Calcareous Species Research Articles

Impact of eutrophication on shallow marine benthic foraminifers over the last 150 years in Osaka Bay, Japan

High-resolution foraminiferal analysis was conducted on a short sediment core from the inner part of Osaka Bay, Japan. Changes in foraminiferal assemblages were associated with eutrophication, bottom water hypoxia, and changes in red tide-causing algae. Before the 1920s, the calcareous species Ammonia beccarii, and the agglutinated species Eggerella advena and Trochammina hadai were rare, but calcareous foraminifers in general were abundant. Between the 1920s and 1940s, calcareous foraminifers decreased abruptly in abundance, while A. beccarii, E. advena and T. hadai increased in abundance. This faunal change corresponded in time to an increase in nutrients flowing in through the Yodo River, and bottom water hypoxia related to eutrophication. In the 1960s and 1970s, A. beccarii, E. advena and T. hadai further increased in abundance to become dominant, and many calcareous foraminifers nearly disappeared, corresponding to increasing bottom water hypoxia related to the rapid increase in discharged nutrients during the high economic growth period from 1953 to 1971. After the 1990s, A. beccarii decreased rapidly in abundance and E. advena and Uvigerinella glabra increased in abundance. The main components of red tide-causing algae changed from dinoflagellates to diatoms in the 1980s through 1990s, thus there was a change in the food supply to the benthos, which may have caused the increase in abundance of E. advena and U. glabra.

Ecophysiological implications of the measurement of transmittance and reflectance of tropical macroalgae

K.S. Beach, H.B. Borgeas and C.M. Smith. 2006. Ecophysiological implications of the measurement of transmittance and reflectance of tropical macroalgae.Phycologia 45: 450–457. DOI: 10.2216/05-30.1.In vivo transmittance and reflectance spectra from 280 to 700 nm were obtained from 14 species for macroalgae to quantitatively compare to what extent species from different divisions, of dissimilar functional forms and with various cell-wall constituents, absorb incident irradiance. Absorptance of photosynthetically active radiation (PAR) ranged from 64 to 92%. Ultraviolet radiation (UV-R) absorptances were found to be higher than absorptances of PAR for all species in both ultraviolet-B radiation (UV-BR) and ultraviolet-A radiation (UV-AR) portions of the spectrum. Transmittance of UV-BR through macroalgal thalli was markedly low compared with other wavelength ranges and is likely due to photoprotective UV-absorbing compounds within macroalgal cells. Reflectance of irradiance off algal thalli was higher than transmittance for all calcified species and for 57% of uncalcified species. Irradiance reflected from the surface of macroalgae accounted for as little as 7% and as much as 23% of incident PAR. Irradiance reflected off of calcified species exposed their chloroplasts to a diminished irradiance environment than species with higher absorptances. Reflectance needs to be quantified for accurate, comparable estimates of quantum yield via oxygen evolution and electron transport rates via chlorophyll fluorescence. Three sympatric members of the order Dictyotales (class Phaeophyceae) differed significantly in their photosynthetic performance. Sun to shade type P vs I curve parameters were strongly correlated with decreased absorptances in Dictyota acutiloba vs Padina japonica and Stypopodium hawaiiensis. Elevated thallus absorptance in D. acutiloba coupled with postabsorbance mechanisms of dissipating photoinhibitory irradiance may contribute to elevated productivity for this species.

Resolving the calibration problem in Cretaceous benthic foraminifera paleoecological interpretation: Cenomanian to Coniacian assemblages from the Benue Trough analyzed by conventional methods and correspondence analysis

