Foraminiferal Species Research Articles

Trophic strategies of intertidal foraminifera explored with single-cell microbiome metabarcoding and morphological methods: What is on the menu?

In mudflats, interactions and transfers of nutrients and secondary metabolites may drive ecosystems and biodiversity. Foraminifera have complex trophic strategies as they often rely on bacteria and eukaryotes or on potential symbionts for carbon and nitrogen resources. The capacity of these protists to use a wide range of adaptive mechanisms requires clarifying the relationships between them and their microbial associates. Here, we investigate the interactions of three foraminiferal species with nearby organisms in situ, by coupling molecular (cloning/Sanger and high-throughput sequencing) and direct counting and morphological identification with microscopy. This coupling allows the identification of the organisms found in or around three foraminiferal species through molecular tools combined with a direct counting of foraminifera and diatoms present in situ through microscopy methods. Depending on foraminiferal species, and in addition to diatom biomass, diatom frustule shape, size and species are key factors driving the abundance and diversity of foraminifera in mudflat habitats. Three different trophic strategies were deduced for the foraminifera investigated in this study: Ammonia sp. T6 has an opportunistic strategy and is feeding on bacteria, nematoda, fungi, and diatoms when abundant; Elphidium oceanense is feeding mainly on diatoms, mixed with other preys when they are less abundant; and Haynesina germanica is feeding almost solely on medium-large pennate diatoms. Although there are limitations due to the lack of species coverage in DNA sequence databases and to the difficulty to compare morphological and molecular data, this study highlights the relevance of combining molecular with morphological tools to study trophic interactions and microbiome communities of protists at the single-cell scale.

Permian foraminifers from the exotic limestone blocks within the central Qiangtang Metamorphic Belt, Tibet and their geological implications

• The age of the exotic limestone blocks within the Central Qiangtang Metamorphic Belt is late Kungurian to Roadian. • The exotic limestone blocks came from the Shuanghu type of Permian sequences in the South Qiangtang Block. • A strong subduction and accretion process happened during the closure of the Longmu Co-Shuanghu Paleotethys Ocean. The Central Qiangtang Metamorphic Belt (CQMB) is a subject of long-standing controversy for decades with respect to its origin and tectonic evolution. In this study, two foraminiferal faunas are reported from the exotic limestone blocks in the Jiaomuchaka and Jiangaizangbu sections within the CQMB. In total, 9 species of fusulines and 32 species of smaller foraminifers have been discovered in the Jiaomuchaka section, and 10 species of fusulines and 15 species of smaller foraminifers have been documented in the Jiangaizangbu section. In terms of the presence of the fusulines Pseudodoliolina ozawai , Presumatrina neoschwagerinoides , Neoschwagerina simplex and Afghanella sp., an age of late Kungurian to Roadian can be assigned to the faunas. A comparative study on the stratigraphic sequence and foraminiferal faunas between the exotic limestone blocks and contemporaneous deposits in the adjacent areas reveals that the exotic limestone blocks resemble strata of the Lugu Formation in the Shuanghu and Minzhuochaka areas in the South Qiangtang Block. The presence of these exotic limestone blocks within the CQMB suggests that the in-situ deposits of the Lugu Formation have been partly subducted beneath the North Qiangtang Block during the closing of the Paleotethys Ocean along the Longmu Co-Shuanghu Suture Zone.

Moscovian (Middle Pennsylvanian) Foraminifers and Biostratigraphy of the Ichinotani Formation, Hida Marginal Terrane, Japan

The Moscovian part of the Ichinotani Formation is subdivided into six fusuline zones from lower to upper, Fusulinella kamitakarensis, Fusulina? sp., Fusulinella hanzawai–Fusulina kamensis, Fusulinella rhomboidalis–Protriticites ovatus, Beedeina lanceolata, and Fusulinella rhomboidalis–Fusulinella soligalichi. The strata underlying the first zone, previously assigned to the Moscovian, are reassigned to the upper part of the Bashkirian. Age-diagnostic species are scarce in the possibly Kashirian F. kamitakarensis Zone and are absent in the F.? sp. Zone. The third to the sixth zones are correlated to the Podolskian, Myachkovian, Podolskian, and Myachkovian of the stratotypes in the Russian Platform, respectively. The fourth zone is inferred to be fault bounded with the fifth zone. The sixth zone is overlain by the lower part of the Kasimovian Protriticites variabilis Zone. Twenty species of fusulines and five species of non-fusuline foraminifers are described. Newly proposed herein are Pseudojanischewskina titanica, Bradyinelloides paranautiliformis, and Fusulinella igoi.

