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Low-latitude, deep-sea faunas remain poorly understood and described. Here, we systematically describe Quaternary deep-sea ostracodes from the Ocean Drilling Program (ODP) Site 925 (Ceara Rise; 4°12.2'N, 43°29.3′W; 3040 m water depth) in the equatorial Atlantic Ocean. Twenty-six genera and 52 species were examined and illustrated with high-resolution scanning electron microscopy images. Six new species are described herein: Pseudocythere spinae, Hemiparacytheridea zarikiani, Pedicythere canis, Xylocythere denticulata, Paracytherois obtusa, and Poseidonamicus sculptus. The results show that deep-sea ostracodes have a tropical faunal element that is distinctive from higher latitude ostracodes, and that is globally distributed in low latitudes. This tropical faunal component is possibly a Tethyan legacy of a fauna that was widely distributed in tropical and extratropical latitudes in deep waters during greenhouse conditions in the Cretaceous and early Cenozoic. Global cooling thereafter shrank its distribution, limiting it to tropical latitudes, perhaps with the relatively warm uppermost bathyal area acting as the source or refuge of this faunal component. Because similar present-day biogeographic patterns (i.e., presence and wide distribution of tropical deep-sea fauna) are known in other deep-sea benthic groups, this scenario might be applicable to the deep-sea benthos more broadly. UUID: http://zoobank.org/552d4cb2-c0db-463a-ae3f-b2efcc0985df. [ABSTRACT FROM AUTHOR]

Aim Little is known about how marine biodiversity responds to oceanographic and climatic changes over the decadal to centennial time-scales which are most relevant for predicted climate changes due to greenhouse gas forcing. This paper aims to reveal decadal-centennial scale deep-sea biodiversity dynamics for the last 20,000 years and then explore potential environmental drivers. Location The North Atlantic Ocean. Methods We investigated deep-sea benthic microfossil records to reveal biodiversity dynamics and subsequently applied comprehensive ecological modelling to test possible environmental factors (i.e. surface productivity, seasonality of productivity or deepwater circulation related to bottom-water temperature) that may have influenced deep-sea biodiversity over these time-scales. Results Deep-sea biodiversity changed synchronously with stadial-interstadial climate changes over the last 20,000 years across a large area of the North Atlantic in both ostracod crustaceans and foraminiferan protozoa (in spite of their different dispersal abilities). Species diversity rapidly increased during abrupt stadial events during the last deglacial and the Holocene interglacial periods. These include the well-known Heinrich 1, the Younger Dryas and the 8.2 ka events when the strength of Atlantic Meridional Overturning Circulation ( AMOC) decreased. There is also evidence for quasi-cyclic changes in biodiversity at a c. 1500-year periodicity, consistent with the well-known '1500-year climatic cycle'. Statistical analyses revealed that AMOC variability (probably specifically the variability in AMOC-driven bottom-water temperature) is correlated with deep-sea biodiversity. Main conclusions Our finding of a significant AMOC-diversity relationship may indicate pervasive control of the diversity of deep-sea benthic species by rapidly changing climate, specifically bottom-water temperature, over decadal to centennial time-scales. Our results, based on highly resolved fossil records, may portend pervasive, synchronous and sudden ecosystem responses to human-induced changes to climate and ocean circulation in this century. [ABSTRACT FROM AUTHOR]

Ocean Drilling Program (ODP) Holes 980 B and C, Feni Drift at the eastern slope of the Rockall Plateau, eastern North Atlantic, were examined for late Quaternary deep-sea ostracode taxonomy. Nineteen genera and 32 species were examined and (re-)illustrated with high-resolution scanning electron microscopy images. One new species Cytheropteron paramassoni n. sp. is described and one new name Eucytherura zehali is proposed for Eucytherura hazeli Yasuhara et al., 2009. This study provides updated taxonomic information for deep-sea ostracode genera and species from the eastern North Atlantic, which is an important baseline for application of deep-sea ostracodes to paleoceanographical reconstructions and paleoecological studies in this region. [ABSTRACT FROM AUTHOR]

