Recent Benthic Foraminifera Research Articles

Foraminíferos bentónicos recientes en sedimentos micróxicos de la bahía Mejillones del Sur (23º S), Chile

The composition of recent benthic foraminifera was analyzed in eight sedimentological interfase samples collected with a box core of 0,16 m 2 surface in Mejillones del Sur bay (23o S) at depths of 56 to 138 m. The study area is characterized by a large relative abundance of Bolivina seminuda Cushman and the presence of Nonionella stella Cushman & Moyer and Bolivina costata Orbigny. The registered diversity (H) is low and varies between 0,8 and 2,4. The deepest station near Punta Angamos, presents the highest index and is the only one with Cancris auriculus (Fichtel & Moll) and Valvulineria inflata (Orbigny). The faunistic density of stations located in the center and external zones of this bay showed the highest values (average= 2600 ind/g), with most of the material representated by Bolivina seminuda. The results showed that the benthic foraminiferal distribution is directly related with bottom-water oxygen content. B. seminuda is adapted notably to microxic conditions (0,01 ml l - 1 ). Buliminella elegantissima (Orbigny) is found in more oxygenated areas (0,5 ml l -1 ), while B. costata and N. stella

Oceanographic Conditions in the Deepest Parts of the Kattegat, Scandinavia, Revealed Through Recent Benthic Foraminifera and Hydrography

The Kattegat has, since the 1980s, been subject to extensive investigations focusing on various aspects of the marine environment. The most important reasons for this concentration of work are marine eutrophication, periodically occurring oxygen deficiency in the bottom-water and subsequent benthic mortality. In this study a previously not discussed sill area separating two deep areas in the Kattegat has been identified. In the contexts of periodically occurring oxygen deficiency in the southern Kattegat, it is most relevant to study the environmental conditions in this area. Hydrographic data from the area inside and outside the sill area suggest that the deep-water on both sides of the sill do communicate. No evidence for stagnation in the deep area inside the sill was found. In addition to hydrography data, benthic foraminifera has been used as environmental tracers. Two characteristic benthic foraminiferal faunas have been defined one representing water depths; exceeding 80m and one representing shallower depths. These faunas occur on both sides of the sill area. Two investigated deep depressions within the deep area inside the sill, the Alkor Depth (138m) and Poseidon Depth (150m) are marked by a fauna that is identical with that in the so-called Kattegat Trench. This suggests that the depressions are not more stagnant, if stagnant at all, than the surrounding Kattegat Trench and the Djupa Rännan Trench located outside the sill area. The information generated in this study is essential for the understanding of the processes resulting in oxygen deficiency in the deep water of the southern Kattegat.

Distribution of Recent Benthic Foraminifera in the Southern Basin of the Venice Lagoon (Italy): Statistical Evaluation of Taxa Significance

The total benthic foraminiferal assemblage (living and dead) is analyzed for 95 samples collected in the southern basin of the Venice Lagoon [Chioggia Basin, Italy]. Quantitative results of the identified 48 species are statistically treated by correspondence analysis and Fuzzy c-means cluster analysis to define both the zonal environmental similarities (biotopes) and the faunal similarities (biofacies). In this lagoon basin, the biotopes delineate the area of marine influence, areas of mixed sea/lagoon, and zones of greater human impact that seem less heavily polluted with respect to the other two lagoon basins. The faunal similarities identified distinguish present sea and lagoon influences from the salt marsh assemblage, which are linked to the paleoenvironment. We show through statistical analyses that abundance is not the only factor governing the importance of the different taxa in defining biotopes. The important factor we found out is significance assumed as the ratio between abundance and distribution for both abundant and rare species. Results complete the knowledge on the present environmental condition of the Venice Lagoon and suggest limits of feasible simplifications to better define biotopes. These limits are given by the significant value of each taxon, which is greater, the smaller the equidistribution of the taxon itself.