Paleoecologic interpretation of Cretaceous benthic foraminiferal assemblages is frequently problematic because of the lack of modern indicator species. Late Cretaceous (Cenomanian to Coniacian) assemblages of the Nkalagu area in southern Nigeria (Lower Benue Trough) were analyzed paleoecologically and compared with isochronous assemblages of the Upper Benue Trough (Futuk and Ashaka). The analyzed sections are forming a transect from near shore to oceanic environments and therefore represent paleocological gradients. Late Cenomanian assemblages of the Nkalagu area are continuously dominated by Ammobaculites spp. Diversity is constantly low and a dysoxic to suboxic, normal marine, inner shelf environment can be assumed for this section. The Middle Turonian to Coniacian Sections at Nkalagu yielded various arenaceous and calcareous species. The most common genera are: Ammobaculites, Flabellammina, Gabonita, Gavelinella, Haplophragmoides, Nonionella, Planulina, Praebulimina and Trochammina. Middle to early Late Turonian sediments at Nkalagu were deposited at paleo-waterdepths of about 600 m, latest Turonian sediments at c. 250 m and Coniacian sediments at c. 600 m. Latest Turonian assemblages indicate unstable, alternating oxygen-rich and oxygen depleted conditions (suboxic to low oxic), changing to more stable conditions in the Coniacian at Nkalagu. The successive deepening indicated by the foraminiferal assemblages documents a change of the depositional environment from inner shelf to upper bathyal in the lower portion of the Benue Trough during the Cenomanian to Coniacian interval. Inner shelf assemblages from the Upper Benue Trough (Futuk and Ashaka localities) vary between brackish and normal marine conditions. Ammobaculites , Haplophragmoides and Gavelinella are the most frequent genera at Futuk, while additional occurrences of Ammotium, Reophax and Saccammina are indicative for brackish conditions at Ashaka. The application of a canonical correspondence analysis (CCA), embracing assemblages from the entire Benue Trough, enables the separation of different depositional environments with partly similar species content. In the present case, CCA is able to distinguish between brackish and normal marine conditions among shallow water assemblages, and between shelf and bathyal depths among normal marine depositional environments. CCA might therefore be used in settings with largely endemic associations and/or without modern species for calibration of assemblages, such as the Cretaceous Benue Trough.

Benthic foraminifera from a relict flood tidal delta along the Virginia/North Carolina Outer Banks

Examination of benthic foraminifera from six vibracores collected from a relict flood tidal delta near the Virginia/North Carolina border documents the assemblages associated with a former inlet and provides geologic evidence of this former inlet that once defined the boundary between Virginia and North Carolina along the Outer Banks. Three distinct foraminiferal assemblages were identified. The oldest assemblage contained abundant and diverse forms, dominated by Elphidium excavatum and several other calcareous species typical of shallow nearshore areas. Sediment immediately below and above this diverse calcareous assemblage was barren or nearly barren of foraminifera. A medium-salinity agglutinated marsh assemblage characterized mainly by Trochammina inflata with fewer Tiphotrocha comprimata overlies the uppermost barren unit. The core top assemblage was dominated by low-salinity marsh species Jadammina macrescens , Miliammina petila and Miliammina fusca . A comparison of these vertically-stacked assemblages with the modern geographic distribution of assemblages in the Outer Banks estuarine system and on the nearby continental shelf reveals a succession of depositional environments proceeding from estuarine and flood tidal delta to medium salinity marsh to lower salinity marsh. These changes in depositional environments reflect a rapid and dramatic increase in salinity caused by the opening of an inlet followed by a gradual decrease in salinity due to inlet shoaling and eventual marsh colonization of the flood tidal delta. These changes cannot be determined through sedimentological studies alone; micropaleonto-logical analysis is required. We conclude this distinctive trend of changing depositional environments constitutes paleontological evidence of the origin and evolution of Old Currituck Inlet that breached the barrier spit prior to 1585AD, actively built a flood tidal delta for more than 145 years, and then closed in 1731AD allowing the flood tidal delta to become colonized by marsh species.

Biologic response to environmental stress in tropical reefs: Lessons from modern Polynesian coralgal atolls and Middle Permian sponge and Shamovella-microbe reefs (Capitan Limestone USA)

Despite prejudices that comparisons of paleoecological patterns in modern and fossil reef communities are of doubtful validity, we compare the biologic response of living coralgal reefs in French Polynesia to environmental stress with an exceptionally well exposed Middle Permian sponge reef and Shamovella-microbial reef of the Capitan Limestone in New Mexico. In the western Tuamotu Archipelago, reef margins are characterized by depth-related changes of biodiversity. The subtidal basic reefbuilding community contains the highest diversity (23 coral and 6 calcareous algal species). With decreasing water depth and increasing environmental stress, diversity reaches a minimum of five taxa on the reef flat. The Capitan consists of two reef stages. Reefbuilders of the lowermost exposed part of Stage 1 formed a cement-rich sponge reef with 42 taxa (28 sponge species). Decreasing water depth along the reef face is accompanied by loss of five taxa, variations in the gross morphology of sponges and changes in framework architecture. Stage 2, dominated by Shamovella obscura, one bryozoan species and microbes, is sandwiched between two unconformities suggesting much shallower water and higher environmental stress. Despite differences in shelf profile and taxonomy, both the modern and Permian reefbuilders respond to increasing environmental stress with diversity impoverishment and dominance of binders.

