank, where we identify a large contourite drift deposit. This drift forms the depositional sink for an along-slope sediment routing system driven by currents associated with the SAF, with sediment being eroded from the Burdwood Terrace, transported ~200 km westward, and plastered against the middle-upper continental slope. The contourite drift is undercut by the core of the current, making the slope inherently unstable in this area. Numerical modelling of the landslides and resultant waves indicates the tsunamigenic potential of these events. Modelled peak wave elevations of up to 40 m inundate the southern coast of the Falklands for a ~100 km3 volume landslide, with a recurrence interval of 1 Ma or less. This research highlights preconditioning mechanisms for submarine failure on continental slopes dominated by strong ocean currents, and specifically, oceanographic controls on the frequency, magnitude and location of submarine landslides associated with contourite systems.

Biogeographical patterns and areas of endemism for the Magellan region based on the distribution of crustacean species (Amphipoda, Copepoda, and Euphausiacea)

Patterns of endemism in marine researches have been traditionally inferred from approaches ignoring the spatial component of endemism of such patterns. In this contribution, we used a method based on an optimality criterion that evaluates the spatial congruence among the distribution of different taxa and provides a value of endemicity to a given area regardless of how that it was hypothesized. This method has been widely applied to land environments, whereas in the sea it has not been well explored yet. We analyzed the geographic distribution of three crustacean groups (Amphipoda, Copepoda, and Euphausiacea) to search for areas of endemism (AEs) in the Magellan region by applying an optimality algorithm. To summarize among numerous resulting AEs, we employed a meta-consensus criterion based on a clustering analysis. We identified three main AEs and, into most of them, we recognized smaller areas for the first time: Chiloe, Atlantic coast (with a smaller area in San Jorge Gulf and Cape Blanco), and Fueguia (Channels and Fjords, Malvinas/Falklands, Burdwood Bank, and South-West Atlantic transition area). Both Atlantic coast and Fueguia do not strictly match the provinces previously defined in the literature. Our study lays the foundation for a biogeographic scheme into the Magellan region and provides new insights on zones currently placed in marine protected areas for the southern tip of South America, such as Burdwood Bank, Yaganes, and Diego Ramirez-Drake Passage. Integrating distribution patterns of many other organisms for the Magellan region will certainly help reinforce the conservation measures currently implemented.

Benthic communities in the Southwest Atlantic Ocean: Conservation value of animal forests at the Burdwood Bank slope

Abstract The characterization of benthic communities at the Burdwood Bank slope (≥200 m depth) is provided, comprising data from the marine protected area (MPA) Namuncurá II (created in December 2018), as well as from some deep bathyal surrounding areas in the Southwest Atlantic Ocean. This information was acquired during two research cruises with RV Puerto Deseado (Argentina) during 2016 and 2017. Marine animal forests were detected in the study area: coral gardens, mainly composed of alcyonaceans, were detected in the south and west of Burdwood Bank (MPA Namuncurá II) and neighbouring areas, whereas pennatulacean aggregations were detected in the north‐west of the plateau. The three‐dimensional structures of live but also dead corals provide substrate and refuge to many associated species. Benthic communities dominated by sponges were also recorded between 200 and 300 m in depth. Six sites that meet the characteristics of vulnerable marine ecosystems (VMEs) are reported. Conservation strategies applied to scarcely known austral Argentinean waters led to the establishment of a pioneer MPA (Namuncurá I). Following the management plan that aimed to establish the biodiversity of Namuncurá I and neighbouring areas, the area of protection has now been enlarged to include the southern slope of the bank (currently Namuncurá II), where marine animal forests were detected, at depths below 200 m. The data presented here provide empirical evidence to support the conservation value of the region.

Energetics and development modes of Asteroidea (Echinodermata) from the Southwestern Atlantic Ocean including Burdwood Bank/MPA Namuncurá

Reproduction is a highly expensive process that during gonadal development requires an important supply of nutrients. The allocation of energy can vary throughout the reproductive cycle, between sexes and development modes. During research cruise aboard the RV Puerto Deseado in April 2016, we collected fifteen species of sea stars from the southernmost region of Argentina. The main purposes of the present study were threefold: first, to revise and report novel information on the reproductive strategies and energetic density (ED) of body components from the asteroids of the southwestern Atlantic Ocean including Burdwood Bank/ MPA Namuncura; second, to compare the ED of these body components across species with contrasting reproductive strategies; third, to provide a tool to estimate the ED from dry mass of organs of the sea star species examined. Ovaries of Diplopteraster verrucosus (a brooder with a nidamental chamber) revealed a significantly greater ED than did the testes (29.81 ± 1.38 and 17.76 ± 1.59, respectively). In Glabraster antarctica (a broadcaster with yolky eggs and facultative planktotrophic larvae), the gonads had EDs of 25.78 ± 3.16 and 19.21 ± 0.52 (females and males, respectively). While in Peribolaster folliculatus (a broadcaster with eggs with low yolk content and inferred planktotrophic larvae) there was no significant difference in the ED values between sexes (females: 22.79 ± 1.10 and males: 20.46 ± 1.05). For the pyloric caeca, ED values did not reveal any difference between sexes, although in P. folliculatus, the ED was significantly higher than that for D. verrucosus and G. antarctica (25.90 ± 1.00, 23.03 ± 0.34, and 22.66 ± 0.65, respectively). The body wall had higher ED values in D. verrucosus and P. folliculatus than that for all the sea star species analyzed (46.48 ± 1.63, 51.17 ± 1.34, respectively). Higher ED values in the ovaries could be related to the nutrition of offspring, while differences found in the body wall may reflect the skeletal structure of this body component. This research provides basic information for understanding the differences on energetic allocation when contrasting development modes are considered.

