Benthic Foraminiferal Tests Research Articles

Factors influencing foraminiferal assemblages in coastal sediments of the Cross River Estuary, Southeast Nigeria, Gulf of Guinea

Estuaries are crucial coastal ecosystems facing increased pressures from human activities. The Cross River Estuary in Nigeria is a vital tropical mesotidal estuary influenced by diverse anthropogenic and natural processes. This study investigated the distribution of foraminiferal assemblages in the estuary's sediments, alongside environmental parameters such as heavy metals, pH, depth, temperature, salinity, mean grain size, and dissolved oxygen. Field sampling involved collecting 55 bottom water and sediment samples, with laboratory analyses focusing on grain-size distribution, foraminiferal identification, and heavy metal concentrations. Results indicated that heavy metal concentrations, except for iron, were within permissible limits. A total of 287 benthic foraminiferal tests representing four species were identified. These were primarily agglutinated species, with Arenoparrella mexicana and Miliammina fusca being the most abundant. Foraminiferal distribution was influenced by sediment type, salinity, and pH, rather than heavy metal concentration. Principal Component Analysis (PCA) revealed weak relationships between foraminiferal species and environmental variables, indicating limited influence of mean grain size and heavy metals on foraminiferal distribution. The study highlights the adaptability of certain foraminiferal species to a wide range of environmental conditions and underscores the need for continuous monitoring of the estuarine ecosystem to assess the impacts of ongoing anthropogenic activities. The findings provide a baseline for future environmental assessments and the use of foraminifera as bioindicators in tropical estuarine environments.

Distribution of Recent Benthic Foraminifera from the Outer Channel in and Around Gabakund Sea Mouth of Chilika Lagoon

Chilika (19°28’ to 19°54’ N; 85°54’N to 85°38’ E) lagoon situated in the east coast of India is considered to be one of the largest tropical coastal brackish water bodies in Asia. The unique setup of 60 km long narrow strip of sand barriers and swampy islands separating the area from the sea with few mouths of interconnections in the east and draining of tributaries of the river Mahanadi in the west while its environmental condition governed by tidal inflows and the southwest monsoon.The study of features of benthic foraminiferal tests, morphology, and abundance shed light upon paleoclimatic changes like monsoon variability, salinity, temperature, etc. Ten sediment samples were collected from the outer channel of Chilika lagoon in and around the Gabakund area and processed for species level study and SEM imaging following standard procedures. Sand dominates as the substrate towards the mouth at Gabakund area and silty to clayey sand towards the southern part of the Outer Channel. A total of 13 genera of benthic foraminifera belonging to 36 species were documented at the sampling stations. In the current study the species diversity and richness on the basis of the physico-chemical attributes of sea and river water incursion during pre-monsoon time in the outer channel of the lagoon is reported. In this region calcareous benthic foraminiferal are dominant while few agglutinated foraminifera have found their unusual niche.

Bioerosion Structures on Benthic Foraminiferal Tests from the Upper Cretaceous and Paleogene of Western Siberia

Bioerosion Structures on Benthic Foraminiferal Tests from the Upper Cretaceous and Paleogene of Western Siberia

New Data on the Expression of the Early Eocene Hyperthermals in Northern Bulgaria: Riben Section Revisited

We present new lithologic, nannofossil biostratigraphic and benthic carbon and oxygen isotope records for a marly-rich, 11 m thick Paleocene-Eocene section, now exposed at an old quarry at Riben Village, northern Bulgaria. The occurrence of NP9, NP10 and NP11 nannofossil zones is evidenced by detailed high-resolution nannofossil biostratigraphy. The carbon dissolution interval is marked by the abrupt drop of CaCO3 content and deposition of a clay interval at the onset of the Paleocene-Eocene Thermal Maximum (PETM). Stable isotope analyses of δ13C and δ18O were performed on benthic-foraminiferal tests. An unusual two-fold carbon isotope excursion (CIE) in the PETM interval is documented (total negative shift of 2.89‰). Moreover, three paired negative excursions: two in the Paleocene within the PETM interval, upper NP9 zone, and one within the early Eocene, NP11 zone are identified. The most prominent negative carbon isotope excursion (4.90‰ negative shift) is related with ETM3 (or “X” event), 52.84 Ma ago.
 Integration of nannofossil biostratigraphy, benthic stable isotope data sets and lithology unravel two separate early Eocene hyperthermal events: the PETM (= ETM1) and the ETM3 (= “X” event), recorded at Riben section.

