Neogloboquadrina pachyderma (sinistral), the dominant planktonic foraminiferal species in the mid-to-high latitude oceans, represents a major component of local calcium carbonate (CaCO3) production. However, the predominant factors, governing the calcification of this species and its potential response to the future marine environmental changes, are poorly understood. The present study utilized an improved cleaning method for the size-normalized weight (SNW) measurement to estimate the SNW of N. pachyderma (sin.) in surface sediments from the Amundsen Sea, the Ross Sea, and the Prydz Bay in the Antarctic Zone of the Southern Ocean. It was found that SNW of N. pachyderma (sin.) is not controlled by deep-water carbonate dissolution post-mortem, and can be therefore, used to reflect the degree of calcification. The comparison between N. pachyderma (sin.) SNW and environmental parameters (temperature, salinity, nutrient concentration, and carbonate system) in the calcification depth revealed that N. pachyderma (sin.) SNWs in the size ranges of 200–250, 250–300, and 300–355 µm are significantly and positively correlated with seawater temperature. Moreover, SNW would increase by ∼30% per degree increase in temperature, thereby suggesting that the calcification of N. pachyderma (sin.) in the modern Antarctic Zone of the Southern Ocean is mainly controlled by temperature, rather than by other environmental parameters such as ocean acidification. Importantly, a potential increase in calcification of N. pachyderma (sin.) in the Antarctic Zone to produce CaCO3 will release CO2 into the atmosphere. In turn, the future ocean warming will weaken the ocean carbon sink, thereby generating positive feedback for global warming.
Continue reading ‘Calcification of planktonic foraminifer Neogloboquadrina pachyderma (sinistral) controlled by seawater temperature rather than ocean acidification in the Antarctic Zone of modern Southern Ocean’Posts Tagged 'sediment'
Calcification of planktonic foraminifer Neogloboquadrina pachyderma (sinistral) controlled by seawater temperature rather than ocean acidification in the Antarctic Zone of modern Southern Ocean
Published 12 September 2022 Science ClosedTags: Antarctic, biological response, field, morphology, multiple factors, protists, sediment, temperature
Calcification response of planktic foraminifera to environmental change in the western Mediterranean Sea during the industrial era
Published 1 September 2022 Science ClosedTags: abundance, biological response, community composition, field, Mediterranean, morphology, otherprocess, protists, sediment
The aim of this work is to investigate the variability of planktic foraminifera calcification in the northwestern Mediterranean Sea on seasonal, interannual and pre-industrial Holocene time scales. This study is based on data from a 12-year-long sediment trap record retrieved in the in the Gulf of Lions and seabed sediment samples from the Gulf of Lions and the promontory of Menorca. Three different planktic foraminifera species were selected based on their different ecology and abundance: Globigerina bulloides, Neogloboquadrina incompta, and Globorotalia truncatulinoides. A total of 273 samples were weighted in both sediment trap and seabed samples. As the traditionally used sieve fractions method is considered unreliable because of the effect of morphometric parameters on the foraminifera weight, we measured area and diameter to constrain the effect of these parameters. The results of our study show substantial different seasonal calcification patterns across species: G. bulloides showed a slight calcification increase during the high productivity period, while both N. incompta and G. truncatulinoides display a higher calcification during the low productivity period. The comparison of these patterns with environmental parameters revealed that Optimum Growth Conditions temperature and carbonate system parameters are the most likely to influence seasonal calcification in the Gulf of Lions. Interannual analysis suggest that both G. bulloides and N. incompta slightly reduced their calcification between 1994 and 2005, while G. truncatulinoides exhibited a constant and pronounced increase in its calcification that translated in an increase of 20 % of its shell weight for the 400–500 µm narrow size class. While our data suggest that carbonate system parameters are the most likely environmental parameter driving foraminifera calcification changes over the years.
Finally, comparison between sediment trap data and seabed sediments allowed us to assess the changes of planktic foraminifera calcification during the late Holocene, including the preindustrial era. Several lines of evidence strongly indicate that selective dissolution did not bias the results in any of our data sets. Our results showed a clear calcification reduction between pre-industrial Holocene and recent data with G. truncatulinoides experiencing the largest calcification decrease (32–40 %) followed by N. incompta (20–27 %) and G. bulloides (18–24 %). Overall, our results provide evidence of clear reduction in planktic foraminifera calcification in the Mediterranean most likely associated with ongoing ocean acidification and consistent with previous observations in other settings of the world’s oceans.