Recent benthic foraminifera from the eastern South Atlantic Ocean: Dependence on food supply and water masses

Sixty surface sediment samples from the eastern South Atlantic Ocean including the Walvis Ridge, the Angola and Cape basins, and the Southwest African continental margin were analysed for their benthic foraminiferal content to unravel faunal distribution patterns and ecological preferences. Live (stained with Rose Bengal) and dead faunas were counted separately and then each grouped by Q-mode principal component analysis into seven principal faunal end-members. Then, multiple regression technique was used to correlate Recent assemblages with available environmental variables and to finally differentiate between four principal groups of environmental agents acting upon the generation of benthic foraminiferal assemblages: (1) seasonality of food supply and organic carbon flux rates, together with oxygen content in the pore and bottom waters; (2) lateral advection of deep-water masses; (3) bottom water carbonate corrosiveness; and (4) energetic state at the benthic boundary layer and grain size composition of the substrate. Food supply and corresponding dissolved oxygen contents in the pore and bottom waters turned out to be the most important factors which control the distribution pattern of the Recent benthic foraminifera. At the continental margin, in the zone of coastal upwelling and its mixing area, benthic foraminiferal assemblages are dominated by stenobathic high-productivity faunas, characterized by elevated standing stocks, low diversities and a large number of endobenthic living species. At the continental shelf and upper continental slope the live assemblages are characterized by Rectuvigerina cylindrica, Uvigerina peregrina s.1., Uvigerina auberiana and Rhizammina spp. while the dead assemblages are characterized by Cassidulina laevigata, Bolivina dilatata, Bulimina costata and B. mexicana. At the lower continental slope strong influence of high organic matter fluxes on the species composition is restricted to the area off the Cunene river mouth, where the live assemblage is dominated by Uvigerina peregrina s.1., the corresponding dead assemblage by Melonis barleeanum and M. zaandamae. In the adjacent areas of the lower continental slope the biocoenosis is characterized by Reophax bilocularis, and Epistominella exigua which becomes dominant in the corresponding dead assemblage. At the Walvis Ridge and in the abyssal Angola and Cape basins, where organic matter fluxes are low and highly seasonal, benthic foraminiferal assemblages reflect both the oligotrophic situation and the deep and bottom water mass configuration. The top and flanks of the Walvis Ridge are inhabited by the Rhizammina, Psammosphaera and R. bilocularis live assemblages, the corresponding dead assemblages are dominated by G. subglobosa on the ridge top and E. exigua on the flanks. Within the highly diverse E. exigua dead assemblage several associated epibenthic species coincide with the core of NADW between about 1600 and 3700 m water depth. These species include Osangularia culter, Cibicidoides kullenbergi, Melonis pompilioides, Bolivinita pseudothalmanni and Bulimina alazanensis. The assemblages of the abyssal Cape and Angola basins are characterized by Nuttallides umbonifer and a high proportion of agglutinated species. These species are adapted to very low organic matter fluxes and a carbonate corrosive environment.

Magnesium and strontium compositions of Recent benthic foraminifera from the Coral Sea, Australia and Prydz Bay, Antarctica

Analyses of the Mg/Ca and Sr/Ca ratios of the modern benthic foraminifera, Cibicides wuellerstorfi (epifaunal) and Uvigerina species (infaunal) from the Coral Sea, and Cibicides refulgens (epifaunal) and Trifarina angulosa (infaunal) from Prydz Bay, Antarctica revealed relationships with temperature that have possible applications for reconstructions of bottom-water paleotemperatures. A positive relationship exists between the Mg/Ca and Sr/Ca ratios of Cibicides wuellerstorfi and Cibicides refulgens and ambient temperatures, at least within the range of - ̊ 2 and 6°C. For the correlation between Mg/Ca compositions and temperature the r 2 values range from 0.78 ( C. wuellerstorfi alone) to 0.88 ( C. wuellerstorfi and C. refulgens together). At present, the Mg/Ca-temperature relationship must be regarded as tentative because of significant overlap of standard error values. The relationship between the Sr/Ca compositions of C. wuellerstorfi and bottom-water temperature yields an r 2 value of 0.95. These results indicate that Sr/Ca and possibly Mg/Ca ratios of Cibicides wuellerstorfi may provide useful information for the assessment of paleotemperature. Single-species data are presently insufficient to assess the influence of ambient temperature on trace-element compositions of Uvigerina species. Trifarina angulosa may have Mg/Ca compositions which are positively related to temperature, but Sr/Ca values seem unaffected by temperature. This may be due to pore-water influences on infaunal tests or to vital effects. Although more modern data are needed, our present results suggest that Sr/Ca ratios and possibly Mg/Ca ratios of some benthic foraminifera have the potential to be useful paleothermometers, at least within a temperature range of −2 to 6°C.