Pore density of the benthic foraminiferal test responded to the hypoxia off the Changjiang estuary in the East China Sea

The benthic foraminiferal assemblages are commonly used to indicate different oxygenation conditions. In the last few decades, pore characteristics of the benthic foraminiferal tests from the micro-perspective using high-spatial-resolution analysis have been extensively suggested to indicate redox changes. Based on the whole test of the living shallow-infaunal species Bolivina robusta using a more representative and comprehensive method, we observed a significant negative correlation between the pore density (PD) and bottom dissolved oxygen (DO) concentration, and the average PD was about 36% higher in hypoxic environments (DO<3 mg/l) than in oxic environments (DO>3 mg/l). In terms of reproduction pattern in hypoxic environments, the species seemed to mainly choose the asexual life cycle (74.60%) to get more small generations with larger pore size (PS) (asexual 7 μm vs. sexual 4 μm) and exterior ornamentation (irregular papillae) as their survival strategy. The results provide new insight into the benthic foraminiferal ecology to reconstruct the pale-oceanography and paleo-ecology changes in the East China Sea. Moreover, this study has the potential to be applied in broad regions as an independent proxy by comparison to other widely-distributed benthic foraminiferal species.

The Middle-Upper Eocene benthic foraminifera from north-west Fayoum area, Egypt: Paleoecology and their similarity to the Tethyan provinces

This study deals with the Middle–Late Eocene benthic foraminiferal assemblage from the Um Rigl succession that is exposed in the northwest of Fayoum area, Egypt. Stratigraphically, two rock units are recognized from base to top as the Gehannam Formation and Birket Qarun Formation. The examination of benthic foraminiferal community identifies 63 species belonging to 36 genera, 22 families and four suborders. Their distribution aids to recognize one benthic foraminiferal biozone, Bulimina jacksonensis-Uvegerina jacksonensis Zone. To detect the paleocological conditions that prevailed during the deposition of the studied succession, a quantitative analysis is done on the foraminiferal assemblage, including the number of taxa, the relative abundances of the recorded suborders, calcareous species, agglutinated species and common species. The morphology of benthic foraminiferal tests is strongly associated with their microhabitat preferences. Therefore, the percentages of epifaunal and infaunal species are also calculated to detect the level of oxygenation. Accordingly, two ecozones are established, ecozone 1 represents the Gehannam Formation, whereas ecozone 2 represents the Birket Qarun Formation (excluding the barren zone in the upper part). Ecozone 1 is dominated by calcareous species (90–100%) and infaunal species (38–99%), while epifaunal species range from 2 to 62%. The most abundant taxa are Bolivina, Bulimina, Uvigerina, Nonion and Lenticulina. Therefore, the ecozone 1 was deposited under an inner-outer neritic environment, with normal salinity and eutrophic to mesotrophic conditions. On the other side, ecozone 2 is characterized by changes in the composition of foraminiferal assemblage, where infaunal species dominate the base of this ecozone, followed by a strong decline in the middle part and then increase again in the upper part. Also, a notable increase in epifaunal species is documented in this ecozone. This variation in foraminiferal assemblage reflects changes in water depth and oxygen content. Consequently, ecozone 2 was deposited under an inner to middle neritic environment, with normal salinity and mesotrophic to oligotrophic conditions. Regarding the paleobiogeographic outline, the results of multivariate analyses indicate that the Egyptian species show a strong similarity to those from the Southern Tethyan Province (Tunisia and Libya), whereas they show a reasonable similarity to the Western Tethyan Province (Spain, Italy, France). This deduction reflects a probable marine connection between both provinces during Eocene.

