Foraminiferal Communities Research Articles

Evolution of shallow benthic communities during the Late Paleocene–earliest Eocene transition in the Northern Tethys (SW Slovenia)

A paleoecological and sedimentological study was carried out on shallow-water carbonates of the Kras Plateau (SW Slovenia) with the goal of reconstructing paleoenvironmental conditions and evolution of foraminiferal communities on the northwestern Adriatic Carbonate Platform (AdCP) during the Late Paleocene–earliest Eocene. Three facies have been recognized and summarized in a carbonate ramp model. Within these facies, six foraminiferal assemblages, representing different ramp sub-environments, have been defined: during the Late Paleocene sedimentation took place in a protected innermost ramp with (1) smaller miliolids- and (2) small benthic foraminifera-dominated assemblages thriving on partly vegetated, soft substrates. In the Uppermost Paleocene, sedimentation primarily occurred along a mid ramp. The upper mid-ramp was sporadically influenced by storms/currents and occupied by (3) Assilina-dominated assemblage occurring on a soft sandy substrate. The deeper mid-ramp was characterized by (4) ‘bioconstructors’- and (5) orthophragminids-dominated assemblages, colonizing biotopes with substrates of different nature. During the earliest Eocene, deposition occurred in an inner-ramp setting with (6) alveolinids-nummulitids assemblage thriving on muddy and sandy substrate, partly covered or close to seagrass beds. The Late Paleocene–earliest Eocene environmental conditions, coupled with the long-term evolution of larger benthic foraminifera (LBF), seem to have favored this low-light dependent group as common sediment contributors. By comparing the evolution of the shallow-water biota from the Adriatic area with data from the Pyrenees and Egypt, a general latitudinal trend can be recognized. However, on a smaller geographical scale, local conditions are likely to have played a pivotal role in promoting the evolution of biota characterized by suites of unique features.

DEEP-SEA BENTHIC FORAMINIFERAL RESPIRATION RATES MEASURED UNDER LABORATORY CONDITIONS

Respiration rates of individual specimens of deep-sea benthic foraminifera were measured under laboratory conditions. Respiration rates of nine foraminiferal species—sampled from the deep-sea floor in Sagami Bay, Japan (750 and 1430 m water depth)—were measured at 5°C with a microcathode oxygen electrode in a microchamber. Respiration rates ranged from 0.9–9.9 nmol O 2 d − 1 ind −1 , with no apparent relationship with test size. However, respiration rates varied by species, even from the same microhabitat. The mineralization rate of organic carbon by the total foraminiferal community was estimated using the respiration data of this study. The total foraminiferal community is estimated to respire~46 mg C m −2 to d −1 , suggesting that the group is an important component of the carbon budget in the deep sea. Measurement of individual rates of respiration will help determine the metabolic activity of populations of foraminifera and their contribution to the carbon budget in sediments.

Benthic foraminifera in the Nazaré Canyon, Portuguese continental margin: Sedimentary environments and disturbance

Living (rose Bengal stained) benthic foraminifera were investigated from thirteen stations ranging from 146–4976 m water depth in the Nazaré Canyon, located on the Western Iberian continental margin. The total standing stocks (TSS), species assemblages and in-sediment distributions are compared between stations located on the highly disturbed axis of the upper (< 2700 m) and middle canyon (2700–4000 m), the adjacent low energy terraces and the lower canyon (> 4000 m). In addition, the community changes were investigated in relation to water depth and bio-available, organic carbon. Overall, low total standing stocks of foraminifera were found in the disturbed canyon axis, which experiences frequent sediment resuspension and gravity flows. At the upper canyon axis station at 1118 m a rather exceptional fauna was recovered, dominated by a species of Technitella that made up 75% of the TSS. The highest TSSs were recorded in the upper canyon terrace stations, where fine grained sediment and organic carbon are able to accumulate. Standing stocks on the terraces decreased with increasing water depths. The quiescent terrace stations recorded high abundances of infaunal species, including Melonis barleeanum, Globobulimina spp. and Chilostomella oolina. The occurrence of these species reflects the low pore water oxygen concentrations and high bio-available carbon supply. Several tubular Bathysiphon species were found in the upper canyon terrace stations. Instead, the deepest stations of the lower canyon were dominated by another large agglutinated protozoan, Saccorhiza ramosa. The change in the arborescent/tubular foraminiferal community may reflect the increase in sediment oxygenation with increasing water depth in the canyon, Bathysiphon spp. occurring in sediments with higher bio-available carbon flux and S. ramosa inhabiting more oligotrophic areas.

