Ocean acidification impacts the physiology of crustaceans as well as marine calcifiers although most of the hitherto studies has focused on calcifiers. Bioconcentration of elements in a marine animal depends on seawater chemistry and the animal’s physiology. Here we studied biokinetics and body distribution of Ag in Baltic shrimp Palaemon adspersus for 47 days by using radiotracer method (110mAg). The bioconcentration of 110mAg was assessed under three pCO2 levels: 370, 795 and 1634 μatm. Uptake rate constants of 110mAg were inversely related to pH (3.1 at pH: 8.1, 4.2 at pH: 7.8 and 4.9 at pH: 7.5). A higher percentage of Ag accumulated in edible parts in the shrimps reared in acidified seawater compared to control. The moulting frequency was significantly higher in acidified seawater conditions compared to the control condition. The results of this study suggest that seawater acidification may partly modify Ag bioconcentration in Baltic shrimp Palaemon adspersus as well as energy-demanding physiological processes like moulting.
Continue reading ‘Biokinetics of 110m Ag in Baltic shrimp Palaemon adspersus under elevated pCO2’Archive for February, 2021
Biokinetics of 110m Ag in Baltic shrimp Palaemon adspersus under elevated pCO2
Published 22 February 2021 Science ClosedTags: Baltic, biological response, crustaceans, laboratory, morphology, physiology
The northern European shelf as an increasing net sink for CO2 (update)
Published 19 February 2021 Science ClosedTags: Arctic, biogeochemistry, chemistry, modeling, North Atlantic, regionalmodeling
We developed a simple method to refine existing open-ocean maps and extend them towards different coastal seas. Using a multi-linear regression we produced monthly maps of surface ocean fCO2 in the northern European coastal seas (the North Sea, the Baltic Sea, the Norwegian Coast and the Barents Sea) covering a time period from 1998 to 2016. A comparison with gridded Surface Ocean CO2 Atlas (SOCAT) v5 data revealed mean biases and standard deviations of 0 ± 26 µatm in the North Sea, 0 ± 16 µatm along the Norwegian Coast, 0 ± 19 µatm in the Barents Sea and 2 ± 42 µatm in the Baltic Sea. We used these maps to investigate trends in fCO2, pH and air–sea CO2 flux. The surface ocean fCO2 trends are smaller than the atmospheric trend in most of the studied regions. The only exception to this is the western part of the North Sea, where sea surface fCO2 increases by 2 µatm yr−1, which is similar to the atmospheric trend. The Baltic Sea does not show a significant trend. Here, the variability was much larger than the expected trends. Consistently, the pH trends were smaller than expected for an increase in fCO2 in pace with the rise of atmospheric CO2 levels. The calculated air–sea CO2 fluxes revealed that most regions were net sinks for CO2. Only the southern North Sea and the Baltic Sea emitted CO2 to the atmosphere. Especially in the northern regions the sink strength increased during the studied period.
Continue reading ‘The northern European shelf as an increasing net sink for CO2 (update)’The seasonal phases of an Arctic lagoon reveal the discontinuities of pH variability and CO2 flux at the air–sea interface
Published 19 February 2021 Science ClosedTags: chemistry, field
The western Arctic Ocean, including its shelves and coastal habitats, has become a focus in ocean acidification research over the past decade as the colder waters of the region and the reduction of sea ice appear to promote the uptake of excess atmospheric CO2. Due to seasonal sea ice coverage, high-frequency monitoring of pH or other carbonate chemistry parameters is typically limited to infrequent ship-based transects during ice-free summers. This approach has failed to capture year-round nearshore carbonate chemistry dynamics which is modulated by biological metabolism in response to abundant allochthonous organic matter to the narrow shelf of the Beaufort Sea and adjacent regions. The coastline of the Beaufort Sea comprises a series of lagoons that account for > 50 % of the land–sea interface. The lagoon ecosystems are novel features that cycle between “open” and “closed” phases (i.e., ice-free and ice-covered, respectively). In this study, we collected high-frequency pH, salinity, temperature, and photosynthetically active radiation (PAR) measurements in association with the Beaufort Lagoon Ecosystems – Long Term Ecological Research program – for an entire calendar year in Kaktovik Lagoon, Alaska, USA, capturing two open-water phases and one closed phase. Hourly pH variability during the open-water phases are some of the fastest rates reported, exceeding 0.4 units. Baseline pH varied substantially between the open phase in 2018 and open phase in 2019 from ∼ 7.85 to 8.05, respectively, despite similar hourly rates of change. Salinity–pH relationships were mixed during all three phases, displaying no correlation in the 2018 open phase, a negative correlation in the 2018/19 closed phase, and a positive correlation during the 2019 open phase. The high frequency of pH variability could partially be explained by photosynthesis–respiration cycles as correlation coefficients between daily average pH and PAR were 0.46 and 0.64 for 2018 and 2019 open phases, respectively. The estimated annual daily average CO2 efflux (from sea to atmosphere) was 5.9 ± 19.3 mmolm−2d−1, which is converse to the negative influx of CO2 estimated for the coastal Beaufort Sea despite exhibiting extreme variability. Considering the geomorphic differences such as depth and enclosure in Beaufort Sea lagoons, further investigation is needed to assess whether there are periods of the open phase in which lagoons are sources of carbon to the atmosphere, potentially offsetting the predicted sink capacity of the greater Beaufort Sea.