Continue reading ‘Calcification response of planktic foraminifera to environmental change in the western Mediterranean Sea during the industrial era’Planktonic foraminifera organic carbon isotopes as archives of upper ocean carbon cycling
Published 1 September 2022 Science ClosedTags: field, methods, North Atlantic, protists, sediment, South Atlantic
The carbon cycle is a key regulator of Earth’s climate. On geological time-scales, our understanding of particulate organic matter (POM), an important upper ocean carbon pool that fuels ecosystems and an integrated part of the carbon cycle, is limited. Here we investigate the relationship of planktonic foraminifera-bound organic carbon isotopes (δ13Corg-pforam) with δ13Corg of POM (δ13Corg-POM). We compare δ13Corg-pforam of several planktonic foraminifera species from plankton nets and recent sediment cores with δ13Corg-POM on a N-S Atlantic Ocean transect. Our results indicate that δ13Corg-pforam of planktonic foraminifera are remarkably similar to δ13Corg-POM. Application of our method on a glacial sample furthermore provided a δ13Corg-pforam value similar to glacial δ13Corg-POM predictions. We thus show that δ13Corg-pforam is a promising proxy to reconstruct environmental conditions in the upper ocean, providing a route to isolate past variations in δ13Corg-POM and better understanding of the evolution of the carbon cycle over geological time-scales.
Continue reading ‘Planktonic foraminifera organic carbon isotopes as archives of upper ocean carbon cycling’Offshore extinctions: ocean acidification impacting interstitial fauna
Published 18 August 2022 Science ClosedTags: biological response, BRcommunity, community composition, methods, multiple factors, otherprocess, oxygen, review, sediment
As problematic as global warming, ocean acidification is a widespread problem, but the consequences of the interstitial fauna are still underrated. The biodiversity within sandy beaches is out of measurement, and its loss will be significantly felt. Estimations of the number of species are still vague. Acting as a key role in the trophic net, the interstitial organisms are threatened by pH value changes. Changing the pH values is already linked with less species richness and weakness of the sea community. The sediments may not be a sufficient buffer. Beyond this, there is another environmental problem aggravating the scenario. The decreasing complexity in the sand structure generated by the destruction of biological-generated sediments will impact the local biodiversity. Other environmental situations such as lack of sufficient O2 levels may be an aggravating combination. Here, I propose a protocol to observe if occur offshore extinctions, the veiled extinctions of interstitial fauna.
Continue reading ‘Offshore extinctions: ocean acidification impacting interstitial fauna’Environmental change and carbon-cycle dynamics during the onset of Cretaceous oceanic anoxic event 1a from a carbonate-ramp depositional system, Abu Dhabi, U.A.E.
Published 30 June 2022 Science ClosedTags: chemistry, Indian, paleo, sediment
Highlights
- Negative δ13C excursion at onset of OAE1a recorded in carbonate-ramp deposits.
- Time-series analysis shows relative complete record of C3 segment of OAE1a.
- Evidence for short-lived carbonate dissolution event at the negative δ13C peak of C3.
- Discussion of effects of seawater temperature, pH, and diagenesis on δ18O record.
Abstract
We report the first high-resolution sedimentological and geochemical record of the negative carbon-isotope excursion (CIE) at the onset of the early Aptian oceanic anoxic event (OAE) 1a from a carbonate-ramp depositional environment, analysed from a well core from c. 2500 m depth, 100 km offshore Abu Dhabi, United Arab Emirates. Time-series analysis of stable oxygen isotope values and concentrations of Si, Al, and Ti resulted in durations of the C3 and C4 segments of the CIE that support relative completeness of the C3 segment and high sediment preservation rates of c. 13 cm/kyr of the studied sedimentary sequence. Stable oxygen-isotope ratios of bulk carbonates are interpreted to indicate two episodes of cooling, separated by rapid warming during the peak of the negative CIE. The contributions of diagenesis and seawater pH on the bulk oxygen-isotope record will have affected the palaeoclimatic signal and are critically discussed. A major shift in oxygen isotope values at the peak of the negative CIE in the C3 segment coincides with relatively carbonate-poor, marly deposits, time-equivalent with other, global evidence for a reduction of carbonate saturation of sea-surface water. According to our chemo- and cyclostratigraphic calibration, this episode of low carbonate saturation of seawater reflects a pulse of major volcanic CO2 release from the Ontong-Java large igneous province that was sufficiently short to have escaped internal buffering by the dynamics of the ocean lysocline.
