Compared with traditional bulk foraminiferal analysis methods, in situ analysis of individual foraminiferal tests (individual foraminiferal analysis or IFA) offers several advantages over traditional bulk methods, including enhanced temporal resolution where fossiliferous sample material is limited as well as potentially resolving seasonal-scale climate variability in deep time. Despite these advantages, applications of element-to‑calcium (El/Ca) ratios and δ11B in benthic foraminifera using IFA remain limited, and the biogeochemical drivers of intra-test and inter-test geochemical variability are poorly constrained. In this study, we systematically evaluate El/Ca ratios and δ11B in individual benthic foraminifera. By analysing Holocene epifaunal benthic foraminiferal species Cibicidoides wuellerstorfi from a deep ocean core site (ODP Site 999), we conclude that intra- and inter-test variabilities are regulated by ontogenetic effects resulting in inter-test variabilities of ±0.14 mmol/mol Mg/Ca, ± 14 μmol/mol B/Ca, and ± 0.18 ‰ δ11B. Application of the IFA method to epifaunal benthic foraminifera species Cibicides lobatulus from a box core in the English Channel, UK reveals ~0.1 pH units acidification and ~ 1 °C warming since the mid-19th century. By demonstrating that individual-level variability in reconstructed temperature and pH tracks seasonal trends in the available contemporaneous water-column instrumental measurements at the same site, we provide a ground-truthing to our multi-proxy IFA methodology, and also demonstrate the potential for benthic IFA to provide seasonal-scale reconstructions of ocean climate over hundreds to millions of years.
Continue reading ‘Individual foraminiferal analysis: a promising tool for high-resolution temperature and pH reconstruction’Posts Tagged 'protists'
Individual foraminiferal analysis: a promising tool for high-resolution temperature and pH reconstruction
Published 27 March 2026 Science ClosedTags: biogeochemistry, biological response, chemistry, field, methods, paleo, protists
Microbial community dynamics over large spatial and environmental gradients in a subtropical ocean basin
Published 9 February 2026 Science ClosedTags: abundance, biogeochemistry, biological response, chemistry, community composition, field, molecular biology, North Atlantic, otherprocess, prokaryotes, protists
Microbes are fundamental to ocean ecosystem function, yet they remain understudied across broad spatial and environmental scales in dynamic regions like the Gulf of America/Gulf of Mexico (GOM). We employed DNA metabarcoding to characterize prokaryotes (16S V4–V5) and protists (18S V9) across 51 stations, spanning 16 inshore–offshore transects and three depths. Cluster analysis revealed three clusters corresponding to depth zones that integrated vertical and horizontal sampling: photic zone (inshore near surface–bottom and offshore surface), deep chlorophyll maximum (offshore), and aphotic zone (offshore near bottom). We applied group-specific generalized additive models (GAMs) to log-transformed abundance data of major taxa in the photic zone, identifying key environmental factors that explained 42%–82% of the variation in abundance. SAR11 and SAR86 were positively associated with temperature and dissolved inorganic carbon, while cyanobacterial genera (Prochlorococcus and Synechococcus) were differently impacted by nutrients, salinity, and pH in ways that often followed their expected ecological niches. Representatives of protist parasites (Syndiniales) and grazers (Sagenista) showed group-specific nonlinear associations with salinity, oxygen, nutrients, and temperature. Using GAMs, we expanded the spatial resolution of DNA sampling and predicted surface log abundances at 84 cruise sites lacking amplicon data. Indicator analysis was performed with sequence-level data, revealing several protists that were indicative of more acidic waters and the absence of any significant prokaryote indicators. Our results provide the first basin-scale survey of microbes in the GOM and highlight the need for coordinated omics and environmental sampling to improve predictions of microbial responses to changing conditions.
Continue reading ‘Microbial community dynamics over large spatial and environmental gradients in a subtropical ocean basin’Ecological stability of late Maastrichtian benthic foraminifera amidst Deccan volcanism
Published 29 December 2025 Science ClosedTags: biological response, community composition, field, morphology, North Atlantic, otherprocess, paleo, protists
Highlights
- Benthic foraminifera assemblage at Bidart reveal a stable, mesotrophic late Maastrichtian seafloor.
- K/Pg boundary at Bidart shows signs of ecological stress and taphonomic dissolution.
- Deccan-induced calcification stress was restricted to surface ocean and had minimal impact on benthic foraminifera.
- Robust test ratio and fragmentation index together serve as effective taphonomic proxies.
Abstract
The late Maastrichtian witnessed profound disruptions in biogeochemical cycles, leading to the fifth mass extinction at the Cretaceous–Paleogene (K/Pg) boundary. At Bidart section (France), the final ∼60 kyr of the Maastrichtian coincide with mercury (Hg) peaks, low magnetic susceptibility, evidence of biological stress and taphonomic alteration in planktic foraminifera, indicative of an ocean acidification event. While this event primarily appears to be a surface-ocean phenomenon, previous studies also documented a minor rise in benthic foraminiferal test fragmentation beginning 0.5 m below the K/Pg boundary, with a pronounced spike at the boundary itself.