Disentangling environmental and diagenetic δ18O and δ13C signals from marine carbonates deposited under warm climate conditions during the early Danian

Paleoceanographic reconstructions are usually based on the chemical composition of foraminiferal tests, and pristine calcite preservation is crucial to support reliable interpretations. Therefore, prior knowledge about the structure and chemical composition of microfossils calcite is important to assess whether geochemical results reflect environmental and/or post-burial signals. Here, we present the first microstructural study of early Danian benthic foraminiferal calcite, and evaluate environmental signals and post depositional biases in benthic and planktonic foraminiferal and bulk carbon (δ13C) and oxygen (δ18O) isotope records at Ocean Drilling Program (ODP) Site 1262 (South Atlantic Ocean). We focused our study on the first ∼350 kyr that followed the Cretaceous-Paleogene (K-Pg) boundary, encompassing the Dan-C2 carbon cycle perturbation. Benthic and planktonic δ13C records show the expected surface-to-bottom gradient, suggesting the preservation of original environmental signals. However, benthic and planktonic δ18O records show strongly overlapping and scattered values, suggesting diagenetic alteration of isotopic signals. We identified the occurrence of authigenic carbonates, such as girvasite and siderite, in benthic foraminiferal tests, which increased Mg, Mn, Ba and Fe contents of tests calcite. Our results support that thermodynamic changes occurred in tandem with the decrease of bottom and pore water oxygenation to favor precipitation of authigenic carbonate phases, which altered isotopic fractionation of δ18O. Nevertheless, bulk sediments clearly depict the negative δ13C and δ18O excursions characteristic of the DanC2, with remarkably low values, characterizing the record of a surface ocean environmental signal. This low δ13C and δ18O were mostly recorded by highly-abundant calcispheres (calcareous dinocysts), suggesting that this group of microfossils has a high potential for surface ocean paleoceanographic reconstructions.

A 600 kyr reconstruction of deep Arctic seawater δ18O from benthic foraminiferal δ18O and ostracode Mg ∕ Ca paleothermometry

Abstract. The oxygen isotopic composition of benthic foraminiferal tests (δ18Ob) is one of the pre-eminent tools for correlating marine sediments and interpreting past terrestrial ice volume and deep-ocean temperatures. Despite the prevalence of δ18Ob applications to marine sediment cores over the Quaternary, its use is limited in the Arctic Ocean because of low benthic foraminiferal abundances, challenges with constructing independent sediment core age models, and an apparent muted amplitude of Arctic δ18Ob variability compared to open-ocean records. Here we evaluate the controls on Arctic δ18Ob by using ostracode Mg/Ca paleothermometry to generate a composite record of the δ18O of seawater (δ18Osw) from 12 sediment cores in the intermediate to deep Arctic Ocean (700–2700 m) that covers the last 600 kyr based on biostratigraphy and orbitally tuned age models. Results show that Arctic δ18Ob was generally higher than open-ocean δ18Ob during interglacials but was generally equivalent to global reference records during glacial periods. The reduced glacial–interglacial Arctic δ18Ob range resulted in part from the opposing effect of temperature, with intermediate to deep Arctic warming during glacials counteracting the whole-ocean δ18Osw increase from expanded terrestrial ice sheets. After removing the temperature effect from δ18Ob, we find that the intermediate to deep Arctic experienced large (≥1 ‰) variations in local δ18Osw, with generally higher local δ18Osw during interglacials and lower δ18Osw during glacials. Both the magnitude and timing of low local δ18Osw intervals are inconsistent with the recent proposal of freshwater intervals in the Arctic Ocean during past glaciations. Instead, we suggest that lower local δ18Osw in the intermediate to deep Arctic Ocean during glaciations reflected weaker upper-ocean stratification and more efficient transport of low-δ18Osw Arctic surface waters to depth by mixing and/or brine rejection.

Pleistocene Paleoceanographic Conditions in the Ioffe Drift Area (South Atlantic) Based on Benthic Foraminiferal Assemblages

The Ioffe Drift located in the western South Atlantic to the north-east to the Vema Channel was discovered in the 32nd cruise of the R/V “Akademik Ioffe” in 2010. The analysis of the seismoacoustic, biostratigraphic, lithological, grain-size, geochemical and X-ray fluorescence data allowed to estimate the Pleistocene age of the upper part of the drift as well as to confirm contourite genesis of the sediments. Quantitative analyses of benthic foraminiferal assemblages are carried out in the sediment core AI-2436 (26°51.6′ S, 34°01.40′ W, 3800 m water depth) collected near the drift summit. The obtained results allowed reconstructing relative changes of the organic matter flux to the seafloor, its periodicity and bottom current intensity as well as suggesting interplay of the deep-water masses during the Pleistocene. Visual evaluation of benthic foraminiferal tests allowed distinguishing three groups of damages of presumably variable genesis. First group includes damages possibly resulted from impacts of particles transporting by bottom currents. Second group consists of damages that appeared due to movement of the tests by strong bottom currents. Third group contains deformations caused by dissolution in carbonate-aggressive bottom-water environment. Thus, specific features of the tests in combination with traditional methods may serve as a supporting technique for diagnostics of contourites. However, this method demands a development of application criteria and should be verified on reliable material.

