Benthic Foraminiferal Distribution Research Articles

The influence of submarine canyons-related processes on recent benthic foraminiferal distribution, Espírito Santo Basin, Southeastern Brazil

The complex topography of submarine canyons may result in different composition of benthic foraminifera assemblages. To understand how trophic, hydrological and sedimentological conditions in submarine canyons can influence the distribution of benthic foraminifera, and to use this information to corroborate paleoenvironmental interpretations for the Holocene, we investigated recent benthic foraminiferal assemblages (total fauna >63 μm) and sedimentological data in two canyons (CANWN and CAND) in the Espírito Santo Basin (ESB) between 18°20′ and 21°20′ S. Surface sediment samples (0–2 cm) were collected inside the canyons (150 to 1300 m water depth) and in shelf-slope adjacent transects (50 to 1300 m water depth). The density, taxonomic diversity, and assemblage composition of benthic foraminifera change with depth and location. The distinct ecological preferences of the most abundant taxa allowed us to recognize five benthic foraminiferal groups. Three groups (V, III, and I) are present in different bathymetric sectors; Group V: outer shelf (50 m), Group III: upper, and middle – lower slope (150 to 400 m), and Group I: middle – lower slope (1000 to 1300 m). Groups II and IV show no characteristic bathymetric distribution and are present only in CAND and in CANWN, respectively. Group V consists of Hanzawaia boueana, Peneroplis planatus, and Quinqueloculina lamarckiana; Group III is dominated by Globocassidulina rossensis and Trifarina spp.; Group I consists of Globocassidulina crassa, Bolivina lowmani, Gavelinopsis versiformis, Alabaminella weddellensis, and Epistominella exigua. The main species in Group II (CAND, 150, 1000 to 1300 m) are Trifarina angulosa, Globocassidulina subglobosa, and Discorbis vilardeboanus. Group IV (middle – lower CANWN, 1000 to 1300 m), consists mainly of agglutinated species Glomospira charoides, Rhabdammina abyssorum, and Psammosphaera fusca. Our data suggest that the quantity (and quality) of food supply, hydrodynamic conditions and sediment properties are the main drivers controlling the bathymetric distribution of benthic foraminiferal assemblages in both canyons. The middle – lower CANNW revealed unstable trophic conditions, related to terrigenous sediment input due to turbidity currents. In CAND, the foraminiferal assemblages ecology indicated sufficient organic matter supply that favors species establishment and diversity, indicating a more productive and less unstable environment than in CANWN.

Benthic Foraminiferal Distribution and their Environmental Significance of Selected Red Sea Coastal Ecosystems, Saudi Arabia

The present study uses benthic foraminiferal abundance and diversity indices in the coastal bottom sediments of the Farasan Island, Southern Cornich of Jeddah (SCJ) and Rabigh areas, Saudi Arabia to identify the ecological controls on their distribution. A total of 20 recent sediment samples were collected from the studied sites. Grain size analysis, CaCO3 content and organic matter were determined. Multivariate analyses were applied to test and represent the diversity indices and distribution of benthic foraminiferal assemblage. Two main benthic foraminiferal assemblages; A and B have been distinguished. The assemblage-A includes a high abundance of T. trigonula (33%), S. communis (30%), Q. bosciana (21%), E. striatopunctatum (18%) with low diversity indices in the Rabigh coastal sediments indicating high ecological stress. The Farasan ecosystem is dominated by sub-assemblage-B1 P. planatus (55%), S. orbiculus (27%), N. calcar (15%), Q. limbata (14%), which totally ranges between 60%-82%, indicating a highly oxic marine environment and normal ecology stress. Sub-assemblage-B2 such as P. planatus (39%),C. hemprichii (26%), V. neostriata (15%),Q. costata (10%) dominate the Southern Corniche of Jeddah (SCJ) with relatively high diversity indices, indicating moderate stress ecology or unstable environmental conditions.The cluster and the canonical correspondence analyses (CCA) indicated that the distribution and diversity pattern of benthic foraminifera are controlled by the enrichment of organic matters, CaCO3 contents, and sediments grain size characteristics. The concept of differentiation between these ecosystems is probably related to several factors, such as seasonal flash floods carrying a considerable amount of dissolved nutrients and mangrove communities on the Rabigh coast. In contrast, it is negligible on the south Jeddah coast and absence on Farasan Island.

