Benthic Foraminifera Research Articles

Comparative analysis of sedimentary metal phases and their respective roles in shaping living benthic foraminiferal communities: Implications for environmental biomonitoring.

Comparative analysis of sedimentary metal phases and their respective roles in shaping living benthic foraminiferal communities: Implications for environmental biomonitoring.

Dataset of benthic foraminiferal community structure from sediment eDNA of Sundarbans mangrove ecosystem.

Dataset of benthic foraminiferal community structure from sediment eDNA of Sundarbans mangrove ecosystem.

Eocene Stratigraphic Sequences in the Prebetic of Alicante (SE Spain) and Their Correlation with Global Sea-Level and Climatic Curves

The Onil and Ibi sections (Prebetic Zone, Betic Cordillera: Alicante, SE Spain) record a late Ypresian (Cuisian) to early Lutetian (~51 to ~43 Myr) carbonate platform succession, dated using larger benthic foraminifera (LBF) and planktonic foraminifera. Seven field lithofacies (L1 to L7) and five thin-section microfacies (Mf1–Mf5) were identified, indicating inner- to mid-ramp environments (from seagrass meadows to Maërl-LBF-dominated) in warm-water and low-latitude conditions. A distinctive feature of these platforms is their dominance by LBF in association with rhodophyceae, contrasting with typical coral reef factories. We propose a novel carbonate production model, “TC-factory”, to describe these warm-temperate systems. Integrated field logging, drone imagery, and microfacies data allowed us to define a sequence stratigraphic framework comprising five lower-frequency sequences (LFS: ~2 Myr average duration), each of them nesting various numbers of high-frequency sequences (HFS: ~0.25 to ~1 Myr). The LFSs belong to a higher-rank sequence bounded by regional unconformities. The five LFSs only broadly match the upper Ypresian and lower Lutetian cycles in global eustatic curves (~51 to ~43 Myr), indicating that other regional or local controls were important. The number of HFSs being fewer than expected also suggests additional controls, such as local tectonics, erosion during lowstands, or carbonate production feedback.

Cyclostratigraphy of the Miocene Nakayama Formation on Sado Island in central Japan and paleoceanographic implications

Although siliceous sediments have the potential to reveal an enigmatic Miocene climate evolution, problems with age model construction are tough to beat. Cyclostratigraphy is a useful tool for the construction of a high-resolution age model. In the Japan Sea region, orbital-scale oscillations in the sedimentary environment of the Miocene sedimentary basins are reported, for example, the Onnagawa Formation in Akita Prefecture in northern Japan and the Nakayama Formation on Sado Island in central Japan. In this study, we constructed a high-resolution age model of the Miocene siliceous sediment in the Japan Sea, the Nakayama Formation, by cyclostratigraphy using the geochemical properties of the sediment. Ratios of the biogenic silica content to the detritus content in the sediment were determined based on the X-ray fluorescence (XRF) and X-ray diffraction (XRD) measurements. Orbital-scale oscillations were identified in the ratios of biogenic silica to detritus, and it was used for cyclostratigraphic correlation with the global oxygen stable isotope (δ18O) curve of benthic foraminifera. Our new cyclostratigraphic age model and method are expected to promote using the Miocene siliceous sediments for paleoceanographic and paleoclimatologic studies. Additionally, major element and mineral compositions determined by XRF and XRD analysis were used to reconstruct the sedimentary environment on which the East Asian Monsoon system may have an influence.

Impact of wave exposure on bleaching of large benthic foraminifera

Abstract During the 2024 global mass bleaching event, a rapid bleaching assessment was conducted on two large benthic foraminifera populations on One Tree Reef, southern Great Barrier Reef. In tropical reef ecosystems, large benthic foraminifera are major carbonate sediment producers and function as important ecological engineers. We documented the thermal stress of Marginopora vertebralis and Baculogypsina sphaerulata from two high-density populations along the leeward and windward side of One Tree Reef in March 2024 following an 8-degree heating week with local on-reef temperatures exceeding 30 °C. Bleaching was more prevalent at the lower-energy leeward site (81.4% of M. vertebralis and 80.2% of B. sphaerulata individuals bleached, respectively) than the windward site (31.1% of M. vertebralis and 40.8% of B. sphaerulata bleached), suggesting localised hydrodynamic exposure has a significant impact on the health and bleaching susceptibility of benthic foraminifera. This study provides a rapid bleaching guide and emphasises the necessity of ongoing monitoring of benthic foraminifera to understand local and regional impacts of climate-induced stressors on reef carbonate production.