A detailed investigation of benthic foraminifera in biozone CF1 at Bidart section (France) reveals a diverse and balanced assemblage preceding the K/Pg boundary, with minimal taphonomic alterations. At the K/Pg boundary, infaunal populations diminished, diversity declined sharply, test fragmentation intensified, yet paradoxically, the absolute abundance of genera rose markedly. Preferential preservation is evident in the dominance of robust taxa (Cibicidoides spp., Coryphostoma spp.), while a high fragmentation index reflects strong taphonomic dissolution and time-averaging. A plausible explanation for this could be CO2-rich waters mixing into the ocean interior over 100–1,000 years, driving dissolution during the ∼10,000-year deposition of the K/Pg boundary red clay. The stark contrast between the planktic and benthic census and morphometric data at Bidart section clearly constrains any Deccan-related calcification stress to the surface mixed layer. Lastly, the integrated planktic and benthic considerations re-emphasize a need to carefully separate taphonomic signals from true ecological stress.
Continue reading ‘Ecological stability of late Maastrichtian benthic foraminifera amidst Deccan volcanism’Deep Pacific carbonate chemistry since the Last Glacial Maximum
Published 19 November 2025 Science ClosedTags: biological response, chemistry, field, morphology, paleo, protists
Quantitative constraints on deep ocean carbonate chemistry are critical for understanding the processes responsible for glacial-interglacial changes in atmospheric pCO2 and the ocean feedbacks that amplify carbon cycle change. Here, we present a new, high-resolution, B/Ca-based record of carbonate ion concentration (Δ[CO32−]) from central equatorial Pacific site ML1208-16BB spanning the last 35 kyr. This site, bathed by Pacific Deep Water, reveals a ∼24 ± 7 μmol/kg rise in deep ocean [CO32−] between ∼20 and 10 kyr, a larger change than previously reconstructed from sites in the western equatorial Pacific and those in the central equatorial Pacific bathed by Lower Circumpolar Deep Water. Our new reconstruction permits estimation of deep Pacific calcite saturation state (Ω), quantifying the degree of deep water undersaturation during the Last Glacial Maximum and implying a critical role for sedimentary porewater saturation state in resolving the Pacific carbonate preservation paradox. Finally, we pair our Δ[CO32−] reconstruction with previously-published benthic δ13C to present a process-oriented understanding of late glacial, deglacial, and Holocene deep Pacific carbonate chemistry changes. Our data suggest a larger role for glacial and deglacial alkalinity changes than previously suggested by records from the equatorial Pacific Ocean.
Continue reading ‘Deep Pacific carbonate chemistry since the Last Glacial Maximum’Consequences of climate change for foraminifera and foraminifera communities
Published 11 November 2025 Science ClosedTags: biological response, morphology, North Atlantic, protists
Single-celled protists called foraminifera perform critical ecosystem functions across the world’s oceans, including cycling of biogeochemically relevant compounds, sequestering carbon, and serving as biological monitoring tools of ecosystem health. However, anthropogenic climate change increases risks for these species in the oceans of the future. As ocean conditions change due to increased carbon dioxide in the atmosphere from anthropogenic sources, dire consequences to the world’s oceans are emerging such as oceanic deoxygenation, or the reduction of dissolved oxygen in water due to increased heat; coastal acidification, or decreases in coastal water pH due to increased dissolved carbon dioxide; and sea-level rise, which is cause by rising temperatures and melting icecaps. Currently, the responses of foraminifera to these important climate change risk-factors have not been well-studied. This study examines the responses of this group to the threats of climate change to predict their ecological success and capacity to serve as bioindicators as oceans continue to change.
In Manuscript I, transcriptomes were collected from two species of foraminifera collected from the Santa Barbara Basin off the coast of California: Nonionella stella and Bolivina argentea. These two species thrive in anoxic to euxinic and hypoxic sediments, respectively. However, the metabolic processes that enable these species to achieve high ecological success in extreme conditions are unclear. This study presented detailed metabolic reconstructions and differential gene expression that illustrated the cellular processes localized to the peroxisome and mitochondria. This metabolism enables survival in oxygen-depleted sediments and suggested that these species are likely to experience range expansion as deoxygenated regions get larger with climate change.
Manuscript II investigated responses of a Rhode Island salt marsh foraminifera, Haynesina sp., to coastal acidification. As carbon dioxide concentrations raise in the atmosphere, chemical equilibria dictate that carbon dioxide concentrations increase in the ocean as well. When carbon dioxide dissolves in seawater, several spontaneous chemical reactions occur that lead to decreased pH, which can have detrimental impacts on calcium carbonate-depositing organisms. These processes can be exacerbated in coastal systems, where conditions fluctuate to higher extremes than in the open ocean. Many foraminifera, including Haynesina sp., have calcium carbonate tests that could leave these species at high risk due to ocean acidification. This study detailed the morphological responses of Haynesina sp. to coastal acidification over biologically relevant timescales to determine that, although Haynesina sp. may be resistant to moderate elevated carbon dioxide, exposure to high elevated pCO2 leads to morphological defects in living cells. Altogether, this study demonstrated that Haynesina are susceptible to extreme coastal acidification and risk dissolution under those conditions.