Late Quaternary sediments from Ocean Drilling Program (ODP) Hole 1055B, Carolina Slope, western North Atlantic (32°47.041′ N, 76°17.179′ W; 1798 m water depth) were examined for deep-sea ostracod taxonomy. A total of 13 933 specimens were picked from 207 samples and c. 120 species were identified. Among them, 87 species were included and illustrated in this paper. Twenty-eight new species are described. The new species are: Ambocythere sturgio, Argilloecia abba, Argilloecia caju, Argilloecia keigwini, Argilloecia robinwhatleyi, Aversovalva carolinensis, Bythoceratina willemvandenboldi, Bythocythere eugeneschornikovi, Chejudocythere tenuis, Cytheropteron aielloi, Cytheropteron demenocali, Cytheropteron didieae, Cytheropteron richarddinglei, Cytheropteron fugu, Cytheropteron guerneti, Cytheropteron richardbensoni, Eucytherura hazeli, Eucytherura mayressi, Eucytherura namericana, Eucytherura spinicorona, Posacythere hunti, Paracytherois bondi, Pedicythere atroposopetasi, Pedicythere kennettopetasi, Pedicythere klothopetasi, Pedicythere lachesisopetasi, Ruggieriella mcmanusi and Xestoleberis oppoae. Taxonomic revisions of several common species were made to reduce taxonomic uncertainty in the literature. This study provides a robust taxonomic baseline for application to palaeoceanographical reconstruction and biodiversity analyses in the deep and intermediate-depth environments of the North Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Aim: Within the intensively‐studied, well‐documented latitudinal diversity gradient, the deep‐sea biodiversity of the present‐day Norwegian Sea stands out with its notably low diversity, constituting a steep latitudinal diversity gradient in the North Atlantic. The reason behind this has long been a topic of debate and speculation. Most prominently, it is explained by the deep‐sea glacial disturbance hypothesis, which states that harsh environmental glacial conditions negatively impacted Norwegian Sea diversities, which have not yet fully recovered. Our aim is to empirically test this hypothesis. Specific research questions are: (1) Has deep‐sea biodiversity been lower during glacials than during interglacials? (2) Was there any faunal shift at the Mid‐Brunhes Event (MBE) when the mode of glacial–interglacial climatic change was altered? Location: Norwegian Sea, deep sea (1819–2800 m), coring sites MD992277, PS1243, and M23352. Time period: 620.7–1.4 ka (Middle Pleistocene–Late Holocene). Taxa studied: Ostracoda (Crustacea). Methods: We empirically test the deep‐sea glacial disturbance hypothesis by investigating whether diversity in glacial periods is consistently lower than diversity in interglacial periods. Additionally, we apply comparative analyses to determine a potential faunal shift at the MBE, a Pleistocene event describing a fundamental shift in global climate. Results: The deep Norwegian Sea diversity was not lower during glacial periods compared to interglacial periods. Holocene diversity was exceedingly lower than that of the last glacial period. Faunal composition changed substantially between pre‐ and post‐MBE. Main conclusions: These results reject the glacial disturbance hypothesis, since the low glacial diversity is the important precondition here. The present‐day‐style deep Norwegian Sea ecosystem was established by the MBE, more specifically by MBE‐induced changes in global climate, which has led to more dynamic post‐MBE conditions. In a broader context, this implies that the MBE has played an important role in the establishment of the modern polar deep‐sea ecosystem and biodiversity in general. [ABSTRACT FROM AUTHOR]

Twelve genera and 19 species of deep-sea ostracods from the Shatsky Rise, north-western Pacific, were examined and illustrated for taxonomy. Three new species, Cytheropteron nasutum sp. nov., Poseidonamicus shatskyensis sp. nov. and Legitimocythere stellae sp. nov., are described. Based on these Shatsky Rise ostracods and a comprehensive literature survey of synonyms, we discuss global biogeography and possible migration pathways of deep-sea species. The four possible deep-water pathways connecting the Atlantic and Pacific Oceans are: the Drake Passage (Southern Ocean), established by 30 Ma; the Tethys Seaway, which had closed by 19-14 Ma; the Central American Seaway, which had closed by 3 Ma; and the Arctic Ocean Seaway via the Bering Strait, which opened about 4.8-7.4 Ma, and via the Fram Strait, which opened between 10 and 20 Ma. The Drake Passage is likely the major pathway. We argue that the Arctic was an important pathway for some deep-sea species before the mid-Pleistocene. Most deep-sea organisms have poor fossil records, and thus the rich fossil record of deep-sea ostracods is an ideal model system for the study of deep-time biogeography of deep-sea organisms. It may well be that other deep-sea organisms had similar palaeobiogeographical histories and patterns. http://zoobank.org/urn:lsid:zoobank.org:pub:3B70B7E5-04E0-4FF7-91EF-88CE1B199C8D [ABSTRACT FROM AUTHOR]

The depth distribution of living specimens of deep-sea benthic ostracods (small crustaceans with calcareous shells that are preserved as microfossils) in sediments is poorly understood, despite the importance of this aspect of basic ostracod biology for paleoecologic and paleoceanographic interpretations. Here, we investigated living benthic ostracod specimens from deep-sea multiple core samples, to reveal their depths distributions within sediment cores. The results showed shallow distribution and low population density of living deep-sea benthic ostracods (which are mostly composed of Podocopa). The living specimens are concentrated in the top 1 cm of the sediment, hence deep-sea benthic ostracods are either epifauna or shallow infauna. This observation is consistent with the information from shallow-water species. We also confirmed shallow infaunal (0.5–2 cm) and very shallow infaunal (0–1 cm) habitats of the deep-sea ostracod genera Krithe and Argilloecia, respectively. [ABSTRACT FROM AUTHOR]