Carboniferous Foraminifers of the Lower Part of the Ichinotani Formation, Hida Marginal Terrane, Japan

The Ichinotani Formation distributed in the Fukuji area, Hida Marginal Terrane, central Japan, consists of fossiliferous bedded limestone intercalating reddish mudstone and sharpstone conglomerate with a continental margin affinity. The lower part of the formation in the studied area is subdivided into five fusuline zones from lower to upper, Eostaffella kanmerai, Pseudostaffella antiqua, Pseudostaffella kanumai, Profusulinella fukujiensis, and Profusulinella dagmarae. These five zones are probably correlated to the Visean/Serpukhovian (Venevian/Tarusian), middle part of the Bashkirian (Akavasian), middle to upper part of the Bashkirian (Askynbashian to Tashatinian), upper part of the Bashkirian (Tashatinian to Asatausian), and uppermost Bashkirian (Asatausian), respectively, of the stratotypes of the Russian Platform and the South Urals based on the biostratigraphy, faunal composition and correlation of foraminifers. There are remarkable faunal transitions between the Eostaffella kanmerai and Pseudostaffella antiqua zones. Almost coeval Pseudostaffella–Profusulinella assemblages are recognized between the upper part of the Lower Member and the lower part of the Middle Member in the type section of the Ichinotani Formation. Thirty-three species of foraminifers are paleontologically noted and compared to those mainly of the type materials and the taxa to have been described from the Ichinotani Formation.

Tracing ecological fluctuations during the Middle to Late Jurassic of Jhura, Kutch, India, using foraminifera

The aim of this work is to examine ecological patterns by analyzing the distribution of foraminifera in the Jurassic sediments of the Jhura area, Kutch, India. 87 foraminiferal species were recovered, which were analyzed for paleoecological interpretations. Three techniques were employed: 1) Diversity indices, in which four episodes are identified based on different indices values; 2) Clustering and nMDS ordination approaches identify four assemblages of benthic foraminifera, which differ in biotic and abiotic characteristics; 3) Morphogroup analysis, which divides the studied sequence into four paleoecological units. Four depositional episodes are recognized within the studied interval: Episode I (Bajocian to Bathonian), Spirillina polygyrata assemblage shows the calm environment with a high diversity of foraminiferal species and enough nutrients in the outer shelf zone having normal salinity and high level of dissolved oxygen. Episode II (Lower Callovian), Miliammina cf. M. valdensis assemblage occurred in a stressed condition with low diversity of species in a shallower portion of mid-shelf in a hypo-saline environment and reduced oxygen condition having low to average food influx. Episode III (Middle to Upper Callovian), Lenticulina subalata assemblage indicates that this portion deposited in stress-free environmental conditions having normal salinity and well‑oxygenated waters in the deepest section of the outer shelf region with high nutrient supply. Episode IV (Oxfordian), Lenticulina bulla assemblage thrived in hyposaline conditions with low oxygen levels and enough nutrients in the deeper portion of the mid-shelf region. An unstable oceanic shelf is interpreted during the deposition of the examined section because of the fluctuations in all inferred parameters.

