Calcareous Species Research Articles

Changes in distribution of calcareous benthic foraminifera in the central Barents Sea between the periods 1965–1992 and 2005–2006

Live benthic foraminifera assemblages from 30 surface sediment samples taken in 2005 and 2006 from the central Barents Sea are compared with total benthic foraminifera assemblages from a database containing samples taken between 1965 and 1992. We evaluate the hypothesis that observed environmental changes in the region have led to observable shifts in benthic foraminiferal fauna. Of the 12 infaunal calcareous species studied marked decreases were observed in cold water species Buccella spp., Elphidium excavatum, Islandiella norcrossi and Nonionellina labradorica. A decline combined with a marked change in spatial distribution is seen in Cassidulina laevigata, Trifarina fluens, Stainforthia loeblichi, Cassidulina reniforme, Cassidulina neoteretis, Melonis barleeanus, and Pullenia bulloides. Warm water species Epistominella nipponica is the only species of these 12 that increased in abundance. The general shift toward dominance of warm water species and temperature tolerant species agrees well with the observed temperature increase in the basin. At the level of individual data points, a relationship between assemblage change and environmental change is not straightforward. The comparison of the new data with the database also displays a shift toward higher abundances of more fragile species, which can be attributed to method differences. The species that display the most pronounced change are those associated with cold water and proximity of the ice edge.The magnitude of benthic foraminiferal change in the study area is largest in a conspicuous belt that appears to follow roughly the Polar Front. This area has a lower temperature and salinity gradient through the last decades than the rest of the study area, and its high faunal change may be due to the position of the Polar Front moving away from this area, and associated changes in the sea ice edge.

Calcareous nannofossils biostratigraphy of the Late Campanian–Early Maastrichtian Age, Block 16, Jiza’-Qamar Basin, Eastern Yemen

One hundred and thirty nine samples have been studied from the Late Campanian–Early Maastrichtian of three deep wells drilled in Jiza’-Qamar Basin, Eastern Yemen to determine the calcareous nannofossil zones and the age of the sediments. Forty-seven calcareous nannofossil species were identified and four biozones were determined in the present study (CC21–CC24). These biozones are assigned to the Late Campanian–Early Maastrichtian ages. Most of the studied species in this work refer to tropical–subtropical environment. The Campanian–Maastrichtian Boundary was determined in Al-Fatk well based on the last occurrence of Eiffelithus eximus and the last occurrences of Uniplanarius sissinghii and Uniplanarius trifidus.

Identifying active foraminifera in the Sea of Japan using metatranscriptomic approach

Metagenetics represents an efficient and rapid tool to describe environmental diversity patterns of microbial eukaryotes based on ribosomal DNA sequences. However, the results of metagenetic studies are often biased by the presence of extracellular DNA molecules that are persistent in the environment, especially in deep-sea sediment. As an alternative, short-lived RNA molecules constitute a good proxy for the detection of active species. Here, we used a metatranscriptomic approach based on RNA-derived (cDNA) sequences to study the diversity of the deep-sea benthic foraminifera and compared it to the metagenetic approach. We analyzed 257 ribosomal DNA and cDNA sequences obtained from seven sediments samples collected in the Sea of Japan at depths ranging from 486 to 3665m. The DNA and RNA-based approaches gave a similar view of the taxonomic composition of foraminiferal assemblage, but differed in some important points. First, the cDNA dataset was dominated by sequences of rotaliids and robertiniids, suggesting that these calcareous species, some of which have been observed in Rose Bengal stained samples, are the most active component of foraminiferal community. Second, the richness of monothalamous (single-chambered) foraminifera was particularly high in DNA extracts from the deepest samples, confirming that this group of foraminifera is abundant but not necessarily very active in the deep-sea sediments. Finally, the high divergence of undetermined sequences in cDNA dataset indicate the limits of our database and lack of knowledge about some active but possibly rare species. Our study demonstrates the capability of the metatranscriptomic approach to detect active foraminiferal species and prompt its use in future high-throughput sequencing-based environmental surveys.