Benthic foraminiferal distribution and environmental monitoring: a case study from Al-Kharrar Lagoon, Red Sea Coast, Saudi Arabia

Benthic foraminiferal distribution and environmental monitoring: a case study from Al-Kharrar Lagoon, Red Sea Coast, Saudi Arabia

Bathymetric and regional benthic foraminiferal distribution on the Espírito Santo Basin slope, Brazil (SW Atlantic)

To understand the main environmental factors controlling the benthic foraminiferal distribution along continental slopes, and corroborate paleoenvironmental interpretations, we investigated benthic foraminiferal assemblages (total fauna >63 μm) and sedimentological data along six transects on the continental slope of the Espírito Santo Basin (ESB) between 18°20′ and 21°20′ S. Surface sediment samples (0–2 cm) were collected perpendicularly to the coast, from the upper (400 m) to the lower slope (3000 m). The density, taxonomic diversity and assemblage composition change with depth. The genus Globocassidulina dominates the upper and lower slope, whereas Bolivina is the most abundant taxon in the deepest lower slope. The differences in ecological preferences among the most abundant taxa allowed us to recognize five benthic foraminiferal groups, distributed in three main bathymetric sectors: upper, middle – lower, and lower slope. Group I (upper slope, 400 m) is characterized by the highest mean relative abundances of Globocassidulina rossensis, Trifarina spp. and Trifarina angulosa. Group II (middle – lower slope, 1000–1300 m) shows the highest mean relative abundances of Globocassidulina subglobosa, Bolivina albatrossi, Bulimina aculeata and Uvigerina peregrina. Group III (middle – lower slope, 1000–1300 m) is characterized by the highest mean relative abundances of Globocassidulina crassa, Gavelinopsis versiformis, Epistominella exigua and the unilocular group. Group IV (lower slope, 1900 m) shows the highest mean relative abundances of Alabaminella weddellensis, Bolivina inflata and E. exigua. Group V (lower slope, 2500–3000 m) is dominated by the genus Bolivina (B. lowmani, B. pseudoplicata and Bolivina spp). The most abundant taxa along the ESB slope are ecologically associated to the organic matter flux, bottom water oxygen concentration, and hydrodynamics conditions. The quantity and quality of food supply is the primary factor controlling the distribution of benthic foraminiferal assemblages along depth. Secondary factors include the properties of water masses, and intermediate and deep boundary currents. The increased fragmentation of benthic and planktic foraminifera tests (>125 μm) on the upper and middle – lower slope is related to abrasion during transport from shallower regions to the slope.

Unique Habitat for Benthic Foraminifera in Subtidal Blue Holes on Carbonate Platforms

Dissolution of carbonate platforms, like The Bahamas, throughout Quaternary sea-level oscillations have created mature karst landscapes that can include sinkholes and off-shore blue holes. These karst features are flooded by saline oceanic waters and meteoric-influenced groundwaters, which creates unique groundwater environments and ecosystems. Little is known about the modern benthic meiofauna, like foraminifera, in these environments or how internal hydrographic characteristics of salinity, dissolved oxygen, or pH may influence benthic habitat viability. Here we compare the total benthic foraminiferal distributions in sediment-water interface samples collected from <2 m water depth on the carbonate tidal flats, and the two subtidal blue holes Freshwater River Blue Hole and Meredith’s Blue Hole, on the leeward margin of Great Abaco Island, The Bahamas. All samples are dominated by miliolid foraminifera (i.e., Quinqueloculina and Triloculina), yet notable differences emerge in the secondary taxa between these two environments that allows identification of two assemblages: a Carbonate Tidal Flats Assemblage (CTFA) vs. a Blue Hole Assemblage (BHA). The CTFA includes abundant common shallow-water lagoon foraminifera (e.g., Peneroplis, Rosalina, Rotorbis), while the BHA has higher proportions of foraminifera that are known to tolerate stressful environmental conditions of brackish and dysoxic waters elsewhere (e.g., Pseudoeponides, Cribroelphidium, Ammonia). We also observe how the hydrographic differences between subtidal blue holes can promote different benthic habitats for foraminifera, and this is observed through differences in both agglutinated and hyaline fauna. The unique hydrographic conditions in subtidal blue holes make them great laboratories for assessing the response of benthic foraminiferal communities to extreme environmental conditions (e.g., low pH, dysoxia).