Foraminifera of Langebaan Lagoon salt marsh and their application to the interpretation of late Pleistocene depositional environments at Monwabisi, False Bay coast, South Africa

The relationship between marine benthic foraminifera assemblages and the environment has been examined from samples collected across the southern edge of Langebaan Lagoon. The assemblages show a vertical zonation that can be related primarily to altitude above mean sea level and secondarily to type and abundance of plant cover. The foraminiferal analysis distinguishes three zones: a high marsh zone dominated by a monospecific Trochammina inflata assemblage, a middle marsh zone consisting of variable abundances of T. inflata and Jadammina macrescens ; and a low-marsh and tidal zone dominated by calcareous species such as Ammonia japonica, Ammonia parkinsoniana , Elphidium sp. A. Elphidium cf. articulatum and Quinqueloculina sp. The altitudinal range of these foraminiferal zones is used to reconstruct relative changes in late Pleistocene sea level from a succession exposed at Monwabisi on the False Bay coast.

The shell or the kernel: biodiversity estimates of benthic foraminifera

Estimates of protist biodiversity and distribution have until recently relied on the morphological identification of individual cells. The advent of environmental‐DNA‐based surveys of these protist communities has broadened our understanding of species richness and diversity. A “total‐evidence biodiversity” approach gives two benefits. First, it allows “back‐comparison” to previous studies of ecosystems, permitting estimates of the amount of cryptic diversity in different sampling regimes (and by extension, the fossil record). Second, it will provide the best possible estimate of the total species richness of current study sites. Here, we use a well‐studied benthic protist community, the foraminiferal assemblage of McMurdo Sound, Antarctica, to determine the effective parameters of both detection methods. We find that molecular‐based techniques detect well‐characterized calcareous species at depths too great to allow calcification, suggesting that these forms may be able to survive without their distinctive tests. “Fragile” taxa also appear to be better represented in molecular surveys than in morphological ones. The strengths of a combined morphological–molecular approach are demonstrated by an assessment of the distribution of two species in the genus Notodendrodes; morphological detection excels in the identification of distinctive, patchily distributed adults, whereas molecular detection with taxon‐specific probes enabled identification in less favorable sampling conditions. Such a “broad‐plus‐deep” approach appears to maximize detection efficiency in this Antarctic setting.Work supported by NSF OPP0003639.

Vegetation and seed bank in a calcareous grassland restored from a Pinus forest

Abstract Question: What is the importance of the seed bank in the maintenance of the restoration potential of a 60-year-old abandoned calcareous grassland overgrown by Pinus trees? Location: ‘Les Pairees’, province of Luxembourg, Belgium. Methods: The seed bank and the above-ground vegetation were surveyed in three adjacent stands, previously forming a unique calcareous grassland: a 60-year-old Pinus forest, a four-year-old clear-cutting and a typical calcareous grassland. Floristic diversity was compared among stands and between vegetation and seed bank. Results: The species richness of the vegetation and the seed bank was significantly lower in the Pinus forest. More floristic similarities were found between the clear-cutting and the calcareous grassland. Seed bank was essentially transient, dominated by annual species. Its correspondence with the above-ground vegetation was weak. Conclusion: Very few calcareous grassland species have persisted in the Pinus stand. Four years after clear-cutting, the sta...

THE DEVELOPMENT OF A MODERN FORAMINIFERAL DATA SET FOR SEA-LEVEL RECONSTRUCTIONS, WAKATOBI MARINE NATIONAL PARK, SOUTHEAST SULAWESI, INDONESIA

We collected modern foraminiferal samples to characterize the foraminiferal environments and investigate the role that temporal and spatial variability may play in controlling the nature and significance of foraminiferal assemblages of the mangroves of Kaledupa, Wakatobi Marine National Park, Southeast Sulawesi, Indonesia. The study of foraminiferal live and dead assemblages indicates that dead assemblages are least prone to vary in time and space, and furthermore, they accurately represent the subsurface assemblages that are the focus of paleoenvironmental reconstructions. Further analyses of the dead assemblages indicate a vertical zonation of foraminifera within the intertidal zone. Zone D-Ia is dominated by agglutinated foraminifera Arenoparrella mexicana, Miliammina fusca , M. obliqua and Trochammina inflata . Zone D-Ib has mixed agglutinated/calcareous assemblages with species such as T. inflata and Ammonia tepida. Zone D-II is dominated by numerous calcareous species including A. tepida , Discorbinella bertheloti, Elphidium advenum and Quinqueloculina spp. Zone D-Ia is found to be the most accurate sea-level indicator and its assemblages are omnipresent world-wide. Zones D-Ib and D-II are subject to both spatial and temporal variations which must be included in any sea-level reconstructions.