Continue reading ‘The seasonal phases of an Arctic lagoon reveal the discontinuities of pH variability and CO2 flux at the air–sea interface’Climate change mitigation effects: how do potential CO2 leaks from a sub-seabed storage site in the Norwegian Sea affect Astarte sp. bivalves?
Published 19 February 2021 Science ClosedTags: biological response, growth, laboratory, mitigation, morphology, mortality, North Atlantic, physiology
Highlights
- Acidification and recovery were assessed with high-pressure bioassays.
- No mortality was reported for Astarte sp. for a pH 7.0 scenario.
- Normal growth of shell length was recorded after CO2 exposure and a recovery period.
Abstract
Carbon capture and storage (CCS) is one of the most promising mitigation strategies for reducing the emissions of carbon dioxide (CO2) to the atmosphere and may substantially help to decelerate global warming. There is an increasing demand for CCS sites. Nevertheless, there is a lack of knowledge of the environmental risk associated with potential leakage of CO2 from the storage sites; and even more, what happens when the seepage stops. Can the environment return to the initial equilibrium? Potential effects on native macrofauna were studied under a scenario of a 50-day CO2 leakage, and the subsequent leak closure. To accomplish the objective, Trondheim Fjord sediments and clams were exposed to an acidified environment (pH 6.9) at 29 atm for 7 weeks followed by a 14-day recovery at normal seawater conditions (pH 8.0, 29 atm). Growth and survival of clams exposed to pressure (29 atm) and reduced pH (6.9) did not significantly differ from control clams kept at 1 atm in natural seawater. Furthermore, bioaccumulation of elements in the soft tissue of clams did not register significant variations for most of the analysed elements (Cd, Cr, Pb, and Ti), while other elements (As, Cu, Fe, Ni) had decreasing concentrations in tissues under acidified conditions in contrast to Na and Mg, which registered an uptake (Ku) of 111 and 9.92 μg g−1dw d−1, respectively. This Ku may be altered due to the stress induced by acidification; and the element concentration being released from sediments was not highly affected at that pH. Therefore, a 1 unit drop in pH at the seafloor for several weeks does not appear to pose a risk for the clams.
Continue reading ‘Climate change mitigation effects: how do potential CO2 leaks from a sub-seabed storage site in the Norwegian Sea affect Astarte sp. bivalves?’NOAA funds VIMS to study impact of ocean acidification on oysters
Published 19 February 2021 Press releases ClosedTeam will assess vulnerability of aquaculture and restoration efforts in Chesapeake Bay
The excess carbon dioxide responsible for global warming also increases the acidity of seawater, challenging the growth and survival of oysters and other shellfish. A team led by researchers at William & Mary’s Virginia Institute of Marine Science is now helping oyster growers and restoration specialists better manage their future responses to acidification in the Chesapeake Bay.
The team, funded by the NOAA Ocean Acidification Program, is led by VIMS researchers Marjy Friedrichs and Emily Rivest, along with David Wrathall of Oregon State University. Other team members include Mark Brush, Pierre St-Laurent, and Karen Hudson of VIMS, Aaron Bever of Anchor QEA, and Bruce Vogt of NOAA’s Chesapeake Bay Office. The team calls their project STAR, for Shellfish Thresholds and Aquaculture Resilience.
“Coastal acidification and its associated co-stressors present a serious and credible threat to the success of both oyster aquaculture and oyster restoration in the Bay,” says Friedrichs. The co-stressors include nutrient pollution, warmer Bay waters, and pulses of freshwater from rainstorms made more intense by global atmospheric changes. Previous research has shown these factors can intensify the negative impacts caused by ocean acidification alone.
