1,721,163 research outputs found
First record of a Xenophyophore (Rhizaria: Foraminifera) on the Chilean margin
No full textThis dataset contains the digitized treatments in Plazi based on the original journal article Araya, Juan Francisco, Gooday, Andrew J. (2018): First record of a Xenophyophore (Rhizaria: Foraminifera) on the Chilean margin. Zootaxa 4455 (3): 589-592, DOI: 10.11646/zootaxa.4455.3.16</span
A new genus and two new species of saccamminid foraminiferans (Protista, Rhizaria) from the deep Southern Ocean
No full textFIGURE 6. Phylogenetic position of Leptammina gen. nov. inferred from partial SSU rDNA sequences using maximum likelihood method. Numbers at internal nodes correspond to bootstrap values higher than 75%.Published as part of Cedhagen, Tomas, Gooday, Andrew J. & Pawlowski, Jan, 2009, A new genus and two new species of saccamminid foraminiferans (Protista, Rhizaria) from the deep Southern Ocean *, pp. 9-22 in Zootaxa 2096 on page 20, DOI: 10.5281/zenodo.18776
Novel benthic foraminifera are abundant and diverse in an area of the abyssal equatorial Pacific licensed for polymetallic nodule exploration
No full textThe benthic biota of the Clarion–Clipperton Zone (CCZ, abyssal eastern equatorial Pacific) is the focus of a major research effort linked to possible future mining of polymetallic nodules. Within the framework of ABYSSLINE, a biological baseline study conducted on behalf of Seabed Resources Development Ltd. in the UK-1 exploration contract area (eastern CCZ, ~4,080 m water depth), we analysed foraminifera (testate protists), including ‘live’ (Rose Bengal stained) and dead tests, in 5 cores (0–1 cm layer, >150-μm fraction) recovered during separate megacorer deployments inside a 30 by 30 km seafloor area. In both categories (live and dead) we distinguished between complete and fragmented specimens. The outstanding feature of these assemblages is the overwhelming predominance of monothalamids, a group often ignored in foraminiferal studies. These single-chambered foraminifera, which include agglutinated tubes, spheres and komokiaceans, represented 79% of 3,607 complete tests, 98% of 1,798 fragments and 76% of the 416 morphospecies (live and dead combined) in our samples. Only 3.1% of monothalamid species and 9.8% of all species in the UK-1 assemblages are scientifically described and many are rare (29% singletons). Our results emphasise how little is known about foraminifera in abyssal areas that may experience major impacts from future mining activities
Radiolarian tests as microhabitats for novel benthic foraminifera: observations from the abyssal eastern equatorial Pacific (Clarion–Clipperton fracture zone)
Full text linkWe investigated benthic foraminifera inhabiting the empty tests of radiolarians in surface sediment samples from the abyssal Clarion–Clipperton Fracture Zone (13°50’N, 116°35’W; ~4080 m water depth), eastern equatorial Pacific, an area licensed for the future mining of polymetallic nodules. Based on two megacore samples (>150 µm, 0–1 cm sediment layer; 78.6 cm2 surface area), we examined 288 radiolarian tests that were occupied by ‘live’ (stained) inhabitants presumed to be foraminifera based on test morphology and wall structure; these quantitative data were supplemented by qualitative records from three additional cores. The radiolarian inhabitants comprised organic-walled and agglutinated monothalamous (single-chambered) and less common polythalamous (multichambered) forms. Among the 27 distinctive morphotypes, a few can be assigned to a described superfamily (Komokiacea) or to genera such as Lagenammina, Thurammina and Hormosinella, while two brown, organic-walled multichambered forms resemble the genera Hospitella and Placopsilinella. The remainder were assigned to informal morphotypes. The radiolarian inhabitants are generally small (<150 µm) and confined within the host test, although some construct