THE EVOLUTIONARY TRENDS AND GEOGRAPHIC DISTRIBUTION OF THE TETHYAN MARKER PALEOCENE BENTHIC FORAMINIFERAL SPECIES OF ANAN

Twenty-four diagnostic Paleocene benthic foraminiferal species of Anan, which related to eighteen genera were erected from five widely separated countries in the Southern and Northern Tethys, its proposed evolutionary trends of them, and the taxonomic revision of these taxa, which will greatly aid paleontologists and biostratigraphers to helpfully understanding. Thirteen species of them were erected from Egypt ((Siphogaudryina strougoi, Pseudoclavulina hewaidyi, P. youssefi, Annulofrondicularia bignoti, Tristix aubertae, Lenticuzonaria misrensis, Percultazonaria alii, P. ameeri, Palmula berggreni, P. salimi, Vaginulinopsis boukharyi, Citharina plummerae, Gyroidinoides luterbacheri), five species from UAE (Repmanina mazeni, Psammolingulina bahri, Laevidentalina hudae, Hemirobulina olae, Ramulina futyani), three species from Pakistan (Textularia haquei, Spiroloculina haquei, S. pakistanica), two species from Jordan: (Pseudoclavulina futyani, Lenticuzonaria hodae), and one species of them is recorded from Tunisia (Leroyia tunisica). The paleogeographic distribution of these taxa are recorded in some other countries in the Southern and Northern Tethys than the original type locality, e.g. Iran, Czech, Bulgaria and Argentina. Some of these species are used to introduce an evolutionary trend marked by changes in the morphology and other characters of these benthic foraminiferal test. The Southern Tethys assemblage indicates an open marine environment, which represents middle-outer neritic environment and shows an affinity with Midway-Type Fauna (MTF).

Characterization of water masses around the southern Ryukyu Islands based on isotopic compositions

We investigated the water-mass structure on the Okinawa Trough and Pacific sides of the southern Ryukyu Island Arc (Yonaguni, Iriomote, and Ishigaki subareas) using the Nd isotope composition (143Nd/144Nd ratios; expressed as εNd values) of benthic foraminiferal tests in surface sediments, which reflect bottom-water composition, along with hydrogen and oxygen isotope compositions (δD and δ18O values, respectively) and physical properties (temperature and salinity) of seawater. The Okinawa Trough side has lower εNd values than the Pacific side due to continental/island material inputs characterized by relatively low εNd values. Moreover, within the Okinawa Trough, other processes control the Nd behavior of seawater and primarily affect the Yonaguni and Iriomote subareas, as follows. (1) Surface and subsurface waters are influenced by Taiwanese river discharge combined with temporospatial variations in oceanographic conditions including Kuroshio Current meandering. (2) Intermediate water is characterized by low εNd values (down to − 8.2), possibly attributable to sediment plumes and turbiditic fluxes. (3) The εNd values of bottom water indicate upwelling and vertical mixing, with composition therefore being similar to those of intermediate water. The εNd profiles are better defined on the Pacific side. High εNd values occur in surface and subsurface (< 300 m depth, potential density < 25.0 kg m−3) waters, and low values (down to − 7.0) occur in subsurface–core-intermediate water (400–600 m depth, 26–27 kg m−3). εNd values increase slightly to − 4.0 below 750 m depth and remain constant down to about 2000 m depth, below which deep water shows a slight decrease in εNd values. Intermediate and bottom/deep waters are distinguished from upper layers by their lower δD and δ18O values.