SHORT-TERM MONITORING OF HALIFAX HARBOUR (NOVA SCOTIA, CANADA) POLLUTION REMEDIATION USING BENTHONIC FORAMINIFERA AS PROXIES

Research Article| July 01, 2012 SHORT-TERM MONITORING OF HALIFAX HARBOUR (NOVA SCOTIA, CANADA) POLLUTION REMEDIATION USING BENTHONIC FORAMINIFERA AS PROXIES Saad A. Dabbous; Saad A. Dabbous * Department of Earth Sciences and Centre for Environmental and Marine Geology, Dalhousie University, Halifax, Nova Scotia, B3H3J5 Canada *Correspondence author. E-mail: saaddabbous@dal.ca Search for other works by this author on: GSW Google Scholar David B. Scott David B. Scott Department of Earth Sciences and Centre for Environmental and Marine Geology, Dalhousie University, Halifax, Nova Scotia, B3H3J5 Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Saad A. Dabbous * Department of Earth Sciences and Centre for Environmental and Marine Geology, Dalhousie University, Halifax, Nova Scotia, B3H3J5 Canada David B. Scott Department of Earth Sciences and Centre for Environmental and Marine Geology, Dalhousie University, Halifax, Nova Scotia, B3H3J5 Canada *Correspondence author. E-mail: saaddabbous@dal.ca Publisher: Cushman Foundation for Foraminiferal Research Received: 06 Oct 2010 Accepted: 24 Apr 2012 First Online: 03 Mar 2017 Online ISSN: 1943-264X Print ISSN: 0096-1191 © 2012 Cushman Foundation for Foraminiferal Research Journal of Foraminiferal Research (2012) 42 (3): 187–205. https://doi.org/10.2113/gsjfr.42.3.187 Article history Received: 06 Oct 2010 Accepted: 24 Apr 2012 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 Saad A. Dabbous, David B. Scott; SHORT-TERM MONITORING OF HALIFAX HARBOUR (NOVA SCOTIA, CANADA) POLLUTION REMEDIATION USING BENTHONIC FORAMINIFERA AS PROXIES. Journal of Foraminiferal Research 2012;; 42 (3): 187–205. doi: https://doi.org/10.2113/gsjfr.42.3.187 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 Short-term monitoring of benthonic foraminifera in Halifax Harbour conducted before, during, and after implementation of an enhanced, municipal pollution-abatement program showed that foraminiferal distribution correlated strongly with the amount of pollution flowing into the harbor. Before enhanced treatment the confined, highly polluted inner harbor and North West Arm contained a fauna of low abundance and diversity, dominated by non-calcareous species with a high percentage of shell deformities and organic inner linings. In contrast the foraminiferal assemblage in the outer harbor, where currents carry away waste material to the ocean, had high diversity and abundance, few shell deformities and organic inner linings, and contained calcareous species. During treatment the composition of the inner harbor assemblage changed dramatically to resemble that of the outer harbor fauna, only to revert to its former characteristics after treatment stopped. This study once again shows that benthonic foraminifera are accurate, quick, and cost effective proxies to monitor continuous environmental changes in polluted environments. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

LIVE BENTHIC FORAMINIFERAL FAUNAS ALONG A BATHYMETRICAL TRANSECT (282-4987 M) ON THE PORTUGUESE MARGIN (NE ATLANTIC)

