Showing papers by "Andrew J. Gooday published in 2008"
TL;DR: This study provides scientific evidence that the conservation of deep-sea biodiversity is a priority for a sustainable functioning of the worlds' oceans and suggests that mutually positive functional interactions can be common in the largest biome of the authors' biosphere.
598 citations
TL;DR: Foraminifera in the bathyal seafloor have been found to have relatively robust, calcareous or agglutinated shells with soft test walls as discussed by the authors.
Abstract: Most fossil deep-sea foraminifera are multichambered and have relatively robust, calcareous or agglutinated shells. Modern assemblages, on the other hand, include many fragile monothalamous (single-chambered) forms and komokiaceans (a superfamily of protist currently placed within the foraminifera) with soft test walls. These groups are poorly known and most of the hundreds of morphospecies recognized in deep-sea samples are undescribed. The relative abundance of robust and fragile taxa varies with water depth and food supply. Calcareous and other hard-shelled species tend to predominate in relatively eutrophic areas, particularly on continental margins, but decrease as a proportion of the ‘entire’ live fauna (i.e. including soft-shelled species) with increasing water depth, even above the CCD (carbonate compensation depth). Most of the species on which the foraminiferal proxies used in palaeoceanography are based live in these bathyal regions. At abyssal depths, and particularly below the CCD, faunas are largely agglutinated and dominated by monothalamous forms. These assemblages have a much lower fossilization potential than those found on continental margins. In addition to carbonate dissolution, these patterns probably reflect adaptations to increasingly oligotrophic conditions on the ocean floor with increasing depth and distance from land. Bathyal species include herbivores and opportunistic deposit feeders (omnivores) that consume labile organic material, in addition to deep-infaunal deposit feeders, and must contribute significantly to carbon cycling. Many abyssal monothalamous foraminifera, in constrast, accumulate stercomata (waste pellets composed of fine sediment particles) and probably ingest sediment, associated bacteria and more refractory organic matter. Some monothalamous species without stercomata may be bacteriovores. Although they probably process organic carbon at a slower rate than calcareous species, the shear abundance of monothalamous taxa at abyssal depths suggests that they are important in carbon cycling on a global scale. The loss of a substantial proportion of foraminiferal biomass and biodiversity from the fossil record should be considered when using foraminifera to reconstruct palaeoproductivity, for example, by using the Benthic Foraminiferal Accummulation Rate (BFAR). Different dietary preferences among calcareous species have implications for the stable carbon isotope signal preserved in their shell
78 citations
TL;DR: This study has revealed a high number of cryptic species within each of the examined genera, and demonstrates the unexplored potential of monothalamous foraminifers for use as a tool to evaluate the origin and biogeography of polar meiofauna.
Abstract: Monothalamous (single-chambered) foraminifers are a major component of the benthic meiofauna in high latitude regions. Several morphologically similar species are common in the Arctic and Antarctic. However, it is uncertain whether these morphospecies are genetically identical, or whether their accurate identification is compromised by a lack of distinctive morphological features. To determine the relationship between Arctic and Antarctic species, we have compared SSU rDNA sequences of specimens belonging to four morphotaxa: Micrometula, Psammophaga, Gloiogullmia, and one morphospecies Hippocrepinella hirudinea from western Svalbard (Arctic) and McMurdo Sound (Antarctic). Wherever possible, we include in our analyses representatives of these taxa from the deep Arctic and Southern Oceans, as well as from Northern European fjords. We found that in all cases, the bipolar populations were clearly distinct genetically. As expected, Arctic specimens were usually more closely related to those from Northern Europe than to their Antarctic representatives. The deep-sea specimens from Weddell Sea branched as a sister to the McMurdo Sound population, while those from the Arctic Ocean clustered with ones from Norwegian fjords. Our study has revealed a high number of cryptic species within each of the examined genera, and demonstrates the unexplored potential of monothalamous foraminifers for use as a tool to evaluate the origin and biogeography of polar meiofauna.
50 citations
01 Jan 2008
44 citations
TL;DR: Four new species and a new genus of very small Foraminifera from the Challenger Deep, the deepest point in the world's oceans, are described, all of which have transparent, mainly organic test walls that incorporate some minute agglutinated mineral particles of various shapes and compositions.