POPULATION DENSITIES AND DIVERSITIES OF EPIPHYTAL FORAMINIFERA ON NEARSHORE SUBSTRATES, NEVIS, WEST INDIES

Research Article| July 01, 2007 POPULATION DENSITIES AND DIVERSITIES OF EPIPHYTAL FORAMINIFERA ON NEARSHORE SUBSTRATES, NEVIS, WEST INDIES Brent Wilson; Brent Wilson 1 Petroleum Geoscience Unit, Department of Chemical Engineering, The University of the West Indies, St. Augustine, Trinidad, West Indies 1Correspondence author. E-mail: bwilson@eng.uwi.tt Search for other works by this author on: GSW Google Scholar Ann Ramsook Ann Ramsook Petroleum Geoscience Unit, Department of Chemical Engineering, The University of the West Indies, St. Augustine, Trinidad, West Indies 2Present address: Petroleum Company of Trinidad and Tobago Limited, Pointe-a-Pierre, Trinidad, West Indies. Search for other works by this author on: GSW Google Scholar Author and Article Information Brent Wilson 1 Petroleum Geoscience Unit, Department of Chemical Engineering, The University of the West Indies, St. Augustine, Trinidad, West Indies Ann Ramsook 2Present address: Petroleum Company of Trinidad and Tobago Limited, Pointe-a-Pierre, Trinidad, West Indies. Petroleum Geoscience Unit, Department of Chemical Engineering, The University of the West Indies, St. Augustine, Trinidad, West Indies 1Correspondence author. E-mail: bwilson@eng.uwi.tt Publisher: Cushman Foundation for Foraminiferal Research Received: 30 Dec 2005 Accepted: 17 Nov 2006 First Online: 03 Mar 2017 Online ISSN: 1943-264X Print ISSN: 0096-1191 © 2007 Journal of Foraminiferal Research Journal of Foraminiferal Research (2007) 37 (3): 213–222. https://doi.org/10.2113/gsjfr.37.3.213 Article history Received: 30 Dec 2005 Accepted: 17 Nov 2006 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Brent Wilson, Ann Ramsook; POPULATION DENSITIES AND DIVERSITIES OF EPIPHYTAL FORAMINIFERA ON NEARSHORE SUBSTRATES, NEVIS, WEST INDIES. Journal of Foraminiferal Research 2007;; 37 (3): 213–222. doi: https://doi.org/10.2113/gsjfr.37.3.213 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Foraminiferal Research Search Advanced Search Abstract Foraminiferal population densities and diversities were monitored on calcareous algae and seagrass in two Caribbean bays, one of which has been polluted by a leaking septic tank, and samples were collected monthly over a year-long period. Population densities on seagrass blades were measured using the mass of dried leaves. On other substrates, population densities were computed as the number of foraminifera per gram of detritus (diatom frustrules, sand, particulate organic matter) washed from the plants. Densities on the heads (capitulae) of the alga Penicillus capitatus in both bays were three times higher than those on either the alga Halimeda opuntia or on exposed seagrass (Syringodium filiforme, Thalassia testinudum) rhizomes and basal leaf bosses. The input of organic matter into one bay may have impacted the assemblage species composition, but it did not affect population densities. The short life span of P. capitatus, coupled with the more dense populations it supports, implies that assemblages on this alga may contribute proportionally more foraminiferal tests to the sediment than do those on other plants.Population dynamics showed that entire foraminiferal communities on all plants fluctuated independently of one another, whether on different plants in the same bay or on the same plants in different bays. This suggests that nearshore foraminifera are patchily distributed and that the populations in the patches wax and wane independently. Population diversities fluctuated from month to month and were significantly higher in the polluted bay. However, monthly diversities and population densities were not correlated. Species dominance was greater in the windward, unpolluted bay. Differences in dominance within each bay suggest that Penicillus capitatus capitulae support a pioneering foraminiferal community, whereas long-lived seagrass rhizomes bear a climax community. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

An expanded Cretaceous−Tertiary transition in a pelagic setting of the Southern Alps (central-western Tethys)

