Showing papers on "Foraminifera published in 2020"

Decadal variability in twentieth-century ocean acidification in the California Current Ecosystem

Abstract: Oceanic uptake of CO2 can mitigate climate change, but also results in global ocean acidification. Ocean acidification-related changes to the marine carbonate system can disturb ecosystems and hinder calcification by some organisms. Here, we use the calcification response of planktonic foraminifera as a tool to reconstruct the progression of ocean acidification in the California Current Ecosystem through the twentieth century. Measurements of nearly 2,000 fossil foraminifera shell weights and areas preserved in a marine sediment core showed a 20% reduction in calcification by a surface-dwelling foraminifera species. Using modern calibrations, this response translates to an estimated 35% reduction in carbonate ion concentration, a biologically important chemical component of the carbonate system. Assuming other aspects of the carbonate system, this represents a 0.21 decline in pH, exceeding the estimated global average decline by more than a factor of two. Our proxy record also shows considerable variability that is significantly correlated with Pacific Decadal Oscillation and decadal-scale changes in upwelling strength, a relationship that until now has been obscured by the relatively short observational record. This modulation suggests that climatic variations will play an important role in amplifying or alleviating the anthropogenic signal and progression of ocean acidification in this region. Ocean acidification in the California Current Ecosystem was twice the global average during the past century and influenced by decadal climate variations, according to a record of the calcification rate of planktonic foraminifera from the Santa Barbara Basin.

New marine data and age accuracy of the Romualdo Formation, Araripe Basin, Brazil.

Abstract: A combined biostratigraphic and palaeoecological study of foraminifera, ostracodes and microfacies was carried out on the Aptian in the Sitio Sobradinho section of the Araripe Basin, northeast Brazil. The analysed section represents a deepening-upward sequence with mid-ramp shoal and outer ramp to basin facies associations on a mixed siliciclastic-carbonate marine ramp. The analysed rocks are dominated by Early Cretaceous planktic foraminifera (Hedbergella aptiana, H. praelippa, H. sigali, Blesfucuiana cf. cumulus, Microhedbergella miniglobularis, Gorbachikella cf. kugleri, Pseudoguembelitria blakenosensis, Globigerinelloides clavatus, Globigerinelloides aff. aptiensis, Gubkinella sp. and Loeblichella sp.). Ostracoda fauna is composed mainly of Pattersoncypris crepata and Pattersoncypris micropapillosa. The occurrence of P. crepata associated with the Aptian planktic foraminifera demonstrates the potential of this ostracode species to date this interval. The planktic foraminifera from the upper Aptian (Microhedbergella miniglobularis Zone) of the Araripe Basin show characteristical Tethyan affinities.

Marine Os isotopic evidence for multiple volcanic episodes during Cretaceous Oceanic Anoxic Event 1b

Abstract: The Aptian-Albian boundary is marked by one of the major oceanic perturbations during the Cretaceous, called Oceanic Anoxic Event (OAE) 1b. Extensive volcanic episodes at the Southern Kerguelen Plateau has been suggested as the trigger of OAE1b, but compelling evidence remains lacking. Here, we reconstructed the temporal variations of marine Os isotopic ratios across the Aptian-Albian boundary in the Tethyan and Pacific pelagic sedimentary records to elucidate the causal links between OAE1b, the biotic turnover, and volcanic episodes. Our new Os isotopic records show two negative spikes that correlate with a period of planktonic foraminiferal turnover across the Aptian-Albian boundary during OAE1b and suggest multiple submarine volcanic events. By comparing our Os isotopic profile with carbon isotopic compositions of carbonate, CaCO3 content, and the relative abundances of agglutinated foraminifera, we conclude that ocean acidification caused by the massive release of CO2 through extensive volcanic episodes could have promoted the major planktonic foraminiferal turnover during OAE1b.