STRATIGRAPHY, TAXONOMICAL CONSIDERATION AND EVOLUTIONARY TRENDS OF FUTYAN BENTHIC FORAMINIFERAL JORDANIAN SPECIES

Two hundred and twenty-seven Maastrichtian-Early Paleogene benthic foraminiferal species were recorded from three widely separated surface Jordanian sections: Wadi Arab in the north, Muwaqqar in the center, and Tell Burma in the south. Forty-two species and subspecies were listed. Fifteen diagnostic species of them are treated by him as new species, which recorded and illustrated in this study. The paleogeographic distribution of them in some other countries in the Southern Tethys are recorded: United Arab Emirates (UAE), Egypt, Tunisia, Tanzania and Angola. One of the original species of Futyan: Siphogenerinoides elnaggari is considered here as a junior synonym of another species Orthokarstenia higazyi (Nakkady). The paratype of the recorded species Vaginulinopsis wadiarabensis Futyan is considered recently, by the present author, as a new genus and species: Lenticuzonaria hodae, while the holotype of it was regarded to be the holotype of the new genus Percultalina. As a token of appreciation of his outstanding career and faunal contributions, one species was recently erected: Pseudoclavulina futyani. Most of the recorded species (10 species) are endemic to Jordan, while others were recorded in other countries in the Southern Tethys. Most of these species are used to introduce an evolutionary trend marked by changes in the morphology and other characters of these benthic foraminiferal test. The Jordanian assemblage indicates an open marine environment, which represents middle-outer neritic environment (100 m ~ 200 m depth) and shows an affinity with Midway-Type Fauna (MTF).

Mineralogical and Crystal-Chemical Constraints on the Glauconite-Forming Process in Neogene Sediments of the Lower Guadalquivir Basin (SW Spain)

Glaucony is a significant green marine facies in the northwestern passive margin of the Guadalquivir Basin (Spain), where glauconite formed authigenically on a sediment-starved continental shelf, with fecal pellets and benthic foraminiferal tests being the main glauconitized substrates. Results from a study using XRD, TGA-DSC, SEM-EDS, and EPMA have revealed that glauconite is remarkably heterogeneous in mineral composition and chemical maturity, even in a single grain, reflecting a complex interaction of micro-environmental factors, substrate influences and post-depositional alterations. In its early stage, the glauconitization process is consistent with the slow precipitation of a Fe-rich smectite phase, most likely intergrade between nontronite and Fe-montmorillonite end-members, which evolved to a regularly interstratified glauconite-smectite (Gl/S). The Fe-smectite-to-Gl/S transformation is interpreted as a diffusion-controlled reaction, involving sufficient Fe availability in pore water and the constant diffusive transport of seawater K+ and Mg2+ ions towards the substrate. The pelletal glauconite is actually a highly evolved Gl/S consisting almost totally of mica layers, with 0.74 ± 0.05 apfu of K+ in the interlayer, while the Gl/S occurring as replacements of foraminiferal tests contains a mean of 7% of expandable layers in the walls and 16% in the chamber fillings, due to rate-limited ion diffusion.

Toward a global calibration for quantifying past oxygenation in oxygen minimum zones using benthic Foraminifera

Abstract. Oxygen minimum zones (OMZs) are oceanic areas largely depleted in dissolved oxygen, nowadays considered in expansion in the face of global warming. To investigate the relationship between OMZ expansion and global climate changes during the late Quaternary, quantitative oxygen reconstructions are needed but are still in their early development. Here, past bottom water oxygenation (BWO) was quantitatively assessed through a new, fast, semi-automated, and taxon-independent morphometric analysis of benthic foraminiferal tests, developed and calibrated using WNP (western North Pacific, including its marginal seas), ENP (eastern North Pacific), and ESP (eastern South Pacific) OMZ samples. This new approach is based on an average size and shape index for each sample. This method, as well as two already published micropalaeontological techniques based on benthic foraminiferal assemblages' variability and porosity investigation of a single species, was calibrated here based on availability of new data from 45 core tops recovered along an oxygen gradient (from 0.03 to 2.88 mL L−1) from the WNP, ENP, EEP (eastern Equatorial Pacific), ESP, SWACM (southwest African continental margin), and AS (Arabian Sea) OMZs. Global calibrated transfer functions are herein proposed for these methods. These micropalaeontological reconstruction approaches were then applied to a palaeorecord from the ENP OMZ to examine the consistency and limits of these methods, as well as the relative influence of bottom and pore waters on these micropalaeontological tools. Both the assemblage and morphometric approaches (which are also ultimately based on the ecological response of the complete assemblage and faunal succession according to BWO) gave similar and consistent past BWO reconstructions, while the porosity approach (based on a single species and its unique response to a mixed signal of bottom and pore waters) showed ambiguous estimations.