Age of the latest marine sedimentation in the western Kunlun area constrained by planktic foraminifera

Surface uplift of the Tibetan Plateau in the Cenozoic has dramatically affected evolutions of climate, environment, and biota in East Asia. The onset time of plateau uplift can be roughly constrained by the termination of the latest marine sedimentation, which shows large spatial differences in the Tibetan Plateau. In the northwest Tibetan Plateau of the western Kunlun area, the Tielongtan Group represents the latest marine sedimentation. However, the age of its depositional cessation is still unknown. For the first time, we conduct taxonomic, paleoecologic and paleogeographic studies of planktic foraminifera in the limestones of the Tielongtan Group. Despite poor preservation and low abundance, ten planktic foraminiferal species are identified, including Globotruncana falsostuarti, G. cf. linneiana, G. cf. ventricosa, Planohedbergella prairiehillensis, P. cf. yaucoensis, Pseudotextularia nuttalli, Planoheterohelix globulosa, P. cf. praenuttalli, Muricohedbergella holmdelensis and Whiteinella brittnensis. The foraminiferal assemblages suggest an age of late Campanian to Maastrichtian, indicating a shallow, neritic marine environment. Combining available research data from other regions, we show that these planktic foraminifera were widely distributed in the Tarim basin, southern Tibet, and the Mediterranean area during the latest Cretaceous. Our result of planktic foraminifera in the Tielongtan Group implies that the surface uplift of the western Kunlun area did not begin until after ∼76–66 Ma.

Benthic foraminifera as bioindicators of anthropogenic pollution in the Red Sea Coast, Saudi Arabia

The concentrations of Fe, Mn, Cu, Ni, Zn, Pb, Cr, Co, and Cd were measured in the tests of two foraminiferal species (Sorites orbibulus and Peneroplis planatus) using ICP-MS to assess the marine contamination. Iron was the most abundant metal (3294 μg/g), followed by Mn (133 μg/g), Cu (34.7 μg/g), Zn (28.3 μg/g), Cr (25 μg/g), Ni (18.9 μg/g), Pb (12.2 μg/g), Co (9.5 μg/g), and Cd (0.85 μg/g). The values enrichment factor, geo-accumulation index, and contamination factor show that the foraminiferal shells are enriched in (Cd, Cu, Pb) posing an ecological risk. Iron shows highest concentration amongst the heavy metals recorded in the study shells, however, shows low concentration in comparison with surrounding areas of Red Sea coast in Saudi Arabia and Egypt. Other heavy metals show higher concentrations than those recorded in Egypt and Saudi Arabia. The elevated heavy metal concentrations in the foraminiferal tests may be attributed to the industrial and urban activities along Yanbu coast.

Distribution and Diversity of Benthic Foraminifera in the Coastal Area of Al-Bawadi Island, Southern Red Sea

ABSTRACT The coastal areas of the southern Red Sea islands are non-urbanized, relatively pristine environments and are located on the main migration pathway of Indo-Pacific foraminiferal species to the northern Red Sea and to the Mediterranean Sea via the Suez Canal. Studying the foraminiferal composition, structure, and distribution in the Red Sea is essential to understanding how Indo-Pacific species can migrate to and survive in the Mediterranean Sea. Al-Bawadi, an uninhabited island located in the southern Red Sea, is an ideal location for such study. The coastal waters are oligotrophic, hypersaline, and very warm, overlying carbonate-rich, sandy-bottom and coral-reef substrata. In 25 sediment samples collected from water depths <6 m, 79 foraminiferal species were recorded. Rotaliids dominated the assemblages, followed by miliolids; agglutinated foraminifers were scarce, and planktic species were not found. The larger-benthic, symbiont-bearing Neorotalia calcar dominated except in very shallow water, where smaller, free-living miliolid species dominated. The FoRAM Index (FI) was calculated for all samples; the symbiont-bearing group included seven genera comprising more than half of the total assemblage such that the FI>4 for most samples from depths >3 m, indicating that water quality is suitable for coral-reef growth and recovery. Diversity indices reflected prevailing normal marine to hypersaline conditions. Depth, presence of coral reefs, and hydrodynamics are the main factors controlling the spatial distribution of the foraminiferal assemblages. Occurrences of aberrant tests in the tidal flat area could be related to naturally occurring stresses, such as rapid changes in temperature and salinity, or to breakage and repair. Monitoring studies of unthreatened environments are essential to understand reef-related assemblages and to predict the migration pathways of thermo-tolerant and thermo-sensitive foraminiferal species.