Continue reading ‘NOAA funds VIMS to study impact of ocean acidification on oysters’Extreme levels of ocean acidification restructure the plankton community and biogeochemistry of a temperate coastal ecosystem: a mesocosm study
Published 18 February 2021 Science ClosedTags: abundance, adaptation, biogeochemistry, biological response, chemistry, chordata, cnidaria, community composition, crustaceans, field, mesocosms, mollusks, North Atlantic, photosynthesis, phytoplankton, primary production, protists, zooplankton
The oceans’ uptake of anthropogenic carbon dioxide (CO2) decreases seawater pH and alters the inorganic carbon speciation – summarized in the term ocean acidification (OA). Already today, coastal regions experience episodic pH events during which surface layer pH drops below values projected for the surface ocean at the end of the century. Future OA is expected to further enhance the intensity of these coastal extreme pH events. To evaluate the influence of such episodic OA events in coastal regions, we deployed eight pelagic mesocosms for 53 days in Raunefjord, Norway, and enclosed 56–61 m3 of local seawater containing a natural plankton community under nutrient limited post-bloom conditions. Four mesocosms were enriched with CO2 to simulate extreme pCO2 levels of 1978 – 2069 μatm while the other four served as untreated controls. Here, we present results from multivariate analyses on OA-induced changes in the phyto-, micro-, and mesozooplankton community structure. Pronounced differences in the plankton community emerged early in the experiment, and were amplified by enhanced top-down control throughout the study period. The plankton groups responding most profoundly to high CO2 conditions were cyanobacteria (negative), chlorophyceae (negative), auto- and heterotrophic microzooplankton (negative), and a variety of mesozooplanktonic taxa, including copepoda (mixed), appendicularia (positive), hydrozoa (positive), fish larvae (positive), and gastropoda (negative). The restructuring of the community coincided with significant changes in the concentration and elemental stoichiometry of particulate organic matter. Results imply that extreme CO2 events can lead to a substantial reorganization of the planktonic food web, affecting multiple trophic levels from phytoplankton to primary and secondary consumers.
Continue reading ‘Extreme levels of ocean acidification restructure the plankton community and biogeochemistry of a temperate coastal ecosystem: a mesocosm study’Weekly reconstruction of pH and total alkalinity in an upwelling-dominated coastal ecosystem through neural networks (ATpH-NN): The case of Ría de Vigo (NW Spain) between 1992 and 2019
Published 18 February 2021 Science ClosedTags: chemistry, field, modeling, North Atlantic, regionalmodeling
Short and long-term variability of seawater carbon dioxide (CO2) system shows large differences between different ecosystems which are derived from the characteristic processes of each area. The high variability of coastal ecosystems, their ecological and economic significance, the anthropogenic influence on them and their behavior as sources or sinks of atmospheric CO2, highlight the relevance to better understand the processes that underlie the variability and the alterations of the CO2 system at different spatiotemporal scales. To confidently achieve this purpose, it is necessary to have high-frequency data sustained over several years in different regions. In this work, we contribute to this need by configuring and training two neural networks with the capacity to model the weekly variability of pH and total alkalinity (AT) in the upper 50 m of the water column of the Ría de Vigo (NW Spain), with an error of 0.031 pH units and 10.9 µmol kg−1 respectively. With these networks, we generated weekly time series of pH and AT in seven locations of the Ría de Vigo in three depth ranges (0–5 m, 5–10 m and 10–15 m), which adequately represent independent discrete measurements. In a first analysis of the time series, a high short-term variability is observed, being larger for the inner stations of the Ría de Vigo. The lowest values of pH and AT were obtained for the inner zone, showing a progressive increase towards the outer/middle zone of the ría. The mean seasonal cycle also reflects the gradient between both zones, with a larger amplitude and variability for both variables in the inner zone. On the other hand, the long-term trends derived from the time series of pH show a higher acidification than that obtained for the open ocean, with surface trends ranging from −0.020 pH units per year in the outer/middle zone to −0.032 pH units per year in the inner zone. In addition, positive long-term trends of AT were obtained ranging from 0.39 µmol kg−1 per year in the outer/middle zone to 2.86 µmol kg−1 per year in the inner zone. The results presented in this study show the changing conditions both in the short and long-term variability as well as the spatial differentiation between the inner and outer/middle zone to which the organisms of the Ría de Vigo are subjected. The neural networks and the database provided in this study offer the opportunity to evaluate the CO2 system in an environment of high ecological and economic relevance, to validate high-resolution regional biogeochemical models and to evaluate the impacts on organisms of the Ría de Vigo by refining the ranges of the biogeochemical variables included in experiments.
Continue reading ‘Weekly reconstruction of pH and total alkalinity in an upwelling-dominated coastal ecosystem through neural networks (ATpH-NN): The case of Ría de Vigo (NW Spain) between 1992 and 2019’UCLA-led study highlights effects of ocean acidification, warming on coral reefs
Published 18 February 2021 Press releases Closed
Rising ocean temperatures and ocean acidification could have negative cumulative effects that slow the growth of tropical coral reefs, according to a UCLA-led study published in early January.
The study examined the growth of two types of tropical corals – commonly known as cauliflower coral and hood coral – at different water temperatures and acidities. At a lower temperature, the corals were able to compensate for the acidification and continue building their skeletons. But at a higher temperature, the corals grew much slower.
