Bathyal Depths Research Articles

A new species of Pogonophryne (Perciformes: Notothenioidei: Artedidraconidae) from the deep Ross Sea, Antarctica

A new species of notothenioid fish, Pogonophryne pavlovi sp. nov., from bathyal depths of the Ross Sea, Antarctica is described. The new species belongs to the “albipinna” group of the genus Pogonophryne and is characterized by having a mental barbel with a long (61.2–65.2% of barbel length) terminal expansion composed of densely packed, brainlike convolutions.

Hirondellea namarensis (Crustacea: Amphipoda: Lysianassoidea: Hirondelleidae), a new deep-water scavenger species from the Mid-Atlantic Ridge

A new species of the deep-sea scavenging genus Hirondellea (Crustacea: Amphipoda) is described from bathyal depths in the Azores region and on the Mid-Atlantic Ridge. The new species belongs to a group of Hirondellea species which possess an incised inner ramus of uropod 2 and an anteriorly directed spine on epimeron 1. It can be distinguished from other members of this group by a combination of characters: the gnathopod 1 and 2 palm shape; the broadly rounded epimeron 3; the longer telson and broadly rounded head lobe; and the broadly rounded epistome. The species most closely resembles H. wolfendeni, from which it can be distinguished by the shape of the propod of gnathopod 2 and the length of the pereopod 7 propodus. An updated key to the genus Hirondellea is provided.

A taxonomical review of the Gnathophausia (Crustacea, Lophogastrida), with new records from the northern mid-Atlantic ridge.

Taxonomy of 11 species contained within the Lophogastrida genus Gnathophausia is presented. We report new records of G. affinis, G. gigas, G. ingens, and G. zoea from the Atlantic Ocean between Iceland and the Azores. We also describe a new species, G. bergstadi that resembles G. zoea, but differs in having a heart-shaped apex on the telson and having the lower later keels of the carapace not fusing with the upper lateral keels. Gnathophausia is found to be most abundant at bathyal depths. G. zoea, G. gigas, and G. ingens are reported distributed throughout the world's oceans. G. affinis and G. bergstadi are confined to Atlantic water masses, whereas G. childressi, G. longispina, and G. elegans, are found in the Pacific. A more limited distribution in tropical regions of the world's oceans is observed in G gracilis, and also G. fagei and G. scapularis that are confined to the South China Sea and Indian Ocean, respectively. We include an identification key and known distribution of all accepted Gnathophausia species.

Trawled megafaunal invertebrate assemblages from bathyal depth of the Mid-Atlantic Ridge (48°–54°N)

We investigated the effects of contrasting surface primary production on the benthic invertebrate megafauna at four sites on the Mid-Atlantic Ridge. The sites, designated NW, NE, SW and SE, were located to the west and east of the Ridge axis and to the north and south of the Charlie–Gibbs Fracture Zone. Benthic megafauna were sampled in 2007 and 2009 with a semi-balloon otter trawl, at a target depth of 2,500m. The total biomass and density of major taxonomic groups did not differ significantly between sites, despite those to the north being characterised by greater surface productivity than those to the south. However, the density and biomass of individual taxonomic groups, as well as diversity and body size, all showed significant differences between sites. Diversity was highest at the SE, and lowest at the NE site. Most species were larger to the north. Community composition was significantly different between all sites, with the greatest number of unique species found at the SE, and noticeably fewer unique species at the northern sites. There was no clear correlation between the surface productivity and community structure, suggesting complex ecological controls on the communities. It is speculated that, in addition to the energy supply, drivers such as strong currents and sediment characteristics, play an important role in shaping the communities at the different sites. To what extent the ridge acts as a dispersal barrier for benthic invertebrate fauna remains unclear. However, high numbers of species unique to the southern site suggest a limited dispersal between the northern and southern areas.