Stable Isotopic Variability in Individual Benthic Foraminifera from the Continental Shelf of Tropical Brazil

ABSTRACT We analyzed nine benthic foraminiferal species from the Açu Reef belonging to the orders Rotaliida and Miliolida, symbiont-bearing (Rotaliida: Amphistegina gibbosa, Heterostegina depressa; Miliolida: Peneroplis carinatus, Archaias angulatus, Amphisorus hemprichii, and Archaias compressus) and symbiont-barren (Rotaliida: Buccella peruviana, Pseudononion atlanticum; Miliolida: Quinqueloculina lamarckiana). Stable isotopes measured on individual tests display a large intraspecific variability (δ18O: ∼1–1.5‰; δ13C: ∼2–3.5‰) that is not associated with site location, sampling season, or water depth. Positive correlation between δ13C and δ18O values is significant in three of the species (A. gibbosa, B. peruviana, and Q. lamarckiana), with a regression slope similar to other marine calcifiers (∼2‰ δ13C/‰ δ18O), perhaps related to the carbonate chemistry of the calcifying fluid. With the exception of A. gibbosa, offsets from δ18O equilibrium, when distinct, tend to be positive. Offsets from δ13C of ΣCO2 of sea water are negative for two of the rotaliids (A. gibbosa and H. depressa) and positive for three of the miliolids (P. carinatus, A. angulatus, A. hemprichii), with non-symbiont-bearing species of both orders being close to the sea water values (∼ 1.3–2‰). These δ13C differences are consistent with calcification pathways of rotaliids versus miliolids, with the former drawing carbon from an internal pool and the latter from ambient seawater. Our study contributes a large data set that illustrates the importance of vital and abiotic effects on the stable isotopic composition of large benthic foraminifera in a tropical continental shelf, limiting their applicability as paleoenvironmental tracers.

Magnetofossils and Benthic Foraminifera Record Changes in Food Supply and Deoxygenation of the Coastal Marine Seafloor During the Paleocene‐Eocene Thermal Maximum

AbstractContinental shelf sediments along the northeast continental margin of North America contain a magnetofossil‐rich interval deposited during the Paleocene‐Eocene Thermal Maximum (PETM), an abrupt global warming event that occurred ∼56 Ma. These magnetofossils were produced by magnetotactic bacteria and unidentified, iron‐biomineralizing organisms. Previous work shows three distinct magnetofossil endmembers identified from principal component analysis of first‐order reversal curves (FORC‐PCA). The relative proportions of these magnetofossil endmembers varied over time during the PETM. Benthic foraminiferal species associations from the same sediments also vary during the PETM. Here, we compare the variability in magnetofossils and benthic foraminifera and statistically test, for the first time, whether they are significantly correlated. We find that changes in the type of magnetofossils present within the sediment correspond to changes in benthic foraminiferal assemblages, thus reflecting syndepositional conditions such as changes in oxygen, nutrients, and organic carbon concentrations, rather than diagenetic processes. We also find that magnetofossil‐producing organisms may respond to specific environmental pressures differently than benthic foraminifera, and in some cases, may better record these environmental signals. Therefore, FORC‐PCA on magnetofossil‐rich sediments can be used to understand discrete changes in ocean and/or early sediment chemistry over episodes of climate change. These environmental responses are inferred from non‐destructive, reproducible magnetic measurements, adding an independent environmental proxy to more commonly studied microfossil and geochemical proxies. Notably, these measurements only require small bulk sediment samples and do not need to contain calcium carbonate, making this approach ideal where sample material is limited and the record is affected by ocean acidification.