An integrated micropalaeontological (planktonic foraminifera and calcareous nannofossils), mineralogical and stable isotope investigation was carried out across the Cretaceous/Tertiary (K/T) boundary in a previously undescribed hemipelagic section (Forada section) cropping out in the Piave River Valley (Southern Alps, Belluno Province, NE Italy). Our results suggest that an apparently complete K/T transition with an expanded basal Danian is preserved in the Forada section. The K/T boundary is marked by a ca. 1.5-cm-thick clay interval intercalated in the pelagic carbonates of the Scaglia Rossa Formation. The boundary clay, characterised by an iridium anomaly, is constituted by a basal 1–2 mm-thick “green layer” and an overlying “red layer”. Below the boundary clay, the calcareous nannofossil Micula murus Zone and the planktonic foraminiferal Plummerita hankteninoides Zone, that characterise the terminal Maastrichtian in complete sections, have been identified. Virtually all the calcareous plankton biohorizons normally utilised in the early Danian have been recognised. Interestingly, the ranking of the various biohorizons is the same observed elsewhere if considering the single plankton groups separately, while several inconsistencies emerge if considering the relative succession of the two calcareous plankton groups simultaneously. We caution to infer hiatuses on a section based only on the spacing of the biohorizons of a single group because of the risk of diachroneities in the stressed early Danian environment. By comparing the “distance” of the key biohorizons (i.e. the First Occurrence (FO) of Cruciplacolithus primus and the Last Occurrence (LO) of Parvularugoglobigerina eugubina) from the boundary clay at Forada and in other complete classical sections, we have inferred that the early Danian is expanded in the Forada section. The section seems ideally suited for studying the recovery pattern of the pelagic ecosystem and calcareous plankton communities in the aftermath of the K/T catastrophe in a pelagic setting of the western central Tethys. The adaptive radiation of planktonic foraminifera was very rapid in contrast with the delayed diversification of coccolithophores. The latter show a ca. 21-cm-thick “dead zone” that is followed by a long-lasting survival interval (ca. 180-cm-thick, that might represent some 200 kyr) dominated by persistent Cretaceous coccolithophores and calcareous dinoflagellate Thoracosphaera spp. The temporal pattern in recovery of the coccolithophore and planktonic foraminiferal communities is decoupled as well pointing to their varying sensitivities to the K/T perturbation. It appears that the ecospace occupied by coccolithophores in the terminal Maastrichtian was occupied in the initial Danian by the calcareous dinoflagellates ( Thoracosphaera spp.), that remained a significant component of the assemblage up to the base of the Prinsius dimorphosus Zone of Romein [Romein, A.J.T., 1979. Lineages in Early Paleogene calcareous nannoplankton. Utrecht Micropaleontological Bulletins, 22. 231 pp.], probably in the early Chron C29n. On the contrary, planktonic foraminifera seem to reach stable conditions earlier, in the late Cruciplacolithus primus Zone. The early Danian interval considered is also characterised by low Sr/Ca ratio of the biogenic carbonates that would suggest dramatically low coccolithophore productivity conditions, in agreement with previous flux studies. We speculate that the altered ecological structure of phytoplankton community and the low productivity of coccolithophores severely affected the efficiency of the transfer of organic carbon from the photic zone to the deep ocean, thus supporting the early Danian “living ocean” model of D'Hondt et al. [D'Hondt, S., Donaghay, P., Zachos, J.C., Luttenberg, D., Lindinger, M., 1998. Organic carbon fluxes and ecological recovery from the Cretaceous–Tertiary mass extinction. Science 282, 276–279].

Community structure of benthic foraminifera in the Gulf of Mexico

The classic papers of Phleger [Phleger, F.B, 1951. Foraminifera Distribution, Part I. Geological Society of America Memoir 46, 1–88.] and Parker [Parker, F.L., 1954. Distribtuion of the foraminifera in the Northeastern Gulf of Mexico. Bulletin of the Museum of Comparative Zoology 111, 453–588, 13 plates.] form the benchmark foraminiferal data sets for the northwestern and northeastern Gulf of Mexico, respectively. These pioneer researchers occupied stations from shelf to abyssal depths. SHE analysis, a method examining the distribution of cumulative sample values of species richness ( S), the information function ( H) and evenness ( E) with increasing number of individuals ( N), was used to establish 18 foraminiferal communities and evaluate their community structure. Regression analyses, as well as plots of ln S, H and ln E versus ln N (Biodiversitygrams, BDGs), indicate that the majority of the communities exhibit a log series pattern. Theoretical log series values of S, H and E are similar to the regression estimates from observed values in the northeastern Gulf. In the northwestern Gulf, however, observed values of species richness are lower and evenness higher than those expected for a log series, indicating a dramatic difference in community structure between east and west. Since the sampling time of Phleger, subsequent workers have found higher values of species richness and lower values of evenness in the northwestern Gulf. Either biodiversity values have changed since Phleger's 1947 (1951) sampling suggesting a fundamental change in the environmental regime of the northwestern Gulf of Mexico or, as has been suggested, Phleger's data are incorrect due to some sampling methodology. A comprehensive study with suitable experimental design including downcore samples will be required to resolve this dichotomy.