In Manuscript III, the scope of foraminifera examined was expanded from individual species to whole communities by using DNA metabarcoding to examine how communities may shift in response to sea-level rise mitigation efforts. As global climate change proceeds, temperatures are expected to rise, which will result in increases in sea-level as water stored in ice and glaciers continues to melt. Due to increases in sea-level, it is expected that many coastal regions of the United States could be submerged in the next 100 years. To mitigate increases sea-level rise, conservation efforts are underway to raise the elevation of salt marshes through thin layer placement of sediment. This restoration technique involves adding large amounts of sediment to the surface of salt marshes and has been noted to have beneficial impacts for vegetation; however, impacts on other associated ecosystems, such as the subtidal and intertidal regions, are unknown. This study found that each of the three sites examined across the Rhode Island coast had distinct foraminiferal communities. Additionally, in the two restored marshes, TLP seemed to significantly impact foraminiferal alpha diversity. Across the two restored marshes, variable responses in alpha and beta diversity were observed. The results show that Rhode Island salt marshes have divergent responses to thin layer placement and need to be studied individually to determine the impacts of restoration. Despite this, our results suggest that TLP can have positive impacts on the health of some intertidal ecosystems.
In conclusion, these studies demonstrate that foraminifera have complex and varied responses to risk factors associated with climate change and climate change mitigation efforts. In some scenarios, such as oceanic deoxygenation, some taxa are poised to experience success and range expansion. However, other scenarios, such as ocean acidification, may lead to increased risk for species within this group under extreme scenarios. Further, foraminifera have the capacity to act as bioindicators, as is seen in the face of sea-level rise mitigation efforts, where foraminifera demonstrate a strong potential to act as an indicator species for ecosystem health.
Continue reading ‘Consequences of climate change for foraminifera and foraminifera communities’Calcifying plankton: from biomineralization to global change
Published 28 October 2025 Science ClosedTags: biological response, mollusks, physiology, phytoplankton, protists, review, zooplankton
BACKGROUND
The production and dissolution of calcium carbonate (CaCO3) is a key component of the ocean carbon cycle. In the open ocean, nearly all CaCO3 is produced by three groups of calcifying plankton: coccolithophores, foraminifers, and pteropods. These taxonomically and functionally diverse organisms play a major role in ocean biogeochemistry by modulating air-sea CO2 exchange, and facilitating the export of carbon and alkalinity to depth.
Despite their biogeochemical importance, these groups are typically considered separately, precluding an integrated understanding. Yet the pathways by which CaCO3 is produced and cycled through the ocean have important consequences for the carbon cycle and ecosystem functioning. Notably, none of the Earth system models included in the current Coupled Model Intercomparison Project (CMIP6) explicitly represents these groups of organisms. Here, we review the distinct functional traits of coccolithophores, foraminifers, and pteropods to elucidate how these traits shape their global distributions, vulnerabilities to climate change and acidification, and their role in modulating ocean chemistry and the Earth system.
ADVANCES
Recent advances in data compilation at multiple levels offer a comprehensive but still incomplete view of the CaCO3 cycle, from biomineralization up to the global ocean, with different traits leading to differing vulnerabilities to environmental change. For example, coccolithophores, as primary producers, are relatively less affected by changes in oxygen concentration compared with heterotrophs, but are particularly sensitive to ocean acidification because of the proton load generated during intracellular calcification, which requires effective pH regulation and proton expulsion. Differing resource requirements contribute to the geographic distributions of each group, while traits such as body size and turnover rate are fundamentally linked to global production, export, dissolution, and burial. Compiling these data allows us to compare the markedly different fates of the CaCO3 produced by each group, from surface production through export to eventual sediment burial. A major imbalance exists in the global CaCO3 cycling related to each calcifying plankton group, with key uncertainties, especially in rates of group-specific production and shallow biologically mediated dissolution. Current best estimates indicate that a large fraction of coccolithophore-derived CaCO3—the dominant source of CaCO3 in the ocean—is dissolved and recycled in the upper ocean. This underscores the central role of ecological processes such as predation, particle aggregation, and microbial respiration in shaping ocean carbonate chemistry.
We suggest that the overlooked process of shallow dissolution, mainly of coccolithophores, is also likely at play within the geological record of this group.
OUTLOOK
The three major groups of calcifying plankton play essential but distinct roles within ocean ecosystems and the marine carbon cycle. Their diverse traits govern global distributions, production, export, and their differing response to environmental change. The magnitude of biologically mediated CaCO3 dissolution in the upper ocean remains broadly unrecognized, with implications for both the global alkalinity budget and interpretations of the fossil record. Sediment cores provide a fossil record going back 65 million years, revealing large variation in organism size and diversity likely linked to changes in seawater carbonate chemistry (acidification) and warming. The extent to which shallow, selective dissolution has biased this record remains an important unresolved question. Addressing discrepancies between CaCO3 production and export from the upper ocean will require renewed focus on both quantifying and understanding the individual and combined contribution of these groups, as well as the biological processes driving shallow dissolution. These efforts are also critical for incorporating a mechanistically resolved CaCO3 cycle into future climate models, thereby supporting a more integrated view of ocean biogeochemistry under climate change.