The distribution of Recent benthic Foraminifera across habitats of Bocas del Toro, Caribbean Panama

We use distributions of Recent benthic foraminifera in Bocas del Toro, Caribbean Panama, to distinguish tropical habitats. Two hundred thirty-seven species occur in 37 samples from substrata of the inner continental shelf (3.7 m) to upper slope (240 m). Cluster analyses of the assemblages primarily differentiate open-ocean from partially restricted, shallow coastal waters, and secondarily differentiate six main habitats with characteristic taxa as follows: shallow lagoon (inner shelf, 10-18 m): Ammonia beccarii, Nonionella atlantica; deep lagoon (inner to shallow middle shelf, 23-35 m): Cancris sagra, Lagenammina atlantica, Reussella minuta; channel (inner to middle shelf, 21-70 m): Bigenerina irregularis, Epistominella vitrea, Hanzawaia concentrica, Reussella spinulosa, Textularia schencki; reef (inner to middle shelf, 6-82 m): Amphistegina gibbosa, Discorbis mira, Eponides antillarum, Hauerina fragilissima, Nodobaculariella casis, Planulina exorna, Pyrgo subspaerica, Quinqueloculina bicornis, Q. collumnosa, Q. lamarckiana, Q. tricarinata, Rotorbinella umbonata, Textularia conica; middle (39 m) to shallow outer (120 m) shelf (excluding middle shelf to upper slope sediments mixed by downshelf transport): Cibicides aff. C. floridanus, C. pachyderma, agglutinated Miliolidae; and deep outer shelf (168 m) to upper slope (235 m): Bolivina lowmani, Cassidulina norcrossi australis, Gyroidina regularis, G. turgida, Uvigerina laevis, U. peregrina. Grain-size analyses show little differentiation of these environments, other than coarse sands of the reef habitat. Distributions of most of the above taxa, except for the reef habitat species, are uncorrelated with grain size and thus are the most useful for paleoenvironmental studies, although the reef taxa should also be useful when comparing samples with similar grain sizes.

Recent benthic foraminifera as tracers of water masses along a transect in the Skagerrak, north-eastern North Sea

Recent benthic foraminifera have been investigated in surface samples (0–8 cm) from thirteen sites along a profile in the Skagerrak, between Norway and Denmark. The investigated transect is sampled in an oceanographically well investigated area. Principal component analysis based on the 32 most abundant taxa is used to recognize similarities within the large data set of benthic foraminifera (a total of 93 samples), which is shown to cluster into four assemblage groups (A–D). The spatial distribution of these foraminiferal groups indicates that they inhabit areas that correspond with the delimitations of different water masses. We have identified areas where it is possible to investigate effects on the sea floor of different tracers, natural or anthropogenic contaminants, related to specific water masses.

Recent benthic foraminifera as tracers of water masses along a transect in the Skagerrak, north-eastern North Sea

Recent benthic foraminifera as tracers of water masses along a transect in the Skagerrak, north-eastern North Sea

Oxygen and carbon isotopic composition of Recent larger and smaller foraminifera from the Madang Lagoon (Papua New Guinea)

Tests of Recent benthic foraminifera from the Madang Lagoon (Papua New Guinea) were analyzed for their oxygen and carbon isotopic composition. Analyses were performed on scuba collected species from backreef and low-oxygenated harbor environments covering a depth range of 0 to 45 m. Both rotaliid and miliolid symbiont-bearing species were found to exhibit increasing δ18O with depth, while only the rotaliids reveal a comparable trend in their δ13C composition. The general trend of depletion in the heavier isotopes, 13C and 18O appears to be depth- and light-dependant. Neither the symbiont type nor the nature of the microhabitat appear to affect the magnitude of 18O16O fractionation in larger foraminifers from this environment.The carbon isotope patterns of symbiont-bearing species revealed distinct differences between rotaliids and miliolids. Consistently lower δ13C values in rotaliid foraminifers may be related to a higher rate of photosynthetic activity. The photosynthetic effect of carbon isotope fractionation may be overprinted by the presence/absence of an internal carbon pool and/or specific modes of biomineralization which may act as isotopic filters.Foraminifera collected from low-oxygenated, organic-rich sediments in harbor inlets at Madang were found to exhibit particularly low δ13C values. Depletion (δ13C) is suggested to be due to oxidative processes in the surrounding organic-rich sediment coupled with preferential incorporation of isotopically lighter 12C.