Sedimentology and foraminiferal paleoecology of the exposed Oligocene–Miocene Ogwashi-Asaba Formation in Issele-Uku area, Anambra Basin, southern Nigeria: A paleoenvironmental reconstruction

Sedimentological and foraminiferal paleoecological studies were carried out for the Oligocene–Miocene Ogwashi-Asaba Formation of the Anambra Basin at the Issele-Uku area in southern Nigeria, to reconstruct paleoenvironments. The pattern of rock successions and textural characteristics suggest the prevalence of fluvio-deltaic setting during the formation of lignites and clastic rocks of Ogwashi-Asaba Formation. Agglutinated benthic foraminiferal species such as Ammotium sp., Textularia sp., Gavelinella sp., Milliamina sp., Reophax sp., Bolivina sp., Eponides sp., Pseudobolivina sp. and Lenticulina sp. dominate the shale units whereas the planktonic forms are absent. All these species have very low population and diversity in the shales, which could be due to the presence of harsh conditions such as low oxygen level and scarcity of food, leading to poor survival. The assessments of benthic foraminifera's habitat suggest middle-to-inner neritic marine environment for the shales. Granulometric results suggest fluvial environment for the sandstone and deltaic for the lignite. The Ogwashi-Asaba Formation in Issele-Uku area of Anambra Basin, southern Nigeria, therefore, have records of shallow marine, and fluvio-deltaic paleoenvironments.

Very high Middle Miocene surface productivity on the U.S. mid-Atlantic shelf amid glacioeustatic sea level variability

The Miocene Climatic Optimum (MCO) provides important insights into how the climate system operates under elevated temperatures and atmospheric CO2 levels. Few western North Atlantic paleotemperature or paleoecological records exist from the MCO, despite their importance for understanding both regional and global climate dynamics. Here we present quantitative MCO paleoecological data from the western North Atlantic, specifically from the Baltimore Gas & Electric (BG&E) marine sediment core from southern Maryland, USA. We examine alkenones and planktic foraminifera and document the first sea surface temperature (SST) and productivity estimates for the MCO and the Middle Miocene Climate Transition (MMCT) from the continental shelf. Increased levels of planktic foraminifer species diversity and surface productivity accompany high sea level intervals of the MCO, indicating coastal upwelling. Cooling episodes correlate to unconformities in the BG&E core that reflect sea level lowstands; these and sedimentary cycles tie the record to eccentricity-paced Antarctic ice sheet growth and decay. This dynamic record not only captures the variability in SST, sea level and coastal productivity during the warm MCO and the transition to cooler global temperatures during the MMCT, but it also demonstrates the variability in local conditions within and between intervals of high sea level.

Uppermost Triassic Halstätt-like cephalopod limestone (Lilu Facies) and Foraminifera, Timor-Leste

Ammonoid-rich wackestone beds forming a ca 2 m section between shallow-marine limestones of the Bandeira Group (Norian to possibly Rhaetian) and a wackestone–calcareous mudstone succession belonging to the Lower Jurassic Wailuli Group are recorded from the western part of Timor Leste. They are included in the Halstätt-like Lilu Facies of the Bandeira Group. Age-diagnostic involutinid foraminiferal species, not previously recorded from Timor, include Involutina liassica, Trocholina sp. ex. gr. Trocholina turris and Lamelliconus permodiscoides, which collectively indicate a Rhaetian age, possibly ranging down to the Sevatian. The conodont Norigondolella steinbergensis, recorded low in the section, is consistent with this age determination. The Lilu Facies was deposited at a water depth of a few tens of metres, as suggested by the presence of extensive cyanobacterial borings into shell fragments and the presence of microbial laminations including the presence of stromatolites and bacinellid-like fabrics. Among macrofossils, common ammonoids are present in the section, and marine reptile bones are conspicuous in the lower beds. Other biogenic components of the rock observed in acetate peels and thin sections are abundant echinoderm debris (including pentacrinoid columnal plates), bivalve fragments and micro-gastropods, rare siliceous sponge spicules, solitary corals, and brachiopod debris. In the studied region, a major drowning of a shallow-marine carbonate platform took place probably in the Rhaetian or possibly latest Norian. Similar ‘ammonitico rosso limestone’ interbedded with thick-bedded limestones of a shallow-marine carbonate platform is present in the uppermost Triassic of Seram. More detailed biostratigraphical comparisons and correlations of similar units in Timor and other nearby islands may indicate a general marine drowning of Late Triassic carbonate platforms, at least in the northern part of the East Gondwana Interior Rift system, during the Rhaetian or possibly latest Norian.