The influence of environmental conditions on the benthic foraminiferal distribution from the recent sediments of Lake Bardawil, Eastern Mediterranean Sea, Egypt

Lake Bardawil, similar to the other Mediterranean Egyptian lakes, is a unique wetland, separated from theMediterranean Seaby a narrowsandbarwith very restricted water exchange that allowed the development of a shallow-hypersaline lagoon. Late Pleistocene tectonics activities divided the lake into two main basins; the eastern and western basins. Twelve surface sediment samples were collected along the Lake and subjected to sediment texture and benthic foraminiferal analyses. In general, benthic foraminifera were abundant in the surface sediments of Lake Bardawil and were characterized by low diversity. The statistical analysis revealed two biotopes that distinguished between the eastern and western basins' environments. The eastern basin biotopes were characterized by fine bottom sediments with the predominance of salinity-tolerant assemblages, thus demonstrating hypersaline stressful restricted environment. The western biotope exhibited coarser bottom sediments associated with relatively narrow salinity-tolerant assemblages. This reflected sandy and less saline sediment of uncontaminated environments, as the western basin was exposed to active hydrodynamic regime that developed more magnitudes of water exchange with the Eastern Mediterranean Sea through the western inlet. Based on the results of this study, the biomonitoring of Lake Bardawil could be assessed by the analysis of its benthic foraminifera as a bioindicator tool that may help in the improvement of the Lake's conditions.

Testing the applicability of random forest modeling to examine benthic foraminiferal responses to multiple environmental parameters

The main environmental variables controlling benthic foraminiferal distributions were identified and used to assess their influence on ecological indices developed as predictors of Ecological Quality Status (EcoQS) in marine ecosystems. Gradient forest and random forest models were applied to assess the predictive value of a selection of abiotic (environmental) and biotic (foraminifera) variables in a costal marine area in the central Adriatic Sea (Italy). This approach yields evidence that the predictor variables sand, silt, Pollution Load Index, and TN have the greatest influence on the distribution of benthic foraminifera in this area. In addition, we identify thresholds for the most important environmental variables that influence ecological indices. These findings contribute to efforts to determine how to best improve sediment quality and environmental stability for marine conservation. Further application of these approaches represents a useful tool for policymakers to survey the diversity of marine organisms and to improve the ability to protect and restore marine ecosystems by identifying predictors of diversity and identifying key thresholds in these predictors.

Multiple Ecological Parameters Affect Living Benthic Foraminifera in the River-Influenced West-Central Bay of Bengal