In search of the Latest Danian Event in a paleobathymetric transect off Kasserine Island, north-central Tunisia

Danian (lower Paleocene) sequences in north-central Tunisia are dominantly composed of marls and shales but a conspicuous, indurated glauconite-bearing marker bed is associated with the P3a–P3b transition. This glauconite bed is considered to correlate with the Latest Danian Event (LDE) described from the Nile Basin in Egypt, with the ‘top Chron C27n event’ (Atlantic and Pacific Oceans) and with the ‘CIE-DS1’ (Zumaia, Spain). The LDE is thought to reflect a short period of global warming, similar to the Paleocene Eocene Thermal Maximum, but of lesser magnitude. The presence of a glauconitic bed at the P3a/P3b transition in Tunisia suggests that the sequence is condensed, which is confirmed by planktic foraminifer and nannofossil biostratigraphy, and by the absence of the typical LDE beds found in most Egyptian sections. Benthic foraminiferal assemblages were quantitatively analyzed in three sections in north-central Tunisia (Sidi Nasseur, Garn Halfaya, Elles) in order to characterize the paleoenvironmental evolution during the late Danian and compare this with sections in Egypt. The benthic foraminiferal assemblages indicate that the Tunisian sections were located along a depth- and a paleoenvironmental gradient on the shelf north of Kasserine Island. The reconstructed depth range is comparable with sections in Egypt, and encompasses middle neritic (Sidi Nasseur section) to shallow upper bathyal depths (Elles section, with up to 16% Gavelinella beccariiformis below the P3a/P3b). Like in Egypt, assemblage shifts across the P3a/P3b subzonal transition indicate shallowing and a transition to a more eutrophic paleoenvironment, characterized by relatively high abundances of buliminids and Stainforthia sp. The δ13C and δ18O records generated on well-preserved specimens of the ostracode species Bairdia failed to demonstrate the presence of the carbon isotope excursion (CIE) associated with the LDE at the base of Subzone P3b. A condensed section or a hiatus associated with the glauconite bed would explain why the CIE is not recorded in the Tunisian sections.

Community composition of scavenging amphipods at bathyal depths on the Mid-Atlantic Ridge

This study focussed on a section of the Mid-Atlantic Ridge with one pair of sampling areas at 49°N and the other at 54°N, north and south of the Charlie–Gibbs Fracture Zone and east and west of the ridge, at a water depth of 2500m. Sixteen baited-trap samples of necrophagous amphipods were collected during three research cruises on the R.R.S. James Cook in 2007, 2009 and 2010. Amphipods of the superfamily Lysianassoidea are numerically dominant and taxonomically diverse and form the most important group of necrophages in most deep-sea environments. A total of 39 scavenging species from 253,306 specimens were identified at the four sampling areas over the 4-year study period. Less than half of the entities could be ascribed to known species. More than 25% of the species recorded were found at all of the sampling areas, supporting the view that necrophagous amphipods are widely distributed animals. The number of lysianassoid species (31) was higher than expected when compared with other studies of necrophagous amphipods, particularly as all sampling was done at one depth (2500m). Deep-sea scavenging amphipods are generally thought to have low diversity and previous studies have supported this view. Sample sizes were large with some traps containing more than 40,000 specimens. The most abundant species, Abyssorchomene abyssorum, dominated all trap samples with percentage compositions over 90% at the NE sites in 2009–2010. Univariate and Multivariate analyses indicated a significant difference in community composition and species richness between the northern and southern stations. There are at least 15 new species to be described from these samples, and particular effort is required in the genus Paracallisoma and the genus Tryphosella.