Foraminifers associated with macroalgae on a wave-cut platform off Abu Qir coastal area, Egypt

Since their earliest history, benthic foraminifers have diversified to inhabit a vast array of habitats, from semi-terrestrial to the deep-sea floor. Epiphytic foraminifers developed morphologies that have allowed them to inhabit macroalgal fronds and thalli. This study examined the presence of benthic foraminiferal species living on algal species inhabiting rocky coastal environments in the southeastern Mediterranean Sea. Fronds of six algal taxa found abundantly on a carbonate wave-cut platform off the east coast of Alexandria were collected and the associated foraminifers living on each frond were identified. Twenty foraminiferal species were recorded, with seven epiphytic species (Asterigerinata mamilla, Elphidium aculeatum, Elphidium crispum, Peneroplis pertusus, Peneroplis planatus, Rosalina bradyi, and Rosalina macropora) comprising > 80% of the assemblage. Nearly 70% of the foraminiferal specimens were found on two algal species, Caulerpa racemosa and Ellisolandia elongata. Two Indo-Pacific foraminiferal species found in the samples (Amphistegina lobifera and Amphisorus hemprichii), in addition to Caulerpa racemosa, are considered invasive species in the Mediterranean. The widespread occurrence of the opportunistic invasive Caulerpa spp., which apparently provides suitable habitat for many epiphytic foraminifers, may partially compensate for the predicted decline in coralline-algal habitat under the effect of ocean acidification.

Volumetric analysis of benthic foraminifera: Intraspecific test size and growth patterns related to embryonic size and food resources

Morphological variation in benthic foraminifera is often used to reconstruct paleoenvironmental conditions and infer their physiological responses to environmental change. Computed-tomographic imaging allows precise measurements of test volume, test surface area, and the internal volume of individual chambers, thus changes in morphology throughout ontogeny can used to test these morphology-environment relationships. Here, I examine morphological changes in five benthic foraminiferal species (Uvigerina peregrina, Buliminella tenuata, Loxostomum pseudobeyrichi, Bolivina argentea, and Bolivina seminuda) during a deglacial deoxygenation event recorded in marine sediments from the Gulf of Alaska to examine morphological responses to oxygenation. Although the mechanics of oxygen diffusion imply that benthic foraminifera should have higher surface area to volume ratios (SA/V) at low oxygen, specimens from the lowest oxygen conditions had lower SA/V due to their larger size. Examination of test volume through ontogeny indicates that specimens achieve large size by having a large initial chamber and not via higher growth rates. Thus, terminal size is a passive result of embryonic size. U. peregrina and B. tenuata have the strongest association between large size and low-oxygen and are sensitive to organic matter availability. The studied low-oxygen event was likely maintained by enhanced organic carbon export, which provided the resources to produce large offspring. Thus, the morphological changes observed along the paleo-oxygen gradient are likely related to food availability and the survival advantage of larger embryos in low-oxygen settings for some species. These results imply that size and SA/V in benthic foraminifera do not reliably reflect physiological responses to oxygenation.