Persistent greenhouse conditions in Eocene North America point to lower climate sensitivity

Oxygen isotope values (δ18O) in benthic foraminifera indicate a marked cooling from the early to late Eocene in the higher latitudes where oceanic bottom water forms. This record is widely interpreted as an indication of global surface cooling, leading to the hypothesis of greater climate sensitivity to atmospheric CO2 concentration in warmer than in cooler climate states. Here we extend the coexistence approach using phylogenetic trees to study Eocene climatic change in the Western Interior of North America based on assemblages of small reptiles. Our results capture and elaborate on climatic features previously inferred for the early Eocene, such as drying during the Palaeocene-Eocene Thermal Maximum, but also show that the late Eocene in mid-latitude North America was considerably warmer and wetter than previously thought. Accordingly, the net Eocene cooling trend in benthic foraminiferal δ18O might reflect not global but rather regional, high-latitude phenomena, and hypothesised extreme values of climate sensitivity to CO2 doubling might be revised downward.

The Potential of Benthic Foraminifera Carbon and Oxygen Isotopic Proxies as Environmental Indicators in Coral Reef Regions

AbstractUsing reef‐dwelling benthic foraminifera for paleoenvironmental reconstruction remains an unresolved challenge. Therefore, to evaluate the efficacy of using the δ18O and δ13C values obtained from benthic foraminifera species as environmental indicators in tropical reef regions, 233 specimens of 20 species collected from Huangyan Island and Lingyang Reef in the South China Sea were studied. The analyzed foraminifera species exhibited significant inter‐ and intraspecific variations for both δ18O and δ13C values, with δ13C values displaying greater overall intraspecific variability. Clear distinctions were observed between the symbiont‐bearing large benthic foraminifera (LBF) and symbiont‐barren small benthic foraminifera, with the latter displaying slight oscillations around the isotopic values of the estimated equilibrium calcite and the δ18O and δ13C values of the LBF miliolids and rotaliids exhibiting markedly divergent trends. Miliolids generally showed higher isotopic values than equilibrium calcite, while rotaliids exhibited lower values, which may be attributed to variations in the calcification patterns and symbiotic algae associations. The δ18O and δ13C values of two LBF species at the two studied sites are generally consistent with the sea surface temperature and productivity levels, providing valuable insight into the utilization of reef‐dwelling foraminifera as environmental indicators. The results of this study support the hypothesis that the δ18O and δ13C values of certain reef‐dwelling foraminifera are reliable environmental indicators and offer valuable insights for paleoenvironmental reconstruction and marine ecosystem forecasting, although the limitations of this method should be considered in practical applications.

Late Eocene-Early Miocene paleoenvironmental shifts in the NW south American margin: Tectonic and climatic drivers inferred from benthic foraminifera

Late Eocene-Early Miocene paleoenvironmental shifts in the NW south American margin: Tectonic and climatic drivers inferred from benthic foraminifera

Taxonomy and Distribution of Recent Benthic Foraminifera from the Savitri Estuary, West Coast of India, Maharashtra

Taxonomy and Distribution of Recent Benthic Foraminifera from the Savitri Estuary, West Coast of India, Maharashtra

Virgulinella fragilis in the North Adriatic Coastal Sediments: A New Non-Indigenous Benthic Foraminiferal Taxon?

The Mediterranean Sea is considered a hotspot for bioinvaders. Nonetheless, information on non-indigenous benthic foraminifera is still fragmented. This study documents for the first time the presence along the northwestern Adriatic coast of the non-indigenous benthic foraminifera species Virgulinella fragilis, Grindell and Collen (1976). Due to the low abundance recorded in the study area, the presence of this species may represent an early colonization phase. We discuss the temporal and spatial patterns of V. fragilis arrival in the Mediterranean and Adriatic Seas, and we hypothesize stowaway transport (via ship fouling or ballast water) as the main introduction pathway. Morphological test analyses suggest that V. fragilis prefers a low oxygen content, consistent with the ecological requirements reported for this taxon in the literature. The application of Maximum Entropy (MaxEnt) modeling indicates that the key factor influencing the presence of V. fragilis in the Mediterranean basin is the bacterial concentration expressed as NO3. Projections under future climate scenarios (RCP 4.5) point to a decline of habitat suitability conditions, making widespread invasion unlikely in the Mediterranean. We emphasize the importance of continuous biomonitoring for early detection of alien species, improving our understanding of invasion dynamics and enabling prompt conservation actions, especially in regions impacted by anthropogenic activities.

Beyond taxonomy: A framework for biological trait analysis to assess the functional structure of benthic foraminiferal communities.