Continue reading ‘Calcifying plankton: from biomineralization to global change’Decreasing foraminiferal flux in response to ongoing climate change in the Santa Barbara Basin, California
Published 2 September 2025 Science ClosedTags: abundance, biological response, community composition, field, North Pacific, otherprocess, protists, review
The rapid response of foraminiferal assemblages to changing climate makes their shells an invaluable geological record of the past. However, the time frame over which foraminifera respond to climatic signals and the specific drivers influencing assemblage composition and abundance remain obscure. We focus on the impact of ongoing, anthropogenic climate change on planktic foraminifera in the California Current ecosystem, which would appear as a nearly instantaneous event in the sediment record. The Santa Barbara Basin sediment trap, located off the coast of California, USA since 1993, provides a record of more than 30 years of particulate and foraminiferal flux in the basin. The sediment trap captures the superposition of the annual cycle of seasonal upwelling, Pacific multiannual El Niño–Southern Oscillation-driven temperature changes, and anthropogenically forced climate change. We present data on planktic foraminiferal flux collected between 2014–2021, at two-week intervals (164 samples, 60 006 individuals) and compare results to previously published data from 1993–1998. Consistent with previous studies, the most abundant species from 2014–2021 were Globigerina bulloides, Neogloboquadrina incompta, and Turborotalita quinqueloba, with peak fluxes occurring in the spring and summer. Lower fluxes and an increase in the abundance of N. incompta and subtropical species characterize the winter season. We find a 37.9 % decrease in total foraminiferal flux relative to the 1990s, primarily driven by a decrease in G. bulloides abundance. This decrease is accompanied by a 21.0 % overall reduction in calcium carbonate flux. We also find a decrease in the relative abundance of subtropical species (Globigerinoides ruber, Orbulina universa, and Neogloboquadrina dutertrei) and their fluxes compared to the 1990s, opposite expectations if assemblages and fluxes were to follow anthropogenic warming signals. We hypothesize that the observed decrease in subtropical species abundance and flux is likely related to an increase in acidification and in the timing and magnitude of upwelling along the California coast. The extremely rapid responses of foraminifera to ongoing changes in carbonate chemistry and temperature suggest that climate change is already having a meaningful impact on coastal carbon cycling. The observed decrease in particulate inorganic carbon (PIC) flux relative to particulate organic carbon (POC) flux may facilitate increased oceanic uptake of atmospheric CO2.
Continue reading ‘Decreasing foraminiferal flux in response to ongoing climate change in the Santa Barbara Basin, California’Pteropods reliably record the aragonite compensation depth in the western Bay of Bengal
Published 21 August 2025 Science ClosedTags: abundance, biological response, community composition, field, Indian, mollusks, otherprocess, protists, zooplankton
Anthropogenic greenhouse gas emissions have a detrimental impact on the carbon sequestration by the oceans. Pteropods, a crucial component of the ocean’s planktic community, secrete aragonite shells that are sensitive to increasing atmospheric carbon dioxide levels, making them the first indicators of ocean acidification. Therefore, pteropods are often used to observe the changes in aragonite compensation depth (ACD). Intriguingly, in the major parts of the northern Indian Ocean, the chemically defined ACD is < 800 m, but pteropods have been reported in surface sediments collected from much deeper depths in the same region, which raises questions about the use of pteropods to trace ACD in this area. To address this ambiguity, we conducted a systematic and detailed evaluation of pteropods to trace the changes in ACD in the western Bay of Bengal, which is the first-ever such study. The pteropods population dominated by Heliconoides inflatus was low on the inner shelf, and isolated pockets of high pteropod abundance were restricted to the upper slope. Based on the pteropod abundance in the surface sediments and the ratio of pteropods to planktic foraminifera, we report the baseline ACD in the western Bay of Bengal at ~ 500 m. The aragonite compensation depth based on the pteropod abundance in the surface sediments correlates well with the chemically defined ACD in this region. These findings will help to assess the impact of ocean acidification on aragonite compensation depth in the western Bay of Bengal.
Continue reading ‘Pteropods reliably record the aragonite compensation depth in the western Bay of Bengal’Species-specific mechanisms of benthic foraminifera in response to shell dissolution
Published 31 July 2025 Science ClosedTags: biological response, dissolution, laboratory, light, mortality, multiple factors, North Atlantic, performance, photosynthesis, protists, respiration
Highlights
- Living specimens and empty tests of two benthic foraminifera species were cultured in different pH and light conditions.
- In acidic conditions, greater dissolution of empty tests compared to living specimens was observed.
- No differences in the degrees of dissolution between the two species were observed.
- Living foraminifera have active mechanism(s) to tolerate acidification.
