Showing papers by "Andrew J. Gooday published in 2012"

Benthic Foraminiferal Biogeography: Controls on Global Distribution Patterns in Deep-Water Settings

Abstract: Benthic foraminifera, shell-bearing protists, are familiar from geological studies. Although many species are well known, undescribed single-chambered forms are common in the deep sea. Coastal and sublittoral species often have restricted distributions, but wide ranges are more frequent among deep-water species, particularly at abyssal depths. This probably reflects the transport of tiny propagules by currents across ocean basins that present few insurmountable barriers to dispersal, combined with slow rates of evolution. Undersampling of the vast deep-sea habitat, however, makes it very difficult to establish the ranges of less common foraminiferal species, and endemism may be more prevalent than currently realized. On continental slopes, some species have restricted distributions, but wide-ranging bathyal species that exhibit considerable morphological variation are more common. This may be linked to the greater heterogeneity of continental slopes compared with oceans basins. Improved knowledge of deep-sea foraminiferal biogeography requires sound morphology-based taxonomy combined with molecular genetic studies.

Possible effects of global environmental changes on Antarctic benthos: a synthesis across five major taxa.

Abstract: Because of the unique conditions that exist around the Antarctic continent, Southern Ocean (SO) ecosystems are very susceptible to the growing impact of global climate change and other anthropogenic influences. Consequently, there is an urgent need to understand how SO marine life will cope with expected future changes in the environment. Studies of Antarctic organisms have shown that individual species and higher taxa display different degrees of sensitivity to environmental shifts, making it difficult to predict overall community or ecosystem responses. This emphasizes the need for an improved understanding of the Antarctic benthic ecosystem response to global climate change using a multitaxon approach with consideration of different levels of biological organization. Here, we provide a synthesis of the ability of five important Antarctic benthic taxa (Foraminifera, Nematoda, Amphipoda, Isopoda, and Echinoidea) to cope with changes in the environment (temperature, pH, ice cover, ice scouring, food quantity, and quality) that are linked to climatic changes. Responses from individual to the taxon-specific community level to these drivers will vary with taxon but will include local species extinctions, invasions of warmer-water species, shifts in diversity, dominance, and trophic group composition, all with likely consequences for ecosystem functioning. Limitations in our current knowledge and understanding of climate change effects on the different levels are discussed.

Possible early foraminiferans in post-Sturtian (716−635 Ma) cap carbonates

Abstract: Foraminifera are an ecologically important group of modern heterotrophic amoeboid eukaryotes whose naked and testate ancestors are thought to have evolved ∼1 Ga ago. However, the single-chambered agglutinated tests of these protists appear in the fossil record only after ca. 580 Ma, coinciding with the appearance of macroscopic and mineralized animals. Here we report the discovery of small, slender tubular microfossils in the Sturtian (ca. 716–635 Ma) cap carbonate of the Rasthof Formation in Namibia. The tubes are 200–1300 μm long and 20–70 μm wide, and preserve apertures and variably wide lumens, folds, constrictions, and ridges. Their sometimes flexible walls are composed of carbonaceous material and detrital minerals. This combination of morphologic and compositional characters is also present in some species of modern single-chambered agglutinated tubular foraminiferans, and is not found in other agglutinated eukaryotes. The preservation of possible early Foraminifera in the carbonate rocks deposited in the immediate aftermath of Sturtian low-latitude glaciation indicates that various morphologically modern protists thrived in microbially dominated ecosystems, and contributed to the cycling of carbon in Neoproterozoic oceans much before the rise of complex animals.

The Porcupine Abyssal Plain fixed-point sustained observatory (PAP-SO): variations and trends from the Northeast Atlantic fixed-point time-series

Abstract: The Porcupine Abyssal Plain sustained observatory (PAP-SO) in the Northeast Atlantic (49°N 16.5°W; 4800 m) is the longest running open-ocean multidisciplinary observatory in the oceans around Europe. The site has produced high-resolution datasets integrating environmental and ecologically relevant variables from the surface to the seabed for >20 years. Since 2002, a full-depth mooring has been in place with autonomous sensors measuring temperature, salinity, chlorophyll-a fluorescence, nitrate, and pCO2. These complement ongoing mesopelagic and seabed observations on downward particle flux and benthic ecosystem structure and function. With national and European funding, the observatory infrastructure has been advanced steadily, with the latest development in 2010 involving collaboration between the UK's Meteorological Office and Natural Environment Research Council. This resulted in the first simultaneous atmospheric and ocean datasets at the site. All PAP-SO datasets are open access in near real time through websites and as quality-controlled datasets for a range of remote users using ftp sites and uploaded daily to MyOcean and the global telecommunications system for use in modelling activities. The combined datasets capture short-term variation (daily–seasonal), longer term trends (climate-driven), and episodic events (e.g. spring-bloom events), and the data contribute to the Europe-wide move towards good environmental status of our seas, driven by the EU's Marine Strategy Framework Directive (http://ec.europa.eu/environment/water/marine).