Biodiversity and community structure of deep-sea foraminifera around New Zealand

The biodiversity and community structure of benthic foraminifera were estimated from 217 stations distributed in four geographic regions (north, south, east, west) around New Zealand. An analytical method accumulating sample values of species richness ( S ) , the information function ( H ) and evenness ( E ) with increasing number of individuals ( N ) called SHE analysis was used to establish 16 foraminiferal communities and their community structure at shelf (0–200 m), bathyal (200–2000 m) and abyssal ( > 2000 m ) depths. A decrease in S, H and E occurs from north to south and this latitudinal gradient extends to abyssal depths. An increase in S and H with depth occurs in the northern and southern areas. For ln S , H and ln E against ln N , regression lines on values obtained from SHE analysis at shelf, bathyal and abyssal depths all diverge in the southern area. Each of the other areas exhibits crossing of regression lines so that establishing the rank order of S, H or E with depth within an area requires consideration of N. For a log series pattern, H is a constant proportional to α , the parameter of the log series, and, based on the decomposition equation ln S = H + ln E , a regression of ln S against ln E yields a regression coefficient of - 1 and an intercept of H. At depths of less than 1000 m, 2 of 8 communities have regression coefficient confidence intervals that include - 1 . At depths of greater than 1000 m, 7 of 8 communities intervals include - 1 . Thus, overall, the majority of cases, but especially those at depths greater than 1000 m, have a log series pattern.

COMMUNITY STRUCTURE OF FORAMINIFERAL COMMUNITIES WITHIN TEMPORAL BIOZONES FROM THE WESTERN ARCTIC OCEAN

Community structure is often an overlooked dimension of biodiversity. Knowledge of community structure, the statistical distribution of the relative species abundance vector, makes possible comparisons and contrasts across time, space and/or environmental conditions. Our results indicate that species of Arctic foraminifera in age-correlated cores from abyssal depths are each best described by log-series distributions. Using this structural information, we were able to determine that structural stability exists for at least 50 ka. The foraminiferal communities in this study show remarkable concordance, distributional similarity and support the neutral theory of biodiversity.

Guilds among epiphytal foraminifera on fibrous substrates, Nevis, West Indies

The nearshore foraminifera of the oligotrophic Caribbean region are predominantly epiphytal, living on calcareous algae and seagrasses. However, their community ecology (interactions between and associations among species) is little understood. Cluster analysis is used here to identify guilds among the epiphytal foraminifera, a guild being a group of species that forms an arena of intense competition within which species' niches overlap considerably in habitat, time and food. Samples were collected monthly between September 1994 and August 1995 from (a) calcareous algae and (b) seagrass rhizomes and leaf bosses from two bays around Nevis, northern Lesser Antilles. One bay was impacted by organic enrichment from a leaking septic tank. Data from both bays were combined to form a metapopulation, analysis of which was conducted using common species (i.e., those that formed > 1% of the recovery from any substrate in either bay). Q-mode cluster analysis using populations on all substrates of common species clearly separated the two bays, despite sampling of the same substrate in both, indicating that the bays occupy different biofacies. However, Q-mode analysis did not separate the different substrates in the individual bays. R-mode cluster analysis of the two-bay metapopulation based on common species revealed three clusters that are interpreted as guilds: Guild I A higher-energy guild intolerant of nutrient enrichment. Guild II A guild of rapidly-reproducing opportunists on short-lived substrates. Guild III A lower-energy guild tolerant of nutrient enrichment. These guilds are not limited to any one bay, but vary in proportion between the two, Guild I being most prolific in the virtually pristine back-reef bay on the windward side of the island, and Guilds II and III forming a greater proportion of the epiphytal foraminiferal fauna in the bay impacted by lower-energy waves and a flux of organic matter. Guild II shows a preference for the bushy capitulae of the alga Penicillus capitatus. In cross-correlation of 12-month time-series for the three guilds, the virtually pristine bay showed that they bloomed sequentially, at intervals of 4 months. The recognition of guilds clears the way for improved understanding of the foraminiferal community ecology of nearshore areas. Nearshore sediments in the Caribbean yield primarily foraminifera washed from phytal substrates. The palaeoecology of these assemblages can now be interpreted with greater confidence.

