Bathyal Depths Research Articles

Macrofaunal abundance and community composition at lower bathyal depths in different branches of the Whittard Canyon and on the adjacent slope (3500 m; NE Atlantic)

We studied benthic macrofaunal abundance and community composition in replicate Megacorer samples obtained from three sites in different branches of the Whittard Canyon (NE Atlantic) and one site on the adjacent slope to the west of the canyon system. All sites were located at a depth of ~3500m. Abundance (macrobenthos sensu stricto, >300μm) varied significantly (p<0.001) among sites, and decreased from east to west; highest in the Eastern branch (6249±standard deviation 1363ind.m−2) and lowest on the slope (2744±SD 269ind.m−2). Polychaetes were the dominant taxon, making up 53% of the macrofauna, followed by isopods (11%), tanaids (10%), bivalves (7%) and sipunculans (7%). Among the polychaetes, the Amphinomidae was the dominant family (27%), followed by the Spionidae (22%). Assemblage composition changed across the sites. From east to west, the proportion of polychaetes and isopods decreased (by 6% in each case), while sipunculans and tanaids increased (by 13% and 8%, respectively). The ranking of the two dominant polychaete families reversed from east to west (Eastern branch—Amphinomidae 36%, Spionidae 21%; Slope—Spionidae 30%, Amphinomidae 10%). Ordination of faunal groups (macrofaunal higher taxa, and polychaete families) revealed that the Central and Eastern branches were substantially similar, while the Western branch and slope sites were relatively distinct. A very similar pattern was evident in a corresponding ordination of environmental variables across the sites. An analysis of faunal similarities (ANOSIM) indicated that the Western branch/slope and Central branch/Eastern branch groups displayed the highest similarity. The clearest separation was between the slope and the Eastern branch. We conclude that, when compared at the same water depth, macrofaunal abundance and composition varies between open slope and canyon location, as well as among canyon branches. These differences probably reflect the influence of organic enrichment together with hydrodynamic activity, both of which are influenced by the topographic profile of individual canyon branches.

A redescription of the type species of Oedicerina Stephensen, 1931 (Crustacea, Amphipoda, Oedicerotidae) and the description of two new species

The poorly known species Oedicerina ingolfi Stephensen, 1931 (Crustacea: Amphipoda: Oedicerotidae) is redescribed, based on new material from the Norwegian Sea. Oedicerina vaderi sp. n. from the northeast Atlantic Ocean and Oedicerina loerzae sp. n. from New Zealand waters are described raising the number of species in the genus to five. The three species treated here together with Oedicerina megalopoda Ledoyer, 1986 and Oedicerina denticulata Hendrycks & Conlan, 2003 are separated by characters of the rostrum, maxilliped, gnathopods, epimera, and by the dorsal armature of pleonites and urosomites. The genus is recorded from the Atlantic, Indian and Pacific Oceans, mainly at bathyal depths.

Delivery of terrigenous material to submarine fans: Biological evidence of local, staged, and full-canyon sediment transport down the Ascension-Monterey Canyon system

Submarine canyons are prevalent in the world’s oceans and are instrumental in transporting sediment from coastal regions to deep-sea fans. Conventional sediment parameters such as mean grain size, sorting, and provenance have typically been used to characterize these deposits, but they provide little information on sediment source or the delivery processes involved. Fortunately, transported along with the mineral grains are the remains of organisms living within the sediment. Biological constituents have unique environmental signatures that are more precise proxies for source areas than are mineral grains alone. They may be used to identify a single biofacies deposit (SBD) due to local sediment transport or a displaced, multiple biofacies deposit (MBD) resulting from staged sediment transport or a full-canyon flushing event. This Ascension-Monterey Canyon system study demonstrates that by using the biological constituents in marine deposits, the source areas and transport mechanisms may be identified. The 19,000 year record of core S3-15G captured hemipelagic mud interspersed with individual turbidites of sand and silt transported to the core site at lower bathyal depths (3491 m). The relative abundance of displaced benthic foraminifera was found to correlate positively with grain size, with 75% of the fauna being displaced in the cross-bedded turbiditic sand (T c ) units, 39% in the laminated turbiditic sand (T d ) units, and 15% in the turbiditic mud (T et ) units. Nineteen samples were SBDs representing local canyon wall sloughing, bioerosion, or hemipelagic deposition at or near the core site. Sixty-five were MBDs, 31 of which were turbiditic sands originating in the estuarine to inner shelf, outer shelf, upper slope, or upper middle slope, and the remaining 34 were turbiditic muds with displacement initiated in the estuarine to inner shelf, outer shelf, and the upper slope. Commonly, the biological remains of several biofacies characterize these MBDs, reflecting staged sediment transport with storage occurring behind slumps that act as barriers to movement until finally released. Sediment bypassing, typically of the deeper biofacies, and full-canyon flushing, were also evident. Identifying and interpreting the distribution of allochthonous biological sediment constituents in marine deposits is a powerful tool in the investigation of sediment transport that can be applied to other submarine canyon systems.