Systematic revision of the globally distributed deep-sea ostracod genera Pennyella Neale, 1974 and Rugocythereis Dingle, Lord and Boomer, 1990, which have been considered to correspond, at least partially, to nomen nudum but widely used genus name ' Oxycythereis,' was conducted to reduce taxonomic uncertainty of these important components of the Modern and fossil deep-sea ostracod community. Approximately 100 specimens from 18 species were examined, ranging in age from the Cretaceous to the present day. Nine new species are described: Pennyella rexi, Pennyella sanfordae, Pennyella liowae, Pennyella schellenbergi, Pennyella majorani, Pennyella iani, Pennyella ayressi, Rugocythereis melonis and Rugocythereis zarikiani. Emended generic concepts of Pennyella and Rugocythereis are proposed, and the palaeobiogeographical distributions of these two genera are discussed. [ABSTRACT FROM AUTHOR]

Twenty-six genera and 34 species of early Miocene Indian shallow-marine ostracodes were examined for taxonomy and paleobiogeography. A new genus Paractinocythereis and new species Costa ponticulocarinata were described. Early Miocene Indian ostracode fauna shows strong affinity to Eocene–Miocene Eastern and Western Tethyan ostracode faunas and Miocene–Recent Indo-Pacific ostracode fauna, supporting the Hopping Hotspot Hypothesis that the Tethyan biodiversity hotspot has shifted eastward through Arabia to Indo-Australian Archipelago (IAA) together with concomitant biogeographic shifts of the Tethyan elements. The result also indicated an inverse westward distributional shift in a genus. It is important to note that Paleogene and Miocene shallow marine ostracodes from the IAA region remain poorly investigated, and more fossil ostracode data are needed to better test the Hopping Hotspot Hypothesis. UUID: http://zoobank.org/d1e29249-8c5b-49bf-a47a-5f18e1fc4426 [ABSTRACT FROM AUTHOR]

Aim: The deep waters around Iceland, known as the North Atlantic Gateway, constitute an ideal location to investigate deep‐sea ecological hypotheses. We constructed a comprehensive deep‐sea macroecological dataset of the North Atlantic Gateway region and investigated the controlling factors of large‐scale, deep‐sea species diversity patterns. Location: Sub‐polar North Atlantic Ocean. Time period: Modern. Major taxa studied: Ostracoda (Crustacea). Methods: We investigated deep‐sea biodiversity patterns and applied ecological modelling (multiple regression and model averaging) to test whether these patterns are governed by environmental factors such as temperature, surface primary productivity, and seasonality. Beta diversity analyses were applied to evaluate the effect of a geographical barrier (Greenland‐Iceland‐Faeroe Ridge) on deep‐sea benthic faunal distributions. Results: We constructed a deep‐sea macroecological dataset with 32 stations, 5,676 specimens, and >122 species. We confirmed a linear latitudinal diversity gradient with higher diversity in the North Atlantic proper than in the Nordic Seas. We report a unimodal depth diversity gradient south of the ridge, but a linear diversity‐decline with depth north of the ridge. The turnover component of beta diversity increased towards the ridge. Main conclusions: We found both temperature and surface primary production are important for deep‐sea biodiversity. For the first time, we report a significant diversity‐temperature relationship in both macroecological (spatial; this study) and existing paleoecological (time‐series) data for the same taxa. In addition to temperature and surface primary production, bathymetric features such as a shallow ridge acting as a barrier are an important factor for deep‐sea biodiversity distribution. The low diversity of the Nordic Seas is likely due to a combination of low temperatures and bathymetric barriers. These results substantially expand our understanding of the well‐known yet poorly understood Greenland‐Iceland‐Faeroe Ridge faunal transition with possible insight to its cause. [ABSTRACT FROM AUTHOR]

Twenty-five genera and 32 species of Eocene shallow-marine ostracods from Madagascar were examined for taxonomy and palaeobiogeography. Eight new species – Paijenborchellina madagascarensis sp. nov., Neocyprideis polygonoreticulata sp. nov., Alciella irizukii sp. nov., Neomonoceratina afroangulosa sp. nov., Muellerina eocenica sp. nov., Stigmatobradleya hunti gen. et sp. nov., Uroleberis paranuda sp. nov., Xestoleberis renemai sp. nov. – and one new genus – Stigmatobradleya gen. nov. – are described. Eocene Malagasy ostracods showed a strong affinity to the Eocene East Tethyan fauna in Arab-Africa and Indo-Pakistan. They also showed certain affinity to the Eocene West Tethyan fauna in Europe. One species, Pokornyella lamarckiana sensu lato, showed a very wide Eocene geographical distribution, covering Europe, Indo-Pakistan, Arab-Africa, Japan and perhaps North America. These results indicate that the East African, Arabian, and Indo-Pakistan regions constitute the East Tethyan palaeobiogeographical sub-realm, with considerable faunal similarity found across the regions. This sub-realm extends to south-eastern Africa in the south and is a part of the broader Tethyan palaeobiogeographical realm with certain, but less, palaeobiogeographical similarity. The spatial extent of the Tethys palaobiogeographical realm sensu lato includes Asia-Oceania in the east and eastern America in the west. Based on our results, we suggest a need to update the scheme of global ostracod biogeographical division. [ABSTRACT FROM AUTHOR]