Response of epiphytic foraminiferal communities to natural eutrophication in seagrass habitats off Man O'War Cay, Belize

AbstractEutrophication from a variety of anthropogenic sources is an increasingly prevalent problem in coastal waters, and is one of the factors contributing to the decline of seagrass ecosystems worldwide. This study investigated the impact of natural nutrient enrichment derived from nesting seabird colonies on Man O'War Cay, Belize, on the epiphytic foraminiferal communities living on the seagrass Thalasssia testudinum. Man O'War Cay, a small mangrove island in the central region of the barrier reef complex, hosts nesting colonies of magnificent frigate birds and brown boobies. Epiphytic foraminiferans were surveyed from five stations spaced at 10‐m intervals along a 40‐m transect in a seagrass meadow located off the eastern end of the island (March 2004). Low species diversity and high dominance of the encrusting, dendritic species Cornuspiramia antillarum characterized the epiphytic foraminiferal biota. Species diversity, as measured by the Shannon's H, and evenness, as measured by Buzas–Gibson's E, decreased in an offshore direction. The density of individuals per square centimeter of blade, however, increased in an offshore direction, with the lowest values observed at the station closest to the island, and the highest values recorded at the station farthest from the shore. The results obtained in this study indicate that epiphytic foraminiferal populations respond to nutrient enrichment, and thus may be useful indicators of ecosystem decline in subtropical–tropical, oligotrophic marine habitats.

Trouble in Paradise? A comparison of 1953 and 2005 benthonic foraminiferal seafloor assemblages at the Ibis Field, offshore eastern Trinidad, West Indies

Abstract. Foraminiferal communities are not static, but change in response to environmental perturbations. Given sufficient time, the change will be recorded in the total (live+dead) seafloor assemblage, from which valuable information regarding environmental trends can be obtained by re-sampling assemblages at the decadal scale.The seafloor assemblage in the 5 km × 6 km Ibis Field, off southeast Trinidad, first surveyed in 1953, was re-examined in 2005. The fauna had changed markedly between the surveys. Overall increases in the proportional abundances of Uvigerina subperegrina, Ammonia pauciloculata/Rolhausenia rolhauseni and Pseudononion atlanticum indicate an increase in nutrient supply that apparently killed off Cibicidoides pseudoungerianus and Miliolinella subrotunda, and reduced the relative abundance of Hanzawaia concentrica, but did not affect the relative abundance of Cancris sagrai. As shown by similar 1953 and 2005 planktonic/benthonic foraminiferal ratios, the increased nutrient supply impacted on both surface and bottom waters.Of the six most abundant species in 2005, five showed the same general biogeographical distributions within the field in 1953 and 2005. However, whereas the proportional abundance of Uvigerina subperegrina in 1953 increased southwards, in 2005 it increased northwards.Trinidad cannot be the source for the nutrient enrichment: the island lies down-current from the Ibis Field. Sources must therefore be sought up-current and to the southeast, in the Amazon, Essequibo and Orinoco river basins, or along the South American shoreline. It is speculated that the nutrient enrichment may be a consequence of increased phytoplankton primary production associated with nitrogen-rich run-off from South American sugarcane plantations, or from flushing of organic carbon from poorly regulated sewage systems or shrimp farms in South America.

Dynamics of planktonic foraminiferal community in the Sea of Japan during the last 2 My

Based on the analysis of the foraminiferal assemblages in 118 sediment samples from the 210-m-long core of ODP Hole 798 drilled near Honshu Island, it is shown that the structure of their tanathocoenoses experienced three large reorganizations during the last 1.9 My, namely 0.68, 1.21, and 1.36 My B.P. The first reorganization coincides with the Matuyama-Brunhes boundary marked by the magnetic polarity reversal. The second reorganization corresponds to the sharp and progressive temperature fall caused by general climate deterioration. The third event is poorly interpretable thus far. Using the K-average method, the assemblages were differentiated into two types differing in their taxonomic structures. The replacement of one type of community with another occurred simultaneously with the cooling onset 1.21 My B.P. Spectral analysis of the variations in the integral characteristics of the taxonomic structure revealed three groups of cycles with average periods of 136, 59, and 33 ky. These estimates are one-third higher as compared to the duration of the Milankovitch climatic cycles. The species structure of the foraminiferal community is shown to be well consistent with the rank model of geometric series.