Composition of the genus Hanleya (Mollusca: Polyplacophora: Lepidopleurida), with the description of two new species

An evaluation of all species of the genus Hanleya showed that they only inhabit the Atlantic Ocean, occurring from off Brazil (25°44′S) to the Barents Sea (74°27′N). The majority of records refer to H. nagelfar which ranges from 9°03′8′′N to 74°27′N in coastal waters of North America, Europe and Africa. There are six Recent species of Hanleya: H. tropicalis Dall, 1881, H. brachyplax Jardim and Simone, 2010b, H. harasewychi sp. nov, H. mediterranea sp. nov, H. hanleyi (Bean in Thorpe, 1844) and H. nagelfar (Lovén, 1846). The phylogenetic relationship of H. hanleyi and H. nagelfar has long been questioned. New data on age variability of Hanleya nagelfar are provided. Hanleya hanleyi is the only species of the genus that also occurs in the intertidal zone. All other members of Hanleya inhabit mainly bathyal or sublittoral depths: H. nagelfar (28–1680 m), H. tropicalis (230 m), H. brachyplax (250–408 m), H. harasewychi (73–115 m), H. mediterranea (50–200 m).http://zoobank.org/urn:lsid:zoobank.org:pub:CB8027AC-6755-4F44-9A02-D5C539D84D1F

Deep-sea trace fossils of the Oligocene–Miocene Numidian Formation, northern Tunisia

Twenty-two ichnogenera and thirty-one ichnospecies have been recorded in the Oligocene–Miocene Numidian Formation of northern Tunisia. Heterolithic successions of thin-bedded turbidite sandstones and interchannel mudstones contain the most diverse trace fossil assemblages. Thick- to very thick-bedded structureless sandstones and conglomerates representing the fill of channel complexes contain a low-diversity trace fossil assemblage. The ichnoassemblage in the lower part of the formation (Oligocene), which includes Paleodictyon isp., Scolicia strozzii, Spirorhaphe isp., ?Cosmorhaphe isp. and Halopoa isp., can be ascribed to the Paleodictyon ichnosubfacies of the Nereites ichnofacies. The ichnoassemblage in the upper part of the formation (Miocene: Aquitanian), including Diplocraterion cf. habichi, Scolicia vertebralis and Ophiomorpha isp., is interpreted as the shallower part of the Ophiomorpha rudis ichnosubfacies of the Nereites ichnofacies. The notable switch in ichnofauna between the Oligocene and lower Miocene reflects variation in environmental and depositional conditions. The common occurrence of trace fossils of the Ophiomorpha rudis ichnosubfacies, and Diplocraterion cf. habichi in the early Miocene, indicates an increase in energy level, greater environmental disturbance and probable shallowing. This is also confirmed by a corresponding decrease in the abundance and diversity of benthic foraminifera. The integration of ichnological, sedimentological and microfossil contents has allowed the distinction of two quite distinct geographical depositional settings within the Numidian Formation. The first domain includes the Numidian succession of the Tabarka, Cap-Negro, Cap-Serrat and Bouhertma areas, which are characterised by “distal” turbidites, showing the Paleodictyon ichnosubfacies that is compatible with a lower bathyal depth in the Oligocene and an upper slope depositional environment during the early Miocene.The second domain includes the NE part of Mogod Mountain (e.g. the Ras El Korane, Jebel Gattous–Zoukar), which exhibit more proximal characteristics compatible with a probable slope canyon interpretation. The southern margin of the Kroumirie (Balta and Zouza areas) and Sejnene area shows a distal setting compared with the Ras El Korane and Jebel Gattous–Zoukar areas. It is ascribed to a mid- to upper slope depositional environment during the Oligocene to early Miocene.