In order for coral reefs to survive despite constant degradation by waves and human activity, individual reef-building corals must be able to efficiently build their skeletons through a process called calcification, said Maxence Guillermic, a UCLA postdoctoral researcher and lead author of the study. The coral must maintain the correct internal carbonate conditions to allow the skeletal building material, calcium carbonate, to precipitate, he added.
Continue reading ‘UCLA-led study highlights effects of ocean acidification, warming on coral reefs’Turf wars: ocean acidification and feedback loops lock in turf algal systems
Published 17 February 2021 Press releases Closed
Researchers from the University of Tsukuba find that in the presence of ocean acidification, feedback loops keep degraded turf algal states stabilized, inhibiting the recruitment of coral and other algae.
Tsukuba, Japan—It’s tough out there in the sea, as the widespread loss of complex marine communities is testament to. Researchers from Japan have discovered that ocean acidification favors degraded turf algal systems over corals and other algae, thanks to the help of feedback loops.
In a study published this month in Communications Biology, researchers from the University of Tsukuba have revealed that ocean acidification and feedback loops stabilize degraded turf algal systems, limiting the recruitment of coral and other algae.
Continue reading ‘Turf wars: ocean acidification and feedback loops lock in turf algal systems’Nuclear technology can help mitigate ocean acidification caused by climate change
Published 17 February 2021 Web sites and blogs ClosedClimate change also causes changes in the oceans, which absorbs about one-fourth of the carbon dioxide emitted to the atmosphere each year. Nuclear and isotopic techniques are powerful tools to study the carbon cycle and ocean acidification. These techniques have widely contributed to the understanding of past and present ocean conditions and to predicting the impact of climate change, according to sources from the International Atomic Energy Agency (IAEA).
Ocean acidification
As the ocean absorbs carbon dioxide (CO2) released into the atmosphere by human activities, the chemistry and acidity of seawater are modified. This process has become a key global issue in the last decade because of its potential to affect marine organisms and biogeochemical cycles.
Nuclear and isotopic techniques are used contribute to the understanding of this process. Researchers look into past changes in ocean acidity and the impacts of ocean acidification on marine organisms and study biological processes like calcification.
The ocean absorbs approximately one fourth of the carbon dioxide released into the atmosphere
Calcification, marine ecosystems and coral reefs
Below a certain pH and its corresponding carbonate concentration conditions become corrosive to calcium carbonate, which is used by many organisms to build their shells and skeletons. Some corals, pteropods, bivalve mollusks and phytoplankton may be particularly sensitive to changes in seawater chemistry. The energy they spend overcoming the higher acidity could reduce the energy available for physiological processes such as reproduction and growth.
Some marine organisms could be especially sensitive to chemical changes in sea water.
Coral reefs are also highly affected. They host some of the most diverse ecosystems on the planet, yet studies have shown that some corals are sensitive to variations in their environment. In the past, ocean acidification episodes in the geological past led to significant changes in ecosystems, including mass extinctions of some deep-sea marine organisms and the collapse of reef-building calcareous algae and corals.
In the past, acidification periods in the ocean caused significant changes to ecosystems
Nuclear and isotopic techniques study the rates of biological processes in marine organisms, such as mussels, oysters and corals. Boron isotopes are used to study past changes in seawater pH; scientists measure their relative amounts in coral skeletons formed thousands of years ago in order to assess past seawater acidity.
Because of the potential impact of CO2 absorption on marine environments and ecosystems, the IAEA’s Environment Laboratories conduct research on topics such as the economic implications of ocean acidification on fisheries. The IAEA also maintains the Ocean Acidification International Coordination Centre (OA-ICC), which helps advance ocean acidification science, capacity-building and global communication.
Nuclear and isotopic techniques study the pH changes in sea water
A major environmental issue of the 21st century
Ocean acidification has emerged as one of the 21st century’s major global threats to marine organisms, ecosystems, and resources and is the specific focus of United Nations Sustainable Development Goal 14.3.
This “other CO2 problem”, still poorly known by the general public, can have potentially dramatic socio-economic consequences for countries depending on marine resources, especially countries with limited possibilities for alternative livelihoods. As world-wide research activities on ocean acidification and related stressors continue to develop, there is a clear need for effective global scientific cooperation.
The 8th of January (08.01) is the Ocean Acidification Day of Action (8.1 is the current pH of the ocean). the IAEA’s Ocean Acidification International Coordination Centre released a video describing its work using nuclear and nuclear-derived technologies to better understand and address the issue of ocean acidification. The video explains how climate change is altering the chemistry of oceans and affecting the health of many marine animals:
Foro Nuclear. More information.