Continue reading ‘Environmental change and carbon-cycle dynamics during the onset of Cretaceous oceanic anoxic event 1a from a carbonate-ramp depositional system, Abu Dhabi, U.A.E.’Environmental change and carbon-cycle dynamics during the onset of Cretaceous oceanic anoxic event 1a from a carbonate-ramp depositional system, Abu Dhabi, U.A.E.
Published 10 June 2022 Science ClosedTags: chemistry, Indian, paleo, sediment
Highlights
- Negative δ13C excursion at onset of OAE1a recorded in carbonate-ramp deposits.
- Time-series analysis shows relative complete record of C3 segment of OAE1a.
- Evidence for short-lived carbonate dissolution event at the negative δ13C peak of C3.
- Discussion of effects of seawater temperature, pH, and diagenesis on δ18O record.
Abstract
We report the first high-resolution sedimentological and geochemical record of the negative carbon-isotope excursion (CIE) at the onset of the early Aptian oceanic anoxic event (OAE) 1a from a carbonate-ramp depositional environment, analysed from a well core from c. 2500 m depth, 100 km offshore Abu Dhabi, United Arab Emirates. Time-series analysis of stable oxygen isotope values and concentrations of Si, Al, and Ti resulted in durations of the C3 and C4 segments of the CIE that support relative completeness of the C3 segment and high sediment preservation rates of c. 13 cm/kyr of the studied sedimentary sequence. Stable oxygen-isotope ratios of bulk carbonates are interpreted to indicate two episodes of cooling, separated by rapid warming during the peak of the negative CIE. The contributions of diagenesis and seawater pH on the bulk oxygen-isotope record will have affected the palaeoclimatic signal and are critically discussed. A major shift in oxygen isotope values at the peak of the negative CIE in the C3 segment coincides with relatively carbonate-poor, marly deposits, time-equivalent with other, global evidence for a reduction of carbonate saturation of sea-surface water. According to our chemo- and cyclostratigraphic calibration, this episode of low carbonate saturation of seawater reflects a pulse of major volcanic CO2 release from the Ontong-Java large igneous province that was sufficiently short to have escaped internal buffering by the dynamics of the ocean lysocline.
Continue reading ‘Environmental change and carbon-cycle dynamics during the onset of Cretaceous oceanic anoxic event 1a from a carbonate-ramp depositional system, Abu Dhabi, U.A.E.’Calcification, dissolution and test properties of modern planktonic foraminifera from the central Atlantic Ocean
Published 6 June 2022 Science ClosedTags: abundance, field, morphology, North Atlantic, otherprocess, physiology, protists, sediment, South Atlantic
The mass of well-preserved calcite in planktonic foraminifera shells provides an indication of the calcification potential of the surface ocean. Here we report the shell weight of 8 different abundant planktonic foraminifera species from a set of core-to sediments along the Mid-Atlantic Ridge. The analyses showed that near the equator, foraminifera shells of equivalent size weigh on average 1/3 less than those from the middle latitudes. The carbonate preservation state of the samples was assessed by high resolution X-ray microcomputed tomographic analyses of Globigerinoides ruber and Globorotalia truncatulinoides specimens. The specimen preservation was deemed good and does not overall explain the observed shell mass variations. However, G. ruber shell weights might be to some extent compromised by residual fine debris internal contamination. Deep dwelling species possess heavier tests than their surface-dwelling counterparts, suggesting that the weight of the foraminifera shells changes as a function of the depth habitat. Ambient seawater carbonate chemistry of declining carbonate ion concentration with depth cannot account for this interspecies difference. The results suggest a depth regulating function for plankton calcification, which is not dictated by water column acidity.
Continue reading ‘Calcification, dissolution and test properties of modern planktonic foraminifera from the central Atlantic Ocean’Increased ocean acidification by upwelling intensification in southern Tethyan margin during the PETM: implication for foraminiferal record
Published 3 June 2022 Science ClosedTags: field, Mediterranean, morphology, paleo, protists, sediment
The upper Thanetian–lowermost Ypresian succession in Tunisia is part of an extensive high-productivity upwelling regime in the southern Tethyan margin. As in several modern coastal upwelling systems, the upwelling strengthening regionally accentuated sustained acidification conditions, which prevailed in the Roman Bridge area (Central Tunisia). The poor-carbonate sedimentation, associated with the bad preservation state of calcifiers, points to the expansion of carbonate undersaturation in the water column and deep-sea sediments. The upwelling of deep CO32− and dissolved oxygen-depleted water significantly put calcifiers under chemically stressed habitats. Foraminiferal dwarfism, decrease in abundance and diversity, and especially occurrence of abundant dissolved and fragmented shells could account for the severe carbonate-corrosive waters. The spoiled primary morphological characteristics of benthic foraminifera emphasize the alkalinity increase in the deep marine waters. The well-preserved organic matter in the Roman Bridge sediments suggested a relatively minor role of remineralization in CaCO3-unsaturated waters. The expansion of carbonate-depleted water in the Roman Bridge area was principally driven by upwelled deep depleted-carbonate waters. These findings highlight the challenge to predict the response of the marine ecosystem to rising ocean acidification in upwelling strengthening regions in the future.