Foraminiferal Distribution Pattern and its Ecological Implications in the Koswari and Van Islands of the Tuticorin Group of Islands

Objectives: The present investigation attempts to map the foraminiferal distribution pattern, its ecological significance, and the elemental composition of the Koswari and Van islands. Methods: Foraminiferal distribution patterns (both planktic and benthic) were recorded, and textural and geochemical analyses were carried out in the present study. Findings: The coastal environments are generally highly dynamic regions of the earth that possess imprints of global climatic variations. The islands of the Gulf of Mannar emerged during the last interglacial period. These islands are getting eroded due to the long-term impact of coral mining and climatic changes. The excess removal of corals from Koswari Island adversely affected the live coral cover of the Island. The Van island is in proximity to the Tuticorin coastal city and one-fourth of the Island has already become submerged due to several natural and anthropogenic factors. Both the islands are affected by the world coral bleaching event witnessed from 2014-2017. This study is an attempt to record how the foraminiferal assemblages of Koswari and Van islands responded to the world coral bleaching event. In the present investigation, we identified fifteen benthic foraminiferal species and two planktic foraminiferal species from both islands. The foraminiferal assemblages mark the abundance of Neorotalia calcar, Quinqueloculina seminulum, Elphidium crispum, Amphistegina lessonii, and Rotalidium annectens. The main ecological parameters which govern the foraminiferal distribution in these islands are coral reef flats, carbonate environments, and shallow coastal waters. Neorotalia calcar and Quinqueloculina seminulum are recorded as the most abundant species of both Koswari and Van islands. N. calcar prefers macroalgal mat as substratum,while the frequent occurrence of deformed tests and stress-tolerant species such as Q. seminulum indicate the influence of pollution in the coastal area. These recorded species are considered characteristic reef benthic foraminifers which prefer coarse sandy substratum. The other abundant species are Elphidium crispum, Amphistegina lessonii, and Rotalidium annectens, which are widely distributed in the inner shelf sediments of Tamil Nadu and Kerala coasts. Textural attributes of the Koswari and Van islands reflect its high energy environment, and the geochemical signature shows the high calcareous content with typical coral reef foraminifera associated with such sediment nature. Novelty: The study tried to map the effect of the global coral bleaching event of 2016 on Koswari and Van islands of the Tuticorin group of Islands in the Gulf of Mannar using foraminifera as a proxy. Keywords: Foraminifera; Coral reefs; Ecology; Coral bleaching; Gulf of Mannar

Sedimentary records of mid-Holocene extreme storm events on the north bank of Hangzhou Bay, East China

Reconstructing the long-term history of tropical cyclones is key to understanding their driving mechanisms and to enable better predictions of future extreme storm events. However, the available history of typhoons, based on sedimentary records in the northwest Pacific basin, remains very limited. In this study, we conducted multi-proxy analyses of sedimentary profiles collected from a chenier ridge on the north bank of Hangzhou Bay, East China. We applied evidences from the lithology, grain size, and marine micro-fossils on sediments in these profiles, dated using OSL and AMS 14C, to reveal the mid-Holocene sedimentary environmental evolution and obtain records of extreme storm events. The lithology and foraminiferal assemblages indicate an aggradational succession from intertidal to supratidal flats incorporating two layers of storm deposits preserved in the chenier ridge. The lower layer of storm deposits was formed in the intertidal flats at ca. 6.0 cal. kyr BP, while the upper layer was formed in the supratidal flats at ca. 5.2–4.9 cal. kyr BP. The storm deposits are characterized by coarsened grain size and the prevalence of allochthonous foraminiferal species, including E. advenum, A. annectens, and A. compressiuscula which occur in the inner and middle shelf of East China Sea. The extreme storm events at ca. 6.0 and 5.2–4.9 cal. kyr BP recorded at the chenier ridge have also been described at different sites on the southeast coast of Hangzhou Bay. Together with previously reported storm deposits at ca. 4.5 cal. kyr BP, we suggest that these mid-Holocene extreme typhoon events on the East China coast resulted from global climate changes driven by solar irradiance.