Invertebrate diversity of the unexplored marine western margin of Australia: taxonomy and implications for global biodiversity

However derived, predictions of global marine species diversity rely on existing real data. All methods, whether based on past rates of species descriptions, on expert opinion, on the fraction of undescribed species in samples collected, or on ratios between taxa in the taxonomic hierarchy, suffer the same limitation. Here we show that infaunal macrofauna (crustaceans and polychaetes) of the lower bathyal depth range are underrepresented among available data and documented results from Australia. The crustacean and polychaete fauna (only partially identified) of the bathyal continental margin of Western Australia comprised 805 species, representing a largely novel and endemic fauna. Overall, 94.6% of crustacean species were undescribed, while 72% of polychaete species were new to the Australian fauna, including all tanaidaceans, amphipods, and cumaceans, as well as most isopods. Most species were rare, and the species accumulation rate showed no sign of reaching an asymptote with increasing area sampled. Similar data are likely for the largely unexplored bathyal regions. This leads us to conclude that the numbers upon which extrapolations to larger areas are based are too low to provide confidence. The Southern Australian and Indo-West Pacific deep-sea regions contribute significantly to global species diversity. These regions and bathyal and abyssal habitats generally are extensive, but are so-far poorly sampled. They appear to be dominated by taxonomically poorly worked and species-rich taxa with limited distributions. The combination of high species richness among infaunal taxa—compared to better known taxa with larger individuals, higher endemism than presently acknowledged because of the presence of cryptic species, the low proportion of described species in these taxa, and the vast extent of unexplored bathyal and abyssal environments—will lead to further accumulation of new species as more and more deep sea regions are explored. It remains to be tested whether ratios of 10 or more undescribed to described species, found in this study for the dominant taxa and for the deep Southern Ocean and the Indo-West Pacific, are replicable in other areas. Our data and similar figures from other remote regions, and the lack of faunal overlap, suggest that Appeltans et al.’s (Current Biology 22:1–14, 2012) estimate that between one-third and two-thirds of the world’s marine fauna is undescribed is low, and that Mora et al.’s (PLoS Biol 9(8):e1001127. doi:10.1371/journal.pbio.1001127, 2011) of 91% is more probable. We conclude that estimates of global species, however made, are based on limited data.

Deep-sea Benthic Ostracodes from Multiple Core and Epibenthic Sledge Samples in Icelandic Waters

AbstractDeep-sea benthic Ostracoda (Crustacea) in Icelandic waters are poorly known. Here we report deep-sea ostracode assemblages from the multiple core (MUC) and the epibenthic sledge (EBS) samples collected from Icelandic waters by the first cruise of the IceAGE (Icelandic Marine Animals: Genetics and Ecology) project. Samples from shelf-edge and lower-bathyal working areas are examined. The results show (1) distinct MUC and EBS faunas due to the large difference in mesh size of MUC and EBS; and (2) distinct shelf-edge and lower-bathyal ostracode faunas. Such remarkable faunal turnover from shelf to bathyal depths is similar to the faunal turnovers reported from depth transects in the adjacent regions of the western North Atlantic Ocean, the Greenland Sea, and the North Sea, but, at the same time, there are certain differences in the faunal composition between the Icelandic waters and these adjacent regions. In addition, we illustrate many Icelandic deep-sea ostracode species with high-resolution scanning electron microscopy and composite all-in-focus stereomicroscopic images for the first time. These results provide important basic information on deep-sea ostracode research and biogeography of this important region connecting North Atlantic proper and Nordic Seas.