Continue reading ‘Increased ocean acidification by upwelling intensification in southern Tethyan margin during the PETM: implication for foraminiferal record’Assessing the effects of ocean warming and acidification on the seagrass Thalassia hemprichii
Published 27 May 2022 Science ClosedTags: biological response, growth, individualmodeling, laboratory, mesocosms, modeling, multiple factors, North Pacific, phanerogams, photosynthesis, physiology, sediment, temperature
Seagrass beds serve as important carbon sinks, and it is thought that increasing the quantity and quality of such sinks could help to slow the rate of global climate change. Therefore, it will be important to (1) gain a better understanding of seagrass bed metabolism and (2) document how these high-productivity ecosystems are impacted by climate change-associated factors, such as ocean acidification (OA) and ocean warming (OW). A mesocosm-based approach was taken herein in which a tropical, Western Pacific seagrass species Thalassia hemprichii was cultured under either control or OA-simulating conditions; the temperature was gradually increased from 25 to 31 °C for both CO2 enrichment treatments, and it was hypothesized that this species would respond positively to OA and elevated temperature. After 12 weeks of exposure, OA (~1200 ppm) led to (1) increases in underground biomass and root C:N ratios and (2) decreases in root nitrogen content. Rising temperatures (25 to 31 °C) increased the maximum quantum yield of photosystem II (Fv:Fm), productivity, leaf growth rate, decomposition rate, and carbon sequestration, but decreased the rate of shoot density increase and the carbon content of the leaves; this indicates that warming alone does not increase the short-term carbon sink capacity of this seagrass species. Under high CO2 and the highest temperature employed (31 °C), this seagrass demonstrated its highest productivity, Fv:Fm, leaf growth rate, and carbon sequestration. Collectively, then, it appears that high CO2 levels offset the negative effects of high temperature on this seagrass species. Whether this pattern is maintained at temperatures that actually induce marked seagrass stress (likely beginning at 33–34 °C in Southern Taiwan) should be the focus of future research.
Continue reading ‘Assessing the effects of ocean warming and acidification on the seagrass Thalassia hemprichii’Ocean acidification alters the predator – prey relationship between hydrozoa and fish larvae
Published 24 May 2022 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, cnidaria, community composition, field, fish, mesocosms, molecular biology, mortality, North Atlantic, otherprocess, photosynthesis, phytoplankton, reproduction, sediment, zooplankton
Anthropogenic CO2 emissions cause a drop in seawater pH and shift the inorganic carbon speciation. Collectively, the term ocean acidification (OA) summarizes these changes. Few studies have examined OA effects on predatory plankton, e.g. Hydrozoa and fish larvae as well as their interaction in complex natural communities. Because Hydrozoa can seriously compete with and prey on other higher-level predators such as fish, changes in their abundances may have significant consequences for marine food webs and ecosystem services. To investigate the interaction between Hydrozoa and fish larvae influenced by OA, we enclosed a natural plankton community in Raunefjord, Norway, for 53 days in eight ≈ 58 m³ pelagic mesocosms. CO2 levels in four mesocosms were increased to ≈ 2000 µatm pCO2, whereas the other four served as untreated controls. We studied OA-induced changes at the top of the food web by following ≈2000 larvae of Atlantic herring (Clupea harengus) hatched inside each mesocosm during the first week of the experiment, and a Hydrozoa population that had already established inside the mesocosms. Under OA, we detected 20% higher abundance of hydromedusae staged jellyfish, but 25% lower biomass. At the same time, survival rates of Atlantic herring larvae were higher under OA (control pCO2: 0.1%, high pCO2: 1.7%) in the final phase of the study. These results indicate that a decrease in predation pressure shortly after hatch likely shaped higher herring larvae survival, when hydromedusae abundance was lower in the OA treatment compared to control conditions. We conclude that indirect food-web mediated OA effects drove the observed changes in the Hydrozoa – fish relationship, based on significant changes in the phyto-, micro-, and mesoplankton community under high pCO2. Ultimately, the observed immediate consequences of these changes for fish larvae survival and the balance of the Hydrozoa – fish larvae predator – prey relationship has important implications for the functioning of oceanic food webs.