Faunal trophic structure at hydrothermal vents on the southern Mohn’s Ridge, Arctic Ocean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 473:115-131 (2013) - DOI: https://doi.org/10.3354/meps10050 Faunal trophic structure at hydrothermal vents on the southern Mohn’s Ridge, Arctic Ocean Andrew K. Sweetman1,2,7,*, Lisa A. Levin3, Hans T. Rapp2,4, Christoffer Schander2,4,5,6,† 1Norwegian Institute for Water Research (NIVA), Thormøhlensgate 53 D, 5005 Bergen, Norway 2Centre for Geobiology (SFF), University of Bergen, Allégaten 41, 5020 Bergen, Norway 3Center for Marine Biodiversity and Conservation and Integrative Oceanography Division, Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, California 92093-0218, USA 4Department of Biology, 5Bergen Museum, and 6Uni research, University of Bergen, 5020 Bergen, Norway 7Present address: International Research Institute of Stavanger (IRIS), 4068 Stavanger, Norway *Email: asw@niva.no †Deceased ABSTRACT: We explore the trophic ecology of heterotrophic fauna associated with a high temperature (HT) vent, 2 low temperature vents, a ‘near-HT vent’ habitat and a non-vent site situated at upper bathyal depths on the southern Mohn’s Ridge in the Arctic Ocean. Only a single taxon (the gastropod Pseudosetia griegi) was found at the high temperature vent habitat. Their mean δ13C values were significantly lighter than conspecifics from a low temperature vent habitat within the same vent field, reflecting the incorporation of sulfide oxidizing bacteria into the biomass of the animals. The majority of fauna from the low temperature, near-HT, and non-vent habitats had isotopic signatures indicative of assimilation of photosynthetic material. However, we found remarkably diverse isotopic compositions among the fauna sampled here, with a small sub-set of fauna at each site possessing C and N isotopic signatures indicative of incorporation of chemosynthetic production. Moreover, when isotopic signatures of similar taxa were compared from the same sample, δ13C signatures suggested a high degree of trophic complexity can exist over relatively small spatial scales at vent habitats on the southern Mohn’s Ridge. The high contribution of photosynthetic food material to faunal diets and variability in food types may result from the upper bathyal venting depth and sedimentary nature of the vents. We hypothesize that the upper bathyal depth of active venting may lead to iron enhancement of surface photosynthetic production, especially in high nutrient areas, which ultimately sinks to the seabed where it is incorporated by fauna around the vents. KEY WORDS: Hydrothermal vents · Fauna · Stable isotopes · Mixing models · Southern Mohn’s Ridge Full text in pdf format Supplementary material PreviousNextCite this article as: Sweetman AK, Levin LA, Rapp HT, Schander C (2013) Faunal trophic structure at hydrothermal vents on the southern Mohn’s Ridge, Arctic Ocean. Mar Ecol Prog Ser 473:115-131. https://doi.org/10.3354/meps10050 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 473. Online publication date: January 21, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Miocene foraminifera from the south-central coast of Chile