Benthic foraminifera, as key components of marine and transitional ecosystems, provide a valuable opportunity to investigate the effects of environmental changes on marine biodiversity. While traditional taxonomic approaches have been instrumental in assessing benthic foraminifera assemblages, a trait-based approach offers a more holistic perspective on their ecological roles. This study introduces a framework for biological trait analysis (BTA) of benthic foraminifera, emphasizing the importance of morphological, physiological, and ecological traits. We examine the potential of morphogroup analysis as a precursor to BTA, acknowledging its limitations, and propose a list of functional traits relevant to benthic foraminifera. These include both response and effect traits, such as wall texture, test size, chamber arrangement, chamber disposition, pore density, pore size, life mode, feeding mode, bioturbation mode, respiration mode, association and indicative value. Additionally, we address the challenges and opportunities associated with quantifying and analyzing foraminiferal functional traits, and outline key statistical methods for exploring trait-environment relationships. By implementing BTA, we can evaluate the functional diversity and ecological roles of foraminiferal communities, identify the drivers of community structure, predict responses to environmental changes, and assess the impacts of anthropogenic disturbances on marine ecosystems.

A nineteenth- and twentieth-century reproductive regime shift in benthic foraminifera from the Santa Barbara Basin, California.

Long-term records that span the past several centuries and capture within-population variation are critical for distinguishing ephemeral ecosystem changes from regime shifts. Using an approximately 2 kyr record of reproductive life history from the central Santa Barbara Basin, we examined population trends in reproductive mode and accumulation rate (i.e. reproductive output) across four species in the biserial benthic foraminiferan genus Bolivina. Bolivina populations were consistently dominated by asexually produced individuals until the mid-nineteenth century, after which they exhibit an increase in variance and a decrease in the mean proportion of asexually produced individuals. At the same time, they underwent an order-of-magnitude decline in accumulation rate. The magnitude and persistence of these changes suggest that the nineteenth and twentieth centuries represent a life-history regime shift. The compounding effects of anthropogenic impacts and long-term trends in the California Current System (such as heightened deoxygenation and altered sedimentation regimes) may have pushed the Santa Barbara Basin towards increased investment in sexual reproduction.

Benthic foraminifera as bioindicators of coral condition near mangrove environments.

Benthic foraminifera as bioindicators of coral condition near mangrove environments.

Benthic foraminifera from the Gulf of Guinea: Implications for paleoenvironmental reconstructions

Benthic foraminifera from the Gulf of Guinea: Implications for paleoenvironmental reconstructions

Shallow‐Marine, Benthic Ecosystems Show Compositional Shifts in Response to the Paleocene‐Eocene Thermal Maximum (PETM) on the Adriatic Carbonate Platform

AbstractThe response of shallow‐marine ecosystems to the Paleocene‐Eocene Thermal Maximum (PETM) is understudied, and analyses that do exist typically focus on larger benthic foraminifera and coral‐algal reef mound evolution. Here we investigate the dynamics of benthic marine assemblages across the PETM in the Kozina and Čebulovica sections (Slovenia) on the Adriatic Carbonate Platform. Our results show significant ecological changes associated with the PETM with a protracted recovery into Shallow Benthic Zone (SBZ) 6. The compositional change corresponds to the reduced dominance of red algae, a turnover in the dominant larger benthic foraminifera, and increased assemblage homogeneity. These changes are not associated with a lithofacies transition, as a shift from reef mounds to a foraminiferal‐dominated carbonate platform occurs prior to the Paleocene/Eocene boundary. The investigated sections also show a transition from coral‐algal mounds to microbial mounds during SBZ 4, but the main difference between these reef types is the increased dominance of the microbes. Moreover, there is no unequivocal evidence that either reef type persisted into the Eocene in this region. Whilst the PETM is not an extinction event, except for deep‐sea benthic foraminifera, the ecological changes recorded show that the ecosystem responses at the PETM are consistent with other hyperthermal events.

Quantitative Biofacies Analysis of Upper Oligocene Reef-Coral Neritic Carbonates (Southern Pakistan)

This study examines four shallow-water, reef-coral-bearing carbonate successions belonging to the Jhill Limestone Unit of the Gaj Formation, exposed in the area near Karachi (southern Pakistan). Sixty-two samples were collected for the quantitative analysis of the skeletal and foraminiferal assemblages. The analysis of large benthic foraminifera suggests a placement within the late Oligocene, characterized by the setup of the Late Oligocene Warming Event. Thanks to quantitative analyses and multivariate statistics, three biofacies were identified: (1) the reef coral biofacies (BFA), indicative of a sheltered, shallow-water environment above fair-weather wave base; (2) the coralline algal biofacies (BFB), deposited within a mesophotic setting and representing the deepest biofacies among the three recognized ones; and (3) the large benthic foraminiferal and coralline algal biofacies (BFC), subdivided into two sub-biofacies, namely (a) the miogypsinid, thin and flat large benthic foraminiferal and coralline algal sub-biofacies (BFC1), indicative of deeper setting, comprised between BFA and BFB, and (b) the miogypsinid and coralline algal sub-biofacies (BFC2), indicative of shallower settings than BFC1, and bearing evidence of paleo-seagrass meadows. All these biofacies were developed within the photic zone, in a relatively flat seafloor punctuated by patch reefs and seagrass meadows and characterized by a notable nutrient influx. Foraminiferal-based experimental paleobathymetric parameters, including the lepidocyclinids/miogypsinids, the flat nummulitids/lepidocyclinids, and the hyaline/porcelaneous foraminifera ratios, were tested and confirmed as reliable tools for paleodepth and paleoenvironmental reconstructions.