Recent benthic foraminifera of a transect from the North Pole to the Yermak Plateau, eastern central Arctic Ocean

The Recent distribution of living and dead benthic foraminifera of the Arctic Ocean proper has been examined in surface sediments that were sampled during the International Arctic Ocean Expedition 1991 ( Arctic 91). The samples represent the Amundsen and Nansen Basins, the Morris Jesup Rise, and the Yermak Plateau from 90°N to 79°42.4′N, 05°15.6′E. Due to the technical difficulties of deep-sea drilling in the Arctic Ocean these areas have, until now, been investigated only in very low density sampling. The Arctic 91 sites of this study cover a water depth range between 552 and 4375 m and represent three sites which are seasonally ice-free, although not yearly, while the other sites are characterized by permanent sea-ice. There is a Recent production of benthic foraminifera in the whole investigation area and all surface samples contain both benthic and planktonic foraminifera. Abyssal assemblages are recorded in the Amundsen and Nansen Basins where Stetsonia arctica dominates with high abundances. It is, however, also possible to distinguish these two basins by the use of diagnostic species. At intermediate water depths (500 to 2000–2500 m) the faunas show higher diversities and higher abundances of Atlantic species than the deep-sea sites. Mixing of North Atlantic water down to approximately 2500 m, is suggested to explain the influx of Atlantic species on the Yermak Plateau and the Morris Jesup Rise. The foraminiferal tests are well preserved within the investigation area and dissolution does not seem to be very obvious in the deeper areas. There is no evidence from the Recent foraminiferal faunas that the bottom waters of the eastern, central Arctic Ocean are undersaturated with respect to calcium carbonate and the deep-sea areas appear, therefore, to lie above the present CCD.

The importance of the oxygen minimum zone and sediment geochemistry in the distribution of Recent benthic foraminifera in the northwest Indian Ocean

The relationship between the distribution of benthic foraminifera and sediment type and depositional environment in the Arabian Sea is discussed. The benthic foraminiferal fauna were sampled in nineteen Recent surface sediment samples, and geochemical variables of the sediment of the same samples were measured. The water depths for the box core samples varies from 440 to 4040 m. A total of 103 species and six species-complexes were identified. The geochemical properties were found to correspond well to the sediment type and depositional environment and six different sediment/depositional environment types could be distinguished. Analysis of the benthic foraminiferal fauna reveals specific faunal assemblages that are closely related to these sediment/depositional environment types.

The distribution of Recent benthic foraminifera in the Polar Front region, southwest Atlantic

Twenty-five core-top samples from the Maurice Ewing Bank (MEB) and Islas Orcadas Rise (IOR) were examined to determine the distribution of benthic foraminifera in the vicinity of the Polar Front in the southwest Atlantic Ocean. The Polar Front has a subsurface expression that effects the areal and depth distribution of benthic foraminifera in this region. Three faunal assemblages were identified by Q-mode factor analysis. The shallowest assemblage, dominated by Bulimina aculeata, is present from 1500 to 2600 m on the Maurice Ewing Bank and is associated with potential temperatures of 1.71-0.50°C, salinities of 34.74-34.70‰ and potential density values of 45.84–46.04 sigma-4. A second assemblage, dominated by Uvigerina peregrina, occurs in water depths from 2600 to 3100 m and is associated with potential temperatures of 0.40-0.26°C, salinities of 34.70-34.69‰ and potential density values of 46.05–46.07 sigma-4. The third assemblage is dominated by Nuttallides umbonifera, Ehrenbergina trigona and secondarily by Oridorsalis umbonatus and Pullenia bulloides (the N. umbonifera-E. trigona assemblage) is present form 2770 to 3120 m on the Islas Orcadas Rise. This assemblage is associated with potential temperatures of 0.36-0.14°C, salinities of 34.69-34.68‰, and potential density values of 46.06–46.09 sigma-4. Although the U. peregrina assemblage and the N. umbonifera-E. trigona assemblage overlap bathymetrically, they are present in waters of slightly different properties. The Bulimina aculeata assemblage is within the core of the Lower Circumpolar Deep Water (LCDW), while the other two assemblages occur within transition zones between the LCDW and Weddell Sea Deep Water (WSDW). The difference in the benthic foraminiferal assemblages at similar depths on the Islas Orcadas Rise and the Maurice Ewing Bank is the result of different water-mass regimes separated by the Polar Front.