Foraminifera are abundant and diverse in the Neogene sedimentary units of south-central Chile (34–43ºS), but their age and depositional paleoenvironment have been points of contention for decades. The marine strata most often referred to the Navidad Formation have been a focal point of study in the region by geoscientists in academia as well as the Chilean oil industry. Most of the foraminiferal assemblages documented in this study are from three sedimentary basins isolated from each other by more than 400km. From north to south, they are (1) the Navidad Formation in the vicinity of the name-bearing town located southwest of Santiago, (2) the Ranquil Formation on the Arauco Peninsula southeast of Concepcíon, and (3) the Lacui Formation on and near Chiloé Island. Also included in this study are two assemblages from deposits of uncertain affinity in San Sebastián (northeast of the Navidad area and just north of San Antonio), and one from the Santo Domingo Formation in the vicinity of Valdivia (about midway between Arauco and Chiloé Island). The 27 localities reported in this study span nearly 1000km of the south-central Chilean margin. Most of the samples are siltstones from coastal bluffs and wave-cut platforms in which bedding is nearly horizontal, but often massive or indistinct. Regional workers have disagreed on which subepochs these units represent. Suggested ages based on macro- and microfossils have ranged from Late Oligocene to Early Pliocene. The planktic foraminifera identified in this study suggest that most, if not all, are Miocene. Excluding the two San Sebastián assemblages, which are slightly younger, one assemblage devoid of planktic foraminifera, and three with only long-ranging planktic foraminifera, all of the remaining 21 concurrent ranges begin or end in the Early Miocene. Nineteen of those ranges are restricted to that subepoch and two range into the early Middle Miocene. Seventeen of 18 localities had an 87Sr/86Sr age ranging into or within the Early Miocene. The exception yielded an isotopic age within the latest Oligocene. The majority of the analytical data presented in this report suggest that most of the assemblages are of late Early Miocene (Burdigalian) age. The most abundant macrofossils in the Navidad, Ranquil, Lacui, and Santo Domingo formations (collectively and informally referred to in this study as the Navidad group) are gastropods typical of neritic habitats, but specimens tend to be widely scattered in the outcrops and they are associated with mixed-depth assemblages of foraminifera. I therefore concluded that there had been significant downslope displacement. The upper depth limits of the deepest-dwelling benthic foraminifera in each assemblage indicate that final deposition occurred at bathyal depths, well below the neritic zone. All of the 358 taxa (336 benthics + 22 planktics) identified in this study are presented systematically and illustrated. New species described are Astacolus novambiguus, Cornuspira libella, Cristellariopsis petersonae, Fissurina ambicarinata, Globocassidulina chileensis, Karreriella biglobata, Percultazonaria encinasi, Percultazonaria obliquispinata, Pseudolingulina nielseni, and Pseudononion ranquilensis. In addition, I propose one new (substitute) name, Lenticulina neopolita, to resolve a synonymy. The presence of Neogene cosmopolitan deep-water benthic foraminifera in all of the assemblages supports the hypothesis that deep water masses derived from the Antarctic Circumpolar Current have enabled many Neogene deep-water foraminifera to disperse widely in the global ocean. This compendium is a useful guide to identification of Neogene foraminifera in subtropical/temperate regions in and beyond south-central Chile, and it also provides a regional dataset that can be incorporated into future studies on benthic foraminiferal biostratigraphy and biogeography.

Challenging cosmopolitanism in the deep sea: The case of “Cythere acanthoderma Brady, 1880” (Crustacea, Ostracoda)

Cythere acanthoderma Brady was described from Recent sediments collected from all world's oceans during the HMS Challenger expedition in the 1870s. Subsequently, this species has been recorded in at least 27 publications, extending its stratigraphical range from the Recent back into the Upper Eocene, its zoogeographical range from Atlantic, Indian, Pacific, Arctic and Southern oceans, and its bathymetric range from the continental shelf (>400m) to deeper regions of the abyss (>5000m). Importantly, C. acanthoderma was erected the type species of the widespread and abundant, deep-sea genus LegitimocythereColes and Whatley, 1989. For the present publication, all the specimens of Legitimocythere acanthoderma housed in the Natural History Museum in London were re-studied. Based on the type material and on previous publications, L. acanthoderma is revised, re-diagnosed and re-illustrated with scanning electron microscopy. Twenty-two specimens are, herein, as Henryhowella, Trachyleberididae gen. nov. and cf. Legitimocythere. Finally, comparisons based on illustrations from earlier publications show that only a few of the over 70 previous records (i.e., fossil and Recent samples) of L. acanthoderma could be confirmed; the remaining records either involved distinct species or genera or are dubious. As a consequence, the revised distribution of L. acanthoderma includes only Recent sediments from bathyal depths of the Subantarctic region of the Southern Ocean, and so it can no longer be considered to be cosmopolitan, eurybathic and to have existed for over 30 million years.