The huge riverine influx and associated processes decrease the ambient salinity, stratify the water column, modulate the oxygen-deficient zone, and are also responsible for the recent acidification in the Bay of Bengal. Here, we have studied the effect of these riverine influx-dominated ecological parameters on living benthic foraminifera in the west-central Bay of Bengal. We report that the pH below 7.6 in front of the Krishna river, reduces the diversity and the richness of living benthic foraminifera on the adjacent shelf and the slope. A similar decreased diversity and richness is also observed in front of the Godavari River. We delineate three prominent assemblages, representing different depth zones with associated distinct physico-chemical conditions. The shallow water assemblage (∼27–100 m) is represented by Nonionella labradorica, Hanzawaia nipponica, Brizalina dilatata, Ammonia tepida, and Nonionella limbato-striata. These species are adapted to relatively warmer temperatures and more oxygenated waters. The deepwater assemblage (∼1,940–2,494 m) includes Bulimina cf. delreyensis, Bulimina marginata, Hormosinella guttifera, Cassidulina laevigata, and Gyroidinoides subzelandica and can tolerate a relatively colder temperature. The intermediate-depth assemblage (∼145–1,500 m) dominated by Eubuliminella exilis, Bolivinellina earlandi, Fursenkoina spinosa, Bolivinellina lucidopunctata, Globobulimina globosa, Fursenkoina spinosa, Eubuliminella cassandrae, Uvigerina peregrina, Rotaliatinopsis semiinvoluta, and Cassidulina laevigata, represents oxygen-deficient and organic carbon-rich environment. Besides the pH, temperature, dissolved oxygen and organic matter, we also report a strong influence of bathymetry, coarse fraction (CF) and the type of organic matter on a few living benthic foraminifera. The ecological preferences of 40 such dominant living benthic foraminifera, each representing a specific environment, have also been reported for site-specific proxy. We conclude that although the huge riverine influx affects living benthic foraminifera on the shelf, the dissolved oxygen and organic carbon mostly control benthic foraminiferal distribution in the deeper west-central Bay of Bengal.

Recent benthic foraminiferal distribution in the Elbe Estuary (North Sea, Germany): A response to environmental stressors

For the past 200 years, estuarine environments experienced intense and rapid environmental degradations due to human interventions. In addition, Global Changes are modifying the estuarine physiography, leading to a re-structuration of marginal marine benthic communities. The aim of this study is to document, the modern assemblage composition and the species-environment relations of benthic foraminifera upstream the Elbe Estuary (southern North Sea) and to observe what has changed since the first survey in 1981. For this purpose, a surface sampling was carried out from 22 stations along the transitional area of the Elbe Estuary. Living (rose-Bengal stained) and dead foraminiferal assemblages were analysed as well as hydrological and sedimentological parameters (such as salinity, pH, grain-size, and organic matter). Living faunas are characterized by very low densities and largely dominated by Ammonia species. Dead assemblages are more diverse and dominated by Ammonia aomoriensis, Haynesina germanica, and Cribroelphidium selseyense. Salinity and grain-size seem to be the major factors influencing foraminiferal distributions in the transitional area. Under the ongoing climate changes, future strategies will be taken to foster the application of benthic foraminifera as biomonitoring tool in the Elbe Estuary, via this baseline investigation.

Paleobiogeography of the Middle Jurassic (Bathonian-Callovian) benthic foraminifera

Evaluating what governs the distribution patterns of an organism, enables better understanding of the role of biotic and abiotic factors that influences these patterns, thus, giving a better insight into their paleobiogeographical distribution. A total of 168 benthic foraminiferal genera (782 species) were analyzed from 39 Bathonian-Callovian localities, across the globe. Nonmetric Multidimensional Scaling (NMDS) and Analysis of Similarities (ANOSIM) were used to analyze the benthic foraminiferal distribution patterns. Analyses revealed statistically significant differences in the foraminiferal distribution patterns between Laurasia and Gondwanaland and further between North and South Gondwanaland in the Bathonian, attributed to their response to global eustatic lowstands. In contrast, the Callovian is marked by a lack of differentiation between Gondwanaland and Laurasia, reflecting a foraminiferal response to global eustatic highstands. But, the continued significant differentiation between North and South Gondwanaland is attributed to a combination of differing paleotemperatures due to their paleolatitudinal positions, coupled with the opening of the Mozambique Corridor that probably played a far greater role at the subprovincial level, as compared to sea level, for the Province. The taxa were also categorized based on their ecological traits such as oxygen availability, life-habit, and shell composition. Statistically significant differences on the geographic patterns based on life-habit (epifaunal and infaunal) and marginally on shell composition (calcareous and agglutinated) were noted, but not for their oxygen preference (oxic, suboxic and dysoxic). Examining the Bathonian-Callovian global occurrence data revealed that both species duration and species diversity greatly influenced the geographic distribution of the benthic foraminifera, where longer duration and higher species diversity ensured wider geographic distribution. • 782 benthic foraminiferal species from 39 localities were analyzed using NMDS and ANOSIM. • Laurasia and Gondwanaland were similar in the Callovian but they differ significantly in the Bathonian. • Eustasy, paleotemperatures and paleolatitude played a major role in the distribution patterns. • Microhabitat preference and shell composition have played a minor role. • Species duration and diversity determine the geographic range of a given taxon.