The influence of productivity on abyssal foraminiferal biodiversity

Abstract: The quantity and quality of organic matter reaching the deep-sea floor is believed to exert a strong control on benthic foraminiferal assemblages, including the diversity and density of populations and the distribution patterns of species. In addition, some species seem to be associated with strong seasonality in primary productivity. We test relationships between diversity and mean annual productivity based on carefully selected datasets (>63-μm sieve fraction including soft-shelled taxa) from the NE Atlantic, Weddell Sea, and Equatorial and North Pacific. We used (1) ‘live’ (Rose Bengal stained) foraminiferal density, (2) mean annual surface productivity and (3) estimated organic carbon flux to the seafloor as proxies for food supply to the benthos. A suite of species richness, diversity and dominance measures all decreased significantly with increasing density, whereas species density showed a significant increase. In contrast, none of the relationships between these measures and primary productivity or its seasonality were significant. Only the Margalef and Brillouin indices exhibited a significant decrease with increasing values of carbon flux to the sea floor. When sites from the NE Atlantic were treated separately, significant relationships (−ve) emerged between flux and all diversity measures, and between foraminiferal densities and most (8 of 9) diversity measures. For the equatorial Pacific, however, these relationships were mostly (16 of 18) not significant. Size fractioned (>150-μm and >63-μm fraction including phytodetritus) data from the NE Atlantic samples yielded significant correlations (−ve) between several diversity measures and foraminiferal densities, but many fewer when related to estimated carbon flux to the seafloor. We also considered published datasets from the Arctic (Wollenburg and Mackensen Mar Micropaleontol 34: 153–185, 1998) and North Atlantic (Corliss et al. Deep-Sea Res 56: 835–841, 2009) Oceans. Diversity values (Fisher α index based on ‘live’ counts) from seasonally and permanently ice-covered areas (depth range, 94–4,427 m) in the Arctic were significantly correlated (+ve) with estimated flux. Correlations were also significant for sites below permanent ice cover (1,051–4,427 m) and for those >4,000 m. Positive correlations between foraminiferal density and diversity were significant for the whole dataset and for sites with permanent ice cover, but not for the deep sites. Analysis of unstained calcareous foraminifera of Holocene age from the N Atlantic (2,118–4,673 m water depth) revealed significant relationships between diversity and seasonality, but not with flux. Additional analyses of ‘seasonal’ and ‘non-seasonal’ N Atlantic sites with a comparable range of estimated flux values (2–4 g C m−2 year−1) revealed that diversity increased with increasing flux and density in both cases, with significantly lower diversity at the seasonal compared to the non-seasonal sites. The contradictions between our data (−ve relationship between food availability and diversity) and those of Wollenburg and Corliss (+ve relationship) are difficult to explain and underline the need for further studies employing consistent methods to analyse ‘entire live’ assemblages across productivity gradients.

Meiobenthos of the Oxic/Anoxic Interface in the Southwestern Region of the Black Sea: Abundance and Taxonomic Composition

Abstract: The Black Sea contains the World’s largest body of anoxic water. Based on new and published data, we describe trends among selected protozoan and metazoan meiofaunal taxa at water depths of 120–240 m in the northwestern part of the Black Sea near the submarine Dnieper Canyon. This transect spans the transition between increasingly hypoxic but non-sulfidic bottom water and the deeper anoxic/sulfidic zone, the boundary between these two domains being located at approximately 150–180 m depth. This transition zone supports a rich rose-Bengal-stained fauna. Among the protozoans, gromiids are common only at 120 and 130 m. All other groups exhibit more or less distinct abundance maxima near the base of the hypoxic zone. Foraminifera peak sharply at ∼160 m while ciliates are most abundant at 120, 160–190, and 240 m, where they are possibly associated with concentrations of bacterial cells. The three most abundant metazoan taxa also exhibit maxima in the hypoxic zone, the nematodes and polychaetes at 160 m, and the harpacticoid copepods at 150 m. Most of the polychaetes belong to two species, Protodrilus sp. and Vigtorniella zaikai, the larvae of which are widely distributed in severely hypoxic water just above the anoxic/sulfidic zone of the Black Sea. Both protozoans and metazoans are usually concentrated in the 0–1 cm layer of the sediment, except at the shallowest (120–130 m) site where deeper layers may yield a substantial proportion of the assemblage. The concentration of nematodes in the 3–5 cm layer at 120 m is particularly notable. Our data suggest that some benthic species can tolerate anoxic/sulfidic conditions in the Black Sea. An important caveat is that anoxia or severe hypoxia may lead to the corpses of nonindigenous organisms being preserved in our samples. However, we argue that the morphological integrity of specimens, the high population densities (associated with high bacterial concentrations in the case of ciliates), the presence of taxa often found in hypoxic settings, and the presence of all life stages (including gravid females) among nematodes and harpacticoids, suggests that at least some of the organisms are indigenous. Further comparative studies of shallow- and deep-water meiobenthic communities in the Black Sea are necessary in order to establish which species are characteristic and indicative of hypoxic/anoxic conditions.