Quantifying Diagenesis, Contributing Factors, and Resulting Isotopic Bias in Benthic Foraminifera Using the Foraminiferal Preservation Index: Implications for Geochemical Proxy Records

AbstractGeochemical records generated from the calcite tests of benthic foraminifera, especially those of the genera Cibicidoides and Uvigerina, provide the basis for proxy reconstructions of past climate. However, the extent to which benthic foraminifera are affected by postdepositional alteration is poorly constrained. Furthermore, how diagenesis may alter the geochemical composition of benthic foraminiferal tests, and thereby biasing a variety of proxy‐based climate records, is also poorly constrained. We present the Foraminiferal Preservation Index (FPI) as a new metric to quantify preservation quality based on objective, well‐defined criteria. The FPI is used to identify and quantify trends in diagenesis temporally, from late Pliocene to modern coretop samples (3.3–0 Ma), as well as spatially in the deep ocean. The FPI identifies the chemical composition of deep‐ocean water masses to be the primary driver of diagenesis through time, while also serving as a supplementary method of identifying periods of changing water mass influence at a given site. Additionally, we present stable isotope data (δ18O, δ13C) generated from individual Cibicidoides specimens of various preservation quality that demonstrate the likelihood of significant biasing in a variety of geochemical proxy records, especially those used to reconstruct past changes in ice volume and sea level. These single‐test data further demonstrate that when incorporating carefully selected tests of only the highest preservation quality, robust paleorecords can be generated.

Species-Specific Settling Behaviors of Benthic Foraminifera: Size, Density and Structure

ABSTRACT Settling velocity is a key hydrodynamic parameter to understand the transport behavior of benthic foraminiferal tests. Both size and density are fundamental in predicting settling velocity, but their relative importance is unclear. We used specimens of four benthic foraminiferal species from a carbonate-sand sample collected from Xisha Qundao, South China Sea, to investigate this question. Measurements on foraminiferal test size, shape, and density were combined with settling velocity observations using a laboratory settling tube. In addition, a micro-Computed Tomography (CT) Scanner was used to extract the internal-structure patterns of the tests of four representative specimens. Our study revealed that both size and density are important in affecting settling velocity, but the relative importance is species-specific. Size is more important than density for Amphistegina lobifera and Heterostegina depressa; these two factors are equally important for Peneroplis pertusus, but the settling velocity of Sorites orbiculus is also considerably controlled by their unique structure, besides size and density. This species-specific pattern was further compared with test development to reveal the associated biological mechanisms. As a result, a novel parameter, DT (density*TND2), is proposed as a better variable for predicting the species-specific settling behaviors.

Fossichnus solus and Oichnus simplex, two peculiar ichnospecies in modern benthic foraminifera from a polluted area in SW coast of Sardina, Italy

The modern benthic foraminiferal tests collected from a coastal area of south-western Sardinia (Portoscuso-Portovesme) that is heavily polluted by industrial activity reveal intense and widespread bioerosional structures induced by diversified microborers. A large number of the foraminifera reveals microscopic round holes (1-60 μm in diameter) and roundish concavities (25x40 μm in external diameter) on their surface that belong, respectively, to the ichnospecies Oichnus simplex Bromley, 1981, and Fossichnus solus Nielsen et al., 2003. These traces just occur in the tests of the foraminifera which are heavily infested by microendolithic cyanobacteria, algae and fungi suggests comparable ethological behaviour between the ichnospecies Fossichnus and Oichnus and the microbial euendoliths that are ascribed to individual biological taxa. The greater occurrence of F. solus and O. simplex in the high-Mg foraminiferal porcelanaceous tests than in the low-Mg foraminiferal hyaline tests reveals that the bioerosional processes seem to be related to the Mg/Ca ratio, as well as to morphological structures of the taxa

Does foraminiferal test size reflect changes in palaeoenvironmental conditions?—a case study from the southern Svalbard shelf