delicate tubes, either flexible or rigid, on the exterior. Our study suggests that radiolarian tests represent an important small-scale (<500 µm) microhabitat for certain abyssal benthic foraminifera, possibly providing concentrations of food (e.g. bacteria) as well as protection. In many cases, the occupancy of radiolarian tests seems to be habitual rather than opportunistic. Thus, 19 of the 27 morphospecies, representing ~31% of total number of radiolarian inhabitants, were not observed outside this microhabitat. These habitual inhabitants represented ~8% of the total number of foraminiferal morphospecies in the samples and >9% of the total ‘live’ (stained) foraminiferal assemblage, thereby making non-negligible contribution to local species diversity and foraminiferal abundance in our study area. Our new observations, and previous studies of benthic foraminifera inhabiting the empty shells of other foraminifera, suggest that high biodiversity among meiofaunal-sized deep-sea organisms (particularly foraminifera) is enhanced by the colonisation of small cryptic microhabitats. Based on their complex test morphology, we suggest that at least some of the diverse monothalamous foraminifera that typically dominate abyssal foraminiferal assemblages have little or no mobility, making them well suited to this mode of life
‘Live’ (stained) deep-sea benthic foraminiferans in the western Weddell Sea: trends in abundance, diversity and taxonomic composition along a depth transect. (In special issue on ANDEEP (Antarctic benthic DEEP-sea) biodiversity: colonization history and recent community patterns: a tribute to Howard L. Sanders, edited by A. Brandt and B. Hilbig)
No full text‘Entire’ live foraminiferal assemblages (i.e. including soft-walled species) were analysed using replicate subcores (3.45 cm2 surface area, 0–1 cm layer; >63 ?m fraction) from multiple corer samples collected along a transect (1100–5000 m water depth) of the continental slope and rise and adjacent abyssal plain to the east of the Antarctic Peninsula. Foraminiferans usually accounted for 61–83% of all meiofaunal organisms. Mean densities were highest (576 individuals (indiv.)10 cm?2) at 2100 m water depth and declined to 240 indiv. 10 cm?2 at 5000 m, although there was considerable variability between replicates at some stations (e.g., 304, 333, 1090 indiv. 10 cm?2 at 2100 m). Foraminiferan and metazoan meiofaunal densities were broadly coherent across the depth range sampled. A total of 158 live foraminiferal species was recognized. Assemblages were most diverse on the lower slope, with species numbers peaking at 3100 m and the Fisher ? diversity index at 3100–4100 m. Monothalamous taxa increased in relative abundance from 8% at 1100 m to 33% at 4975 m, and there was a corresponding decrease in the proportion of calcareous taxa from 65% to 16%. On the continental slope (1100–3100 m), the most abundant hard-walled species were Epistominella exigua, Adercotryma glomeratum, Alabaminella weddellensis and Stetsonia hovarthi. In the deeper samples (4100–5000 m), A. glomeratum became the dominant hard-walled species. Important soft-walled species included Tinogullmia riemanni and Bathyallogromia weddellensis. In some samples from 1100 and 2100 m, more than a third of the live assemblage was hidden within phytodetrital aggregates; species such as E. exigua, A. weddellensis and T. riemanni were concentrated within these microhabitats. Many of the Weddell Sea species are typical bathyal and abyssal forms well known from the North Atlantic and elsewhere. The phytodetrital assemblages are strikingly similar to those reported from abyssal sites in the North Atlantic. Our observations suggest that there are close faunal links between the deep-water faunas of the Weddell Sea and those of other oceanic regions, perhaps mediated by thermohaline circulation
Precambrian Biota: Protistan Origin of Trace Fossils?