Aim Cenozoic dynamics of large-scale species diversity patterns remain poorly understood, especially for the Western Pacific, in part, because of the paucity of well-dated fossil records from the tropics. This article aims to reveal the spatiotemporal dynamics of species diversity in the Western Pacific through the Cenozoic, focusing on the tropical Indo-Australian Archipelago ( IAA) biodiversity hotspot. Location Tropical and north-western Pacific Ocean. Methods We analysed well-preserved fossil ostracodes from the tropical Western Pacific and combined their diversity data with other published data from the region to reconstruct Cenozoic dynamics of species diversity in the tropical and north-western Pacific Ocean. We fitted generalized additive models to test for differences in richness over time and across geographical regions while accounting for sample-size variation among samples. Results Low-, mid- and high-latitude regions all show a similar diversity trajectory: diversity is low in the Eocene and Oligocene, increases from the Early Miocene to the Plio-Pleistocene but then declines to the present day. Present-day high biodiversity in these regions was established during the Pliocene with a remarkable diversity increase at that time. Latitudinal diversity patterns are relatively flat and never show a simple decline from the tropics to higher latitudes. Main conclusions Western Pacific Cenozoic ostracodes exhibit a spatiotemporal pattern of species diversity that is inconsistent with the commonly reported and persistent pattern of declining diversity from the tropics to the extratropics. While this inconsistency could be interpreted as evidence that ostracodes are a contrarian clade, Atlantic ostracodes display a standard latitudinal species diversity gradient. Contrasting patterns between oceans suggest an important role for regional factors (e.g. plate tectonics and temporal geomorphological dynamics) in shaping the biodiversity of the Western Pacific. [ABSTRACT FROM AUTHOR]

A benthic microfaunal record from the equatorial Atlantic Ocean over the past four glacial-interglacial cycles was investigated to understand temporal dynamics of deep-sea latitudinal species diversity gradients (LSDGs). The results demonstrate unexpected instability and high amplitude fluctuations of species diversity in the tropical deep ocean that are correlated with orbital-scale oscillations in global climate: Species diversity is low during glacial and high during interglacial periods. This implies that climate severely influences deep-sea diversity, even at tropical latitudes, and that deep-sea LSDGs, while generally present for the last 36 million years, were weakened or absent during glacial periods. Temporally dynamic LSDGs and unstable tropical diversity require reconsideration of current ecological hypotheses about the generation and maintenance of biodiversity as they apply to the deep sea, and underscore the potential vulnerability and conservation importance of tropical deep-sea ecosystems. [ABSTRACT FROM AUTHOR]

We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Allerod Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until ≈8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. [ABSTRACT FROM AUTHOR]

Better understanding of deglacial meltwater pulses (MWPs) is imperative for future predictions of human-induced warming and abrupt sea-level change because of their potential for catastrophic damage. However, our knowledge of the second largest meltwater pulse MWP-1B that occurred shortly after the start of the Holocene interglacial remains very limited. Here, we studied fossil ostracods as paleoenvironmental indicators of water depth, salinity, and temperature in two marine sediment cores from Storfjorden, Svalbard margin (the Arctic Ocean), to investigate near-field (i.e. areas located beneath continental ice sheets at the Last Glacial Maximum) evidence of MWP-1B. The depositional environment changed from a cold bathyal environment to a warmer bathyal environment at ∼11,300 yr BP indicating incursion of warm Atlantic water into the Nordic seas, and eventually to a cold neritic environment by ∼11,000 yr BP because of melting of the Svalbard-Barents Sea ice sheet and resultant isostatic rebound. This process corresponds to rapid relative sea-level fall of 40–80 m of MWP-1B from ∼11,300 to 11,000 yr BP. • Near-field evidence of meltwater pulse 1-B was discovered in Svalbard. • Warm Atlantic water incursion melted reginal ice sheet at ∼11.3 kyr BP. • Isostatic uplift caused abrupt relative sea-level fall of 40–80 m at 11.3–11 kyr BP. • Neoglacial cooling and glacier advance occurred after ∼2 kyr BP. [ABSTRACT FROM AUTHOR]