Living and dead benthic foraminiferal distribution in two areas of the Ross Sea (Antarctica)

We investigated the living (stained) and dead benthic foraminiferal assemblages collected in surface sediment samples (0–1 cm) from two different areas (JOIDES Basin and Mawson Bank) of the Ross Sea (Antarctica). Samples were collected during the BEDROSE oceanographic cruise from January to February 2017. Four living and dead benthic foraminiferal fauna assemblages have been distinguished based on cluster analysis. The differences observed in the living and dead foraminiferal content from the two investigated areas are the result of taphonomic processes induced by the different oceanographic settings and environmental conditions. In the JOIDES Basin, agglutinated taxa Rhabdamminella cylindrica, Lagenammina difflugiformis, Adercotryma glomeratum, Recurvoides contortus, Reophax subfusiformis with high percentages of Trochammina group and Reophax spiculifer associated with the calcareous species Nonionella bradii and Astrononion echolsi characterize the living assemblages. The comparison between living and dead benthic foraminifera reveals considerable similarities in terms of the presence/absence of agglutinated species and differences in relative abundance of calcareous taxa. However, the major influencing factor in foraminiferal preservation appears to be the carbonate dissolution. Results from Mawson Bank show an almost exclusive presence of calcareous taxa with high percentages of Globocassidulina group in both living and dead assemblages. The dead fauna assemblage differs from the corresponding living assemblage by being more diverse documenting high-energy current influence on marine sedimentation. Graphic abstract

Environmental factors affecting recent benthic foraminiferal distribution in the south-eastern Baltic Sea

The Baltic Sea is characterized by a restricted exchange of deep waters due to permanent stratification of the water column. The aim of the present study is to investigate the distribution of benthic foraminifera in the south-eastern part of the Baltic Sea in relation to environmental parameters. The distribution of benthic foraminifera was analyzed in 26 surface sediment samples collected in the south-eastern part of the Baltic Sea and in the Bornholm Basin during springtime and wintertime 2016. Foraminiferal diversity in the studied region was extremely low. Agglutinated specimens dominated the assemblages and were represented by small-sized individuals which belong to Psammosphaera, Pseudothurammina, Saccammina, and Reophax genera. Calcareous foraminifera were dominated by Cribroelphidium genus. Micropaleontological data were compared to the environmental parameters characterizing bottom water (temperature, salinity, and dissolved oxygen content) and substrate conditions (grain size composition and total organic carbon content). Higher foraminiferal concentrations and diversity were found in deeper parts of the study region where fine-grained sediments with a higher total organic carbon content were accumulated under stable hydrographical conditions. Calcareous tests were found only at the stations with elevated salinity, indicating that bottom water salinity is the main factor limiting the distribution of calcareous foraminifera. On the other hand, substrate parameters and hydrodynamic conditions appear to play a major role in the distribution of agglutinated foraminifera.

Ecological study based on the distribution of recent foraminifers from southeast of Buenos Aires province, Argentinean Continental Shelf.