Associations between living benthic foraminifera and dead tests of Syringammina fragilissima (Xenophyophorea) in the Darwin Mounds region (NE Atlantic)

The xenophyophore Syringammina fragilissima is abundant in a bathyal region of the NE Atlantic (950m water depth) characterised by large numbers of 100m wide sandy mounds (the Darwin Mounds). We examined “live” (i.e., rose Bengal-stained) benthic foraminifera associated with fragments of four dead S. fragilissima tests from four box-cores collected in this region. Many of the abundant species associated with the xenophyophore tests were common bathyal species that also occurred in the surrounding sediment (e.g., Nonionella iridea and Eponides pusillus). Foraminifera associated with the xenophyophore tests were generally more abundant than those inhabiting the surrounding sediments, although species richness and diversity were not significantly different. Foraminiferal abundances were lower than those previously reported from comparable sites in the Northeast Atlantic. Some species had patchy distributions. In particular, the organic-walled Cylindrogullmia sp., the overall top-ranked species, was abundant in one test, where it constituted 36% of the foraminiferal assemblage, and rare or absent in others.Four distinct microhabitats, inhabited by particular foraminiferal species, were present within the complex structure of the xenophyophore tests: (1) Within the tests, in the remains of the organic tubes (granellare) that enclose the protoplasm in live xenophyophores (various monothalamous foraminifera, e.g., the elongate organic-walled Nemogullmia sp.). (2) Within the branches of the test, but outside the granellare tubes; sometimes associated with dark-grey sediment presumed to be the decayed remains of xenophyophore waste products (e.g., the allogromiid Cylindrogullmia sp. and the calcareous species Chilostomella elongata). (3) The outer surface of the test (numerous small calcareous foraminifera). (4) In mud trapped between the test branches (common bathyal species, many of which also occurred in the surrounding sediments). A number of metazoans, mainly nematodes, were also found occupying specific microhabitats within the tests, but these were generally less abundant than the foraminifera.

Behaviour and taphonomic loss in foraminiferal assemblages of mangrove swamps of French Guiana

Fifty-three surface sediment samples were collected in January 1999, July 2000 and December 2000 on mud flats and in mangrove swamps of French Guiana. Sampling stations were selected to provide information on different environmental conditions, on the mud flats and in the mangrove forest. Thirteen samples were also collected at a depth of about 8–12 cm in the sediment. Additional samples were collected from three long cores in the channel of the Kaw River. The main parameter controlling the distribution of recent foraminiferal assemblages is the seasonally variable relative influence of coastal water of reduced salinity and low pH, low-Ca river water. Areas under the influence of coastal water are dominated by calcareous species, mainly Ammonia tepida and Cribroelphidium spp., even in mangrove swamps during the dry season. River water influences almost all the study area during the rainy season and leads to the dominance of agglutinated species, with the nature of the assemblages depending on local environmental characteristics. On the mud flats, tests are typically well preserved in the 10 cm below the surface that is the most important taphonomically active zone for foraminifera. However, owing to intense bioturbation, the taphonomic processes in the mangrove swamp may result in the total destruction of the microfauna, including agglutinated tests. This study shows that the preservation of thanatocoenoses in mangrove swamp environments of French Guiana only occurs in exceptional circumstances. When they are preserved, the remaining assemblages, even if modified by taphonomic processes, give valuable information for paleoenvironmental reconstructions in this environment.

Seasonal and spatial variation of species toxicity in Mediterranean seaweed communities: correlation to biotic and abiotic factors

The toxicity of crude extracts of 32 seaweed species from the western Mediterranean was analysed by Microtox ® assay in spring and autumn of 1996 and 1997. The species analysed rep- resented more than 76% of seaweed coverage in the 3 algal communities studied: photophilic and sciaphilic communities from the Cabrera Archipelago (Balearic Islands), and a hemisciaphilic com- munity from the Medes Archipelago (northeastern Iberian Peninsula). Most species showed seasonal variation of toxicity, which was greater in species from Cabrera than in those from Medes. Both, intra and interspecies variation of toxicity were found. Moreover, comparison of mean toxicity of these communities showed that toxicity was higher in November than in June in all cases, and that the photophilic community had both the highest number and the most toxic species. To make an ecolog- ically relevant interpretation of the toxicity detected by Microtox ® , we compared the toxicity of extracts analysed by the Microtox ® test and those analysed by the commonly used sea urchin embryo assay. In addition to seaweeds, some species of invertebrates (sponges and ascidians) were compared to ascertain whether the relationship between the 2 tests was applicable to species belonging to dif- ferent phyla. These comparisons allowed us to establish that 0.5 gamma units in Microtox ® assay is the threshold value between toxic and non-toxic species. Following a light gradient from the photo- philic to the sciaphilic communities, the seaweed species that were occasionally toxic increased while the always-toxic seaweeds decreased. Rhodophyta and Phaeophyta had a higher percentage of toxic species than Chlorophyta. Non-encrusting seaweed forms were more toxic than the encrusting ones, and in contrast to most other seaweeds, the non-encrusting calcareous species that increased cover- age from June to November simultaneously displayed a marked decrease in toxicity. We conclude that the temporal variation of toxicity observed in the seaweeds studied may be partially explained by intrinsic factors of the species (growth rates and growth shapes).