Geochronologic and paleontologic evidence for a Pacific–Atlantic connection during the late Oligocene–early Miocene in the Patagonian Andes (43–44°S)

Cenozoic marine strata occur in the western, eastern, and central parts of the North Patagonian Andes between ∼43°S and 44°S. Correlation of these deposits is difficult because they occur in small and discontinuous outcrops and their ages are uncertain. In order to better understand the age and sedimentary environment of these strata, we combined U–Pb (LA-MC-ICPMS) geochronology on detrital zircons with sedimentologic and paleontologic (foraminifers and molluscs) studies. Sedimentologic analyses suggest that the Puduhuapi Formation on the western flank of the Andean Cordillera was deposited in a deep-marine setting, the Vargas Formation in the central part of the Andes was deposited at outer-neritic or bathyal depths, and the La Cascada Formation on the eastern flank of the range was deposited in a shallow-marine environment. Geochronologic and paleontologic results indicate that the three marine units were deposited during the late Oligocene-early Miocene interval, although it is not clear whether this occurred during one or more marine incursions in the area. The alluvial(?) conglomeratic deposits of the La Junta Formation, exposed in the proximity of the Vargas Formation outcrops, have a maximum depositional age of ∼26 Ma and could have been deposited during the initial stage of subsidence that affected this region prior to the marine transgression over this area. The occurrence of both Pacific and Atlantic molluscan taxa in the La Cascada and Vargas formations suggests that a marine strait connected both oceans during the accumulation of these units. The new data on the age of the Puduhuapi, Vargas, and La Cascada formations indicate that these units may correlate with lower Miocene marine deposits in the forearc of central and southern Chile (Navidad Formation and equivalent units) and on the eastern flank of the Patagonian Andes (Río Foyel Formation and equivalent units). A late Oligocene−early Miocene age for these marine deposits is a reliable maximum age for the deformation and uplift of the North Patagonian Andes.

In situ observation of chimaerid species in the Gorringe Bank: new distribution records for the north-east Atlantic Ocean

In the framework of the R.V. Nautilus exploration programme, remotely operated vehicle (ROV) surveys were conducted at bathyal depths in the Gorringe Bank. Video transects revealed the presence of the chimaerids Chimaera opalescens and Hydrolagus affinis in the region. An identification key for the north-east Atlantic species of the family Chimaeridae is proposed.

Lost and found: the Eocene family Pyramimitridae (Neogastropoda) discovered in the recent fauna of the Indo-Pacific.

Most neogastropod families have a continuous record from the Cretaceous or Paleogene to the Recent. However, the fossil record also contains a number of obscure nominal families with unusual shell characters that are not adequately placed in the current classification. Some of these are traditionally regarded as valid, and some have been "lost" in synonymy. One such "lost" family is the Pyramimitridae, established by Cossmann in 1901 for the Eocene genus Pyramimitra, and currently included in the synonymy of Buccinidae. Examination of several species of inconspicuous, small turriform gastropods has revealed a radula type so far unknown in Neogastropoda, and their shell characters identify them as members of the "extinct" family Pyramimitridae. Neither the radular morphology nor the anatomy reveal the relationships of this enigmatic, "living fossil" family. Molecular data (12S, 16S, 28S, COI) confirm the recognition of Pyramimitridae as a distinct family, but no sister group was identified in the analysis. The family Pyramimitridae Cossmann, 1901, is thus restored as a valid family of Neogastropoda that includes the genera Pyramimitra Conrad, 1865, Endiatoma Cossmann, 1896, Vaughanites Woodring, 1928, Hortia Lozouet, 1999, and Teremitra new genus. Pyramimitrids occur in the Recent fauna at bathyal depths of the Indo-Pacific from Taiwan to Madagascar and New Zealand, with three genera and nine species (all but one new).

The cephalopod Taningia danae Joubin, 1931 observed near bottom at over 2,000 m depth on Seine seamount

We report the first in situ observations of a large Taningia danae Joubin, 1931, close to the seafloor at bathyal depths of 2,157 m. The observation was made in the subtropical northeast Atlantic Seine seamount during daytime on 29 September 2012, over a silt-covered seafloor (33o40.1142′N, 14o22.7301′W). Seawater temperature was 4.2 oC, salinity 35.40 ppt, oxygen saturation 50.87 Ox%, and pressure 2,178.29 dbar. Mantle length was estimated from imagery to be 65.3 cm (STD = 6.3). A repeated behaviour was observed every time the ROV approached: (1) swimming away from the ROV by flapping the fins twice (moving forward or backward), (2) gliding slightly inclined downward, until colliding against the seafloor, and (3) ascending obliquely or vertically in relation to the seafloor, finally evading the area moving upward using jet propulsion. These observations greatly extend the species depth range and document behaviour patterns. T. danae is able to explore beyond the mesopelagic zone where it has previously been reported.