Abstract
Ammonia confertitesta and Haynesina germanica are two common estuarine benthic foraminifera subject to sediment acidification. Nevertheless, mechanisms involved in their response to acidification are still poorly understood. Since H. germanica is kleptoplastic and photosynthetically active, unlike A. confertitesta, these species were cultured in controlled experiments to determine whether these mechanisms could mitigate acidification-induced shell dissolution. Both living and dead specimens were incubated at two pH (8.0 and 6.8) and two light conditions (0 and 24 μmol photon m-2.s-1) for 18 days. For each species, respiration and photosynthesis rates were calculated based on oxygen measurements. At the end of incubation, foraminiferal viability was assessed with CellTracker Green™ biomarker, and each test was categorised according to a dissolution scale (DS) using SEM. For both species, in acidic conditions, the tests of dead specimens were significantly more dissolved than the tests of living specimens, suggesting active mechanisms providing tolerance to acidification. For the living specimens, no significant difference in the DS distribution was observed between the two species at both conditions, suggesting that kleptoplast photosynthetic activity in H. germanica does not provide additional resistance to acidification. Until at least day 12, respiration data revealed a different biological activity for the two species, and we observed distinct behaviours (e.g., encystment and pseudopod emission). These suggest each species exhibits species-specific responses to cope with acidification. On day 18, respiration rates and binocular observations showed low biological activity, suggesting dormancy or death. Further investigation is required to identify the cellular mechanisms involved to counter acidification stress.
Continue reading ‘Species-specific mechanisms of benthic foraminifera in response to shell dissolution’Morphological responses of a temperate intertidal foraminifer, Haynesina sp., to coastal acidification
Published 17 July 2025 Science ClosedTags: biological response, dissolution, laboratory, morphology, North Atlantic, protists
Coastal acidification could have widespread impact on marine organisms, affecting the ability of calcifying organisms to build shells and skeletons through calcium carbonate precipitation. As an abundant group of calcifying organisms, some protists within the phylum Foraminifera demonstrate potential success under elevated partial pressure of carbon dioxide (pCO2) due to their ability to modulate intracellular pH. However, little is known about their responses under more extreme acidification conditions that are already seen in certain coastal environments. Here we exposed specimens of Haynesina sp., which belongs to a genus that is prevalent in temperate intertidal salt marshes, to moderate (pCO2 = 2386.05+/−97.14 μatm) and high acidification (pCO2 = 4797.64+/−157.82 μatm) conditions through the duration of 28 days. We demonstrate that although this species is capable of withstanding moderate levels of coastal acidification with little impact on overall test thickness, it can experience precipitation deficiency and even dissolution of the calcareous test under highly elevated pCO2. Interestingly, such a deficit was primarily seen among live foraminifera, as compared to dead specimens, throughout the four-week experiment. This study suggests that a combination of environmental stress and the physiological process of test formation (i.e., calcite precipitation) could induce thinning of the test surface. Therefore, with the acceleration of coastal acidification due to anthropogenic production of CO2, benthic foraminifera and other calcifying organisms among coastal ecosystems could reach a tipping point that leads to thinning and dissolution of their calcareous tests, which in turn, will impair their ecological function as a carbon sink.
Continue reading ‘Morphological responses of a temperate intertidal foraminifer, Haynesina sp., to coastal acidification’Brachiopods and forams reduced calcification costs through morphological simplification during mass extinction events
Published 3 July 2025 Science ClosedTags: biological response, brachiopods, field, morphology, paleo, protists
Environmental stressors have exacerbated the collapse of marine ecosystems during mass extinctions. However, the survival strategies of marine species during mass extinctions remain unclear. Here, we investigated morphological evolution of brachiopods across the Permian–Triassic mass extinction (PTME) using a database of 3,225 specimens representing 1,061 species and foraminifera across the PTME and early Toarcian oceanic anoxic event (T-OAE) using a database of 757 specimens representing 12 species. We found a significant reduction in the number and proportion (plicae length/shell length) of shell plicae of brachiopods (36.4% and 60.0%, respectively) across the PTME and a significant decrease in the shell thickness of foraminifera (18.9% and 42.4% across the PTME and 36.9–61.8% across the T-OAE). We calculated that these adaptive strategies could reduce the energetic costs of calcification by more than half for brachiopods across the PTME, and by ~20–62% for foraminifera across the PTME and T-OAE, to compensate for the elevated cost of calcification due to environmental and ecological pressures. We propose that simplification of morphological features, such as reduced shell ornamentation and shell thinning, serves as a potential economic strategy for calcifying organisms to cope with extinction events by reducing energy demands, but further studies with a broader range of taxa and extinction events are needed to confirm the generality of this bioenergetic strategy.