Climate-induced wind upwelling could further acidify Chesapeake Bay
Published 17 February 2021 Press releases 1 CommentA NCCOS and NOAA Ocean Acidification Program sponsored study investigated how physical properties such as winds, tides, and currents impact estuarine acidification and carbonate chemistry in the Chesapeake Bay estuary, a complex and little studied undertaking. A coupled hydrodynamic-carbonate chemistry model was used to understand the wind-driven variability in the estuarine carbonate system. Large temporal pH fluctuations and low pH events were documented that could negatively impact acidification-sensitive species such as oysters.
A major challenge in the study of estuarine acidification is the strong temporal and spatial variability of carbonate chemistry resulting from a wide array of physical forces such as winds, tides and river flows. Most studies of estuarine carbonate system dynamics have been limited to the along-channel direction, while lateral pH dynamics (e.g., channel to shore) has received less attention.
Feedback mechanisms stabilise degraded turf algal systems at a CO2 seep site
Published 17 February 2021 Science ClosedTags: abundance, algae, biological response, BRcommunity, chemistry, community composition, corals, field, North Pacific, otherprocess, reproduction, vents
Human activities are rapidly changing the structure and function of coastal marine ecosystems. Large-scale replacement of kelp forests and coral reefs with turf algal mats is resulting in homogenous habitats that have less ecological and human value. Ocean acidification has strong potential to substantially favour turf algae growth, which led us to examine the mechanisms that stabilise turf algal states. Here we show that ocean acidification promotes turf algae over corals and macroalgae, mediating new habitat conditions that create stabilising feedback loops (altered physicochemical environment and microbial community, and an inhibition of recruitment) capable of locking turf systems in place. Such feedbacks help explain why degraded coastal habitats persist after being initially pushed past the tipping point by global and local anthropogenic stressors. An understanding of the mechanisms that stabilise degraded coastal habitats can be incorporated into adaptive management to better protect the contribution of coastal systems to human wellbeing.
Continue reading ‘Feedback mechanisms stabilise degraded turf algal systems at a CO2 seep site’Alkalinization scenarios in the Mediterranean Sea for efficient removal of atmospheric CO2 and the mitigation of ocean acidification
Published 16 February 2021 Science ClosedTags: chemistry, mitigation, modeling, regionalmodeling
It is now widely recognised that in order to reach the target of limiting global warming below 2 °C above pre-industrial levels (as the objective of the Paris agreement) there is the need for development and implementation of active Carbon Dioxide Removal (CDR) strategies. Relatively few studies have assessed the mitigation capacity of ocean-based Negative Emission Technologies (NET) and the feasibility of their implementation on a larger scale to support efficient implementation strategies of CDR. This study investigates the case of marine alkalinisation, which has the additional potential of contrasting the ongoing acidification resulting from increased uptake of atmospheric CO2 by the seas. More specifically, we present an analysis of ocean alkalinisation applied to the Mediterranean Sea taking into consideration the regional characteristics of the basin. Rather than using idealised spatially homogenous scenarios of alkalinisation as done in previous studies, we use a set of numerical simulations of alkalinisation based on current shipping routes to quantitatively assess the alkalinisation efficiency via a coupled physical-biogeochemical model over the next decades. Simulations suggest the potential of nearly doubling the carbon-dioxide uptake rate of the Mediterranean Sea after 30 years of alkalinisation, and of neutralising the mean surface acidification trend of the baseline scenario without alkalinisation over the same time span. These levels are achieved via two different strategies: a first approach applying constant annual discharge of 200Mt Ca(OH)2 over the alkalinisation period and a second approach with gradually increasing discharge proportional to the surface pH trend of the baseline scenario reaching similar amounts of annual discharge by the end of the alkalinisation period. We demonstrate that via the latter approach it is possible to stabilise the mean surface pH at present day values and substantially increase the potential to counteract acidification relative to the alkalinity added while the carbon uptake efficiency is only marginally reduced. Nevertheless, significant local alterations of the surface pH persist, calling for an investigation of the physiological and ecological implications of the extent of these alterations to the carbonate system in the short to medium term in order to support a safe, sustainable application of this CDR implementation.
Continue reading ‘Alkalinization scenarios in the Mediterranean Sea for efficient removal of atmospheric CO2 and the mitigation of ocean acidification’Transgenerational effects on the coral Pocillopora damicornis microbiome under ocean acidification
Published 16 February 2021 Science ClosedTags: abundance, biological response, BRcommunity, community composition, corals, North Pacific, otherprocess, physiology, prokaryotes, protists
Reef-building corals are inhabited by functionally diverse microorganisms which play important roles in coral health and persistence in the Anthropocene. However, our understanding of the complex associations within coral holobionts is largely limited, particularly transgenerational exposure to environmental stress, like ocean acidification. Here we investigated the microbiome development of an ecologically important coral Pocillopora damicornis following transgenerational exposure to moderate and high pCO2 (partial pressure of CO2) levels, using amplicon sequencing and analysis. Our results showed that the Symbiodiniaceae community structures in adult and juvenile had similar patterns, all of which were dominated by Durusdinium spp., previously known as clade D. Conversely, prokaryotic communities varied between adults and juveniles, possibly driven by the effect of host development. Surprisingly, there were no significant changes in both Symbiodiniaceae and prokaryotic communities with different pCO2 treatments, which was independent of the life history stage. This study shows that ocean acidification has no significant effect on P. damicornis microbiome, and warrants further research to test whether transgenerational acclimation exists in coral holobiont to projected future climate change.