Neogene history of the Carapita Formation, Eastern Venezuela Basin

Based on the stratigraphic distribution of planktonic microfossils (mostly planktonic foraminifera) and abundance patterns of benthic foraminifera we determine the temporal completeness of one land section and three wells through the Lower and Middle Miocene Carapita Formation of eastern Venezuela, compare the extent of the hiatuses in the sections and document changes in paleodepth at these localities during the early and Middle Miocene. We determine that changes in paleodepth are associated with hiatuses, but see no relationshipwith the global changes in sea-level inferred from deep sea isotope records. This strongly suggests that there was a strong tectonic forcing on stratigraphic architecture at upper and middle bathyal depths, as to be expected in a tectonically active area. However, similar stratigraphic patterns are also observed elsewhere, implying that a widespread tectonic structuring of the stratigraphic architecturemay have been operative. Recognition of hiatuses (not merely unconformities) as primary stratigraphic components will make possible an uninterrupted documentation of sequences boundaries from subaerial to bathyal environments, and help determine objectively the structural mechanism(s) operating on the genesis of stratigraphic sequences (sensu Catuneanu et al. 2009). Biostratigraphy (and biochronology) are the main tools to understanding this structuring.

First records of Thyone inermis and Labidoplax buskii (Echinodermata: Holothuroidea) in Canadian waters

This work presents records of two endobenthic species of sea cucumber (Holothuroidea: Echinodermata) not previously reported in Canadian waters. Thyone inermis (Dendrochirotida) and Labidoplax buskii (Apodida) were collected south-west of Nova Scotia (eastern Canada) in 2009 in Georges and Crowell Basins in the upper 2 cm of muddy seafloor at upper bathyal depths (240–370 m). Both species are of small size, 3.7–8 mm and 5–8 mm long, respectively.

Diversification of chemosymbiotic bivalves: origins and relationships of deeper water Lucinidae

Although species of the chemosymbiotic bivalve family Lucinidae are often diverse and abundant in shallow water habitats such as seagrass beds, new discoveries show that the family is equally speciose at slope and bathyal depths, particularly in the tropics, with records down to 2500 m. New molecular analyses including species from habitats down to 2000 m indicate that these cluster in four of seven recognized subfamilies: Leucosphaerinae, Myrteinae, Codakiinae, and Lucininae, with none of these comprising exclusively deep-water species. Amongst the Leucosphaerinae, Alucinoma, Epidulcina, Dulcina, and Myrtina live mainly at depths greater than 200 m. Most Myrteinae inhabit water depths below 100 m, including Myrtea, Notomyrtea, Gloverina, and Elliptiolucina species. In the Codakinae, only the Lucinoma clade live in deep water; Codakia and Ctena clades are largely restricted to shallow water. Lucininae are the most speciose of the subfamilies but only four species analyzed, Troendleina sp., ‘Epicodakia’ falkandica, Bathyaustriella thionipta, and Cardiolucina quadrata, occur at depths greater than 200 m. Our results indicate that slope and bathyal lucinids have several and independent originations from different clades with a notable increased diversity in Leucosphaerinae and Myrteinae. Some of the deep-water lucinids (e.g. Elliptiolucina, Dulcina, and Gloverina) have morphologies not seen in shallow water species, strongly suggesting speciation and radiation in these environments. By contrast, C. quadrata clusters with a group of shallow water congenors. Although not well investigated, offshore lucinids are usually found at sites of organic enrichment, including sunken vegetation, oxygen minimum zones, hydrocarbon seeps, and sedimented hydrothermal vents. The association of lucinids with hydrocarbon seeps is better understood and has been traced in the fossil record to the late Jurassic with successions of genera recognized; Lucinoma species are particularly prominent from the Oligocene to present day. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 401–420.