A Subantarctic rare gastropod reveals a new type of spawn among heterobranchs

Abstract Spawn and specimens of Toledonia biplicata comb. nov. were collected from Burdwood Bank during March 2013. Species-level identification was derived from radular, shell and spawn characters. A low number of eggs laid per spawn (one to three), absence of an external gelatinous mass and a considerably thickened capsule wall (~50 µm) constitute a unique combination of spawn characters among heterobranchs. Egg capsules are ovoid in shape and measure 600–763 × 450–656 µm. They are filled with albuminous liquid, allowing complete intracapsular development of a single embryo. The developmental stages recognized are uncleaved eggs (153 µm in average diameter), veliger stages (279–378 µm in maximal length) and prehatchling juveniles (442–609 µm). Toledonia biplicata increases its volume 40-fold during its intracapsular development, whereas other comparable cephalaspids increase ≤ 4-fold. The role of the capsule wall as protection and an additional source of food is discussed. The adaptive value of these characters in relationship to the environmental conditions of the Magellanic region is discussed. A comparison with the spawn of other cephalaspids, nudibranchs and pleurobranchids is conducted, and the taxonomic implications are discussed. This is the first description of the spawn and developmental stages of a representative of the genus Toledonia.

Strike-slip related folding within the Malvinas/Falkland Trough (south-western Atlantic ocean)

The Malvinas/Falkland Trough (M/FT) is an E-W trending bathymetric depression along which runs the present-day South American-Scotia plate boundary. To the north of the M/FT lies the southern sector of the South Malvinas/Falkland Basin, and to the south lies the Burdwood Bank, an elongated morphological high constituting part of the South Scotia Ridge. Analysis of bathymetric and slope maps, integrated with seismic reflection profiles, have allowed describing in detail the M/FT in the sector comprised between 60° and 57° W. Data show the presence of an array of folds forming a thin-skinned fold-and-thrust Belt (FTB), previously interpreted as an active compressional field. The thin-skinned FTB is developed in a triangular-shaped area, which extends ca. 100 km in the E-W direction and 16 km in the N-S direction. Four parallel, asymmetric folds that develop to progressively greater water depths (between 1600 and 2600 m depth) towards the north, with orientations ESE-WNW and lengths that vary between 22 and 98 km, have been recognized. These folds are constituted by Late Cenozoic sediments that are undeformed in the Malvinas/Falkland Trough. The development of folds, which began in the late Miocene (ca. 7 Ma), was associated with the left-lateral strike-slip tectonic regime of the Magallanes-Fagnano-Malvinas lineament, the western segment of the South American-Scotia plate boundary.

Pole to pole: the deep-sea king crab Lithodes couesi (Decapoda: Lithodidae) in the Burdwood Bank, Southwestern Atlantic Ocean

In recent years, remote exploration around the Scotia Arc and waters off the Antarctic Peninsula yielded new records of Lithodidae suggesting our knowledge on their distribution is biased by our ability to sample areas with difficult access. In the present study, we used molecular methods to identify and report the occurrence of the deep-sea king crab Lithodes couesi, so far reported as a North Pacific lithodid, in the marine protected area (MPA) Namuncura/Burdwood Bank II, Southwestern Atlantic Ocean; more than 10,000 km away from its known distribution. Our finding suggests that the distributions of deep-water lithodid species are more extensive than they have been previously thought. We emphasize the need for a worldwide key to identify lithodid species, and prompt to barcoding specimens, at least those from poorly known species or remote locations, in order to corroborate their specific status. Finally, our study stresses the importance of MPAs in the conservation of biodiversity, as well as the processes involved in its evolution.

Ideogorgia laurae, an uncommon new octocoral species (Alcyonacea: Keroeididae) from a newly established Marine Protected Area at Burdwood Bank, Argentina

A new deep-sea keroeidid octocoral, Ideogorgia laurae, is described from Burdwood Bank, Argentina. It is distinguished from its single congener by the presence of conspicuous calyces, anthocodial sclerites (flattened and warted rods) and large coenenchymal triradiates. This is the deepest and the first record of that genus outside southern African waters. In addition, this is the first new species described for the recently created Marine Protected Area Namuncura II at Burdwood Bank, Argentine Sea. This discovery in a very well-sampled area shows how little we know about that fauna, and also reinforces the importance of creating MPAs to safeguard hotspots of biodiversity in Subantarctic waters. Finally, the new species is an evidence of early connections between deep Subantarctic and shallow South African benthic faunas.

The Burdwood Bank Circulation

AbstractA suite of high‐resolution numerical simulations characterizes the oceanic circulation in the Burdwood Bank, a shallow seamount located in the northeastern end of the Drake Passage. Model analysis shows energetic upwelling and mixing uplifting deep and benthic waters into the photic layer. Tides and the Antarctic Circumpolar Current are the primary drivers of the bank's circulation. Tidal forcing is the main driver for the entrainment of deep waters into the upper layers of the bank and local wind forcing for the detrainment of these waters into the deep ocean. Passive tracer diagnostics suggest that the dynamical processes triggered by the Burdwood Bank could have a significant impact on local ecosystems and the biogeochemical balance of the southwestern Atlantic region, which is one of the most fertile portions of the Southern Ocean. Model results are robust—they are reproduced in a wide array of model configurations—but there is insufficient observational evidence to corroborate them. Satellite color imagery does not show substantial chlorophyll blooms in this region but it shows strong phytoplankton plumes emanating from the bank. There are several potential explanations for the chlorophyll deficit, including lack of light due to persistent cloud cover, deep mixing layers, fast ocean currents, and the likelihood that blooms, while extant, might not develop on the surface. None of these possibilities can be confirmed at this stage.