Live benthic foraminifera were studied in eight cores collected along a depth transect ranging 282-4987 m on the Portuguese margin. Total standing stocks (TSS) and species assemblages from both 63-150- and >150-mu m fractions are compared between stations along the transect and with previous live foraminiferal studies from the Bay of Biscay and western Iberian margin. Based on the sedimentary organic matter contents and ecological traits of the retrieved foraminifera, three groups of stations are distinguished: (1) eutrophic upper-slope stations (282-1002 m) with faunas dominated by Uvigerina mediterranea, U. elongatastriata, Melonis barleeanus, Bigenerina nodosaria, Trifarina bradyi, Epistominella vitrea, Cribrostomoides bradyi, and Bolivina robusta, (2) mesotrophic middle- to lower-slope stations (1374-2475 m) with faunas dominated by Uvigerina peregrina, Globobulimina affinis, and Repmanina charoides, and (3) oligotrophic lower-slope and abyssal-plain stations (2908-4987 m) with faunas in the larger size fraction dominated by Cibicides kullenbergi and agglutinated species such as Reophax fusiformis and Recurvoides sp. 1. The smaller size fraction is dominated by opportunistic calcareous species such as Bulimina translucens, Epistominella exigua, and Nuttallides pusillus, along with Reophax fusiformis, but most of these species are diminished at 4987 m, where Reophax fusiformis, Pullenia salisburyi, and various monothalamous agglutinates are dominant. This succession of assemblages probably reflects the increasing scarcity of trophic resources with water depth. This hypothesis is corroborated by 1) the clear decrease of TSS with increasing water depth, and 2) the decreasing sediment phytopigment concentrations towards deeper sites. Moreover, the decreasing percentage of perforate calcareous foraminifera, and increasing percentage of agglutinated foraminifera with water depth, suggests that, in general, perforate calcareous species have higher trophic requirements than agglutinated ones.

Calcareous Nannofossils from the Paleogene Deposits of the Northern Forecaucasus (Russia) and South-Eastern Part of Great Donbas (Ukraine)

This article includes the results of the electron microscope study and the first taxonomic description of 13 calcareous nannofossil species from the Paleocene-Eocene sediments from the borehole material of Northern Precaucasus (Russia) and the south-eastern part of the Great Donbas (Ukraine). The described species belong to the genus of Helicosphaera, Chiasmolithus and Nannotetrina.

The “White Ocean” Hypothesis: A Late Pleistocene Southern Ocean Governed by Coccolithophores and Driven by Phosphorus

Paleoproductivity is a critical component in past ocean biogeochemistry, but accurate reconstructions of productivity are often hindered by limited integration of proxies. Here, we integrate geochemical (phosphorus) and micropaleontological proxies at millennial timescales, revealing that the coccolithophore record in the Subantarctic zone of the South Atlantic Ocean is driven largely by variations in marine phosphorus availability. A quantitative micropaleontological and geochemical analysis carried out in sediments retrieved from Ocean Drilling Program Site 1089 (Subantarctic Zone) reveals that most of the export productivity in this region over the last 0.5 my was due to coccolithophores. Glacial periods were generally intervals of high productivity, with productivity reaching a peak at terminations. Particularly high productivity was observed at Termination V and Termination IV, events that are characterized by high abundance of coccolithophores and maxima in the phosphorus/titanium and strontium/titanium records. We link the increase in productivity both to regional oceanographic phenomena, i.e., the northward displacement of the upwelling cell of the Antarctic divergence when the ice-sheet expanded, and to the increase in the inventory of phosphorus in the ocean due to enhanced transfer of this nutrient from continental margins during glacial lowstands in sea level. The Mid-Brunhes interval stands out from the rest of the record, being dominated by the small and highly calcified species Gephyrocapsa caribbeanica that provides most of the carbonate in these sediments. This likely represents higher availability of phosphorus in the surface ocean, especially in mesotrophic and oligotrophic zones. Under these condition, some coccolithophore species developed an r-strategy (opportunistic species; growth rate maximized) resulting in the bloom of G. caribbeanica. These seasonal blooms of may have induced “white tides” similar to those observed today in Emiliania huxleyi.