The origin of modern agglutinated foraminiferal assemblages: evidence from a stratified fjord

Loch Etive, a silled 145 m deep fjord on the Scottish west coast, provides an example of modern benthic foraminiferal assemblages at intermediate depths (i.e., below the intertidal zone and above the CCD) consisting almost exclusively of organic-cemented agglutinated forms. Since such faunas from intermediate depths are rare in modern oceans but relatively common in the fossil record, the present study allows new insights into one kind of ancient environment for which there are few modern analogues. The strong dominance of agglutinated forms (both living and in some dead assemblages of foraminifera to the exclusion of calcareous taxa) is attributed to the unusual oceanographic conditions. These include a combination of restricted deep-water renewals and strong influence of freshwater which drains through large areas (relative to the size of the loch) of vegetated land. The result is calm bottom water conditions with commonly occurring oxygen depletion (although not anoxic), brackish water throughout the water column (salinity 28 in the deeper parts), and organic-rich (mostly terrestrially derived) sediments with geochemical properties, which, to a much larger degree than open marine ones, are controlled by local input. This environment supports low abundance and low diversity live assemblages, mainly restricted to the surface 1 cm of sediment. The dead assemblages show similar faunal characteristics, but the calcareous components are, due to carbonate dissolution, even more reduced. One of the calcareous species in Loch Etive is Elphidium albiumbilicatum. Its occurrence is the first record in British waters and it matches the previously suggested southern limit of its distribution. Analysis of a 90 cm long core representing sediments deposited over the past two centuries shows the presence of a calcareous dominated assemblage, including more marine species, with a higher diversity, in the lower part. This suggests that Loch Etive is in the process of going from a marine, to a more terrestrial dominated environment. The relatively high sedimentation rate (0.5 cm per yr), the apparent lack of smearing through bioturbation, and the presence of faunal changes in response to reduced marine influence over the past centuries, shows that Loch Etive has a good potential for performing high-resolution climatic studies.

Calcareous plankton dissolution pattern and coccolithophore assemblages during the last 600 kyr at ODP Site 1089 (Cape Basin, South Atlantic): paleoceanographic implications

Coccolithophore assemblages at ODP Site 1089 in the southern Cape Basin (∼41°S) were used to reconstruct surface-water conditions for the late Quaternary (Marine Isotope Stages (MIS) 1–15) in a region of strong hydrographic gradients in the southeast Atlantic. Stratigraphic control was provided by oxygen isotope stratigraphy and calcareous nannofossil events that are thought to be synchronous over a broad range of latitudes. The greatest coccolith abundances occurred at glacial terminations and, to a lesser degree, during glacial stages. Conversely, coccolithophores were the least abundant during the transition between interglacial to glacial stages, when calcium carbonate dissolution was strong. With the exception of these intervals, coccolith preservation is moderate to good, allowing study of the assemblages. The total abundance of coccolithophores and calcium carbonate variations at Site 1089 result both from variations in dissolution and carbonate production. During terminations, for example, the greatest calcium carbonate concentrations occurred at the same time as a moderate-to-poor preservation of coccoliths and foraminifers. Carbonate production was relatively high during these intervals. However, during terminations IV and V, maxima in carbonate production in the ocean were linked to high-dissolution processes at Site 1089. This trend is not observed for terminations I, II and III [Hodell et al., Earth Planet. Sci. Lett. 192 (2001) 109–124]. The interval from MIS 9 to 13 is coincident with high abundances of highly calcified species such as Gephyrocapsa caribbeanica. Here we discuss the contribution of this ubiquitous species to the production of calcium carbonate and their paleoecological significance. Except for occasional coccolith-barren intervals during interglacial periods, subtropical coccolith species were present continuously at ODP Site 1089 during the late Pleistocene. This suggests that the Polar Front has been south of Site 1089 for the last 600 kyr.