The study about the distribution of benthic foraminifers in relationship with the type of substrate is presented. Samples of surface sediments from 15 to 60 m of depth from the southeast coast of the province of Buenos Aires (40º 30´ - 42ºS), Argentina were analysed. The foraminiferal assemblage was constituted by forty-eight species that belong to 22 genera. It was characterized mostly by the free-living style, epifaunal microhabitats, oxic levels and a detritivore trophic strategy. Based on statistical analysis, three zones were determinated: at 15 m depth , characterized mainly by Buccella peruviana (d´Orbigny), and species of Bolivina reflected a littoral environment with sandy sediments and the most important clay contribution, whereas it also presented the lowest oxygen levels were determinated; between 24-48 m depth, associted by Ammonia parkinsoniana (d´Orbigny), Buccella peruviana and Quinqueloculina seminula (Linné), this zone displayed an oxygenated environment with coarse grainsize from inner shelf where local water circulation may explain the high energy observed; and the last one located between 36 to 58 m of depth was characterized by Buccella peruviana, Ammonia parkinsoniana, Elphidium macellum (Fichtel Moll), Cibicides dispars (d´Orbigny) and Cibicides aknerianus (d´Orbigny) regflecting an inner shelf environment with sandy sediments, the lowest water temperature and the highest oxygen levels.

Bottom-water deoxygenation at the Peruvian margin during the last deglaciation recorded by benthic foraminifera

Abstract. Deciphering the dynamics of dissolved oxygen in the mid-depth ocean during the last deglaciation is essential to understand the influence of climate change on modern oxygen minimum zones (OMZs). Many paleo-proxy records from the eastern Pacific Ocean indicate an extension of oxygen-depleted conditions during the deglaciation, but the degree of deoxygenation has not been quantified to date. The Peruvian OMZ, one of the largest OMZs in the world, is a key area to monitor such changes in near-bottom-water oxygenation in relation to changing climatic conditions. Here, we analysed the potential to use the composition of foraminiferal assemblages from the Peruvian OMZ as a quantitative redox proxy. A multiple regression analysis was applied to a joint dataset of living (rose-bengal-stained, fossilizable calcareous species) benthic foraminiferal distributions from the Peruvian continental margin. Bottom-water oxygen concentrations ([O2]BW) during sampling were used as the dependant variable. The correlation was significant (R2=0.82; p<0.05), indicating that the foraminiferal assemblages are rather governed by oxygen availability than by the deposition of particulate organic matter (R2=0.53; p=0.31). We applied the regression formula to three sediment cores from the northern part of the Peruvian OMZ between 3 and 8∘ S and 997 and 1250 m water depth, thereby recording oxygenation changes at the lower boundary of the Peruvian OMZ. Each core displayed a similar trend of decreasing oxygen levels since the Last Glacial Maximum (LGM). The overall [O2]BW change from the LGM and the Holocene was constrained to 30 µmol kg−1 at the lower boundary of the OMZ.

The Campanian paleoenvironment: Inferences based on benthic foraminifera from northeastern Iran