Foraminiferal biodiversity associated with cold-water coral carbonate mounds and open slope of SE Rockall Bank (Irish continental margin—NE Atlantic)

Abstract: Cold-water coral (CWC) ecosystems are hotspots of macro- and microfaunal biodiversity and provide refuge for a wide variety of deep-sea species. We investigated how the abundance and biodiversity of ‘live’ (Rose Bengal stained) foraminifera varies with, and is related to, the occurrence of CWC on the Rockall Bank (NE Atlantic). Qualitative and quantitative analyses were performed on 21 replicate samples from 8 deep-sea stations, including 4 stations on CWC-covered carbonate mounds at depths of 567–657 m, and 4 stations on the adjacent slope at depths of 469–1958 m where CWC were absent. This sampling strategy enabled us to demonstrate that sediments surrounding the living CWC were characterised by higher foraminiferal abundance and biodiversity than open-slope sediments from the same area. A total of 163 foraminiferal species was identified. The dominant species in CWC sediments were: Spirillina vivipara, Allogromiid sp. 1, Globocassidulina subglobosa, Adercotryma wrighti, Eponides pusillus, Ehrenbergina carinata, Planulina ariminensis, Trochammina inflata and Paratrochammina challengeri. Foraminifera were nearly absent in adjacent open slope areas subject to strong tidal currents and characterised by coarse grained deposits. We suggest that CWC create a heterogeneous three-dimensional substrate offering microhabitats to a diverse benthic foraminiferal community.

Large, enigmatic foraminiferan-like protists in the eastern part of the Clarion-Clipperton Fracture Zone (abyssal north-eastern subequatorial Pacific): biodiversity and vertical distribution in the sediment

Abstract: Komokiaceans and similar large (millimetre-sized to centimetre-sized) testate protists resembling Foraminifera are a ubiquitous and often dominant component of abyssal macrofaunal assemblages. Yet they are often overlooked and many forms are undescribed, often at the genus or higher taxon level. As a result, they represent a major source of unknown biodiversity in the deep sea. We studied the diversity and vertical distribution of these delicate, often fragmentary organisms in sediment samples (0- to 6-cm layer) collected from three sites in the eastern part of the Clarion-Clipperton polymetallic nodule field (subequatorial NE Pacific) during the 1997 cruise of the RV Professor Logachev organised by the Interoceanmetal Joint Organization (IOM). A total of 102 morphospecies and morphotypes was recorded (28-69 per station), indicating an extremely diverse assemblage. Although most were found in the uppermost 2 cm, deeper sediment layers also yielded some species. This is one of only a few studies of komokiaceans and related organisms in this part of the Pacific. It contributes to baseline knowledge of abyssal communities in an area targeted for future commercial nodule mining operations.

Southern Ocean Deep Benthic Biodiversity

Abstract: The deep sea is the largest environment on the planet, the least well known and one of the least studied. It contains extremely large habitats, and millions of km2 of continental slopes and abyssal plains. These incorporate other geological structures, including canyons, seamounts, reefs, hydrothermal vents, mud volcanoes, and faults at active and passive margins, which support unique microbiological and faunal communities. Despite our limited knowledge of deep-sea biodiversity, we now know that the Southern Ocean (SO) deep sea is very speciose within many taxa, and it is therefore likely that more species occur in the deep sea than any other biome on earth (Gage&Tyler, 1991). In many taxa far more than 90% of the species collected in a typical abyssal sediment sample are new to science, and usually H 50% of these appear to be rare (Glover et al., 2002; Brandt et al., 2007a–c; Ellingsen et al., 2007; Smith et al., 2008). Some authors have demonstrated that the occurrence of rare species in samples is the result of sampling the regional fauna only (Rex et al., 2005b). However, analyses comparing abundance across different spatial scales in SO deepsea isopods have revealed high biological variability, which indicates patchiness rather than rarity, of most isopod taxa (Kaiser et al., 2007).