Continue reading ‘Ocean acidification alters the predator – prey relationship between hydrozoa and fish larvae’Global record of “ghost” nannofossils reveals plankton resilience to high CO2 and warming
Published 20 May 2022 Science ClosedTags: paleo, phytoplankton, review, sediment
RELATED PERSPECTIVE
Fossil imprints from oceans of the past
Ghosts of the past
The marine geological records of some past global warming events contain relatively few nannoplankton fossils, the lack which some interpret as being evidence of the impact of ocean acidification and/or related environmental factors on biocalcification. Slater et al. present a global record of imprint, or “ghost,” nannofossils throughout several of those intervals during the Jurassic and Cretaceous periods (see the Perspective by Henderiks). This finding implies that a literal interpretation of the fossil record can be misleading, and demonstrates that nannoplankton were more resilient to past warming events than traditional fossil evidence would suggest. —HJS
Abstract
Predictions of how marine calcifying organisms will respond to climate change rely heavily on the fossil record of nannoplankton. Declines in calcium carbonate (CaCO3) and nannofossil abundance through several past global warming events have been interpreted as biocalcification crises caused by ocean acidification and related factors. We present a global record of imprint—or “ghost”—nannofossils that contradicts this view, revealing exquisitely preserved nannoplankton throughout an inferred Jurassic biocalcification crisis. Imprints from two further Cretaceous warming events confirm that the fossil records of these intervals have been strongly distorted by CaCO3 dissolution. Although the rapidity of present-day climate change exceeds the temporal resolution of most fossil records, complicating direct comparison with past warming events, our findings demonstrate that nannoplankton were more resilient to past events than traditional fossil evidence suggests.
Continue reading ‘Global record of “ghost” nannofossils reveals plankton resilience to high CO2 and warming’Effect of different pCO2 concentrations in seawater on meiofauna: abundance of communities in sediment and survival rate of harpacticoid copepods
Published 16 May 2022 Science ClosedTags: abundance, biological response, community composition, crustaceans, laboratory, mortality, otherprocess, sediment, zooplankton
The amount of CO2 dissolved in the ocean has been increasing continuously, and the results using climate change models show that the CO2 concentration of the ocean will increase by over 1000 ppm by 2100. Ocean acidification is expected to have a considerable impact on marine ecosystems. To find out about the impacts of ocean acidification on meiofaunal communities and copepod groups, we analyzed the differences in the abundance of meiofauna communities in sediment and the survival rate of harpacticoid copepod assemblages separated from the sediment, between 400 and 1000 ppm pCO2 for a short period of 5 days. In experiments with communities in sediments exposed to different pCO2 concentrations, there was no significant difference in the abundance of total meiofauna and nematodes. However, the abundance of the harpacticoid copepod community was significantly lower at 1000 ppm than that at 400 ppm pCO2. On the other hand, in experiments with assemblages of harpacticoid copepods directly exposed to seawater, there was no significant difference in their survival rates between the two concentrations. Our findings suggest that a CO2 concentration of 1000 ppm in seawater can cause changes in the abundance of specific taxa such as harpacticoid copepods among the meiofauna communities in sediments.
Continue reading ‘Effect of different pCO2 concentrations in seawater on meiofauna: abundance of communities in sediment and survival rate of harpacticoid copepods’CaCO3 dissolution in carbonate-poor shelf sands increases with ocean acidification and porewater residence time
Published 13 May 2022 Science ClosedTags: chemistry, laboratory, North Pacific, sediment
Carbonate-poor sandy sediments comprise much of the shelf area, and—despite their low CaCO3 content—contain a significant pool of CaCO3 base available to neutralize ocean acid. Here, we conducted flow-through column experiments on permeable, carbonate-poor sand obtained from Catalina Island, CA, to quantify CaCO3 dissolution across a range of current and future seawater conditions. Using 13C isotope mass balance, we show that dissolution depends both on the CaCO3 saturation state (Ω) of the inflowing seawater, as well as porewater residence time. At current ocean conditions (Ωaragonite =2.4 and Ωcalcite =3.7 at our field site), dissolution was negligible for porewater residence times <1.8 h, but increased thereafter, following sufficient production of CO2 from aerobic respiration. As Ω of inlet water was lowered, simulating future ocean conditions, dissolution began earlier and rates increased. The response to acidification was similar to previously reported observations in carbonate-rich shelf environments, suggesting that carbonate-poor sediments have the potential to support enhanced dissolution in an acidifying ocean, given sufficient CaCO3 substrate. With continued acidification projected to occur this century, these sediments could transition from a net source of acid to the overlying seawater (production of alkalinity to dissolved inorganic carbon, ΔAlk/ΔDIC<1) to net source of buffering capacity (ΔAlk/ΔDIC>1) when overlying seawater Ωaragonite reaches 0.96 to 0.69 (Ωcalcite = 1.50 and 1.07), depending on porewater residence time. In some areas with naturally acidic water, this threshold has already been reached.