The benthic foraminifera from the Campanian rocks (Globotruncanita elevata to Globotruncana aegyptiaca zones) exposed in the Kopeh-Dagh Basin (northeast Iran) are studied quantitatively to reconstruct the Campanian paleoenvironment. Based on unconstrained heriarchial clustering, Nonmetric Multidimensional Scaling (NMDS), and analysis of similarity (ANOSIM), three statistically significant benthic foraminiferal assemblages are noted, Paralabamina lunata (lower and upper), Haplophragmoides spp., and Gyroidinoides nitida. Based on benthic foraminiferal marker species, the following paleodepths are assigned - lower P. lunata: upper bathyal; upper P. lunata: upper-middle bathyal boundary; Haplophragmoides spp. and G. nitida: outer neritic. The P. lunata Assemblage can be further subdivided into a lower Coryphostoma incrassata-dominated interval, whereas the upper interval is P. lunata-dominated, and reflects a change in the quality of food; the upper experienced higher input of fresh phytodetritus. The overall P. lunata Assemblage reflects a stable bottom water environment. The Haplophragmoides spp. Assemblage is characterized by reduced paleoproductivity and environmental instability, whereas the G. nitida Assemblage is marked by increasing oligotrophy within a well-oxygenated bottom water and ventilated basinal conditions. The Partial Least Squares regression yielded significant correlations with % Planktic (positive; proxy for sea level) and % agglutinated species (negative; proxy for shallow depths and low organic-flux); the Reduced Major Axis regression models also yielded significant negative correlations with % agglutinated and % infaunal species (nutrient availability), suggesting that these factors were responsible for the inferred benthic foraminiferal distribution patterns. Two globally comparable shallowing trends are also noted - one in the middle of the R. calcarata Zone (= Haplophragmoides spp. Assemblage) and the other in the G. aegyptiaca Zone (= Gyroidinoides nitida Assemblage) that coincide with KCa6 and KCa7 sequence boundaries and lowstands, respectively. For the KCa6 event, the occurrence of Spiroplectammina (= Haplophragmoides spp. Assemblage) represents a shallow-water outer neritic fauna invasion event within a deeper upper bathyal setting (= Paralabamina lunata Assemblage) and for the KCa7 event, a similar shallowing from upper-middle bathyal boundary to outer neritic depths is noted (= G. nitida Assemblage), and attributed to eustasy and basinal paleohighs and lows.

Foraminiferal biotopes in a shallow continental shelf environment: Esperance Bay (southwestern Australia)

The Great Australian Bight is a large carbonate cold water environment located on the central and western portions of the southern Australia. Seagrasses (Posidonia sp.) and macroalgae benthic habitats are widely distributed in the shallow water environment of southern Australia, contributing to the carbonate factory. This study investigated the distribution of modern benthic foraminiferal assemblages in the microtidal wave-dominated inner-shelf of Esperance Bay (southwestern Australia), that lies on the western margin of the Great Australian Bight.Benthic foraminifera were taxonomically identified and biotic parameters (species richness, density, Fisher-α index, Shannon–Weaver index, dominance) were calculated. Multivariate analyses (Hierarchical Cluster Analysis, Principal Component Analysis) were performed to understand foraminiferal distribution in the context of environmental conditions. Four main Foraminiferal assemblages have been recognized: (I) a nearshore assemblage of dense seagrass meadow, dominated by Lamellodiscorbis dimidiatus, Elphidium craticulatum, Elphidium crispum, Cibicidoides lobatulus, II) a second assemblage associated with unvegetated seabed (approximately 30 m depth) with Lamellodiscorbis dimidiatus, Elphidium crispum, Quinqueloculina disparilis, III) a third assemblage in the central sector of the bay, characterized by a discontinuous and mixed seagrass-algae coverage with Lamellodiscorbis dimidiatus, Elphidium crispum, Elphidium macellum, Cibicides refulgens, and Quinqueloculina poeyana, and IV) an epiphytic assemblage of transitional zone from the coastline to the upper limit of a mixed seagrass-algae meadow, dominated by Elphidium crispum, Chrysalidinella dimorpha, Planulinoides biconcava, Planoglabratella opercularis, Rugobolivinella elegans. The spatial distribution of the four assemblages appears closely related to sediment texture, seagrass cover and depth, but it is also influenced by the shoreface morphology and the hydrodynamic energy. The understanding of the ecological parameters that influence benthic foraminiferal distribution, composition and assemblage structure within seagrass meadows is useful for paleoecological and paleoenvironmental interpretations.