Repeated bottom-water oxygenation during OAE 2: timing and duration of short-lived benthic foraminiferal repopulation events (Wunstorf, northern Germany)

Abstract. Published proxy data for Oceanic Anoxic Event 2 (OAE 2 or Cenomanian–Turonian Boundary Event) and other mid-Cretaceous OAEs indicate widespread anoxic bottom-water conditions. However, increasing evidence shows that anoxia was not permanent but subject to significant fluctuations. We have generated X-ray fluorescence elemental concentration and benthic foraminiferal assemblage records for a short section of OAE 2 black shales from Wunstorf, northern Germany. Two intervals of low sulphur elemental concentration are interpreted as periods of increased oxygenation of bottom waters. This is supported by benthic foraminiferal assemblage data showing repopulation events associated with these intervals. These repopulation events are characterized mainly by the occurrence of agglutinated taxa, with Lingulogavelinella globosa being the only abundant calcareous species. This observation is interpreted in terms of short-term interruptions of the otherwise anoxic bottom-water environment. Comparison with repopulation events during OAE 1b and Quaternary sapropels make it reasonable to speculate that short-term cooling and an associated increase in bottom-water ventilation at the NW European shelf sea are the main trigger mechanisms for the observed repopulation events at Wunstorf. As source area for benthic foraminifera, shallower parts of the Lower Saxony basin are proposed.

Sensitivity of coccolithophores to carbonate chemistry and ocean acidification

About one-third of the carbon dioxide (CO(2)) released into the atmosphere as a result of human activity has been absorbed by the oceans, where it partitions into the constituent ions of carbonic acid. This leads to ocean acidification, one of the major threats to marine ecosystems and particularly to calcifying organisms such as corals, foraminifera and coccolithophores. Coccolithophores are abundant phytoplankton that are responsible for a large part of modern oceanic carbonate production. Culture experiments investigating the physiological response of coccolithophore calcification to increased CO(2) have yielded contradictory results between and even within species. Here we quantified the calcite mass of dominant coccolithophores in the present ocean and over the past forty thousand years, and found a marked pattern of decreasing calcification with increasing partial pressure of CO(2) and concomitant decreasing concentrations of CO(3)(2-). Our analyses revealed that differentially calcified species and morphotypes are distributed in the ocean according to carbonate chemistry. A substantial impact on the marine carbon cycle might be expected upon extrapolation of this correlation to predicted ocean acidification in the future. However, our discovery of a heavily calcified Emiliania huxleyi morphotype in modern waters with low pH highlights the complexity of assemblage-level responses to environmental forcing factors.

Effects of ocean acidification on macroalgal communities

There are high levels of uncertainty about how coastal ecosystems will be affected by rapid ocean acidification caused by anthropogenic CO 2, due to a lack of data. The few experiments to date have been short-term (< 1 year) and reveal mixed responses depending on the species examined and the culture conditions used. It is difficult to carry out long-term manipulations of CO 2 levels, therefore areas with naturally high CO 2 levels are being used to help understand which species, habitats and processes are resilient to the effects of ocean acidification, and which are adversely affected. Here we describe the effects of increasing CO 2 levels on macroalgal communities along a pH gradient caused by volcanic vents. Macroalgal habitat differed at taxonomic and morphological group levels along a pH gradient. The vast majority of the 101 macroalgal species studied were able to grow with only a 5% decrease in species richness as the mean pH fell from 8.1 to 7.8. However, this small fall in species richness was associated with shifts in community structure as the cover of turf algae decreased disproportionately. Calcitic species were significantly reduced in cover and species richness whereas a few non-calcified species became dominant. At mean pH 6.7, where carbonate saturation levels were < 1, calcareous species were absent and there was a 72% fall in species richness. Under these extremely high CO 2 conditions a few species dominated the simplified macroalgal assemblage and a very few exhibited enhanced reproduction, although high CO 2 levels seemed to inhibit reproduction in others. Our data show that many macroalgal species are tolerant of long-term elevations in CO 2 levels but that macroalgal habitats are altered significantly as pH drops, contributing to a scant but growing body of evidence concerning the long-term effects of CO 2 emissions in vegetated marine systems. Further study is now needed to investigate whether the observed response of macroalgal communities can be replicated in different seasons and from a range of geographical regions for incorporation into global modelling studies to predict effects of CO 2 emissions on Earth's ecosystems.