Continue reading ‘CaCO3 dissolution in carbonate-poor shelf sands increases with ocean acidification and porewater residence time’The effects of ocean acidification on microbial nutrient cycling and productivity in coastal marine sediments
Published 12 May 2022 Science ClosedTags: biological response, community composition, Indian, laboratory, mitigation, molecular biology, otherprocess, photosynthesis, physiology, sediment
Ocean Acidification (OA), commonly referred to as the “other CO₂ problem,” illustrates the current rise in atmospheric carbon dioxide (CO₂) levels, precipitated in large by human-related activity (e.g., fossil fuel combustion and mass deforestation). The dissolution of atmospheric CO₂ into the surface of the ocean over time has reduced oceanic pH levels by 0.1 units since the start of the pre-industrial era and has resulted in wholesale shifts in seawater carbonate chemistry on a planetary scale. The chemical processes of ocean acidification are increasingly well documented, demonstrating clear rates of increase for global CO₂ emissions predicted by the IPCC (Intergovernmental Panel on Climate Change) under the business-as-usual CO₂ emissions scenario. The ecological impact of ocean acidification alters seawater chemical speciation and disrupts vital biogeochemical cycling processes for various chemicals and compounds. Whereby the unidentified potential fallout of this is the cascading effects on the microbial communities within the benthic sediments. These microorganisms drive the marine ecosystem through a network of vast biogeochemical cycling processes aiding in the moderation of ecosystem-wide primary productivity and fundamentally regulating the global climate. The benthic sediments are determinably one of the largest and most diverse ecosystems on the planet. Marine sediments are also conceivably one of the most productive in terms of microbial activity and nutrient flux between the water-sediment interface (i.e., boundary layer). The absorption and sequestering of CO₂ from the atmosphere have demonstrated significant impacts on various marine taxa and their associated ecological processes. This is commonly observed in the reduction in calcium carbonate saturation states in most shell-forming organisms (i.e., plankton, benthic mollusks, echinoderms, and Scleractinia corals). However, the response of benthic sediment microbial communities to a reduction in global ocean pH remains considerably less well characterized. As these microorganisms operate as the lifeblood of the marine ecosystem, understanding their response and physiological plasticity to increased levels of CO₂ is of critical importance when it comes to investigating regional and global implications for the effects of ocean acidification.
Continue reading ‘The effects of ocean acidification on microbial nutrient cycling and productivity in coastal marine sediments’Potential resilience to ocean acidification of benthic foraminifers living in Posidonia oceanica meadows: the case of the shallow venting site of Panarea
Published 29 April 2022 Science ClosedTags: biological response, BRcommunity, community composition, field, Mediterranean, otherprocess, phanerogams, protists, sediment, vents
This research shows the results regarding the response to acidic condition of the sediment and Posidonia foraminiferal assemblages collected around the Panarea Island. The Aeolian Archipelago represents a natural laboratory and a much-promising study site for multidisciplinary marine research (carbon capture and storage, geochemistry of hydrothermal fluids and ocean acidification vs. benthic and pelagic organisms). The variability and the complexity of the interaction of the ecological factors characterizing extreme environments such as shallow hydrothermal vents did not allow us to carry out a real pattern of biota responses in situ, differently from those observed under controlled laboratory conditions. However, the study provides new insights into foraminiferal response to increasing ocean acidification (OA) in terms of biodiversity, faunal density, specific composition of the assemblages and morphological variations of the shells. The study highlights how the foraminiferal response to different pH conditions can change depending on different environmental conditions and microhabitats (sediments, Posidonia leaves and rhizomes). Indeed, mineral sediments were more impacted by acidification, whereas Posidonia microhabitats, thanks to their buffer effect, can offer “refugia” and more mitigated acidic environment. At species level, rosalinids and agglutinated group represent the most abundant taxa showing the most specific resilience and capability to face acidic conditions.