Evaluating performance of foraminifera stress index as tropical-water monitoring tool in Strait of Malacca

Abstract Determining the environmental health status of the Strait of Malacca is crucial to prevent further deterioration of its unique marine ecosystems. A total of 18 surface sediment samples were collected from the northern sector of the strait for sediment quality analyses and assessment of the benthic Foraminifera Stress Index (FSI). The results indicated that heavy metal enrichment has resulted in shifts in benthic foraminiferal assemblages. Canonical correspondence analyses confirmed that dissolved oxygen, heavy metal concentrations, and water depth were major factors influencing benthic foraminiferal distributions in the study area. Q-mode cluster analyses classified benthic foraminiferal assemblages into three groups based on environmental conditions: Group A represented very poor environmental conditions (FSI

Factors Determining Benthic Foraminiferal Distribution in the Shallow Water Coastal Environments of Southwest Nigeria Sector of the Gulf of Guinea

Factors Determining Benthic Foraminiferal Distribution in the Shallow Water Coastal Environments of Southwest Nigeria Sector of the Gulf of Guinea

Benthic Foraminifera in Arctic Methane Hydrate Bearing Sediments

Benthic foraminifera have been widely used as proxy for paleo-methane emissions, mainly based on their stable isotopic signature. In cold seeps, the ecology of these organisms remains uncertain, in particular their ability to thrive during active phases of seepage. In this study, we evaluate the benthic foraminiferal response to methane seepage in Arctic sediments. We do so by examining living and dead benthic foraminiferal assemblages (>63 µm) of eleven push cores collected in two of the most active pockmarks (Lunde and Lomvi) along Vestnesa Ridge, offshore western Svalbard. Benthic foraminiferal assemblages are interpreted in the context of sediment geochemistry, seafloor images, and pore water analyses, which are used to characterize the different microhabitats. At the sampling locations, methane is currently being released making these the ideal sites to investigate the connection between the benthic foraminiferal distribution and methane seepage in the Arctic Ocean. Our results show that benthic calcareous foraminifera live in methane charged sediments, even if the faunal density and diversity is low. We note that the eutrophic-tolerant species Melonis barleeanus withstand the methane-induced hostile geochemical conditions and that it seems to prosper on the additional food availability represented by microbial mats growing at methane seeps. We also observe that the methane transport mechanisms affect different species differently. For example, sediments characterized by advective-like conditions are distinguished by a high density of living individuals, dominated by Cassidulina neoteretis, whereas sediments characterized by methane diffusion exhibit a very low faunal density. Agglutinated foraminifera are less abundant in sediments influenced by methane seepage, suggesting that this group of foraminifera does not tolerate the geochemical conditions at seeps. A comparison between the size fractions >63 and >125 µm highlights the importance of studying the finer size fraction for ecological studies in the Arctic Ocean. In the light of our results, we conclude that benthic foraminiferal can thrive at active methane seeps, where assemblages are clearly affected by methane flux.

Tracing clinothem geometry and sediment pathways in the prograding Holocene Po Delta system through integrated core stratigraphy

AbstractThough clinothem geometry represents a key control on fluid flow in reservoir modelling, tracing clinothem boundaries accurately is commonly limited by the lack of sufficiently precise outcrop or subsurface data. This study shows that in basin systems with strongly heterogeneous compositional signatures, the combination of bulk‐sediment geochemistry and benthic foraminiferal distribution can help identify clinothem architecture and generate realistic models of 3D deltaic upbuilding and evolution. Middle‐late Holocene deposits in the Po Delta area form an aggradational to progradational parasequence set that reveals the complex interaction of W–E Po Delta progradation, S‐directed longshore currents (from Alpine rivers) and Apennines rivers supply. Unique catchment lithologies (ophiolite rocks and dolostones) were used to delineate basin‐wide geochemical markers of sediment provenance (Cr and Mg) and to assess distinctive detrital signatures. The geochemical characterization of cored intervals across different components of the sediment routing system enabled a direct linkage between clinothem growth, transport pathways and provenance mixing to be established. On the other hand, abrupt microfaunal variations at clinothem boundaries were observed to reflect the palaeoenvironmental response to sharp changes in sediment flux and fluvial influence. This study documents the ability of an integrated geochemical and palaeoecological approach to delineate three distinct sources (Po, Alps and Apennines) that contributed to coastal progradation and to outline the otherwise lithologically cryptic geometries of clinothems that using conventional sedimentological methods it would be virtually impossible to restore.