Grazing of intertidal benthic foraminifera on bacteria: Assessment using pulse-chase radiotracing

Although foraminifera are a dominant component of many marine benthic communities, quantification of their predation on prokaryotes remains an experimental challenge. We have developed an approach that allows us to study grazing by adult specimens of the calcareous species Haynesina germanica and Ammonia beccarii, and the single-chambered agglutinated species Psammophaga sp., on bacteria ( Halomonas sp.), pulse-chase-labelled with 3H- and 14C-Leucine. The bacterivorous ciliate Uronema sp. and flagellate Pteridomonas sp. were used as positive controls. The rate of release of 3H when protozoa were incubated with the labelled bacteria indicated the predator's grazing rate; the proportion of 14C found in the foraminiferal biomass and shell indicated the prey assimilation rate. All three foraminiferal species grazed bacteria at a rate of 3.2–5.7 ng C ind −1 h −1 depending on bacterial concentrations. About 23% of the biomass of the 14C-labelled prey was most likely assimilated into foraminiferal pseudopodia, 12% was expelled in dissolved waste material, about 62% was respired and only 0.1% was incorporated into the carbonate shell. Extracellular digestion associated with pseudopodia could explain the very low proportion of the labelled food assimilated in the cell body and the significant proportion located in pseudopodial networks. These experiments also suggest that very little of the carbon ingested by adult calcareous foraminifera is incorporated into the shell. However, we cannot conclude that diet has no influence on the stable isotope composition of the shell since none of our calcareous specimens grew new chambers during the experiments.

Changes in plant species composition in abandoned and restored limestone grassiands - the effects of tree and shrub cutting

Abandoned semi-natural limestone grasslands are often overgrown by shrubs and trees. Little is know if and to what extant xerothermic limestone grasslands can be restored by tree cutting. This was tested in a 12-year experiment after the clearing of a 35-year-old secondary pine wood developed on unmanaged grassland in the close proximity of not overgrown old grassland. After 12 years, there were no significant differences in the number of field layer species on the plots in the old and restored grasslands. But over this period the number of meadow species increased in all sites, while the number of xerothermic calcareous species increased significantly only in the old grassland plots. The developing shrub layer negatively influenced the number of nitrophilous and ruderal species in grasslands restored in the former close and open woods, and the number of all species, including the number of non-tufted perennials and perennials with vegetative spread, in the former open wood. The number of meadow species increased in years with higher precipitation in late spring and early summer. The obtained results suggest that in overgrowing grasslands shrubs and trees should be cut every few years, before their covers increase to about 30%. However, this treatment alone will not stop the changes to communities with dominance of tall and vegetatively spreading grasses and forbs. Cutting trees and shrubs in sites where most grassland species have already vanished, without additional managements supporting their dispersal, seedling recruitment and development, is not sufficient to restore limestone grasslands rich in xerothermic species.

Spatial Variability of Sponge Assemblages on the Wellington South Coast,New Zealand

The aim of this study was to provide baseline data for sponge biodiversity on the Wellington South Coast, New Zealand. Eighteen sites were qualitatively sampled resulting in the identification of 65 different sponge taxa. Forty-three of these species were also reported from a quantitative survey of three vertical wall sites in 8-10m depth conducted as part of a long-term monitoring study. All three sites had a similar mean number of species per quadrat, however, the percentage cover of sponges and sponge density varied significantly between sites. ANOSIM showed that all three sites were significantly different from each other (P<0.001), which is likely the result of differences in environmental conditions. The Wellington South Coast has a diverse sponge assemblage, which is atypically dominated by calcareous species of the genus Clathrina. This appears to be unusual for New Zealand, and although the reasons for this situation are unknown, we hypothesise that this situation is explained by the low levels of nutrients on the Wellington South Coast, allowing calcareous sponges to proliferate at the expense of the demosponges.