Continue reading ‘Transgenerational effects on the coral Pocillopora damicornis microbiome under ocean acidification’Biogeochemical timescales of climate change onset and recovery in the North Atlantic interior under rapid atmospheric CO2 forcing
Published 15 February 2021 Science ClosedTags: chemistry, modeling, North Atlantic, regionalmodeling
Anthropogenic climate change footprints in the ocean go beyond the mixed layer depth, with considerable impacts throughout mesopelagic and deep-ocean ecosystems. Yet, little is known about the timing of these environmental changes, their spatial extent, and the associated timescales of recovery in the ocean interior when strong mitigation strategies are involved. Here, we simulate idealized rapid climate change and mitigation scenarios using the Norwegian Earth System Model (NorESM) to investigate timescales of climate change onset and recovery and the extent of change in the North Atlantic (NAtl) interior relative to Pre-industrial (PI) variability across a suite of environmental drivers (Temperature – T; pH; Dissolved Oxygen – DO; Apparent Oxygen Utilization – AOU; Export Production – EP; and Calcite saturation state – Ω<sub>c</sub>). We show that, below the subsurface domains, responses of these drivers are asymmetric and detached from the anthropogenic forcing with large spatial variations. Vast regions of the interior NAtl experience detectable anthropogenic signal significantly earlier and over a longer period than those projected for the subsurface. In contrast to surface domains, the NAtl interior remains largely warmer relative to PI (up to +50%) following the mitigation scenario, with anomalously lower EP, pH and Ω<sub>c</sub> (up to -20%) south of 30°N. Oxygenation in the upper mesopelagic of up to +20% is simulated, mainly driven by a decrease in consumption during remineralization. Our study highlights the need for long-term commitment focused on pelagic and deep-water ecosystem monitoring to fully understand the impact of anthropogenic climate change on the North Atlantic biogeochemistry.
Continue reading ‘Biogeochemical timescales of climate change onset and recovery in the North Atlantic interior under rapid atmospheric CO2 forcing’CO2 fluxes in the Northeast Atlantic Ocean based on measurements from a surface ocean observation platform
Published 15 February 2021 Science ClosedTags: chemistry, field, North Atlantic
Highlights
- The SST controls the seasonal and spatial variation of CO2 fugacity and fluxes.
- The pH and fCO2 shows spatial variability associated with upwelling influence.
- NCT variation was mainly governed by biological activity and slightly affected by air-sea fluxes.
- During 2019, the Northeast Atlantic region behaved as an annual CO2 sink of -2.65 ± 0.44 Tg CO2 yr-1
- VOS lines are a powerful tool to study de CO2 system and fluxes in the coastal surface area.
Abstract
The seasonal and spatial variability of the CO2 system parameters and CO2 air-sea exchange were studied in the Northeast Atlantic Ocean between the northwest African coastal upwelling and the oligotrophic open-ocean waters of the North Atlantic subtropical gyre. Data was collected aboard a volunteer observing ship from February 2019 to February 2020. The seasonal and spatial variability of CO2 fugacity in seawater (fCO2,sw) was strongly driven by the seasonal temperature variation, which increased with latitude and was lower throughout the year in coastal regions where the upwelling and offshore transport was more intense. The thermal to biological effect ratio (T/B) was approximately 2, with minimum values along the African coastline related to higher biological activity in the upwelled waters. The fCO2,sw increased from winter to summer by 11.84 ± 0.28 μatm°C-1 on the inter-island routes and by 11.71 ± 0.25 μatm°C-1 along the northwest African continental shelf. The seasonality of total inorganic carbon normalized to constant salinity of 36.7 (NCT) was studied throughout the region. The effect of biological processes and calcification/dissolution on NCT between February and October represented >90% of the reduction of inorganic carbon while air-sea exchange described <6%. The seasonality of air-sea CO2 exchange was controlled by temperature. The surface waters of the entire region acted as a CO2 sink during the cold months and as a CO2 source during the warm months. The Canary basin acted as a net sink of -0.26 ± 0.04 molC m-2 yr-1. The northwest African continental shelf behaved as a stronger sink at -0.48 ± 0.09 molC m-2 yr-1. The calculated average CO2 flux for the entire area was -2.65 ± 0.44 TgCO2 yr-1 (-0.72 ± 0.12 TgC yr-1).