Continue reading ‘Brachiopods and forams reduced calcification costs through morphological simplification during mass extinction events’Variable responses to ocean acidification among mixotrophic protists with different lifestyles
Published 13 June 2025 Science ClosedTags: biological response, growth, laboratory, performance, photosynthesis, protists
Marine phytoplankton are facing increasing dissolved CO2 concentrations and ocean acidification caused by anthropogenic CO2 emissions. Mixotrophic organisms are capable of both photosynthesis and phagotrophy of prey and are found across almost all phytoplankton taxa and diverse environments. Yet, we know very little about how mixotrophs respond to ocean acidification. Therefore, we studied responses to simulated ocean acidification in three strains of the mixotrophic chrysophyte Ochromonas (CCMP1391, CCMP2951, and CCMP1393). After acclimatization of the strains to treatment with high-CO2 (1000 ppm, pH 7.9) and low-CO2 concentrations (350 ppm, pH 8.3), strains CCMP1393 and CCMP2951 both exhibited higher growth rates in response to the high-CO2 treatment. In terms of the balance between phototrophic and heterotrophic metabolism, diverse responses were observed. In response to the high-CO2 treatment, strain CCMP1393 showed increased photosynthetic carbon fixation rates, while CCMP1391 exhibited higher grazing rates, and CCMP2951 did not show significant alteration of either rate. Hence, all three Ochromonas strains responded to ocean acidification, but in different ways. The variability in their responses highlights the need for better understanding of the functional diversity among mixotrophs in order to enhance predictive understanding of their contributions to global carbon cycling in the future.
Continue reading ‘Variable responses to ocean acidification among mixotrophic protists with different lifestyles’Record of foraminifera test composition throughout the Phanerozoic
Published 17 April 2025 Science ClosedTags: biological response, morphology, paleo, protists, review
Marine calcifiers produce calcareous structures (e.g. shells, skeletons or tests) and are therefore sensitive to ocean chemistry. Nevertheless, the long-term evolutionary consequences of marine carbonate changes are not well understood. This article compares calcareous and non-calcareous responses to ocean chemistry changes throughout the Phanerozoic Eon (541 million years ago to present). To accomplish this, we calculated proportional wall-type diversity, origination rates and extinction rates for 2282 benthic foraminiferal genera. Calcareous origination and extinction rates fluctuated throughout the Palaeozoic Era (541–251.9 million years ago), but during the Mesozoic Era (251.9–66 million years ago), calcareous origination and extinction rates stabilized following the evolution of pelagic calcifiers. Despite variations in Cenozoic Era (66–0 million years ago) foraminifera diversity, calcareous wall types maintained around 77% proportional diversity. Although calcareous wall-type extinction rates decline during the Mesozoic and Cenozoic, Phanerozoic foraminifera wall-type changes during individual events are largely contingent upon contemporaneous conditions rather than overarching trends. Of the Big Five mass extinction events, calcareous wall-type proportions only decreased at the end-Permian (73% to 26% diversity) and end-Triassic (56% to 50% diversity). These results suggest long-term ocean chemistry changes were not the main driver of foraminiferal wall-type diversity through time.
Continue reading ‘Record of foraminifera test composition throughout the Phanerozoic’Calcification of planktonic foraminifer Neogloboquadrina dutertrei and its indicative significance for ocean acidification
Published 16 April 2025 Science ClosedTags: biological response, dissolution, field, morphology, paleo, protists
Planktonic foraminifera are widespread calcifying protozoa and represent a primary source of marine biogenic calcium carbonate. Elucidating the mechanisms underlying the calcification processes of planktonic foraminifera holds significant importance for understanding the marine biological pump and carbon cycling.
The present study investigated the controlling mechanisms of calcification in modern planktonic foraminifer Neogloboquadrina dutertrei by analyzing the foraminiferal shell weight data from 92 sets of surface sediments from different ocean areas, including the eastern tropical Indian, the western tropical Pacific, the eastern tropical Pacific, and the western tropical Atlantic. First, this study reveals that deep-ocean carbonate dissolution, which is related to deep-ocean carbonate ion saturation state (Δ[CO32-]), is the dominant factor influencing the shell weight of N. dutertrei in surface sediments. Then, by correcting the dissolution effect on the shell weight of N. dutertrei, we estimated the initial shell weight from which to assess secular changes in the degree of calcification of N. dutertrei. The initial shell weight results suggest that the calcification of N.dutertrei is mainly controlled by seawater carbonate system parameters such as pH, carbonate ion concentration ([CO32-]), and carbon dioxide concentration (pCO2). Calcification of N. dutertrei would decrease with ocean acidification.
Furthermore, we reconstructed initial shell weight of N.dutertrei at sites KX97322-4 and U1490 in the western tropical Pacific to evaluate the response of N. dutertrei calcification to climate changes over glacial-interglacial time scales. Calcification of N. dutertrei in the western tropical Pacific has increased during glacial periods in response to lower atmospheric pCO2 since 800 ka, confirming the dominant influence of ocean acidification on N. dutertrei calcification. We suggest that the shell weight of specific planktonic foraminiferal species may serve as a potential proxy for past seawater carbonate system reconstructions.