Zooplankton in the Southern Ocean from the continuous plankton recorder: Distributions and long-term change

Abstract: We provide an analysis of zooplankton distributions in the circumpolar Southern Ocean based on samples collected by the international SCAR Southern Ocean Continuous Plankton Recorder Survey (SO-CPR). We analysed SO-CPR measurements in relation to satellite and oceanographic model hind-cast data over the period 1997–2018. These environmental data were chlorophyll-a concentration, net primary productivity (VGPM model), sea-surface temperature (SST), mixed layer depth, sea ice and the spatial gradient of SST (as an indicator of ocean fronts). Boosted Regression Tree (BRT) models were used to extrapolate in space and time measurements of the abundances of six key taxonomic groups of zooplankton: Copepoda (Calanoida), Euphausiidae (numerically dominated in SO-CPR data by Thysanoessa macrura), Foraminifera, Fritillaria spp., Oithona similis, and pteropods. Based on the BRT models, we present predictions of the spatial and seasonal (October–March) environmental suitability for these groups in the Southern Ocean. Trend analysis suggests that between 1997 and 2018 the environmental suitability for copepods (both cyclopoid and calanoid), Foraminifera, and Fritillaria spp. has increased by 0.72% per year average, and at higher rates in frontal regions especially in the Indian sector of the Southern Ocean. In contrast, for pteropods in some areas (particularly over the Ross Sea shelf) the environmental suitability has significantly worsened over the last 20 years.

Anaerobic metabolism of Foraminifera thriving below the seafloor.

Abstract: Foraminifera are single-celled eukaryotes (protists) of large ecological importance, as well as environmental and paleoenvironmental indicators and biostratigraphic tools. In addition, they are capable of surviving in anoxic marine environments where they represent a major component of the benthic community. However, the cellular adaptations of Foraminifera to the anoxic environment remain poorly constrained. We sampled an oxic-anoxic transition zone in marine sediments from the Namibian shelf, where the genera Bolivina and Stainforthia dominated the Foraminifera community, and use metatranscriptomics to characterize Foraminifera metabolism across the different geochemical conditions. Relative Foraminifera gene expression in anoxic sediment increased an order of magnitude, which was confirmed in a 10-day incubation experiment where the development of anoxia coincided with a 20-40-fold increase in the relative abundance of Foraminifera protein encoding transcripts, attributed primarily to those involved in protein synthesis, intracellular protein trafficking, and modification of the cytoskeleton. This indicated that many Foraminifera were not only surviving but thriving, under the anoxic conditions. The anaerobic energy metabolism of these active Foraminifera was characterized by fermentation of sugars and amino acids, fumarate reduction, and potentially dissimilatory nitrate reduction. Moreover, the gene expression data indicate that under anoxia Foraminifera use the phosphogen creatine phosphate as an ATP store, allowing reserves of high-energy phosphate pool to be maintained for sudden demands of increased energy during anaerobic metabolism. This was co-expressed alongside genes involved in phagocytosis and clathrin-mediated endocytosis (CME). Foraminifera may use CME to utilize dissolved organic matter as a carbon and energy source, in addition to ingestion of prey cells via phagocytosis. These anaerobic metabolic mechanisms help to explain the ecological success of Foraminifera documented in the fossil record since the Cambrian period more than 500 million years ago.

Vertical niche definition of test-bearing protists (Rhizaria) into the twilight zone revealed by in situ imaging

Abstract: Author(s): Biard, T; Ohman, MD | Abstract: The Rhizaria is a super-group of amoeboid protists with ubiquitous distributions, from the euphotic zone to the twilight zone and beyond. While rhizarians have been recently described as important contributors to both biogenic silica and carbon fluxes, we lack the most basic information about their ecological habitats and preferences. Here, using in situ imaging (Underwater Vision Profiler 5), we characterize the vertical ecological niches of different test-bearing pelagic rhizarian taxa in the southern California Current Ecosystem. We define three vertical layers between 0 and 500 m occupied, respectively, by (1) surface dwelling and mostly symbiont-bearing rhizarians (Acantharia and Collodaria), (2) flux-feeding phaeodarians in the lower epipelagic (100–200 m), and (3) Foraminifera and Phaeodaria populations adjacent to the oxygen minimum zone. We then use Generalized Additive Models to analyze the response of each rhizarian category to a suite of environmental variables. The models explain between 9% and 93% of the total variance observed for the different groups. While temperature and the depth of the deep chlorophyll maximum appear as the main abiotic factors influencing populations in the upper 200 m, dissolved silicon concentration is related to the abundance of mesopelagic phaeodarians, though it explains only a portion of the variance. The importance of biotic interactions (e.g., prey availability, predation, parasitism, symbiosis) is still to be considered, in order to fully incorporate the dynamics of test-bearing pelagic rhizarians in ecological and biogeochemical models.