The Lomonosov Ridge as a natural extension of the Eurasian continental margin into the Arctic Basin

The inregrated geological and geophysical studies carried out in recent years in the Lomonosov Ridge and at its junction with the Eurasian shelf revealed evidence for thinned (reduced) crust in the ridge (20–25 km) and its relationship with shelf structures. We compared the parameters of deep seismic cross-sections of the shelf and Lomonosov Ridge, thus proving the existence of continental crust in the latter. Also, we analyzed the deep structure of the junction between the Lomonosov Ridge and the shelf and established a genetic geologic relationship, with no evidence that the Lomonosov Ridge moved as a terrane with respect to the shelf. In addition, seismological studies independently confirm the relationship between the Lomonosov Ridge and the adjacent shelf.The Lomonosov Ridge is a continental-crust block of a craton. The craton was reworked during the Caledonian tectonomagmatic activity with the formation of a Precambrian–Caledonian seismically unsegmented basement (upper crust) and an epi-Caledonian platform cover. Afterward, the block subsided to bathyal depths in the Late Alpine. This block and the adjacent areas of the Eastern Arctic shelf developed in the platform regime till the Late Mesozoic.

Patterns of Deep-Sea Genetic Connectivity in the New Zealand Region: Implications for Management of Benthic Ecosystems

Patterns of genetic connectivity are increasingly considered in the design of marine protected areas (MPAs) in both shallow and deep water. In the New Zealand Exclusive Economic Zone (EEZ), deep-sea communities at upper bathyal depths (<2000 m) are vulnerable to anthropogenic disturbance from fishing and potential mining operations. Currently, patterns of genetic connectivity among deep-sea populations throughout New Zealand’s EEZ are not well understood. Using the mitochondrial Cytochrome Oxidase I and 16S rRNA genes as genetic markers, this study aimed to elucidate patterns of genetic connectivity among populations of two common benthic invertebrates with contrasting life history strategies. Populations of the squat lobster Munida gracilis and the polychaete Hyalinoecia longibranchiata were sampled from continental slope, seamount, and offshore rise habitats on the Chatham Rise, Hikurangi Margin, and Challenger Plateau. For the polychaete, significant population structure was detected among distinct populations on the Chatham Rise, the Hikurangi Margin, and the Challenger Plateau. Significant genetic differences existed between slope and seamount populations on the Hikurangi Margin, as did evidence of population differentiation between the northeast and southwest parts of the Chatham Rise. In contrast, no significant population structure was detected across the study area for the squat lobster. Patterns of genetic connectivity in Hyalinoecia longibranchiata are likely influenced by a number of factors including current regimes that operate on varying spatial and temporal scales to produce potential barriers to dispersal. The striking difference in population structure between species can be attributed to differences in life history strategies. The results of this study are discussed in the context of existing conservation areas that are intended to manage anthropogenic threats to deep-sea benthic communities in the New Zealand region.

Record of a tectonically-controlled regression captured by changes in carbonate skeletal associations on a structured island shelf (mid-Pleistocene, Rhodes, Greece)

The Plio–Pleistocene warm-temperate carbonate deposits along the SE coast of Rhodes (Greece) formed on a highly structured island ‘shelf’ during a major transgression-regression cycle, which reached bathyal depth during maximal transgression. The complex palaeobathymetry exhibits many characteristics of submarine canyons, especially of so-called ‘blind’ or ‘headless’ canyons — a canyon type, which is especially common in the modern Mediterranean.This study presents the palaeoenvironmental evolution of one of these canyons, which is today represented by the Lardos valley, eastern central Rhodes. The studied section comprises the middle Pleistocene (900–300ka) and describes a shallowing-upward trend from bathyal to circalitoral depth. Thin fossiliferous debris flow layers document turnovers and abundance changes in fauna and floral of hard-bottom communities, which developed on the adjacent basement slopes and highs. The comparison of the obtained results with other studies from the southeastern coast of Rhodes suggests a high degree of diachroneity of lithological boundaries of these Plio–Pleistocene deposits, which can be best explained by progressive infill of small depocentres located at different altitude levels. Hence, lithological changes are interpreted to be time-transgressive from distal (low altitude) to proximal (high altitude) during transgression while time-transgressive from proximal to distal during regression. Consequently, the best chronostratigraphic correlation horizon is the surface of maximal transgression. The most probable age for this surface could be estimated at 1.1 to 0.8Ma, 0.2–0.5Ma younger than previous estimates. Furthermore, the current lithostratigraphic schemes for the Plio–Pleistocene deposits of southeastern Rhodes are reviewed and revised.