Aptian–Albian benthic foraminifera from DSDP Site 364 (offshore Angola): A paleoenvironmental and paleobiogeographic appraisal

This work presents a paleoenvironmental and paleobiogeographical appraisal of the benthic foraminiferal assemblages recovered from the Aptian–Albian carbonate-dominated succession of Deep Sea Drilling Project (DSDP) Site 364, located in the Kwanza Basin (offshore Angola). Forty-two species were identified within the studied interval, and their stratigraphic distributions enabled the recognition of two events of diversification, the first within the latest Aptian and the second within the late Albian. Q-mode and R-mode cluster analyses of the benthic foraminifera allowed to recognize three associations (Bathysiphon sp., Gyroidinoides infracretaceus and Kadriayina gradata), which seem to have been mainly controlled by paleobathymetry. The studied fauna is characteristic of neritic to upper bathyal depths. At and/or close to black shale levels low values of benthic foraminiferal abundance and species richness could be indicative of low-oxygen (dysoxic) bottom water conditions. The black shales deposition in Site 364, cores 42 to 39 (likely related to an Aptian dysoxic-anoxic event), occurred at shallow to middle neritic water depths. Some typical tropical/subtropical planktic biostratigraphic markers are missing from specific stratigraphic intervals of Site 364, in which shallow (neritic) water depths were inferred. Their absence from the northern South Atlantic Ocean (north to the Walvis Ridge–Rio Grande Rise) may be rather a result of their deeper-dwelling habitat preferences, than to the influx of colder-water masses from the southern South Atlantic Ocean, as previously reported. Paleobiogeographically, the studied Aptian–Albian benthic foraminifera present a predominant Austral/Transitional affinity, in contrast to the evidence of the planktic foraminifera, which indicate the influence of tropical/subtropical conditions in surface waters.

Explaining bathymetric diversity patterns in marine benthic invertebrates and demersal fishes: physiological contributions to adaptation of life at depth.

Bathymetric biodiversity patterns of marine benthic invertebrates and demersal fishes have been identified in the extant fauna of the deep continental margins. Depth zonation is widespread and evident through a transition between shelf and slope fauna from the shelf break to 1000 m, and a transition between slope and abyssal fauna from 2000 to 3000 m; these transitions are characterised by high species turnover. A unimodal pattern of diversity with depth peaks between 1000 and 3000 m, despite the relatively low area represented by these depths. Zonation is thought to result from the colonisation of the deep sea by shallow-water organisms following multiple mass extinction events throughout the Phanerozoic. The effects of low temperature and high pressure act across hierarchical levels of biological organisation and appear sufficient to limit the distributions of such shallow-water species. Hydrostatic pressures of bathyal depths have consistently been identified experimentally as the maximum tolerated by shallow-water and upper bathyal benthic invertebrates at in situ temperatures, and adaptation appears required for passage to deeper water in both benthic invertebrates and demersal fishes. Together, this suggests that a hyperbaric and thermal physiological bottleneck at bathyal depths contributes to bathymetric zonation. The peak of the unimodal diversity–depth pattern typically occurs at these depths even though the area represented by these depths is relatively low. Although it is recognised that, over long evolutionary time scales, shallow-water diversity patterns are driven by speciation, little consideration has been given to the potential implications for species distribution patterns with depth. Molecular and morphological evidence indicates that cool bathyal waters are the primary site of adaptive radiation in the deep sea, and we hypothesise that bathymetric variation in speciation rates could drive the unimodal diversity–depth pattern over time. Thermal effects on metabolic-rate-dependent mutation and on generation times have been proposed to drive differences in speciation rates, which result in modern latitudinal biodiversity patterns over time. Clearly, this thermal mechanism alone cannot explain bathymetric patterns since temperature generally decreases with depth. We hypothesise that demonstrated physiological effects of high hydrostatic pressure and low temperature at bathyal depths, acting on shallow-water taxa invading the deep sea, may invoke a stress–evolution mechanism by increasing mutagenic activity in germ cells, by inactivating canalisation during embryonic or larval development, by releasing hidden variation or mutagenic activity, or by activating or releasing transposable elements in larvae or adults. In this scenario, increased variation at a physiological bottleneck at bathyal depths results in elevated speciation rate. Adaptation that increases tolerance to high hydrostatic pressure and low temperature allows colonisation of abyssal depths and reduces the stress–evolution response, consequently returning speciation of deeper taxa to the background rate. Over time this mechanism could contribute to the unimodal diversity–depth pattern.