Continue reading ‘CO2 fluxes in the Northeast Atlantic Ocean based on measurements from a surface ocean observation platform’Impaired antioxidant defenses and DNA damage in the European glass eel (Anguilla anguilla) exposed to ocean warming and acidification
Published 15 February 2021 Science ClosedTags: biological response, fish, laboratory, molecular biology, multiple factors, physiology, temperature
Highlights
- European glass eels were lab-exposed to future warming and acidification conditions
- Selected biomarkers were used to study physiological responses of glass eels
- The antioxidant enzymatic machinery was impaired in the muscle and viscera
- Heat shock response was different between tissues, increasing with temperature
- The results emphasize the higher vulnerability of eels under climate change
Abstract
The European eel (Anguilla anguilla) has attracted scientific inquiry for centuries due to its singular biological traits. Within the European Union, glass eel fisheries have declined sharply since 1980, from up to 2000 t (t) to 62.2 t in 2018, placing wild populations under higher risk of extinction. Among the major causes of glass eels collapse, climate change has become a growing worldwide issue, specifically ocean warming and acidification, but, to our knowledge, data on physiological and biochemical responses of glass eels to these stressors is limited. Within this context, we selected some representative biomarkers [e.g. glutathione peroxidase (GPx), catalase (CAT), total antioxidant capacity (TAC), heat shock proteins (HSP70), ubiquitin (Ub) and DNA damage] to study physiological responses of the European glass eel under distinct laboratory-climate change scenarios, such as increased water temperature (+ 4 °C) and pH reduction (− 0.4 units), for 12 weeks. Overall, the antioxidant enzymatic machinery was impaired, both in the muscle and viscera, manifested by significant changes in CAT, GPx and TAC. Heat shock response varied differently between tissues, increasing with temperature in the muscle, but not in the viscera, and decreasing in both tissues under acidification. The inability of HSP to maintain functional protein conformation was responsible for boosting the production of Ub, particularly under warming and acidification, as sole stressors. The overproduction of reactive oxygen species (ROS), either elicited by warming – due to increased metabolic demand – or acidification – through H+ interaction with O2−, generating H2O2 – overwhelmed defense mechanisms, causing oxidative stress and consequently leading to protein and DNA damage. Our results emphasize the vulnerability of eels’ early life stages to climate change, with potential cascading consequences to adult stocks.
Continue reading ‘Impaired antioxidant defenses and DNA damage in the European glass eel (Anguilla anguilla) exposed to ocean warming and acidification’Gene expression responses of larval gopher (Sebastes carnatus) and blue (S. mystinus) rockfish to ocean acidification and hypoxia
Published 15 February 2021 Science ClosedTags: biological response, fish, laboratory, molecular biology, multiple factors, North Pacific, oxygen, physiology, reproduction
Global climate change is driving shifts in ocean chemistry, which combined with intensification of coastal upwelling, reduces ocean pH and dissolved oxygen (DO) content in the nearshore habitats of the California Current System. Physiological plasticity, within and across generations, might be especially important for long-lived, late-to-mature species, like rockfishes (genus Sebastes), that may be unable to keep pace with climate change via genetic adaptation. Rockfishes exhibit matrotrophic viviparity and may be able to buffer their offspring from environmental stress through early developmental exposure or transgenerational plasticity (non-genetic inheritance of phenotypes). In this study, mature female gopher (S. carnatus) and blue (S. mystinus) rockfish were pre-exposed to one of four treatments; 1) control conditions, 2) low pH, 3) low DO, or 4) combined low pH/DO stressors during embryonic growth (i.e. fertilization and gestation), followed by a 5-day larval exposure after birth in either the same or a different treatment received by mothers. I used RNA sequencing to determine how the maternal environment affected larval rockfish gene expression (GE) at birth, after the 5-day larval exposure in either the same maternal treatment or a novel pH/DO environment, and between larvae sampled at birth and after the 5-day larval exposure within each treatment. For both species, I found that the maternal exposure drove larval GE patterns regardless of sampling time point or treatment. Furthermore, the maternal environment continued to strongly influence larval GE for at least the first five days after birth. In gopher rockfish, larvae differentially expressed fewer genes at birth between the control and hypoxic groups than larvae that gestated in and remained in the same treatment and were sampled after the 5-day larval exposure. Gene functions also shifted; at day 5, there was an increase in differentially expressed genes that were related to metabolic pathways, implying that the larvae in the hypoxic treatment are responding to the stressor. In both species, I found that larvae which experienced a pH and/or hypoxic stressor during the maternal exposure had fewer differentially expressed genes across time compared to larvae that experienced control conditions. This pattern remained consistent, even if the larvae were placed into control conditions for the 5-day larval exposure, indicating that exposure to low pH/DO stressors might cause a delay in development. These data suggest that rockfish may not be able to buffer their offspring from environmental stressors, highlighting the important role of the maternal environment during gestation. Between the two species, however, blue rockfish may in fact fare better in future conditions as their reproductive season occurs before the onset of strong spring upwelling, when more hypoxic and low pH water intrudes the nearshore. However, if future climate models are correct, shifts in the timing and intensity of upwelling season may overlap with the reproductive season in blue rockfish. Elucidating the critical role of the maternal environment on offspring physiology can help us better understand how economically and ecologically important species will fare in the face of climate change.