Live (Rose Bengal stained) and dead benthic foraminifera from the oxygen minimum zone of the Pakistan continental margin (Arabian Sea)

Live (Rose Bengal stained) and dead benthic foraminiferal communities (hard-shelled species only) from the Pakistan continental margin oxygen minimum zone (OMZ) have been studied in order to determine the relation between faunal composition and the oxygenation of bottom waters. Samples were taken from 136 m to 1870 m water depth during the intermonsoon season of 2003 (March–April). Live foraminiferal densities show a clear maximum in the first half centimetre of the sediment only few specimens are found down to 4 cm depth. The faunas exhibit a clear zonation across the Pakistan margin OMZ. Down to 500 m water depth, Uvigerina ex gr. U. semiornata and Bolivina aff. B. dilatata dominate the assemblages. These taxa are largely restricted to the upper cm of the sediment. They are adapted to the very low bottom-water oxygen values (≈ 0.1 ml/l in the OMZ core) and the extremely high input of organic carbon on the upper continental slope. The lower part of the OMZ is characterised by cosmopolitan faunas, containing also some taxa that in other areas have been described in deep infaunal microhabitats. The contrast between faunas typical for the upper part of the OMZ, and cosmopolitan faunas in the lower part of the OMZ, may be explained by a difference in the stability of dysoxic conditions over geological time periods. The core of the OMZ has been characterised by prolonged periods of stable, strongly dysoxic conditions. The lower part of the OMZ, on the contrary, has been much more variable over time-scales of 1000s and 10,000 years because of changes in surface productivity and a fluctuating intensity of NADW circulation. We suggest that, as a consequence, well-adapted, shallow infaunal taxa occupy the upper part of the OMZ, whereas in the lower part of the OMZ, cosmopolitan deep infaunal taxa have repeatedly colonised these more intermittent low oxygen environments.

NOVEL APPLICATION OF MTT REDUCTION: A VIABILITY ASSAY FOR TEMPERATE SHALLOW-WATER BENTHIC FORAMINIFERA

Research Article| July 01, 2006 NOVEL APPLICATION OF MTT REDUCTION: A VIABILITY ASSAY FOR TEMPERATE SHALLOW-WATER BENTHIC FORAMINIFERA L. J. de Nooijer; L. J. de Nooijer 1Department of Stratigraphy and Paleontology, Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands. Email: nooijer@geo.uu.nl Search for other works by this author on: GSW Google Scholar I. A. P. Duijnstee; I. A. P. Duijnstee 1Department of Stratigraphy and Paleontology, Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands. Email: nooijer@geo.uu.nl2Department of Biogeology, Faculty of Sciences, Radboud University, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands. Search for other works by this author on: GSW Google Scholar G. J. van der Zwaan G. J. van der Zwaan 1Department of Stratigraphy and Paleontology, Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands. Email: nooijer@geo.uu.nl2Department of Biogeology, Faculty of Sciences, Radboud University, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands. Search for other works by this author on: GSW Google Scholar Journal of Foraminiferal Research (2006) 36 (3): 195–200. https://doi.org/10.2113/gsjfr.36.3.195 Article history received: 18 Mar 2005 accepted: 19 Mar 2006 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation L. J. de Nooijer, I. A. P. Duijnstee, G. J. van der Zwaan; NOVEL APPLICATION OF MTT REDUCTION: A VIABILITY ASSAY FOR TEMPERATE SHALLOW-WATER BENTHIC FORAMINIFERA. Journal of Foraminiferal Research 2006;; 36 (3): 195–200. doi: https://doi.org/10.2113/gsjfr.36.3.195 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Foraminiferal Research Search Advanced Search Abstract Studies on living benthic foraminifera commonly involve staining samples with rose Bengal (RB) to distinguish living from dead individuals. Since RB also stains individuals that have died recently (sometimes weeks earlier) and are not fully decayed, standing stocks of foraminiferal communities are usually overestimated. To overcome this bias, we discuss a new viability assay based on the reduction of a tetrazolium salt, MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide or thiazolyl blue) by living foraminifera. The tetrazolium salt MTT is actively ingested by cells and subsequently converted enzymatically from a yellow, soluble form to a reddish purple crystal. Experiments confirm that living individuals of Ammonia beccarii and Globobulimina turgida convert MTT and become stained within 24 hours. Some dead foraminifers may continue enzymatic activity for several days, but produce a different coloration than that of stained living foraminifers. With the reduced problem of false positives, this assay is an improvement over staining samples with RB whenever a higher accuracy is required (e.g., in short-term laboratory experiments). You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Environmental perturbation in the southern Tethys across the Paleocene/Eocene boundary (Dababiya, Egypt): Foraminiferal and clay mineral records