Contemporary foraminiferal distributions of a mangrove environment, Great Barrier Reef coastline, Australia: implications for sea-level reconstructions

Contemporary foraminiferal samples and associated environmental information were collected from Cocoa Creek, a mesotidal fringing mangrove environment on the Great Barrier Reef (GBR) coastline, Australia, to elucidate the relationship of the foraminiferal assemblages with elevation and environment. There is a strong and highly significant relationship between elevation and the foraminiferal assemblages, supporting the intertidal vertical zonation concept, which suggests that the distribution of foraminifera in the intertidal zone is usually a direct function of elevation, with the most important controlling factors being the duration and frequency of subaerial exposure. Multivariate analyses separate the intertidal foraminiferal assemblages into three elevational zones, with Zone I the highest and Zone III the lowest: Zones I and II are dominated by agglutinated species Trochammina inflata and Miliammina fusca, respectively; and Zone III is dominated by calcareous species, notably Ammonia tepida and Elphidium discoidale multiloculum. These assemblage zones are similar to those found in both tropical and temperate intertidal environments. A predictive transfer function has been developed to allow reconstruction of former sea levels for tropical environments, based upon the relationship between foraminiferal assemblage and elevation. Results suggest that a precision of ±0.07 m should be attainable, superior to most similar studies from temperate, mid latitude environments. Our work has produced the first foraminifera-based transfer function for environmental interpretations for tropical Australia, and allows the potential development of a new generation of high-resolution sea-level reconstructions for the post-glacial sequences of the GBR shelf.

The Greenland‐Norwegian Seaway: A key area for understanding Late Jurassic to Early Cretaceous paleoenvironments

The paleoclimatology and paleoceanology of the Late Jurassic and Early Cretaceous are of special interest because this was a time when large amounts of marine organic matter were deposited in sediments that have subsequently become petroleum source rocks. However, because of the lack of outcrops, most studies have concentrated on low latitudes, in particular the Tethys and the “Boreal Realm,” where information has been based largely on material from northwest Germany, the North Sea, and England. These areas were all south of 40°N latitude during the Late Jurassic and Early Cretaceous. We have studied sediment samples of Kimmeridgian (∼154 Ma) to Barremian (∼121 Ma) age from cores taken at sites offshore mid‐Norway and in the Barents Sea that lay in a narrow seaway connecting the Tethys with the northern polar ocean. During the Late Jurassic‐Early Cretaceous these sites had paleolatitudes of 42–67°N. The Late Jurassic‐Early Cretaceous sequences at these sites reflect the global sea‐level rise during the Volgian‐Hauterivian and a climatic shift from warm humid conditions in Volgian times to arid cold climates in the early Hauterivian. The sediments indicate orbital control of climate, reflected in fluctuations in the clastic influx and variations in carbonate and organic matter production. Trace element concentrations in the Volgian‐Berriasian sediments suggest that the central part of the Greenland‐Norwegian Seaway might have had suboxic bottom water beneath an oxic water column. Both marine and terrigenous organic matter are present in the seaway sediments. The Volgian‐Berriasian strata have unusually high contents of organic carbon and are the source rocks for petroleum and gas fields in the region. The accumulation of organic carbon is attributed to restricted conditions in the seaway during this time of low sea level. It might be that the Greenland‐Norwegian segment was the deepest part of the transcontinental seaway, bounded at both ends by relatively shallow swells. The decline in organic matter content of the sediments in the Valanginian‐Hauterivian indicates greater ventilation and more active flow through the seaway as the sea level rose. The same benthic foraminifera assemblages are encountered throughout the seaway. Endemic assemblages of arenaceous foraminifera in the Volgian‐Berriasian give way to more diverse and cosmopolitan Valanginian‐Hauterivian benthic communities that include calcareous species. The foraminiferal assemblages also suggest low oxygen content bottom waters during the earlier Cretaceous, changing to more fully oxygenated conditions later. The calcareous nannoplankton, particularlyCrucibiscutum salebrosum, which is rare at low latitudes and abundant in high latitudes, reflect the meridional thermal gradient. They indicate that the Greenland‐Norwegian segment of the seaway was north of a subtropical frontal zone that acted as a barrier between the Tethyan and Boreal Realms. This implies the existence of stable climatic belts during the early Valanginian and Hauterivian, significant meridional temperature gradients, and moderate “ice house” conditions.