Benthic foraminifera in the Arabian Gulf: Biodiversity and geographical trends

Utilizing a 60-year history of studies of benthic foraminiferal species distributions in the Arabian Gulf, this study applied a regional-synoptic approach to evaluate the total benthic foraminiferal biodiversity. By compiling, examining, and integrating available data, a conservative analysis yielded 753 benthic foraminiferal species and subspecies belonging to 236 genera, 99 families, 43 superfamilies and 11 orders. These values are comparable to those reported in other basins and are unexpectedly high, considering the extreme conditions of the Gulf. Yet these figures likely represent an underestimation of total diversity, as some areas have been poorly sampled (i.e., south-western part of the Gulf), reference materials are lacking (i.e., a taxonomic atlas), and the difficulty in the identification of taxa at species level has resulted in frequent use of open nomenclature. We contend that these conservative figures nonetheless reflect the actual benthic foraminiferal diversity of the Gulf and reduce the number of modern species left in open nomenclature. The diverse oceanographic, sedimentological and environmental conditions that occur in the Gulf are well mirrored by geographical trends of diversity and in the composition of benthic foraminiferal species. In addition, this paper helps to unify and resolve issues relating to the use of synonyms and taxonomic-name revisions that invariably affect species counts and result in misaligned datasets. This study is part of ongoing research endeavors to establish the much-needed comprehensive knowledge of benthic foraminiferal species and diversity worldwide.

Northeast Greenland: ice‐free shelf edge at 79.4°N around the Last Glacial Maximum 25.5–17.5 ka

The size of the last glacial ice sheet on the Northeast (NE) Greenland shelf and its interaction with ocean circulation have been the subject of debate. Here we provide insights into the extent of the ice sheet around the Last Glacial Maximum (LGM) and investigate timing and strength of changes in the flow of Atlantic Water. The study is based on a multiproxy investigation of a marine sediment core, gravity core DA17‐NG‐ST01‐019G, from 323‐m water depth at the NE Greenland shelf edge at 79.4°N. We present benthic and planktic foraminiferal distribution data, AMS‐14C dates, sedimentological (ice‐rafted debris (IRD) and grain sizes), and geochemical (XRF) data in combination with geophysical (sub‐bottom profiler) data. The oldest sediments at the study site are dated to 25.5–17.5 ka, encompassing the time frame from the beginning of the LGM to the early deglaciation. This part is overlain by sediments from the late deglaciation and Holocene. The deposits dating from the LGM are very rich in both planktic and benthic foraminifera and macrofossils of excellent preservation. The faunas show that the site generally was affected by a strong flow of relatively warm subsurface Atlantic Water during the LGM and Early Holocene. Conditions turned more polar with cold bottom water flow in the Middle–Late Holocene (c. 7.5 ka to Recent) with presence of mainly agglutinated benthic foraminiferal species. Our data from the LGM also indicate that the deposits were mixed by iceberg scouring, confirmed by the geophysical data showing extensive ploughing of the sediments on the outer shelf area. The results further indicate that the Greenland Ice Sheet did not reach to the edge of the NE Greenland shelf at 79.4°N during the LGM 24–18 ka.

DISTRIBUTION OF BENTHIC FORAMINIFERA IN THE CORAL REEFS ECOSYSTEM OF PULAU BIDONG, TERENGGANU, SOUTHERN SOUTH CHINA SEA

A study on the distribution of benthic foraminiferal species in the surface sediments of coral reefs was carried out in Pulau Bidong in the southern South China Sea (SCS). Samples were collected at 12 sites around Pulau Bidong at water depths ranging from 5 m to 30 m. Live (rose bengal stained) and optimally preserved empty tests of benthic foraminifera were analysed based on their chamber and apertural characteristics observed under binocular microscope (Leica Zoom 2000). The results revealed that 32 genera of benthic foraminifera were found in the coral reefs sediments. Amphistegina was the most abundant genus with relative abundance of 68% and frequently recorded at depths of between 10-15 m and 25-30 m. Other common genera that were found were Calcarina, Elphidium, Heterolepa, Heterostegina, Quinqueloculina, Peneroplis and Triloculina. These genera showed depth distribution preference in the shallow water zone (5 m depth). The highest diversity index (2.3) and number of taxa (26 genera) were recorded at station W2, located at the western part of Pulau Bidong. The lowest diversity index (0.2) and number of taxa (seven genera) were recorded at station S3, located at the southern part of Pulau Bidong. The frequency distribution and diversity of benthic foraminifera in the study area were related to water depth.