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 ), 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 µ mol kg −1 at the lower boundary of the OMZ.

Foraminiferal δ18O reveals gas hydrate dissociation in Arctic and North Atlantic ocean sediments

Abstract: Paleoceanographic investigations in the Arctic and north Atlantic are crucial to understanding past and current climate change, in particular considering amounts of pressure-temperature sensitive gas stored in marine sediments of the region. Many paleoceanographic studies are based on foraminiferal oxygen and carbon stable isotope compositions (δ18O, δ13C) from either planktonic specimens, benthic specimens or both. However, in seafloor regions promixal to high upward methane fluxes, such as where seafloor gas emission and shallow gas hydrate-bearing sediment occur, foraminiferal δ18O and δ13C display a wide range of values. Our study focuses on foraminiferal stable isotope signatures in shallow sediment at core sites in the Arctic and North Atlantic affected by significant upward flow of methane. This includes cores with shallow sulfate methane transitions that are adjacent to seeps and containing gas hydrate. We place emphasis on potential effects due to gas hydrate dissociation and diagenesis. Gas hydrate dissociation is known to increase pore-water δ18O, but our results indicate that precipitation of methane-derived authigenic carbonate (MDAC) also affects the foraminiferal δ18O of both planktonic and benthic species. In addition to this post-depositional overprint, we investigate the potential bias of the stable isotope record due to ontogenetic effects. Our data show that the size fraction does not impact the isotopic signal of planktonic and benthic foraminifera.

Holocene climate variability of the Western Mediterranean: Surface water dynamics inferred from calcareous plankton assemblages

Abstract: A high-resolution study (centennial scale) has been performed on the calcareous plankton assemblage of the Holocene portion of the Ocean Drilling Program Site 976 (Alboran Sea) with the aim to iden...

Benthic foraminifera as tracers of brine production in the Storfjorden “sea ice factory”

Abstract: . The rapid response of benthic foraminifera to environmental factors (e.g. organic matter quality and quantity, salinity, pH) and their high fossilisation potential make them promising bio-indicators for the intensity and recurrence of brine formation in Arctic seas. Such an approach, however, requires a thorough knowledge of their modern ecology in such extreme settings. To this aim, seven stations along a north–south transect across the Storfjorden (Svalbard archipelago) have been sampled using an interface multicorer. This fjord is an area of intense sea ice formation characterised by the production of brine-enriched shelf waters (BSW) as a result of a recurrent latent-heat polynya. Living (rose bengal-stained) foraminiferal assemblages were analysed together with geochemical and sedimentological parameters in the top 5 cm of the sediment. Three major biozones were distinguished. (i) The “inner fjord” zone, dominated by typical glacier proximal calcareous species, which opportunistically respond to fresh organic matter inputs. (ii) The “deep basins and sill” zone, characterised by glacier distal agglutinated fauna; these are either dominant because of the mostly refractory nature of organic matter and/or the brine persistence that hampers the growth of calcareous species and/or causes their dissolution. (iii) The “outer fjord” zone, characterised by typical North Atlantic species due to the intrusion of the North Atlantic water in the Storfjordrenna. The stressful conditions present in the deep basins and sill (i.e. acidic waters and low food quality) result in a high agglutinated ∕ calcareous ratio ( A∕C ). This supports the potential use of the A∕C ratio as a proxy for brine persistence and overflow in Storfjorden.