Micropalaeontological evidence for the late Oligocene Oi‐2b global glaciation event at the Zarabanda section, Spain

We present an integrated micropalaeontological study (using smaller and larger benthic foraminifera, planktonic foraminifera and calcareous nannofossils) of the late Oligocene from the Zarabanda section (western Tethys), in order to reconstruct the palaeoenvironmental turnover and to precisely establish the chronology of the palaeoclimatic events. Planktonic foraminifera show that the Zarabanda section is apparently continuous and spans the planktonic foraminiferal zones O5 (upper part), O6 and O7, and the calcareous nannofossil zones CP19b and CN1a (lower part). The quantitative analysis of smaller benthic foraminiferal assemblages enabled us to determine a middle–lower bathyal depth of deposition for most part of the section. The smaller benthic foraminifera show a bloom of neritic species, an increase in the percentages of cool‐water species, a decrease of the Planktonic/Benthic ratio, generic richness, heterogeneity and diversity all around a 10m thick succession of calcarenites, in the lower part of the planktonic foraminifera O6 Zone and the middle part of the calcareous nannofossil CP19b Zone. These changes coincide with the major turnover in the larger benthic foraminiferal assemblages; the last occurrence of Eulepidina dilatata and the first occurrence of Nephrolepidina morgani. These variations in the smaller and larger benthic foraminiferal assemblages may be associated with the major expansion of the Antarctic Ice Sheet at approximately 26.7Ma, which is known as the Oi‐2b global glaciation event.

Light and vision in the deep-sea benthos: I. Bioluminescence at 500–1000 m depth in the Bahamian Islands

Bioluminescence is common and well studied in mesopelagic species. However, the extent of bioluminescence in benthic sites of similar depths is far less studied, although the relatively large eyes of benthic fish, crustaceans and cephalopods at bathyal depths suggest the presence of significant biogenic light. Using the Johnson-Sea-Link submersible, we collected numerous species of cnidarians, echinoderms, crustaceans, cephalopods and sponges, as well as one annelid from three sites in the northern Bahamas (500-1000 m depth). Using mechanical and chemical stimulation, we tested the collected species for light emission, and photographed and measured the spectra of the emitted light. In addition, in situ intensified video and still photos were taken of different benthic habitats. Surprisingly, bioluminescence in benthic animals at these sites was far less common than in mesopelagic animals from similar depths, with less than 20% of the collected species emitting light. Bioluminescent taxa comprised two species of anemone (Actinaria), a new genus and species of flabellate Parazoanthidae (formerly Gerardia sp.) (Zoanthidea), three sea pens (Pennatulacea), three bamboo corals (Alcyonacea), the chrysogorgiid coral Chrysogorgia desbonni (Alcyonacea), the caridean shrimp Parapandalus sp. and Heterocarpus ensifer (Decapoda), two holothuroids (Elasipodida and Aspidochirota) and the ophiuroid Ophiochiton ternispinus (Ophiurida). Except for the ophiuroid and the two shrimp, which emitted blue light (peak wavelengths 470 and 455 nm), all the species produced greener light than that measured in most mesopelagic taxa, with the emissions of the pennatulaceans being strongly shifted towards longer wavelengths. In situ observations suggested that bioluminescence associated with these sites was due primarily to light emitted by bioluminescent planktonic species as they struck filter feeders that extended into the water column.