Changes in segetal vegetation in the Borská nížina Lowland (Slovakia) over 50 years

This article reports changes in the segetal vegetation in the Borska nižina Lowland (Western Slovakia) over 50 years. The study was based on phytosociological releves obtained by Krippelova in the years 1949–1955, as well as our own recent data from the years 2002–2006. Using ordination and statistical methods, structural and floristic changes to four associations recorded in the area in both time periods were evaluated: Veronicetum trilobae-triphyllidi, Consolido-Anthemidetum austriacae, Echinochloo-Setarietum pumilae and Setario viridis-Erigeronetum canadensis. These plant communities are found in arable fields or young fallows. In some of these communities the proportion of invasive species, as well as archaeophytes and native species, has increased. Some agricultural practices (like fertilization and liming) support the spread of nitrophilous and calcareous species. Several ruderal species and herbicide-resistant species have expanded in the fields. In all studied associations the proportion of nutrient-demanding species has increased. Some rare and threatened species have declined or disappeared, but some threatened species that are missing from historical material are now present. However, the changes detected are not as substantial as expected based on data from other countries.

Stratigraphy of Paleogene Strata within the Mesihovina - Rakitno Area (Western Herzegovina)

The paper presents the stratigraphy of Paleogene strata from the central part of carbonate Dinarides. The carbonate and the clastic rock units were stu died. Their contact with underlying Senonian limes tone is marked by unconformity as a result of Laramian tectonic phase. The unconformity is denoted by the abundance of bauxite deposits. The abundance of calcareous nanoplancton species as well as ben tic foraminifera points at the sedimentation of Paleogene strata during the Eocene period. The succession of sediments with easily recognizeable transgressive, inundation and regres sive features has been established. Lithostratigraphical characteristics enabled the distinguishing of larger lithofacies groups. The simultaneousness of carbonate rocks with lower part of clastic succession as well as the transitionallitho· facies have been approved. The simultaneous overburden of bauxite deposits regardless of its lithology (carbonate of clastic) speaks in favour of the unite bauxitebearing phase.

Modern benthic foraminifers at Northern shallow sites of Adriatic Sea and soft-walled, monothalamous taxa: a brief overview

Sediment subsamples (0-2cm layer, &gt;63µm fraction) from box cores taken at four sites (Stns 120, 121, 122, 123) located along a transect in theGulf of Trieste (water depth range 8-22m)were sorted for foraminifers, including soft-walledmonothalamous taxa (organic-walled allogromiids, agglutinated saccamminids and psammosphaerids). The distribution of foraminiferal species differed among samples, corresponding to differences in water depth, granulometry, distance from fresh water source and other chemical and physical parameters (temperature, salinity and dissolved oxygen). In general, the absolute and relative abundance of monothalamous foraminifers tended to decrease with distance from the coast, i.e. with distance from the inflow of the Isonzo River, whereas polythalamous taxa exhibited the opposite trend. Therewas also a switch in dominance by polythalamous agglutinated species at Stn 122 to polythalamous calcareous species at Stn 123. Among polythalamous foraminifers, the calcareous species Ammonia perlucida was dominant at the innermost station (Stn 120), together with the agglutinated species Cribrostomoides spp. and Haplophragmoides spp. These species were absent or less common at the other stations. Textularia agglutinans was abundant at the two inner stations (121, 122). Stn 122 was further characterized by Reophax nana, Leptohalysis scottii and the calcareous species Nonionella stella. The latter is also themost abundant taxa at the outer station (Stn 123) where the agglutinated taxa Reophax nana and Textularia conica are alsowell represented. All themonothalamous taxa found are previously unreported from North Adriatic waters; all are undescribed at the species level and, in most cases, at the generic level also. Two genera (Psammophaga, Vellaria), however, are common in other shallow-water settings and Micrometula, previously known from habitats ranging from coastal to deep sea, is also present. One of the allogromiid morphotypes closely resembles Goodayia rostellaum, recently described from the Black Sea. Psammophaga and Vellaria are also known from the Black Sea, but the populations are probably distinct at the species level.