Alien and cryptogenic Foraminifera in the Mediterranean Sea: A revision of taxa as part of the EU 2020 Marine Strategy Framework Directive

Abstract: The human-mediated translocation of marine alien species beyond their natural ranges started as early as people began navigating the sea and is of growing concern to nature conservation. The Mediterranean Sea is among the most severely affected areas by biological invasions, a phenomenon that has been fostered by the opening and recent extension of the Suez Canal, the transport and release of ballast water, aquaculture and aquarium trade, ichthyochory and other active or passive dispersal mechanisms. The increase of marine invasions has stimulated considerable research, but for some important groups, in particular microorganisms, data are still limited. In this paper we have reviewed the current status of marine alien foraminifera in the Mediterranean Sea. Our survey includes a comrephensive taxonomic revision of previously recognized alien taxa, and new information obtained from the fossil record and from molecular studies. Our survey and reexamination of alien benthic foraminifera yielded a total of 44 validly recognized species and two species of cryptogenic taxa and reduces the number of previous recordings. The revised list includes both larger symbiont-bearing and smaller benthic foraminifera, including 16 hyaline-perforate, 3 agglutinated and 25 porcelaneoustaxa. The vast majority of alien foraminifera recorded so far have become established in the Eastern and Central Mediterranean Sea, indicative for translocation and introduction via the Suez Canal pathway. Only one species, Amphistegina lobifera , causes significant ecological impacts and fulfills the criteria to be considered as an invasive alien. This species is a prolific carbonate producer, and displays extreme forms of ecosystem invasibility with capabilities to reduce native diversity and species richness. The proliferation and rates of recently observed range extensions, track contemporary sea surface temperature increases, provide strong support for previous species distribution models, and corroborate findings that rising water temperatures, global climate change and the extension of climate belts are major drivers fueling the latitudinal range expansion of larger symbiont-bearing and smaller epiphytic foraminifera. Intensified efforts to study alien foraminifera on a molecular level, in dated cores and in ballast water are required to trace their source of origin, to identify vectors of introduction and to verify their status as true aliens.

Flux variability of phyto- and zooplankton communities in the Mauritanian coastal upwelling between 2003 and 2008

Abstract: . Continuous multiyear records of sediment-trap-gained microorganism fluxes are scarce. Such studies are important to identify and to understand the main forcings behind seasonal and multiannual evolution of microorganism flux dynamics. Here, we assess the long-term flux variations and population dynamics of diatoms, coccolithophores, calcareous and organic dinoflagellate cysts, foraminifera and pteropods in the eastern boundary upwelling ecosystem of the Canary Current. A multiannual, continuous sediment trap experiment was conducted at the mooring site CBeu (Cap Blanc eutrophic; ∼20 ∘ N, 18 ∘ W; trap depth is ca. 1300 m ) off Mauritania (northwest Africa), between June 2003 and March 2008. Throughout the study, the reasonably consistent good match of fluxes of microorganisms and bulk mass reflects the seasonal occurrence of the main upwelling season and relaxation and the contribution of microorganisms to mass flux off Mauritania. A clear successional pattern of microorganisms, i.e., primary producers followed by secondary producers, is not observed. High fluxes of diatoms, coccolithophores, organic dinoflagellate cysts, and planktonic foraminifera occur simultaneously. Peaks of calcareous dinoflagellate cysts and pteropods mostly occurred during intervals of upwelling relaxation. A striking feature of the temporal variability of population occurrences is the persistent pattern of seasonal groups contributions. Species of planktonic foraminifera, diatoms, and organic dinoflagellate cysts typical of coastal upwelling, as well as cooler-water planktonic foraminifera and the coccolithophore Gephyrocapsa oceanica, are abundant at times of intense upwelling (late winter through early summer). Planktonic foraminifera and calcareous dinoflagellate cysts are dominant in warm pelagic surface waters, and all pteropod taxa are more abundant in fall and winter when the water column stratifies. Similarly, coccolithophores of the upper and lower photic zones, together with Emiliania huxleyi, and organic dinoflagellate cysts dominate the assemblage during phases of upwelling relaxation and deeper layer mixing. A significant shift in the “regular” seasonal pattern of taxa relative contribution is observed between 2004 and 2006. Benthic diatoms strongly increased after fall 2005 and dominated the diatom assemblage during the main upwelling season. Additional evidence for a change in population dynamics is the short dominance of the coccolithophore Umbilicosphaera annulus, the occurrence of the pteropod Limacina bulimoides and the strong increase in the flux of calcareous dinoflagellate cysts, abundant in warm tropical oligotrophic waters south of the study area after fall 2005. Altogether, this suggests that pulses of southern waters were transported to the sampling site via the northward Mauritania Current. Our multiannual trap experiment provides a unique opportunity to characterize temporal patterns of variability that can be extrapolated to other eastern boundary upwelling ecosystems (EBUEs), which are experiencing or might experience similar future changes in their plankton community.