No full textSome Precambrian trace fossils have been presented as evidence for the early origin of bilaterians; the recent finding that large amoeboid protists leave macroscopic traces at the bottom of the deep ocean questions the metazoan nature of early trace fossils, stressing the importance of single-cell organisms in Precambrian biota.<br/
Foraminiferal faunal responses to monsoon-driven changes in organic matter and oxygen availability at 140 m and 300 m water depth in the NE Arabian Sea
No full textThe faunal responses of benthic Foraminifera were investigated during 2003 at two contrasting sites in the Pakistan margin oxygen minimum zone (OMZ). Bottom-water-dissolved oxygen concentrations at the seasonally hypoxic 140 m site varied from 2.06 ml l-1 (92±4 µM) during the intermonsoon period (April) to 0.11 ml l-1 (5.0±0.4 µM) during the post-monsoon period (October); corresponding values at the 300 m site in the OMZ core, were 0.053 and 0.057 ml l-1 (2.36±0.09 and 2.56±0.29 µM). Live macrofaunal (>300 µm) Foraminifera (including soft-walled species) and Metazoa were examined in replicate multicore samples taken at each site during the 2003 intermonsoon and post-monsoon seasons. A low-diversity foraminiferal assemblage was dominated (>60%) by calcareous species at both sites. A total of 36 species was recognised and diversity was not greatly affected by water depth or season. At both sites, >86% of Foraminifera were restricted to the 0–1 cm layer of sediment and the ALD5 decreased from the intermonsoon to the post-monsoon periods. Densities increased from 124 (intermonsoon) to 153 (post-monsoon) indiv. 10 cm–2 at 140 m and from 86 to 122 indiv. 10 cm-2 at 300 m. Much of this increase was accounted for by the dominant species, Uvigerina ex. gr. semiornata. At 140 m, Foraminifera were 3.6 times more abundant than metazoans during the intermonsoon period, rising to 13.9 times during the post-monsoon period. The corresponding proportions at 300 m, where metazoans were rare, were 12.4 and 14.5. We conclude that calcareous Foraminifera, in particular U. ex. gr. semiornata, play a central role in OM cycling on the sea floor in the upper part of the Pakistan margin OMZ.<br/
Taxonomic composition and distribution of soft-walled monothalamid foraminifera in the area of Zernov’s hyllophora Field (NW Black Sea)
No full textWe studied assemblages of soft-walled, single-chambered foraminifera (monothalamids) at eight stations in the area of Zernov's Phyllophora Field (ZPF) on the NW continental shelf of the Black Sea. This work is based on samples collected during Cruise 70 of the RV Professor Vodyanitsky and provides the first analysis of the taxonomic composition of monothalamids from this region. These delicate, poorly known foraminifera were found at all stations in the studied area. They were represented by nine forms that are identified to species or genus level as well as 14 undescribed species, nine of which are found in the Black Sea for the first time. Four species, Psammophaga sp., Vellaria pellucida, Goodayia rostellata and Krymia fusiformis, were most abundant, with Psammophaga sp. being the dominant species overall. Previous studies have suggested a link between members of this genus and eutrophication. There are a number of taxonomic parallels between these ZPF assemblages and those from the Adriatic Sea, e.g. the occurrence of the genera Goodayia, Psammophaga and Vellaria, although it is possible that some other taxa are endemic to the Black Sea
Global genetic homogeneity in the deep-sea foraminiferan Epistominella exigua (Rotaliida: Pseudoparrellidae)
No full textEpistominella exigua is one of the most common deep-sea foraminiferal morphospecies and has a world-wide
distribution. A recent molecular study revealed high genetic similarity between Arctic, Atlantic and Antarctic
populations of this species. Here, we show that the small-subunit (SSU) and internal transcribed spacer (ITS) rDNA
sequences of an E. exigua population from Pacific are almost identical to those reported previously from the other three
oceans. This result confirms the genetic homogeneity of E. exigua, which contrasts with the prevalence of highly
differentiated populations in planktonic and shallow-water benthic foraminiferans. We discuss special features of
diversifications mechanisms in the deep sea that may be responsible for the lack of genetic differentiation and global
distribution of some meiofauna species
First record of a Xenophyophore: (RhizariaForaminifera) on the Chilean margin
No full textXenophyophores are a group of large foraminifera, confined to deep-sea habitats below ~500 m, whose often fragile agglutinated tests may attain sizes up to 10–15 cm or more; their agglutinated tests incorporate a variety of foreign particles (termed ‘xenophyae’), including mineral particles, foraminiferan and radiolarian tests, diatom frustules and sponge spicules, and form structures ranging from simple tubes, plates and rounded lumps to complex folded, branching or reticulated formations (Tendal, 1972). Xenophyophores are widely distributed around the world, particularly in the Pacific and Atlantic Oceans with comparatively few records from the Indian Ocean and from Arctic and Antarctic seas; they occur at all depths in the oceans from ~500 m to >10,900 m (Tendal, 1972, 1996) and are particularly abundant in regions of high surface production, for example beneath upwelling zones, or on seamounts and sloped topography where particle flux is high (Levin and Gooday, 1992). There are scant records regarding xenophyophores in the SE Pacific. Species of the order Stannomida are recorded from the Ecuador and Peru margins (north of ~12°S) (Tendal 1972: Figs 18, 19), while species of the order Psamminida are common in the DISCOL experimental area of the Peru Basin (~7° 4ˈS, 88° 28’W; ~4150 m depth). Maybury and Evans (1994) illustrated two specimens of an undescribed Psammina species collected during the 1989 DISCOL campaign, but otherwise these collections remain largely unpublished
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