Comparative phosphate acquisition in giant-celled rhizophytic algae (Bryopsidales, Chlorophyta): Fleshy vs. calcified forms

Phosphate uptake through above-ground thalli vs. subterranean rhizoids has been compared in siphonaceous rhizophytic green algal species from five globally distributed tropical genera: Avrainvillea nigricans Decaisne, Caulerpa lanuginosa J. Agardh, Halimeda incrassata (J. Ellis) J.V. Lamouroux, Penicillus capitatus Lamarck, and Udotea flabellum (J. Ellis & Solander) M. Howe. Plants were collected, acclimated to lab conditions for 3 days, and then incubated for 8 h at saturating light intensity with 30 μM PO 4 3− added to their above-ground thallus or below-ground rhizoids. Percent tissue phosphorus was then compared to control specimens, which were run simultaneously in the absence of phosphate. The two fleshy species, A. nigricans and C. lanuginosa, showed no significant differences in tissue nutrient status, and displayed much larger variation among controls than the three calcified species. Calcified species showed greater phosphorus content after being exposed to either above- or below-ground thallus portions, indicating that these seaweeds can respond to short term increases in nutrient availability and have a more regulated nutrient acquisition mechanism. Results suggest that calcification may play an important role in phosphorus absorption.

Methane seepages recorded in benthic foraminifera from Miocene seep carbonates, Northern Apennines (Italy)

Benthic foraminifera from seep carbonates and from enclosing non-seep marls present within Miocene formations in the Northern Apennines (Italy) were investigated as proxies of methane seepage in the marine environment. Negative δ 13C values of benthic foraminifera from these seeps indicate unambiguously the local influence of CO 2 produced by microbial anaerobic methane oxidation on the benthic ecosystem. Calcareous species living within methane seeps display δ 13C values ranging from − 9.04 to − 25.74‰ PDB, whereas in the coeval surrounding marls the same species display δ 13C values from − 1.54 to 0.62‰ PDB. Different species ( Cibicidoides kullenbergi, C. pachyderma, Siphonina rethiculata, Planulina wuellestorfi, Bolivina miocenica, Brizalina dilatata, Vulvulina pennatula, and Cibicides praecinctus) in different seep carbonates indicate that benthic foraminifera, independently of the taxa and of microhabitat preferences, have more negative δ 13C values than those found in the enclosing marls. Therefore each species represents a potential proxy for past seafloor methane emissions. In addition to the calcareous species, the agglutinated species Vulvulina pennatula displays − 27.5‰ PDB in seep carbonates against − 2.69‰ PDB in the enclosing marls. This suggests that the species utilized strongly 13C depleted carbonate particles from authigenic carbonate precipitation during the mineralization of their tests.

Taphonomic signatures and patterns of test degradation on tropical, intertidal benthic foraminifera