A Warm, Stratified, and Restricted Labrador Sea Across the Middle Eocene and Its Climatic Optimum.

Abstract: Several studies indicate that North Atlantic Deep Water (NADW) formation might have initiated during the globally warm Eocene (56–34 Ma). However, constraints on Eocene surface ocean conditions in source regions presently conducive to deep water formation are sparse. Here we test whether ocean conditions of the middle Eocene Labrador Sea might have allowed for deep water formation by applying (organic) geochemical and palynological techniques, on sediments from Ocean Drilling Program (ODP) Site 647. We reconstruct a long‐term sea surface temperature (SST) drop from ~30°C to ~27°C between 41.5 to 38.5 Ma, based on TEX86. Superimposed on this trend, we record ~2°C warming in SST associated with the Middle Eocene Climatic Optimum (MECO; ~40 Ma), which is the northernmost MECO record as yet, and another, likely regional, warming phase at ~41.1 Ma, associated with low‐latitude planktic foraminifera and dinoflagellate cyst incursions. Dinoflagellate cyst assemblages together with planktonic foraminiferal stable oxygen isotope ratios overall indicate low surface water salinities and strong stratification. Benthic foraminifer stable carbon and oxygen isotope ratios differ from global deep ocean values by 1–2‰ and 2–4‰, respectively, indicating geographic basin isolation. Our multiproxy reconstructions depict a consistent picture of relatively warm and fresh but also highly variable surface ocean conditions in the middle Eocene Labrador Sea. These conditions were unlikely conducive to deep water formation. This implies either NADW did not yet form during the middle Eocene or it formed in a different source region and subsequently bypassed the southern Labrador Sea.

Foraminifera in the World Register of Marine Species (Worms) Taxonomic Database

Abstract: Most foraminiferal research is founded on sound taxonomy. To clearly communicate such research, similar species concepts and consistent use of names is desirable. As a contribution to this larger goal, the World Foraminifera Database (http://www.marinespecies.org/foraminifera) was set up in 2010 as a subset within the World Register of Marine Species (WoRMS). The purpose is to provide an authoritative, open-access inventory of all foraminiferal taxonomic names. The inventory is almost complete for both fossil and Recent foraminiferal taxa, containing 4932 generic and 55,884 species (including infraspecies) names. There are ∼61,000 genus-species combinations of which ∼54,600 are currently “accepted” species and infraspecies (with 9600 extant). Associated data includes 14,700 linked foraminiferal literature sources, ∼6600 images, and species-level links to many other databases and images, such as the Cushman Collection (Smithsonian Institution), American Museum of Natural History, Mikrotax (planktic foraminifera), GenBank, and Zootaxon. The WoRMS database is owned by the global taxonomic community and hosted and serviced by the Flanders Marine Institute (VLIZ), Belgium. We recommend that all researchers working with foraminifera both use and contribute to the World Foraminifera Database, as that will improve the accuracy of the database's content and save investigators many hours of searching elsewhere.