Paleobiodiversity, Paleobiogeography, and Paleoenvironments of the Middle–Upper Eocene Benthic Foraminifera in the Fayum Area, Western Desert, Egypt

The middle–upper Eocene successions of northwest Fayum, Egypt, provide a crucial archive for reconstructing paleoenvironmental conditions and paleobiogeographical patterns of the southern Tethys realm. Stratigraphically, the investigated section is subdivided into three rock units: the Gehannam Formation (Bartonian-Priabonian), the Birket Qarun Formation, and the Qasr El Sagha Formation (Priabonian). A total of 101 benthic foraminiferal taxa, representing 31 genera, 23 families, 13 superfamilies, and four suborders, were identified. The middle–late Eocene age is primarily determined by the co-occurrence of index spinose planktonic foraminifera (Acarinina spp., Morozovelloides spp., and Globigerinatheka semiinvoluta) and benthic foraminiferal assemblages, further supported by the presence of the nannofossil marker Chiasmolithus oamaruensis. Four local benthic biozones are identified and correlated with coeval zones in nearby areas. Quantitative analyses of benthic foraminiferal individuals, diversity indices, ecological parameters, and the benthic foraminiferal oxygen index (BFOI) reveal distinct environmental shifts. The rock unit occupied by the late middle Eocene assemblages is diversified and dominated by calcareous infaunal taxa (e.g., Bolivina spp., Fursenkoina spp., and Nonionella spp.), indicative of low-oxygen outer neritic conditions associated with elevated organic influx. In contrast, the late Eocene Birket Qarun and Qasr El Sagha showed an increase in epifaunal forms and reduced diversity, suggesting a transition to dysoxic-oxic conditions. Paleobiogeographical analysis indicates a strong affinity with the Tethyan realm, with potential faunal exchange through the Trans-Saharan Seaway. These findings enhance our understanding of Paleogene marine connections between the Tethyan and Indo-Pacific realms, contributing to broader discussions on Eocene paleobiogeography and depositional dynamics in North Africa.

Contrasts in the marine inorganic carbon chemistry of the Benguela Upwelling System since the Last Glacial Maximum

Abstract. Upwelling regions are dynamic systems where relatively cold, nutrient-, and CO2-rich waters reach to the surface from the deep. CO2 sink or source properties of these regions are dependent not only on the dissolved inorganic carbon content of the upwelled waters, but also on the efficiency of the biological carbon pump which constrains the drawdown of atmospheric CO2 in the surface waters. The Benguela Upwelling System (BUS) is a major upwelling region with one of the most productive marine ecosystems today. However, contrasting signals reported on the variation in upwelling intensities based on, for instance, foraminiferal and radiolarian indices over the last glacial cycle indicate that a complete understanding of (local) changes is currently lacking. To reconstruct changes in the CO2 history of the northern Benguela upwelling region over the last 27 kyr, we used a box core (64PE450-BC6) and piston core (64PE450-PC8) from the Walvis Ridge. Here, we apply various temperature and pCO2 proxies, representing both surface (U37K′ and δ13C of alkenones) and subsurface (Mg / Ca and δ11B in planktonic foraminiferal shells) processes. Reconstructed pCO2 records suggest enhanced storage of carbon at depth during the Last Glacial Maximum (LGM). The offset between δ13C of planktonic (high δ13C) and benthic foraminifera (low δ13C) suggests evidence of a more efficient biological carbon pump, potentially fueled by remote and local iron supply through eolian transport and dissolution in the shelf regions, effectively preventing release of the stored glacial CO2.

NOVALESIA PRODUCTA (MAGNIEZ, 1972), A LITTLE-KNOWN BENTHIC FORAMINIFER FROM THE APTIAN TAFT FORMATION OF CENTRAL IRAN

The larger benthic foraminifera Novalesia producta (Magniez) is a common constituent in the faunal assemblages of inner platform wackestone-packstone microfacies of the Aptian Taft Formation, Central Iran. The abundant specimens observed in thin-sections allow a detailed morphological and biometrical analysis of the taxon that extends the known data.

Recent benthic foraminifera communities offshore of Thwaites Glacier in the Amundsen Sea, Antarctica: implications for interpretations of fossil assemblages

Recent benthic foraminifera communities offshore of Thwaites Glacier in the Amundsen Sea, Antarctica: implications for interpretations of fossil assemblages