Limestone interbedded with submarine volcanics: the Early–Middle Miocene Conejo Volcanics, California

Carbonate sedimentation concurrent with submarine volcanism is very rare in the geologic record but is well displayed in the Early to Middle Miocene Conejo Volcanics of the central Santa Monica Mountains of southern California. Limestone occurs as lenticular deposits on the surface of composite flows units, as matrix within breccia of pebble- to cobble-size volcanic clasts, within primary voids extending down from flow surfaces, as lenses between flows within composite flow units, and as neptunian dikes. The common depositional sequence is of limestone lying on a flow and being overlain by hyaloclastic breccia. Limestone is not deposited on hyaloclastic breccia. Limestone deposition was controlled locally by relief on the sea floor that formed as the volcanic rocks accumulated. The limestone is predominantly skeletal packstone; volcanic clasts ranging in size from silt to boulders are locally common. Major constituent fossils are shallow-water bivalve mollusks, barnacles, serpulids, and regular echinoids; most are epifaunal and hard-substrate taxa in contrast to the soft-substrate and burrowing infaunal biota otherwise dominant in Cenozoic strata along the Pacific Coast of North America. The biota is diagnostic of a non-tropical, warm temperate environment. The limestone was deposited within a local basin that formed along the plate boundary at the western margin of the North American Plate. While volcanic rocks accumulated in the basin at bathyal depth, carbonate sediment accumulated on the outer-shelf margin of the basin and was transported intermittently into the basin by gravity flow. Neogene limestone occurs at only a few other sites in southern California. These have an origin that is similar to those in the Conejo Volcanics but differ in occurring with basin fill of diatomaceous sedimentary rocks rather than of submarine volcanics.

The ecology and biogeography of Discospirina tenuissima (Foraminifera) in the Atlantic and Indian Oceans

The large (≥1cm diameter) miliolid foraminifera Discospirina tenuissima (Carpenter and Jeffreys, 1870) is common at four sites (NW, NE, SW, and SE), located on either side of the Mid-Atlantic Ridge to the north (54°N) and south (49°N) of the Charlie–Gibbs Fracture Zone. The white discoidal tests of this epifaunal species were visible in video surveys of flat and gently (10°) sloping, sediment-covered areas of seafloor (replicate 500-m-long transects, 1000m2 surface area) obtained using the Remote Operated Vehicle Isis. Average densities varied from 0.07 (SE site) to 1.12(NW)indm−2 for sloped transects and 0.02 (NW) to 1.75(SW)indm−2 for flat transects. Considerable variation was also evident between individual transects (0–2.25indm−2). The tests displayed no consistent dispersion pattern; both significantly random and clumped patterns were observed, in some cases within a single site. Isis was also used to make detailed in situ observations of D. tenuissima and to collect individual specimens. The delicate test margin sometimes exhibited angular notches and other signs of damage, presumably a result of megafaunal activity; in some cases the damage had been repaired. Specimens perforated by a large central hole occurred at the SE site. Smaller sessile organisms, including agglutinated foraminifera and occasional brachiopods, use D. tenuissima tests as a substratum for attachment. In all areas, some tests were surrounded by a ring of sediment, presumably surface material collected by pseudopodia. We interpret these features as being comparable to the feeding cysts created by other foraminiferal species. They were particularly common at the SE site, where one or two abandoned rings indicated that some tests had moved distances of several centimetres across the seafloor. Most previous records of D. tenuissima are from well-oxygenated sites in the NE Atlantic. We provide the first records from the Indian Ocean. Here, this species occurs at bathyal depths in the northwest (1980m) and northeast (938m) Arabian Sea, where bottom-water oxygen concentrations are depressed.

Global diversity of brittle stars (Echinodermata: Ophiuroidea).