Continue reading ‘Calcification of planktonic foraminifer Neogloboquadrina dutertrei and its indicative significance for ocean acidification’Uncertain fate of pelagic calcifying protists: a cellular perspective on a changing ocean
Published 26 February 2025 Science ClosedTags: adaptation, biological response, molecular biology, otherprocess, physiology, protists, review
Pelagic calcifying protists such as coccolithophores and foraminifera represent an important microbial component of the marine carbon cycle. Although their calcitic shells are preserved in oceanic sediments over millennia, their resilience in the future decades is uncertain. We review current literature describing the response of calcifying protists to ocean acidification and temperature warming. We examine these key ecological and biogeochemical processes through the cellular perspective, exploring the physiological, metabolic, and molecular responses of calcifying protists. Ocean acidification is a chemical process that takes place in the seawater outside the cell, whereas protists calcify inside a modified cellular microenvironment. The function of these calcification compartments depends on cellular response to ocean acidification, such as maintaining pH homeostasis. The response of calcifying protists to ocean acidification and temperature warming is species-specific, with no unifying trends but rather a range of sensitivity levels. Coccolithophores and foraminifera display physiological sensitivity that may hamper their ecological success in comparison to non-calcifying species. Yet, certain species may be more adaptable, especially when comparing to highly vulnerable calcifying molluscs as pteropods. As the molecular machinery mediating cellular calcification is not fully resolved, as well as the functional role of the calcitic shell, our ability to predict the fate of calcifying microorganisms in a warmer, more acidic ocean is limited. We propose the urgent need to expand the study of these model systems by advancing cell biology approaches, to better understand the impact of climate change on microbial food webs in the ocean.
Continue reading ‘Uncertain fate of pelagic calcifying protists: a cellular perspective on a changing ocean’What controls planktic foraminiferal calcification?
Published 17 February 2025 Science ClosedTags: biological response, BRcommunity, chemistry, field, globalmodeling, modeling, morphology, protists
Planktic foraminifera are key producers of pelagic carbonate, and their shell weight is suggested to have been influenced by the environment in which they calcify. However, there is debate about the use of size-normalised weight (SNW) as a proxy, as some authors invoke a carbonate system control on calcification (and by extension SNW as a pCO2 proxy), while others suggest that species optimum conditions, nutrient concentration, or temperature drive shell weight. To better understand this proxy, we investigate what drives SNW and whether discrepancies in the proposed control on weight are due to differing data collection methodologies and/or regionally different drivers. We integrate new and published SNW data with environmental hindcast data from the CMIP6 modelling suite. Using Bayesian regression modelling, we find that the environment alone does not explain the variability in SNW across species. Although physiology likely modulates the response to the environment, we find little evidence of a unifying driver at the ecogroup level. Instead, we identify species-specific responses associated with drivers including (but not limited to) the carbonate system, which are likely different between ocean basins. We hypothesise that this is partly influenced by cryptic species and regional phenotypic plasticity in changes to shell weight that are not well understood, such as the thickness of calcite deposited during some species’ reproductive phases. Consequently, which species to use as a pCO2 proxy or whether multiple species should be used in parallel to reduce uncertainty should be carefully considered. We strongly encourage the regional testing and calibration of pCO2–SNW relationships.
Continue reading ‘What controls planktic foraminiferal calcification?’Morphological responses of a temperate salt marsh foraminifer, Haynesina sp., to coastal acidification
Published 15 January 2025 Science ClosedTags: biological response, laboratory, morphology, North Atlantic, protists
Coastal acidification leads to widespread impacts on calcifying organisms across the world’s oceans, which could result in decreased calcium carbonate deposition and the dissolution of calcium carbonate. As an abundant group of calcifying organisms, some protists within the phylum Foraminifera demonstrate potential success under elevated partial pressure of carbon dioxide (pCO2) due to their ability to modulate intracellular pH. However, little is known about their responses under more extreme acidification conditions that are already seen in certain coastal environments. Here we exposed Haynesina, a foraminiferal genus that is prevalent in temperate coastal salt marshes, to moderate (pCO2 = 2386.05+/-97.14 μatm) and high acidification (pCO2 = 4797.64+/-157.82 μatm) conditions through the duration of 28 days. We demonstrate that although this species is capable of withstanding moderate levels of coastal acidification with little impact on their overall test thickness, they could experience deposition deficiency and even dissolution of the calcareous test under highly elevated pCO2. Interestingly, such a deficit was primarily seen among live foraminifera, as compared to dead specimens, throughout the four-week experiment. We propose that a combination of environmental stress and the physiological process of test formation (i.e., calcite precipitation) could induce thinning of the test surface. Therefore, with the acceleration of coastal acidification due to anthropogenic production of CO2, benthic foraminifera amongst coastal ecosystems could reach a tipping point that leads to thinning and dissolution of their calcareous tests, which in turn, will impair their ecological function as a carbon sink.