Foraminiferal and clay mineral records were studied in the upper Paleocene to lower Eocene Dababiya section (Egypt). This section hosts the GSSP for the Paleocene/Eocene boundary and as such provides an expanded and relatively continuous record across the Paleocene/Eocene Thermal Maximum (PETM). Deposition of illite–smectite clay minerals is interpreted as a result of warm and arid conditions in the southern Tethys during the latest Paleocene. Benthic foraminiferal assemblages are indicative of seasonal variation of oxygen and food levels at the seafloor. A sea-level fall occurred in the latest Paleocene, followed by a rise in the earliest Eocene. Foraminiferal diversity and densities decreased strongly at the P/E boundary, coinciding with the level of global extinction of benthic foraminifera (BEE) and start of the Carbon Isotope Excursion (CIE) and PETM. In the lower CIE, the seafloor of the stratified basin remained (nearly) permanently anoxic and azoic. A sudden increase in mixed clay minerals (kaolinite and others) suggests that warm and perennial humid conditions prevailed on the continent. High levels of TOC and phosphathic concretions in the middle CIE are evidence for increased organic fluxes to the sea floor, related to upwelling and to augmented continental runoff. Low densities of opportunistic taxa appeared, indicating occasional ephemeral oxygenation and repopulation of the benthic environment. The planktic community diversified, although conditions remained poor for deep-dwelling taxa. An increase in illite–smectite dominated clay association is considered to mark the return of a seasonal signature on climatic conditions. During the late CIE environmental conditions changed to seasonally fluctuating mesotrophic conditions and diverse and rich benthic and planktic foraminiferal communities developed. Post-CIE planktic faunas consisted of both deep and shallow-dwelling taxa and buliminid-dominated benthic assemblages reflect fluctuating mesotrophic conditions. The frequent environmental perturbations during the CIE/PETM at Dababiya provided a rather specialized group of foraminiferal taxa (i.e., Anomalinoides aegyptiacus) the opportunity to repopulate, survive and subsequently dominate by a hypothesized capacity to switch to an alternative life strategy (population dynamics, habitat shift) or different metabolic pathway. The faunal record of Dababiya provides insight into the cause and development of the BEE: various severe global changes during the PETM (e.g., ocean circulation, CaCO 3-dissolution, productivity and temperature changes) disturbed a wide range of environments on a geologically brief timescale, explaining together the geographically and temporally variable character of the BEE. This allowed a number of specific but different foraminiferal assemblages composed of stress-tolerant and opportunistic taxa to be successful during and after the periods of environmental perturbations associated with the PETM.

Planktic Foraminiferal Content in a Mature Agulhas Eddy from the SE Atlantic: Any Influence on Foraminiferal Export Fluxes?

The Agulhas eddies, large-scale rings of warm salty water, occasionallyintrude into the Benguela Current system from the Indian Ocean and progress northwards across the Cape Basin and the Walvis Ridge. This inter-ocean exchange of heat and salt along the Cape of Good Hope is considered to play a crucial role for the global thermohaline circulation. Yet, the modern faunal composition of mature eddies from the northern Cape Basin and Walvis Ridge was uninvestigated in spite of the global importance of the Agulhas inflow, preventing firm micropalaeontological study of the palaeoceanographic variability of the ocean exchange in this area.This paper describes the composition of the modern planktic foraminiferal assemblages collected from a mature Agulhas eddy when it entered into the northern Benguela Current system. The effect of the eddy’s gradual decay on the foraminiferal communities in the upper water column is specifically examined, using plankton tow and CTD-rosette profiles, obtained within and outside the ring. In addition,exported foraminiferal fluxes beneath the eddy were investigated in order to determine their impact on the accumulation assemblages as recorded in sediment traps moored near the sea floor and in the core-top sediment from a box corer.The examined mature eddy “W” was clearly evident on the satellitealtimetry images by its elevated surface. It was distinguished from the surrounding ocean by a slightly higher salinity, deeper surface mixed layer and higher planktic foraminiferal standing stocks. Similarto planktic foraminiferal fauna in freshly formed eddies from the Agulhas retroflection, species such as Globigerinoides trilobus s.l., Globigerinoides ruber, Orbulina universa, Globigerinella siphoni-fera and Globorotalia scitula dominated in the ring “W” assemblages. However, Globorotalia menardii, a species previously believed to be characteristic for the Agulhas leakage into the S. Atlantic, was virtuallyabsent in the eddy “W” fauna. Also Globorotaloides hexagona, a species endemic in Indian Ocean waters, was not found in the water column, in the export flux or underlying sediment. The February to July foraminiferal flux patterns recorded by the sediment traps mirror the February standing stocks from the water column. Here in contrast, the core-top results show dominance of intermediate/cold water speciesthat originate from the seasonal spring bloom. This signal prevailsin sediment to the extent that any potential Agulhas eddy signaturein the sediment was overprinted.