ECOLOGICAL DISTRIBUTION OF RECENT DEEP-WATER FORAMINIFERA AROUND NEW ZEALAND

Census counts (>63 μm) of 461 species in 361 samples are used as the basis for recognizing and mapping associations of deep-sea benthic foraminifera (50–5000-m depth) around New Zealand, southwest Pacific (28–60°S, 155°E–170°W). Fourteen faunal associations are identified by cluster analysis with five of these subdivided into 20 subassociations. The deepest associations, dominated by Nuttallides spp., Globocassidulina subglobosa , and diverse agglutinated species, occur at middle–lower abyssal depths (>3600 m) right around New Zealand, where they have been impacted by differing levels of taphonomic modifications. Two large associations are widespread throughout the region: one ( Alabaminella weddellensis-Epistominella exigua ) at lower bathyal–middle abyssal depths (~1500–4000 m) and the other ( Cassidulina carinata - A. weddellensis - Abditodentrix pseudothalmanni ) mostly at mid-bathyal–upper abyssal depths (~500–3000 m). Two deep-water associations occur on current-swept submarine highs: one ( Trifarina angulosa-Ehrenbergina glabra ) at lower bathyal–upper abyssal depths (1000–2400 m) along the southeastern margin of the Camp-bell and Bounty plateaux and the other ( Bolivina robusta-Globocassidulina canalisuturata ) at mid–upper bathyal depths in coarse sediment east and southeast of New Zealand. Two large associations occur at mid-shelf–uppermost-bathyal depths (50–400 m): one ( Cassidulina carinata - Bulimina marginata - Gavelinopsis praegeri ) around the coast beneath warm Subtropical Water and the other ( C. carinata - T. angulosa - G. praegeri ) further south beneath the cooler Subtropical Front and Subantarctic Water. A major reason for this study was to understand the environmental drivers of foraminiferal faunal distribution in this region to assist in paleoenvironmental interpretations of fossil faunas which have a significant regional character. Canonical correspondence analysis indicates that the distribution of bathyal and abyssal associations is more strongly influenced by depth-related variables, while shallower associations are influenced by latitude-related differences in surface-water characteristics. Environmental variables that influence faunal patterns at abyssal and bathyal depths appear to be, in decreasing order: food supply (organic-carbon flux, chlorophyll- a proxies), bottom-oxygen concentration, and carbonate corrosiveness (Fragmentation Index, planktic % proxies). Latitude-related variables driving mid-shelf–uppermost bathyal faunal patterns are water temperature, followed by primary productivity (phosphate and chlorophyll- a proxies). Environmental variables related to bottom-current strength appear to drive the faunal composition of three associations at shelf and bathyal depths. Cluster analysis enables the recognition of 22 anomalously deep faunas that are inferred to have a significant displaced content. There are no significant diversity trends correlated with depth, but species diversity decreases with increasing latitude at all depths.

A New Species ofDoraster(Echinodermata: Asteroidea) from the Lower Miocene of Central Japan: Implications for its Enigmatic Paleobiogeography

Abstract A new species of well preserved zoroasterid asteroid was discovered from the lower Miocene Yamami Formation (approx. 16 Ma), Morozaki Group in Aichi Prefecture, central Japan. The specimens possess a small disc and long arms, and show clear stellate ossicles on the aboral disc surface, clearly supporting their placement within the genus Doraster. Currently Doraster is widely distributed in bathyal depths in the western Atlantic, represented only by one modern species, D. constellatus. The new discovery of fossil Doraster species not only extends the stratigraphic range of this genus but also suggests it was widely distributed in the Pacific before the closure of the Isthmus of Panama.

Can the morphology of deep-sea benthic foraminifera reveal what caused their extinction during the mid-Pleistocene Climate Transition?