Planktonic foraminiferal zonation in the Cretaceous Yezo Group, Central Hokkaido, Japan

The mudstone of the Yezo Group exposed in Central Hokkaido yields abundant microfossils of calcareous nannofossils, foraminifers, radiolarians and dinoflagellates. Benthic foraminifers consisting of both agglutinated and calcareous species occur abundantly and consistently throughout the sequence, while specimens of planktonic foraminifers are generally fewer than benthics in all samples. We recognized the following 13 planktonic foraminiferal zones assigned to the late Aptian to early Campanian in the Oyubari and Haboro–Kotanbetsu areas; (1) Globigerinelloides spp., (2) Ticinella primula, (3) Biticinella breggiensis, (4) Rotalipora subicinensis– Rotalipora ticinensis, (5) Rotalipora appenninica, (6) Rotalipora globotruncanoides, (7) Rotalipora cushmani (8), Whiteinella archaeocretacea (9) Helvetoglobotruncana helvetica, (10) Marginotruncana pseudolinneiana, (11) Marginotruncana sinuosa, (12) Contusotruncana fornicata, (13) Globotruncana arca. The Globigerinelloides spp. to H. helvetica Zones (late Aptian to early Turonian) can be correlated with standard zones in the Tethyan regions, whereas the assemblages from the M. pseudolinneiana to G. arca zones lack tropical zonal markers of Dicarinella concavata, D. asymetrica and Globotruncanita elevata in many studied sections. The scarcity or lack of tropical zonal species during the late Turonian to early Campanian suggests that the Oyubari and Haboro–Kotanbetsu regions in Hokkaido were located in the Transitional to Boreal biogeographical provinces.

Selective feeding by benthic foraminifera on phytodetritus on the western Antarctic Peninsula shelf: evidence from fatty acid biomarker analysis

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 262:153-162 (2003) - doi:10.3354/meps262153 Selective feeding by benthic foraminifera on phytodetritus on the western Antarctic Peninsula shelf: evidence from fatty acid biomarker analysis Stephanie B. Suhr1,*, David W. Pond2, Andrew J. Gooday1, Craig R. Smith3 1Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, UK 2British Antarctic Survey, Biological Sciences Division, Madingley Road, Cambridge CB3 0ET, UK 3University of Hawaii at Manoa, Department of Oceanography, Honolulu, Hawaii 96822, USA *Email: stephanie.suhr@usap.gov ABSTRACT: This study presents the first direct evidence, based on biochemical analysis of fresh material, that certain benthic foraminifera feed selectively on specific components of seasonally deposited phytodetritus in their natural environment. Three abundant species of benthic foraminifera, the calcareous species Globocassidulina subglobosa and Quinqueloculina seminula and the agglutinated species Thurammina albicans, collected after the deposition of phytoplankton bloom material at a shelf site (560 m water depth) west of the Antarctic Peninsula in March 2001, showed significant differences in their fatty acid profiles compared to the surrounding phytodetritus. Furthermore, the 2 calcareous species contained significantly higher amounts of polyunsaturated fatty acids (PUFAs) than were found in their presumptive phytodetrital food source, indicating that the foraminifera discriminate between, and selectively feed on, the different components of the deposited material. Possible implications for the benthic food web are discussed. KEY WORDS: Foraminifera · Selective feeding · Polyunsaturated fatty acids · Benthic food web · Antarctic Peninsula shelf Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 262. Online publication date: November 07, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Ecological Factors Acting on the Microfauna in Mangrove Swamps. The Case of Foraminiferal Assemblages in French Guiana

Thirty-seven surface sediment samples were collected in January 1999 and July 2000 in the mangrove swamps and mud flats of French Guiana where strong seasonal contrasts occur. Sampling stations were selected to provide information on the foraminiferal assemblages associated with different environmental conditions, on the mud banks and in the mangrove forest. A total of 44 species have been identified. The main parameter acting on the distribution of foraminiferal assemblages is the hydrodynamics of the estuary, characterized by the double influence of coastal water and low-Ca fresh water, with drastic seasonal changes. The coastal end member is dominated by the calcareous species Ammonia tepida, A. parkinsoniana and Cribroelphidium spp., the continental (freshwater) end member is characterized by Miliammina fusca and Trochamminita irregularis . The calcareous species penetrate into the estuary, even into the mangrove forest during the dry season, but totally disappear from the estuary during the rainy season. The second parameter acting on the distribution of foraminiferal assemblages is the vertical elevation that acts indirectly by influencing the time of aerial exposure and the colonization by mangrove trees. Both canopy and litter of the mangrove forest protect the sediment from heating, drying and increases in salinity due to sun and wind. Foraminifera are very rare or absent on the open mud banks affected by mud cracks, but begin to grow as soon as young Avicennia are present. In the mangrove swamps, local conditions influence the composition of the assemblages and the taphonomic processes.