Continue reading ‘Potential resilience to ocean acidification of benthic foraminifers living in Posidonia oceanica meadows: the case of the shallow venting site of Panarea’Acidification impacts and acclimation potential of foraminifera
Published 19 April 2022 Science ClosedTags: biological response, BRcommunity, laboratory, mortality, North Atlantic, physiology, protists, sediment
Ocean acidification is expected to negatively affect many ecologically important organisms. Here we explored the response of Caribbean benthic foraminiferal communities to naturally discharging low-pH waters similar to expected future projections for the end of the 21st century. At low-pH (~ 7.7 pH units), low calcite saturation, agglutinated and symbiont-bearing species were relatively more abundant, indicating higher resistance to potential carbonate chemistry changes. Diversity and other taxonomical metrics declined steeply with decreasing pH despite exposure of this ecosystem for millennia to low pH conditions, suggesting that tropical foraminifera communities will be negatively impacted under acidification scenarios SSP3-7.0 and SSP5-8.5. The species Archaias angulatus, a major contributor to sediment production in the Caribbean was able to calcify at conditions more extreme than those projected for the late 21st century (7.1 pH units), but the calcified tests were of lower density than those exposed to high-pH ambient conditions (7.96 pH units), indicating that reef foraminiferal carbonate budget might decrease. Smaller foraminifera were highly sensitive to decreasing pH and our results demonstrate their potential as indicators to monitor increasing OA conditions.
Continue reading ‘Acidification impacts and acclimation potential of foraminifera’An evaluation of the efficacy of shell hash for the mitigation of intertidal sediment acidification
Published 28 March 2022 Science ClosedTags: chemistry, field, mitigation, North Pacific, sediment
Our objectives were twofold: (1) to determine whether the addition of shell hash to intertidal sediments would mitigate porewater acidification and (2) whether its effectiveness was dependent on the type of sediment as described by organic matter (OM) and particle grain size (PGS). Field experiments were conducted at two sites within Burrard Inlet, British Columbia; Maplewood Mudflats (MM), high in OM and silt and Whey-ah-Wichen/Cates Park (WAW), low in OM and an equal PGS among very coarse, coarse, fine sand, and silt. Shell hash was added to triplicate treatment plots matched with triplicate controls at each site and porewater pH measured at flood and ebb tide over eight tidal cycles. Sampling occurred during June and July when tidal cycles were at their maximum inundation and exposure. Porewater pH was significantly greater for ebb versus flood tide and also between sites with MM significantly lower (7.59) as compared to WAW (8.03). Although pH was not mitigated by the shell hash, for WAW, variation in pH was reduced as compared to MM, as indicated by coefficients of variation over the 6-week sampling period. We suggest that the application of shell hash to reduce the impact of ocean acidification (OA) on intertidal sediments will be site dependent. The combined processes of eutrophication in sediments with high OM and respiration of infauna, especially at high densities, could act in concert with OA to create an intertidal region unsuitable for bivalve larvae settlement and development.
Continue reading ‘An evaluation of the efficacy of shell hash for the mitigation of intertidal sediment acidification’Revisiting the carbonate chemistry of the Sea of Japan (East Sea): from water column to sediment
Published 25 March 2022 Science ClosedTags: chemistry, field, North Pacific, sediment
In this study, we investigated the carbonate system in sediments and water columns from five stations in the Sea of Japan (East Sea) (JES) during the R/V Hakuho Maru KH-10-2 research cruise in the summer of 2010. The total alkalinity (TA) and pH were measured. Adopting a saturation degree of 91% and 80% for the lysocline depth and calcite compensation depth (CCD), respectively, we found that those depths corresponded to 1360 and 1980 m. A comparison of the calcite saturation depths, lysocline depths, and CCD depths obtained for 1999 and 2010 suggests that acidification of the interior of the JES occurred. Sediment cores were retrieved using a multi-corer. In the sediment cores, a sharp decrease in the pH by 0.3–0.4 pH units was observed in the subsurface horizons (0–10 cm) compared with the pH of the seawater from the bottom horizons. The TA in the porewaters was significantly higher than that in the overlying seawater. The anaerobic degradation of organic matter is probably the main cause for the increasing TA in the sediments. The porewaters were significantly undersaturated with calcite and aragonite, except in that from the shallowest station, where the sediments below 7.5 cm were saturated, and even supersaturated, with calcite and aragonite. A linear correlation between the dissolved inorganic carbon and the TA for sediments with a slope of 0.9993 was found, despite there being potentially different ways for the diagenesis of the organic matter to occur. The diagenesis of organic matter in the top sediments of the JES forms gradients of TA and CO2* concentrations on the interface of “bottom water–sediments”. Averaged fluxes of TA and dissolved inorganic carbon (DIC) from the sediments to the bottom waters estimated by means of Fickian diffusion were calculated as 44 and 89 mmol/(m2 year) for TA and DIC, respectively.