Over 100 cosmopolitan species of deep-sea benthic foraminifera (Extinction Group, Ext. Gp) became extinct during the late Pliocene-middle Pleistocene (3.6–0.55 Ma). Most had elongate, cylindrical tests and terminal apertures with complex modifications. This study provides new hypotheses on the functions of the morphologies that characterised the Ext. Gp and how these features could have been associated with their demise. From our functional morphological analysis we infer that: i) their elongate cylindrical or flabelliform tests, combined with fine perforations and a complex terminal apertural face are indicative of infaunal k-strategists with a low rate of metabolism; and ii) their complex apertural faces may also have been an adaptation for gathering or processing their specific phytodetrital food. We propose three alternative hypotheses for the cause of these extinctions, and where possible test them using our high resolution micropaleontological and geochemical record through the last 1.07 Ma in lower bathyal site MD 97-2114 in the SW Pacific Ocean. Hypothesis 1 is that the Ext. Gp species were unable to adapt to increased variability in the overall quantity or pulsed seasonality of the food supply to the sea floor and were out-competed by opportunistic r-strategist benthic foraminifera. This is supported by the highly variable and increasing abundance of opportunistic foraminifera at our study site during the final phase of the extinction in the mid-Pleistocene Climate Transition, MPT. We doubt however, that there was increased variability in phytoplankton productivity throughout the world's oceans sufficient to bring about the global demise of the Ext. Gp. Hypothesis 2 is that lowered pCO 2 during increasingly severe MPT glacials, which coincided with the final phases of the extinction, may have caused the decline and possible loss of the Ext. Gp's phytoplankton food source. Declining pCO 2 during Neogene cooling was coeval with declining relative abundance of the Ext. Gp and reticulofenestrid nannofossils, but the final demise of this latter phytoplankton group occurred slightly later than the MPT in our study site and cannot be implicated with the extinction. If this hypothesis has any validity maybe the phytoplankton group left no fossil record. Our third alternative hypothesis is that maybe our Ext. Gp had much common DNA which made them the selective target of pathogens that caused their extinction. This does not easily explain their earlier disappearance at abyssal depths than at bathyal depths in our study region, which can be accommodated by hypotheses 1 and 2. • Functional morphology of Extinction group suggests they had low rates of metabolism. • Lowered pCO 2 during MPT glacials caused the decline of reticulofenestrid nannofossils. • Ext. Gp species may have been out-competed by opportunistic benthic foraminifera. • Ext. Gp demise was probably caused by the loss of a particular phytoplankton group particular phytoplankton.

Seasonality in reproduction of the deep-water pennatulacean coral Anthoptilum grandiflorum

The deep-sea pennatulacean coral Anthoptilum grandiflorum exhibits a cosmopolitan distribution and was recently determined to serve as habitat for other invertebrates and fish larvae in the northwest Atlantic. Colonies collected at bathyal depths between 2006 and 2010 in eastern Canada were analysed to determine their fecundity and characterize spatial and temporal trends in their reproductive cycle. Anthoptilum grandiflorum is a gonochoric broadcast spawner with a sex ratio that does not differ significantly from equality (although one hermaphrodite colony was observed). In male colonies, all the spermatocysts synthesized become mature over the annual cycle, while only ~21 % of the initial production of oocytes reaches maturity in female colonies. Female potential fecundity based on mature oocytes just before spawning was on average 13 oocytes polyp−1; male potential fecundity was 48 spermatocysts polyp−1. The spawning period of A. grandiflorum differs between geographic regions, from April (in southern Newfoundland) to July (in Labrador), closely following regional spring phytoplankton blooms after accounting for the deposition of planktic detritus. Release of oocytes by a live colony held in the laboratory was recorded in April 2011, coincident with field data for similar latitudes. Seawater temperatures at the time of spawning were around 3.6–4.8 °C in all regions and in the laboratory. Early stages of gametogenesis were detected in colonies collected shortly after the spawning season, and early and late growth stages occurred successively until December. Mature colonies were observed between April and July (depending on latitude). The diameter of mature oocytes (~1,100 μm maximum diameter) is consistent with lecithotrophic larval development.