MODERN DISTRIBUTION OF BENTHIC FORAMINIFERA ON THE NORTH ICELANDIC SHELF AND SLOPE

Research Article| July 01, 2002 MODERN DISTRIBUTION OF BENTHIC FORAMINIFERA ON THE NORTH ICELANDIC SHELF AND SLOPE Frank Rytter; Frank Rytter 1University of Aarhus, Department of Earth Sciences, DK-8000 Aarhus C, Denmark. Correspondence Address: Frank Rytter, University of Aarhus, Department of Earth Sciences, DK-8000 Aarhus C, Denmark. E-mail: frank.rytter@geo.au.dk Search for other works by this author on: GSW Google Scholar Karen Luise Knudsen; Karen Luise Knudsen 1University of Aarhus, Department of Earth Sciences, DK-8000 Aarhus C, Denmark. Search for other works by this author on: GSW Google Scholar Marit-Solveig Seidenkrantz; Marit-Solveig Seidenkrantz 1University of Aarhus, Department of Earth Sciences, DK-8000 Aarhus C, Denmark. Search for other works by this author on: GSW Google Scholar Jón Eiríksson Jón Eiríksson 2University of Iceland, Science Institute, IS-101 Reykjavik, Iceland. Search for other works by this author on: GSW Google Scholar Author and Article Information Frank Rytter 1University of Aarhus, Department of Earth Sciences, DK-8000 Aarhus C, Denmark. Karen Luise Knudsen 1University of Aarhus, Department of Earth Sciences, DK-8000 Aarhus C, Denmark. Marit-Solveig Seidenkrantz 1University of Aarhus, Department of Earth Sciences, DK-8000 Aarhus C, Denmark. Jón Eiríksson 2University of Iceland, Science Institute, IS-101 Reykjavik, Iceland. Correspondence Address: Frank Rytter, University of Aarhus, Department of Earth Sciences, DK-8000 Aarhus C, Denmark. E-mail: frank.rytter@geo.au.dk Publisher: Cushman Foundation for Foraminiferal Research Received: 08 Sep 2000 Accepted: 14 Sep 2001 First Online: 03 Mar 2017 Online ISSN: 1943-264X Print ISSN: 0096-1191 © 2002 Journal of Foraminiferal Research Journal of Foraminiferal Research (2002) 32 (3): 217–244. https://doi.org/10.2113/32.3.217 Article history Received: 08 Sep 2000 Accepted: 14 Sep 2001 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 Frank Rytter, Karen Luise Knudsen, Marit-Solveig Seidenkrantz, Jón Eiríksson; MODERN DISTRIBUTION OF BENTHIC FORAMINIFERA ON THE NORTH ICELANDIC SHELF AND SLOPE. Journal of Foraminiferal Research 2002;; 32 (3): 217–244. doi: https://doi.org/10.2113/32.3.217 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 Forty-six surface samples from the north Icelandic shelf and slope were analyzed with respect to both living (stained) and total (living/stained + dead/unstained) benthic foraminiferal faunas. Near-coastal samples are strongly dominated by species indicating a high-energy environment, among these various species of the genus Cibicides. Nonionellina labradorica, which has a strong affinity to areas of high surface primary production, is constrained to oceanic boundaries on the outer shelf. Faunistically, the area is further divided into eastern and western parts, the submarine Kolbeinsey Ridge forming a barrier. Calcareous species, particularly Melonis barleeanus, prevail in the western part, while the assemblages in the eastern part are strongly dominated by agglutinated foraminifera. Principal Component Analyses (PCA) help distinguish four main components of both the total (living + dead) assemblage (TA) and the total living assemblage (TLA), as well as of the total (living + dead) calcareous assemblage (CA) and the living calcareous assemblage (CLA). The components of the TA and TLA are similar, the major differences being controlled by species-dependent variables such as adaptability to changes in food supply and, in the eastern part of the area, depth of microhabitat and possibly a limited primary production. The PCA analyses of the calcareous species alone (CA and CLA) define components with significant differences in the foraminiferal population. The calcareous distribution in particular is important in application of modern distribution patterns to paleoceanographical and paleoclimatological reconstructions in areas where post-mortem disintegration of the agglutinated fauna may have occurred. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.