A 3-stage pollution identification system with an example of final stage decimation

Abstract

Foraminiferal response to the Northeast Monsoon in the western and southern Arabian Sea

Sediments from the western and southern part of the Arabian Sea were collected periodically in the spring intermonsoon between March and May 1997 and additionally at the end of the Northeast Monsoon in February 1998. Assemblages of Rose Bengal stained, living deep-sea benthic foraminifera, their densities, vertical distribution pattern, and diversity were analysed after the Northeast Monsoon and short-time changes were recorded. In the western Arabian Sea, foraminiferal numbers increased steadily between March and the beginning of May, especially in the smaller size classes (30–63 μm, 63–125 μm). At the same time, the deepening of the foraminiferal living horizon, variable diversity and rapid variations between dominant foraminiferal communities were observed. We interpret these observations as the time-dependent response of benthic foraminifera to enhanced organic carbon fluxes during and after the Northeast Monsoon. In the southern Arabian Sea, constant low foraminiferal abundances during time, no distinctive change in the vertical distribution, reduced diversity, and more stable foraminiferal communities were noticed, which indicates no or little influence of the Northeast Monsoon to benthic foraminifera in this region.

Facies Variability of Recent Sediments in the Hornsunn Fjord, Western Spitsbergen

The study of bottom sediments and suspended matter (SM) in the Hornsunn Fjord of western Spitsbergen reveals that SM is largely deposited in its central part. The model of recent sedimentation in the fjord is proposed based on the analysis of grain-size distribution, petrographic-mineralogical composition, physical properties of recent sediments, and benthic foraminiferal communities therein.

Benthic foraminiferal evidence for the formation of the Holocene mud-belt and bathymetrical evolution in the central Adriatic Sea

Detailed analyses of modern and fossil benthic foraminiferal assemblages collected in the central Adriatic Sea are used as tools to reconstruct the environmental changes that occurred between the Last Deglaciation and the Present (last 14 Kyrs); in particular we focus on the timing and formation of the mud-belt. The modern benthic foraminiferal assemblages display a parallel zonation to the Italian coast controlled by the interaction between food/oxygen availability and water depth. Cluster analysis of 4 sediment cores separates the fossil foraminiferal assemblages in 6 groups: Cluster A is dominated by three Ammonia species; Cluster B consists of Ammonia papillosa, Nonionella turgida, Elphidium advenum and Elphidium decipiens; Cluster C is composed of two taxa, Hyalinea balthica and Trifarina angulosa; Cluster D is dominated by 5 species, Cibicides lobatulus, Buccella granulata, Reussella spinulosa, Textularia agglutinans and Elphidium crispum; Cluster E contains Bulimina spp., Gavelinopsis praegeri, Bolivina spp., Cassidulina neocarinata and Asterigerinata mamilla; and Cluster F is dominated by Bulimina marginata, Valvulineria bradyana, Globocassidulina subglobosa and Melonis padanum. The cluster analysis and contemporary distribution patterns of these taxa are used together with ecological preferences of the most frequent species to reconstruct the spatial and temporal distribution of the different biofacies in the past. This reveals information about Holocene palaeoenvironmental changes that are related to water depth fluctuations and the installment of the coast-parallel mud-belt. The benthic assemblage records the transition from a infralitoral environment (Biofacies I) to deeper marine condition (Biofacies III). After that the sea level reached about the modern level (Biofacies IV) the benthic foraminiferal community evidences the development of the mud-belt and the subsequent transformation of the ecological niches linked to the trophic evolution of the environment.