Canonical Variate Analysis of Selected Benthic Foraminifera: A Preliminary Study of a Potential Paleobathymetric Tool

Published data on the distribution of Recent benthic foraminifera in the northern Gulf of Mexico indicate that many species have wide-ranging depth distributions and occur throughout the area. In general, the potential ecologic information from such ubiquitous (or nearly so) species has been ignored because visual differences in shell morphology within species are not easily detectable. Because canonical variate analysis has the statistical power to detect such subtle differences, it is used in this study to analyze measured morphologicfeatures of several ubiquitous species: Bolivina albatrossi, B. lowmani, B. subspinescens, and Cassidulina subglobosa. These species were obtained from previous collections from the western Gulf of Mexico in depths rangingfrom less than 100 meters (inner neritic) to more than 2000 meters (abyssal). The statistical analyses were able to discriminate between populations of these ubiquitous species from these different depths; that is, specimens collected from the neritic zone have statistically significant morphometric differences from all bathyal and abyssal samples, and specimens collected from upper, middle and lower bathyal zones have statistically significant morphometric differences from each other as well as from abyssal zone samples. This approach has the potential of expanding our capability to estimate paleobathymetry and enhancing the precision of such estimates.

Distribution of Recent benthic foraminifera off the Pacific coast of Mexico and Central America

Distribution of Recent benthic foraminifera off the Pacific coast of Mexico and Central America

Recent benthic Foraminifera from the central North Atlantic : Hermelin, J.O.R. and D.B. Scott, 1985. Micropaleontology, 31(3):199–220

Recent benthic Foraminifera from the central North Atlantic : Hermelin, J.O.R. and D.B. Scott, 1985. Micropaleontology, 31(3):199–220

Recent benthic Foraminifera in the Polar Front region of the southwest Atlantic : Mead, G.A., 1985. Micropaleontology, 31(3):221–248

Recent benthic Foraminifera in the Polar Front region of the southwest Atlantic : Mead, G.A., 1985. Micropaleontology, 31(3):221–248

Inflated later chambers; ontogenetic changes of some Recent hyaline benthic foraminifera

Inflated later chambers; ontogenetic changes of some Recent hyaline benthic foraminifera

Distribution of recent benthic Foraminifera off the North American Pacific coast from Oregon to Alaska : Culver, S.J. and M.A. Buzas, 1985. Smithson. Contr. mar. Sci., 26:234pp

Distribution of recent benthic Foraminifera off the North American Pacific coast from Oregon to Alaska : Culver, S.J. and M.A. Buzas, 1985. Smithson. Contr. mar. Sci., 26:234pp

Recent Benthic Foraminifera in the Polar Front Region of the Southwest Atlantic

Recent Benthic Foraminifera in the Polar Front Region of the Southwest Atlantic

Recent benthic foraminifera from the continental margin of northwest Africa: Community structure and distribution

Sediment grab samples were collected at 107 locations along the continental margin of northwest Africa. These samples form a series of depth transects between the Straits of Gibraltar and Dakar, Senegal. The greater than 250 μm size fraction was retained for a census of both the live and dead foraminifera. After deleting trace occurrences, Jaccard and correlation coefficient-based cluster analyses were performed to decipher the community structure for this margin. The geographic distribution of the four major faunal provinces recognized is conventional in that for both the live and dead assemblages three are related to depth: upper slope and shelf, middle slope, and lower slope and continental rise. The biotopes and thanatotopes within these provinces are strongly restricted along vertical or latitudinal boundaries when the data are analysed using Jaccard coefficients. Dendrograms constructed from correlation coefficients emphasize depth-related faunal communities. Dominant species such as Cibicides lobatulus, Trifarina fornasinii, Planulina ariminensis, Uvigerina finisterrensis, and C. wuellerstorfi are generally distributed within a definite depth range along this margin and strongly influence the correlation coefficient-based dendrograms. Other distributions are clearly not depth-related but correspond to various environmental variables, for example: Cancris auriculus — coarse substrate; Bolivina subaenariensis — oxygen minimum; Cibicidoides kullenbergi and Hoeglundina elegans — low organic carbon. Uvigerina peregrina is also a notable exception to depth-dependence in that this dominant species and the province it represents are generally confined to the continental slope south of Cape Blanc. Its preference for that region may arise from the high organic carbon and fine grain-size of the sediment there, from low salinity of the bottom water, or from other unknown variables. The most important vertical faunal boundary occurs between Cape Barbas and Cape Blanc (between 22° and 21°N latitude). In contrast, the Canary Island Ridge intersects the continental margin at a saddle depth of about 1500 m, but that physiographic barrier has little effect on provincialism of the deep-water benthic foraminifera.