Continue reading ‘Gene expression responses of larval gopher (Sebastes carnatus) and blue (S. mystinus) rockfish to ocean acidification and hypoxia’Ocean acidification reduces skeletal density of hardground‐forming high‐latitude crustose coralline algae
Published 15 February 2021 Science ClosedTags: algae, biological response, dissolution, laboratory, morphology, multiple factors, temperature
Crustose coralline algae (CCA) function as foundation species by creating marine carbonate hardground habitats. High‐latitude species may be vulnerable to regional warming and acidification. Here, we report the results of an experiment investigating the impacts of CO2‐induced acidification (pCO2 ∼350, 490, 890, 3200 µatm) and temperature (∼6.5, 8.5, 12.5°C) on the skeletal density of two species of high‐latitude CCA: Clathromorphum compactum (CC) and C. nereostratum (CN). Skeletal density of both species significantly declined with pCO2. In CN, the density of previously deposited skeleton declined in the highest pCO2 treatment. This species was also unable to precipitate new skeleton at 12.5°C, suggesting that CN will be particularly sensitive to future warming and acidification. The decline in skeletal density exhibited by both species under future pCO2 conditions could reduce their skeletal strength, potentially rendering them more vulnerable to disturbance, and impairing their production of critical habitat in high‐latitude systems.
Continue reading ‘Ocean acidification reduces skeletal density of hardground‐forming high‐latitude crustose coralline algae’Spectrophotometric determination of the bicarbonate dissociation constant in seawater
Published 15 February 2021 Science ClosedTags: chemistry, methods
Highlights
- K1K2 values were obtained via spectrophotometric pH measurements.
- New method improved precision in CO2 system dissociation constants.
- New K2 parameterization improves internal consistency of CO2 system calculations.
Abstract
The aqueous carbon dioxide (CO2) system stoichiometric dissociation constants K1 and K2 express the relative concentrations of CO2, HCO3− (bicarbonate), and CO32− (carbonate) in terms of pH. These constants are critical in the study of seawater and the oceans because any mathematical expression that relates the four major CO2 system parameters (pH, here expressed on the total hydrogen ion concentration scale, pHT; total dissolved inorganic carbon, CT; total alkalinity, AT; and CO2 fugacity, fCO2) requires the use of K1 and K2. Uncertainties associated with current characterizations of pK1 and pK2 (where pK = −log K), on the order of 0.01 and 0.02, limit the accuracy of marine CO2 system calculations. This work reports the results of a spectrophotometric method to experimentally determine the product K1K2 over environmentally relevant ranges of temperature (288.15 ≤ T ≤ 308.15 K) and salinity (19.6 ≤ Sp ≤ 41) where Sp denotes the practical salinity scale. Using previously published parameterizations of K1, values of pK2 could then be calculated from the new K1K2 values. The resulting set of pK2 values was fitted as a function of Sp and T to obtain a new pK2 parameterization (denoted as SWpK2) calculated with the K1 of Waters and Millero (2013) as revised by Waters et al. (2014): SWpK2 = 116.8067 – 3655.02 T−1 – 16.45817 ln T + 0.04523 Sp – 0.615 Sp0.5 – 0.0002799 Sp2 + 4.969 (Sp/T)
The average root mean square deviation between the equation and the observed data is 0.003. Residuals of this pK2 fitting function (i.e., measured pK2 minus parameterized pK2) are substantially smaller than the residuals obtained in previous works. Similarly, the total standard uncertainty in pK2 is reduced from 0.015 (previous characterizations) to 0.010 (this work). Internal consistency assessments (comparisons of measured versus calculated values of AT, CT, pHT, and fCO2) were used to evaluate the computational utility of the new K2 parameterization. Assessments from both laboratory and shipboard data indicate that the internal consistency of CO2 system calculations is improved using the K2 parameterization of this work. This new K2 parameterization provides the most precise, and potentially the most accurate, bicarbonate dissociation constant characterization presently available for open ocean conditions.
Continue reading ‘Spectrophotometric determination of the bicarbonate dissociation constant in seawater’