Continue reading ‘Revisiting the carbonate chemistry of the Sea of Japan (East Sea): from water column to sediment’The distribution of intact polar lipid-derived branched tetraethers along a freshwater-seawater pH gradient in coastal East China Sea
Published 23 March 2022 Science ClosedTags: archaea, biological response, laboratory, North Pacific, physiology, sediment
In view of the application of microbial branched tetraether lipids (i.e., brGDGTs) in terrestrial pH reconstructions, their potential as seawater pH proxy is investigated from the Yangtze River Estuary (YRE) to the shelf region in the East China Sea (ECS). BrGDGTs occurring as ‘fossil’ core and in ‘living’ intact polar lipids (CL-brGDGTs and IPL-brGDGTs, respectively) in surface sediments are separately analyzed. The results show that riverine IPL-brGDGTs are rapidly lost at the transition from the YRE to the marine settings and sedimentary IPL-brGDGTs are predominantly produced in situ in brackish water environments. Among environmental parameters, surface water pH is a determinant factor controlling the cyclization of IPL-brGDGTs, with higher cyclization at higher pH. Hereby, two IPL-brGDGTs-based seawater pH calibrations are established in the brackish seawater environment in this study: surface pH = 7.28 + 1.08 × #Ringstetra (n = 18, r2 = 0.87, RMSE = 0.05, p < 0.01) and surface pH = 7.13 + 3.82 × f(Ic) + 4.29 × f(IIb’) + 4.21 × f(IIIa) (n = 18, r2 = 0.90, RMSE = 0.04, p < 0.01), which are different from those established in terrestrial environments. This is the first work demonstrating that in situ produced microbial brGDGTs can trace seawater pH change in marine environment, which makes it promising to apply brGDGTs for seawater pH reconstructions in marine settings where the terrestrial inputs are negligible.
Continue reading ‘The distribution of intact polar lipid-derived branched tetraethers along a freshwater-seawater pH gradient in coastal East China Sea’Unraveling ecological signals from a global warming event of the past
Published 23 March 2022 Science ClosedTags: paleo, sediment
This article has related content: Isotopic filtering reveals high sensitivity of planktic calcifiers to Paleocene–Eocene thermal maximum warming and acidification Brittany N. Hupp, D. Clay Kelly, John W. Williams
As we face the increasing threat of global warming and its associated effects, paleontologists and paleoclimatologists alike look to the geological record to investigate how rapid, natural global warming events of the past have impacted the Earth system. One of the most important archives for investigating climate change in the geological past is the marine sediment record (1). In the open oceans, sediment particles, organic matter, and the shells of marine microorganisms, are constantly raining down on the seafloor and accumulating as marine sediments (1). In the relative quiescence of the deep sea, these sediments can build up relatively undisturbed for millions of years (1). Analysis of the chemical signals in these sediments that are influenced by temperature has allowed for the reconstruction of changing global climates throughout the last 70 million years (2).
The first half of the Cenozoic (66 million years to 34 million years ago) was characterized by “hothouse” and “warmhouse” climates, when global temperatures were between 5 °C and 10 °C warmer than the present day (2), and atmospheric CO2 was estimated to be between 500 and 3,000 parts per million (3). Against this backdrop of an already warm world, between 56 million and 46 million years ago, there were a series of rapid global warming events called “hyperthermals” (2). These hyperthermal events are geologically brief, typically <200,000 y in duration, and associated with sharp negative carbon isotope excursions (2). The Paleocene–Eocene thermal maximum (PETM), which occurred ∼56 million years ago, was the largest of these events (2). It was first discovered in the early 1990s as a pronounced shift in the climate records of a deep-sea sediment core from the Southern Ocean (4). Since that time, the PETM has become the most studied Cenozoic hyperthermal, and, due to its potential analogy to anthropogenic climate change, it remains a key interval of Earth history for climatological research.
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Continue reading ‘Unraveling ecological signals from a global warming event of the past’