This review presents a comprehensive overview of the current status regarding the global diversity of the echinoderm class Ophiuroidea, focussing on taxonomy and distribution patterns, with brief introduction to their anatomy, biology, phylogeny, and palaeontological history. A glossary of terms is provided. Species names and taxonomic decisions have been extracted from the literature and compiled in The World Ophiuroidea Database, part of the World Register of Marine Species (WoRMS). Ophiuroidea, with 2064 known species, are the largest class of Echinodermata. A table presents 16 families with numbers of genera and species. The largest are Amphiuridae (467), Ophiuridae (344 species) and Ophiacanthidae (319 species). A biogeographic analysis for all world oceans and all accepted species was performed, based on published distribution records. Approximately similar numbers of species were recorded from the shelf (n = 1313) and bathyal depth strata (1297). The Indo-Pacific region had the highest species richness overall (825 species) and at all depths. Adjacent regions were also relatively species rich, including the North Pacific (398), South Pacific (355) and Indian (316) due to the presence of many Indo-Pacific species that partially extended into these regions. A secondary region of enhanced species richness was found in the West Atlantic (335). Regions of relatively low species richness include the Arctic (73 species), East Atlantic (118), South America (124) and Antarctic (126).

First Molecular Evidence for Underestimated Biodiversity of Rhachotropis (Crustacea, Amphipoda), with Description of a New Species

The crustacean genus Rhachotropis has a worldwide distribution and amongst the largest bathymetric range known from any amphipod genus. DNA barcoding of new material from around New Zealand and the Ross Sea indicated depth-related biogeographic patterns. New Zealand Rhachotropis do not form a monophyletic clade. Species from bathyal depths on the Chatham Rise, east of New Zealand, show lower sequence divergence to bathyal species from California and the Arctic than to abyssal New Zealand species. Species sampled in the Kermadec Trench, north of New Zealand below 5000 m, seem to be more closely related to Ross Sea abyssal species than to the New Zealand shelf species. The worldwide geographic and bathymetric distribution for all Rhachotropis species is presented here. Depth may have a greater influence on phylogeny than geographic distance.Molecular and morphological investigations of Rhachotropis specimens from the Chatham Rise, New Zealand revealed a species new to science which is described in detail, including scanning electron microscopy. This increases the number of described species of Rhachotropis to 60 worldwide.

Recent Ostracods (Family Trachyleberididae) from the Southern Brazilian Continental Shelf

The present study is a further contribution to the systematic knowledge of the ostracods from the southern Brazilian continental shelf. Twelve species of Trachyleberididae are recorded, including the following six new taxa: Cativella ornelasae sp. nov., C. sudbrasilienis sp. nov. sp., Henryhowella inflata sp. nov., Henryhowella verrucosa sp. nov., Ambocythere venusta sp. nov. and Basslerites costata sp. nov. The other six species have been recorded in previous studies, either in shallow or bathyal depths in both Brazilian waters and adjacent areas. Most species recorded herein are distributed in the neritic zone, except three, i.e., Trachyleberis aorata, Ambocythere venusta sp. nov. and C. sudbrasilienis sp. nov. The first two species are eurybathic, while C. sudbrasilienis sp. nov. is restricted to the inner shelf.

Mesoscale Eddies Are Oases for Higher Trophic Marine Life

Mesoscale eddies stimulate biological production in the ocean, but knowledge of energy transfers to higher trophic levels within eddies remains fragmented and not quantified. Increasing the knowledge base is constrained by the inability of traditional sampling methods to adequately sample biological processes at the spatio-temporal scales at which they occur.By combining satellite and acoustic observations over spatial scales of 10 s of km horizontally and 100 s of m vertically, supported by hydrographical and biological sampling we show that anticyclonic eddies shape distribution and density of marine life from the surface to bathyal depths. Fish feed along density structures of eddies, demonstrating that eddies catalyze energy transfer across trophic levels. Eddies create attractive pelagic habitats, analogous to oases in the desert, for higher trophic level aquatic organisms through enhanced 3-D motion that accumulates and redistributes biomass, contributing to overall bioproduction in the ocean.Integrating multidisciplinary observation methodologies promoted a new understanding of biophysical interaction in mesoscale eddies. Our findings emphasize the impact of eddies on the patchiness of biomass in the sea and demonstrate that they provide rich feeding habitat for higher trophic marine life.