The preservational condition of benthic foraminifera from tropical intertidal sediments in Cleveland Bay, north Queensland, Australia was examined in order to provide systematic descriptions of taphonomic signatures and semi-quantitative estimates of test degradation. The primary aim was to improve understanding of the processes of test degradation experienced by intertidal foraminifera during early burial. Eight common tropical, intertidal foraminiferal species were examined: Arenoparrella mexicana, Miliammina fusca, Miliammina obliqua and Trochammina inflata from two upper mangrove stations, and Ammonia aoteana, Elphidium excavatum clavatum, Pararotalia venusta and Parrellina hispidula from two mudflat stations. Taphonomic alteration was broadly divided into surface/textural features and larger-scale, structural losses to tests. Surface alteration of calcareous tests was dominated by the etching and roughening associated with dissolution processes, with limited evidence for bioerosion and abrasion. Both surficial etching and larger-scale structural damage were closely related to test architecture, with degradation most intense on porous chamber walls, as opposed to non-porous-areas, interlocular walls and chamber tips. Furthermore, all calcareous species exhibited consistent pathways of degradation whereby the most recently formed chambers were the most vulnerable to degradation. The correspondence between larger-scale test loss and these patterns of surface textural alteration, suggests calcareous test degradation is primarily driven by dissolution. Degradation of agglutinated tests contrasts in a number of ways. Pristine tests of all four species examined exhibited a smooth, outer organic coating, which may be missing from other specimens. The extent to which this initial loss effects further test breakdown is uncertain, but appears to differ between species. M. obliqua and some specimens of A. mexicana exhibited structural damage which corresponded to clear cement losses and agglutinant disaggregation. More generally, agglutinated species displayed fracturing and test breakages which bore no conspicuous relation to cement loss. Furthermore, neither surface alteration nor structural loss affected any part of agglutinated tests preferentially, and therefore pathways of degradation were inconsistent across specimens. The fact that agglutinated tests degrade in a more arbitrary manner, compared with calcareous tests, is taken as evidence that their degradation is (1) not entirely controlled by test architecture, and (2) at least partially driven by physical/mechanical processes. We suggest that, if agglutinated tests are not already inherently weaker than their calcareous counterparts, the loss of organic cements may sufficiently weaken agglutinated tests so as to increase susceptibility to physical damage. Tests were also graded according to the extent to which they were structurally degraded. Average taphonomic grades and taphonomic variability (i.e. standard deviation) for all species at Cocoa Creek were statistically invariant with depth, contrary to expectations based on the concept of progressive burial through a taphonomically-active zone. This indicates that shallow sub-surface sediments are significantly homogenised, and that sediment mixing and infaunal test production imparts a considerable effect on the development of surface and sub-surface dead assemblages at the study site.

Morphometrical variability of Helicosphaera ampliaperta (calcareous nannoplankton) in the Central Paratethys: biostratigraphic and paleogeographic applications

Biometrical variability of the calcareous nannofossil species Helicosphaera ampliaperta was evaluated for 1021 helicoliths from the Early Miocene of the Central Paratethys. Morphometrical changes of helicoliths expressed by their length and width of central opening are gradual. Three morphogroups can be separated: (1) small helicoliths ( 10 μm) at the level of the first common occurrence of Helicosphaera ampliaperta in the later Eggenburgian. The new morphotypes migrated to the Central Paratethys from the Mediterranean via the Pre-Alpine passage in two steps. The first occurrence of Helicosphaera ampliaperta (event 1) may be connected with the transgression of Aq3/Bur1 global sea-level cycle and the first occurrence of large Helicosphaera ampliaperta (event 2) with the base of the Bur 2 cycle. Biometrical changes in the Ottnangian/ Karpatian boundary interval (late Burdigalian) were realized also in two steps: (3) disappearance of small morphotypes at the level of the FAD of the endemic bivalve Rzehakia; (4) appearance of morphotypes with a very wide central opening (> 5 μm) at the level of the FAD of the endemic benthic foraminifera Uvigerina graciliformis (base of the Karpatian). These events were recorded after the opening of a new connection between the Mediterranean and the Central Paratethys via the “Trans-Tethyan Trench Corridor”. The heterochronal transgression of the local sea-level cycle CPC 2 can be approximately correlated with the global sea-level cycle Bur 4. (5) The last occurrence of Helicosphaera ampliaperta in the Early Badenian (Langhian). The Helicosphaera ampliaperta biometrical events were initiated by palaeogeographic changes in the Central Paratethys and are therefore of regional significance.