Although the environmental factors influencing the growth rate and reproduction of benthic foraminifera are known, the relationship between foraminifera test size and environmental variables remains unclear, especially on geological timescales. In this article, we present two records of benthic foraminiferal test size over the last 14 000 years from the southern Svalbard shelf. We use statistical correlation to relate test size changes with environmental conditions recorded by other proxies, including benthic&nbsp;δ18O and&nbsp;δ13C, foraminiferal flux and abundance, and relative abundances of different ecologically indicative foraminiferal groups. The general trends in test size were relatively consistent between the two cores. Still, we found that none of the analysed proxies was statistically correlated with the test size in both records. This leads to a conclusion that foraminifera size is primarily impacted by local oceanographic conditions. These local conditions are partly influenced by global oceanographic transitions. Therefore, large-scale changes can have a secondary impact on foraminiferal test size. The analysis of test size correlation between species similarly revealed that not all species react consistently to environmental changes. Our results indicate that foraminiferal test size cannot be used as a universal and straightforward proxy, but in combination with other methods it can yield valuable palaeoenvironmental information.

Paleoenvironmental Reconstruction off Southern Brazil during a Glacial Period (66.5–47 kyr BP): Continental and Oceanic Environments

Souza Pereira de Avila, A.; Leonhardt, A., and Diniz, D., 2020. Paleoenvironmental reconstruction off southern Brazil during a glacial period (66.5–47 kyr BP): Continental and oceanic environments. Journal of Coastal Research, 36(6), 1204–1214. Coconut Creek (Florida), ISSN 0749-0208.Based on the palynological record of core REG 972, this work aimed to reconstruct the paleoclimatic and paleoenvironmental history from 66.5 to 47 kyr BP at the south Brazilian continental margin, as well as to identify the influence of continental discharge in the southern portion of the Rio Grande Cone. Nineteen samples were processed following the standard methodology for palynological studies. Organic matter (OM) content was measured in the sediments. The age model was established according to 18O isotopes analyses in benthic foraminiferal tests. The studied interval corresponds to a glacial interval, divided in palynozones (PZs): PZIa (66.5–64.5 kyr), PZIb (64.5–53.5 kyr), and PZII (53.5–47 kyr). PZIa was characterized by drier conditions, with grassland and salt marsh taxa dominance (Cyperaceae and Amaranthaceae). During PZIb and PZII, the increase of Bryophyta, Pteridophyta, Araucaria angustifolia, Arecaceae, and Alchornea triplinervia points to wetter and warmer conditions that may be related to the beginning of marine isotope stage 3 and later to the sea-level rise. In the oceanic environment, the presence of freshwater algae and marine indicators lead to the conclusion that marine conditions prevailed during Rio Grande Cone sedimentary formation, even under low sea-level conditions when terrigenous influence was stronger. The data on OM content, dinoflagellate taxa, and mean sea level changes point to a period of low productivity during PZI. In PZII, a period of higher productivity took place because of Subantarctic Shelf Water influence, bringing cold and nutrient-rich waters to the area.

Relationship between substrate, physico-chemical parameters and foraminiferal tests in the Doñana National Park, a Biosphere Reserve in SW Spain

A multidisciplinar analysis of sediments collected in different environments of the Donana National Park (Guadalquivir estuary, SW Spain) provides an overview of the textural, mineralogical and physico-chemical parameters that control the distribution of benthic foraminiferal tests in this Biosphere Reserve. These microorganisms are absent in the fine quartzitic sands that constitute the substrate of temporary ponds with brief hydroperiods located in the dune systems and spits, as well as in other ponds with low conductivities or hypersaline conditions located in the inner marshlands or near the Guadalquivir river banks. Dead benthic foraminifera are mainly found on phyllosilicate-rich, silty-clayey substrates. The taphonomic analysis of the main species (Ammonia tepida, Haynesina germanica, Trochammina inflata, Entzia macrescens) points to its deposit in situ. Cluster analysis permits to delimitate six foraminiferal assemblages. Cluster II (A. tepida + H. germanica) is the dominant assemblage in the central ponds and the margins of the main channels, while cluster IV (T. inflata + E. macrescens) is restricted to some ponds located on the high marsh and cluster VI (Ammonia beccarii + Quinqueloculina spp.) is abundant on external beaches. Tidal fluxes cause the transport of these last marine benthic species and some plaktonic forms both to the inner areas of the estuary and to these beaches.