Continue reading ‘Morphological responses of a temperate salt marsh foraminifer, Haynesina sp., to coastal acidification’Multi-interacting global-change drivers reduce photosynthetic and resource use efficiencies and prompt a microzooplankton-phytoplankton uncoupling in estuarine communities
Published 10 January 2025 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, otherprocess, photosynthesis, phytoplankton, protists, South Atlantic, zooplankton
Highlights
- Multi-interacting driver effects were evaluated on South Atlantic estuarine plankton
- Warming×pH×nutrients×UVR reduced the photosynthetic and resource use efficiencies
- A multi-driver change condition prompted a microzooplankton-phytoplankton uncoupling
- Altered trophic interactions could reduce the energy transfer efficiency in food webs
Abstract
Plankton communities are subjected to multiple global change drivers; however, it is unknown how the interplay between them deviates from predictions based on single-driver studies, in particular when trophic interactions are explicitly considered. We investigated how simultaneous manipulation of temperature, pH, nutrient availability and solar radiation quality affects the carbon transfer from phytoplankton to herbivorous protists and their potential consequences for ecosystem functioning. Our results showed that multiple interacting global-change drivers reduced the photosynthetic (gross primary production-to-electron transport rates ratios, from 0.2 to 0.6-0.8) and resource use efficiencies (from 9 to 1 μg chlorophyll a (Chl a) μmol nitrogen-1) and prompted uncoupling between microzooplankton grazing (m) and phytoplankton growth (μ) rates (μ > m). The altered trophic interaction could be due to enhanced intra-guild predation or to microzooplankton growing at suboptimal temperatures compared to their prey. Because phytoplankton-specific loss rates to consumers grazing are the most significant uncertainty in marine biogeochemical models, we stress the need for experimental approaches quantifying it accurately to avoid bias in predicting the impacts of global change on marine ecosystems.
Continue reading ‘Multi-interacting global-change drivers reduce photosynthetic and resource use efficiencies and prompt a microzooplankton-phytoplankton uncoupling in estuarine communities’Ocean acidification signals through deep time: a review of proxies
Published 8 January 2025 Science ClosedTags: biological response, paleo, protists, review
Highlights
- A comprehensive review of multiple ocean acidification proxies from the geologic past.
- Proxies classified by data type, time, and required facilities: observational or analytical.
- Observational: shell weight, dwarfism, carbonate size, fragmentation, preservation.
- Analytical: calcium carbonate, magnetic susceptibility, isotopes, and trace elements.
- Proxy use depends on calibration, diagenesis, timescale, and conditions it reflects.
Abstract
Anthropogenic CO₂ levels have increased by nearly 40% from preindustrial levels, with about 30% absorbed by the ocean leading to ocean acidification (OA). The associated carbonate undersaturation can critically affect marine calcifying communities. Major disruptions in the marine carbonate cycling are common throughout the Phanerozoic stratigraphic record, and often coincide with major mass extinctions and faunal turnover events. The anthropogenic OA is progressing at a rate nearly ten times faster than similar events of the past 300 million years. This makes OA research of high priority, and entails a rigorous evaluation of OA events from deep time for perspective. Such efforts are contingent upon reliable proxies. This review compiles geochemical and foraminifera-based proxies, offering a critical assessment of their fidelity, ease of use, and application scope.
This study evaluates the scope and utility of documented observational and analytical proxies based on factors like the nature of data, and the time, effort and advanced analytical facilities involved. Foraminifera-based observational proxies like morphological and community responses to OA are effective but demand taxonomic expertise. They are further complicated by vital effects, metabolic trade-offs, the influence of stressors other than ocean acidification, and paleogeographic variability in both the magnitude of stress and the organisms’ response to it. Well-calibrated analytical (geochemical) proxies offer the potential for rapid, high-resolution records across various sites. All proxies face challenges from diagenetic alterations, which can affect their reliability. However, this review offers the pros/cons and practical recommendations for proxy utility, emphasing the need for a multi-proxy approach to enhance accuracy and cross-verification. Future research must urgently address plankton community responses, OA-tolerant taxa, and localized calcification environments to grasp the full impact of acidification. It is critical to refine lesser-known proxies (e.g., S/Ca) and to rapidly expand datasets on carbonate system parameters across Phanerozoic OA events to advance our understanding and mitigation strategies.
Continue reading ‘Ocean acidification signals through deep time: a review of proxies’The effect of carbonic anhydrase on foraminiferal Mg/Ca
Published 30 December 2024 Science ClosedTags: biological response, laboratory, morphology, physiology, protists
Marine biogenic calcium carbonate production plays a role in the exchange of CO2 between ocean and atmosphere. The effect of increased CO2 on calcification and on the resulting chemistry of shells and skeletons, however, is only partly understood. Foraminifera are among the main marine CaCO3 producers and the controls on element partitioning and isotope fractionation is the subject of many recent investigations. The enzyme carbonic anhydrase (CA) was, for example, shown to be vital for CaCO3 deposition in benthic foraminifera and indicates their ability to manipulate their intracellular inorganic carbon chemistry. Here, we tested whether CA affects the partitioning of Na, Mg and Sr in the perforate, large benthic, symbiont-bearing foraminifer Amphistegina lessonii by addition of the inhibitor acetazolamide (AZ). The effect of dissolved CO2 on the effect of CA on element partitioning was also determined using a culturing setup with controlled atmospheric carbon dioxide levels (400–1,600 ppm). Results show that inhibition by AZ reduces calcification greatly and that CO2 has a small, but positive effect on the amount of calcite formed during the incubations. Furthermore, the inhibition of CA activity has a positive effect on element partitioning, most notably Mg. This may be explained by a (n indirect) coupling of inorganic carbon uptake and inward calcium ion pumping.
Continue reading ‘The effect of carbonic anhydrase on foraminiferal Mg/Ca’