40 citations
TL;DR: Fatty acid analyses on samples from early (November 7, 2001) and late (January 31, 2002) austral summer revealed that the 3 species contained substantial amounts of polyunsaturated fatty acids (PUFAs), indicating the downwards transfer of carbon from sea-ice associated primary production.
Abstract: Astrammina rara, Crithionina delacai, and Notodendrodes hyalinosphaira are 3 of the largest and most abundant members of the foraminiferal assemblage at a shallow-water (28 to 32 m) site in Explorers Cove, Antarctica. This study summarizes observations from 2 decades of research, during which we employed laboratory-based feeding experiments and fatty acid biomarker analysis to characterize trophic dynamics and ecological roles of the 3 species. In feeding experiments, A. rara consumed a variety of co-occurring metazoans (several Crustacea, Mollusca, Echinodermata, and a Nephtys species). C. delacai, N. hyalinosphaira, and a number of other foraminiferal species from Explorers Cove successfully trapped Artemia sp. nauplius prey in a setup designed to examine the efficiency of prey capture. Fatty acid analyses on samples from early (November 7, 2001) and late (January 31, 2002) austral summer revealed that the 3 species contained substantial amounts (33 to 45.5%) of polyunsaturated fatty acids (PUFAs), which are produced by microalgae, indicating the downwards transfer of carbon from sea-ice associated primary production. In the case of A. rara, this may be due to the ingestion of herbivorous metazoa, rather than direct uptake of microalgal mater- ial. A. rara contained significantly (p < 0.05) higher amounts of the zooplankton biomarkers 20:1(n-9) and 22:1(n-11), and C. delacai contained more PUFAs early, compared to late, in the season. Two morphotypes of N. hyalinosphaira had different fatty acid profiles, indicating distinct trophotypes. Our results illustrate specific adaptations to different trophic resources in these protists, and they demonstrate the potential impact that large carnivorous species of Foraminifera may have on the structure of benthic communities where they are abundant.
33 citations
TL;DR: A conservative position is adopted and Chitinosiphon is regarded as a junior synonym of Nodellum, which is related to tubular agglutinated taxa such as Bathysiphon and Resigella, which may have similar affinities.
Abstract: Using a morphology-based approach, we explore the relationships between three poorly understood species of organic-walled Foraminifera. Thalmann and Bermudez (1954) described Chitinosiphon rufescens as the type species of a new monotypic genus which they compared to the tubular agglutinated foraminiferan Bathysiphon. Loeblich and Tappan (1964), however, considered C. rufescens to be identical to Reophax membranacea Brady 1879, type species of another organic-walled genus, Nodellum. Based on a re-examination of the type specimens of both species, new material of C. rufescens from the Lost City hydrothermal field, and new material of N. membranacea from the NE Atlantic and Pacific Oceans, we show that these two deep-sea species are distinguished by the following features. (1) Chitinosiphon rufescens lacks the distinct, regular constrictions that divide the tubular test of N. membranacea into a series of segments. (2) The proloculus is spindle-shaped in C. rufescens but sub-cylindrical in N. membranacea. (3) A distinctive, pocket-like invagination is developed at the base (proximal end) of the proloculus in N. membranacea but not in C. rufescens. However, a series of undescribed species which occur in deep-sea sediments blur the distinction between the two genera. We therefore adopt a conservative position and regard Chitinosiphon as a junior synonym of Nodellum. We also examined the holotype and new material of Nodellum moniliforme Resig, 1982, the type species of Resigella Loeblich and Tappan, 1984, in which the organic-walled test comprises a series of bulbous chambers. This species exhibits a basal invagination, identical to the feature present in Nodellum membranacea. These three remarkable species are united by the basically tubular test and the nature of the test wall which is largely organic, brownish in colour, and exhibits no internal structure when broken sections are examined by SEM. The surface of the organic test of Nodellum rufescens from Lost City is strewn with tiny (?1 ?m), needle-shaped mineral particles, visible only by SEM. More equidimensional, micron-sized particles are present in the other two species. We agree with Thalmann and Bermudez (1954) that N. rufescens is related to tubular agglutinated taxa such as Bathysiphon. Resigella may have similar affinities, although this needs to be tested using molecular approaches.
11 citations