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Primitive Foraminifera and Xenophyophorea in IOS epibenthic sledge samples from the northeast Atlantic
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Biological responses to seasonally varying fluxes of organic matter to the ocean floor: a review
No full textDeep-sea benthic ecosystems are sustained largely by organic matter settling from the euphotic zone. These fluxes usually have a more or less well-defined seasonal component, often with two peaks, one in spring/early summer, the other later in the year. Long time-series datasets suggest that inter-annual variability in the intensity, timing and composition of flux maxima is normal. The settling material may form a deposit of phytodetritus on the deep-seafloor. These deposits, which are most common in temperate and high latitude regions, particularly the North Atlantic, evoke a response by the benthic biota. Much of our knowledge of these responses comes from a few time-series programmes, which suggest that the nature of the response varies in different oceanographic settings. In particular, there are contrasts between seasonal processes in oligotrophic, central oceanic areas and those along eutrophic continental margins. In the former, it is mainly small organisms (bacteria and protozoans) that respond to pulsed inputs. Initial responses are biochemical (e.g. secretion of bacterial exoenzymes) and any biomass increases are time lagged. Increased metabolic activity of small organisms probably leads to seasonal fluctuations in sediment community oxygen consumption, reported mainly in the North Pacific. Metazoan meiofauna are generally less responsive than protozoans (foraminifera), although seasonal increases in abundance and body size have been reported. Measurable population responses by macrofauna and megafauna are less common and confined largely to continental margins. In addition, seasonally synchronised reproduction and larval settlement occur in some larger animals, again mainly in continental margin settings. Although seasonal benthic responses to pulsed food inputs are apparently widespread on the ocean floor, they are not ubiquitous. Most deep-sea species are not seasonal breeders and there are probably large areas, particularly at abyssal depths, where biological process rates are fairly uniform over time. As with other aspects of deep-sea ecology, temporal processes cannot be encapsulated by a single paradigm. Further long time-series studies are needed to understand better the nature and extent of seasonality in deep-sea benthic ecosystems
The distribution of the xenophyophore Syringammina fragilissima in the northeast Atlantic and its influence on the diversity of bathyal foraminiferal assemblages
Full text linkSoft-shelled monothalamous foraminifera are abundant at an intertidal site on the south coast of England
No full textForaminifera associated with phytodetritus deposits at a bathyal site in the northern Rockall Trough (NE Atlantic): seasonal contrasts and a comparison of stained and dead assemblages
No full textHyperammina micaceus sp. nov.: a new foraminferan species (Protista) from the Porcupine Abyssal Plain, northeast Atlantic
No full textBenthic foraminiferal trends in relation to an organic enrichment gradient on the continental slope (850 m water depth) off North Carolina (USA)
No full textWe analyzed benthic foraminiferal assemblages in core samples collected by a submersible at three sites (I, II, III) along an isobathyal gradient of organic enrichment on the North Carolina slope (850 m water depth). The 0–2, 2–5, 5–10, 10–15 cm layers of each core were sieved into 63–125, 125–150 and 150–300 µm size fractions, and each fraction was stained with rose Bengal and dry sorted. Together, the samples yielded 284 benthic foraminiferal species. The vast majority of tests (97%) were unstained; live specimens were scarce at Site I and very rare at Site II, but more common at Site III. The preservation of dead calcareous benthic and planktonic foraminiferal tests varied between sites. Calcareous tests were abundant at Sites I and II, but virtually absent at Site III except in the 2–5 cm layer, where they were more numerous than at the other two sites. Dead benthic tests were also less abundant in the 0–2 cm, 5–10 cm and particularly the 10–15 cm layers at Site III than in the corresponding layers at Sites I and II, and were dominated by species with agglutinated rather than calcareous walls. These patterns suggest that substantial dissolution has occurred at Site III. In striking contrast, the 2–5 cm layer of our Site III core yielded numerous calcareous planktonic and benthic foraminiferal tests. Possibly, this layer consisted of sediment that had been transported by a local mass movement event. In general, diversity trends exhibited by the dead assemblages (63–300 and 63–125 µm fractions) were similar to those reported by Gooday and others (2001) for the live metazoan and foraminiferal macrofauna (>300 µm): diversity and species richness were higher at Sites I and II than at the organically enriched Site III; dominance was higher at Site III than at the other two sites. However, at Site III, diversity was apparently depressed by the destruction of calcareous foraminiferal tests. Some species (Angulogerina angulosa, Bolivina paula, Bulimina aculeata, Cibicidoides pseudoungerianus, Globocassidulina subglobosa, Rosalina floridana and Stetsonia minuta) were common to all three sites. However, the most abundant species (Bolivina spissa, Eggerella advena, Paratrochammina ?bartrami, Veleroninoides jeffreysii) at Site III were different from those at Sites I and II, among both the live and dead assemblages. The common species (e.g., Eggerella advena) at Site III are more typical of shallow-water, inner shelf settings, a result that is consistent with published observations on metazoan macrofauna (>300 µm) at similar depths on the slope off Cape Hatteras
Conqueria laevis gen. and sp. nov., a new soft-walled, monothalamous foraminiferan from the deep Weddell Sea
No full textConqueria laevis gen. and sp. nov., a new monothalamous agglutinated foraminiferan, is described from core samples collected in the abyssal western Weddell Sea. The species is characterized by a very elongate, almost cylindrical test that usually follows a more or less curved course and has a single terminal aperture located at the end of a short neck. The wall has a very smooth outer surface and is composed of tiny (<5 [mu]m) agglutinated particles. Very similar and presumably congeneric morphotypes occur at northern hemisphere sites, including Arctic fjords around Svalbard and the Porcupine Abyssal Plain. Molecular phylogenetic analyses, based on small subunit rRNA gene sequences, indicate that the new Weddell Sea species forms an independent lineage branching among monothalamous foraminiferans as a sister group to the clade of Psammophaga
Biodiversity and ecology of deep-sea benthic foraminifera of the Weddell Sea, Antarctica
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