With a biomass of ∼4 million tonnes, and annual catches of 900 000 tonnes, the northeast Atlantic (NEA) cod stock in the Barents Sea is the world’s largest. Scientists have been trying to explain the variability in recruitment of this stock for over 100 years, in particular connecting it to spawning stock biomass and environmental factors such as temperature. It has been suggested that the combination of ocean acidification and global warming will lead to a significant decrease in the spawning stock biomass and an eventual (end of this century) collapse of the NEA cod stock in the Barents Sea. We show that a temperature- and OA-driven decline in recruits will likely lead to a smaller cod stock, but not to a collapse. Instead, the level of fishing pressure and, not least, the choice of the recruitment function applied in simulations and how it relates to temperature, is extremely important when making such forecasts. Applying a non-linear relationship between temperature and spawning stock biomass—as has been done in studies that predict a collapse of the NEA cod stock—does not improve accuracy and, in addition, adds a large decrease in number of recruits that is not biologically supported.
Continue reading ‘The combined effects of warming, ocean acidification, and fishing on the northeast Atlantic cod (Gadus morhua) in the Barents Sea’Posts Tagged 'Arctic'
The combined effects of warming, ocean acidification, and fishing on the northeast Atlantic cod (Gadus morhua) in the Barents Sea
Published 19 April 2024 Science Leave a CommentTags: Arctic, fisheries, methods, modeling, regionalmodeling
Anthropogenic climate change drives non-stationary phytoplankton internal variability
Published 19 March 2024 Science ClosedTags: Arctic, biological response, globalmodeling, modeling, North Atlantic, North Pacific, phytoplankton, regionalmodeling
Earth system models suggest that anthropogenic climate change will influence marine phytoplankton over the coming century with light-limited regions becoming more productive and nutrient-limited regions less productive. Anthropogenic climate change can influence not only the mean state but also the internal variability around the mean state, yet little is known about how internal variability in marine phytoplankton will change with time. Here, we quantify the influence of anthropogenic climate change on internal variability in marine phytoplankton biomass from 1920 to 2100 using the Community Earth System Model 1 Large Ensemble (CESM1-LE). We find a significant decrease in the internal variability of global phytoplankton carbon biomass under a high emission (RCP8.5) scenario and heterogeneous regional trends. Decreasing internal variability in biomass is most apparent in the subpolar North Atlantic and North Pacific. In these high-latitude regions, bottom-up controls (e.g., nutrient supply, temperature) influence changes in biomass internal variability. In the biogeochemically critical regions of the Southern Ocean and the equatorial Pacific, bottom-up controls (e.g., light, nutrients) and top-down controls (e.g., grazer biomass) affect changes in phytoplankton carbon internal variability, respectively. Our results suggest that climate mitigation and adaptation efforts that account for marine phytoplankton changes (e.g., fisheries, marine carbon cycling) should also consider changes in phytoplankton internal variability driven by anthropogenic warming, particularly on regional scales.
Continue reading ‘Anthropogenic climate change drives non-stationary phytoplankton internal variability’Sea-ice loss accelerates carbon cycling and enhances seasonal extremes of acidification in the Arctic Chukchi Sea
Published 4 March 2024 Science ClosedTags: Arctic, chemistry, field
The Chukchi Sea shelf (CSS) is a highly productive region in the Arctic Ocean and it is highly efficient for absorbing atmospheric carbon dioxide and exporting and retaining carbon in the deep sea. However, with global warming, the carbon retention time in CSS may decrease, leading to less efficient carbon export. Here, we investigate the seasonal variability of carbonate chemistry in CSS using three sets of late- vs. early-summer reoccupations of the same transect. Our findings demonstrate substantially increased and rapid degradation of biologically produced organic matter and therefore acidification over time in the southern CSS due to earlier sea-ice retreat, resulting in significantly shorter carbon retention time. In sharp contrast, no increased degradation has been observed in the northern CSS where photosynthesis has just commenced. In the future, climate change would further diminish the carbon export capacity and exacerbate seasonal acidification not only within CSS but also across other polar coastal oceans.
Continue reading ‘Sea-ice loss accelerates carbon cycling and enhances seasonal extremes of acidification in the Arctic Chukchi Sea’Trends and projections in climate-related stressors impacting Arctic marine ecosystems – a CMIP6 model analysis
Published 4 March 2024 Science ClosedTags: Arctic, chemistry, modeling, regionalmodeling
Eleven Earth System Models (ESMs) contributing to the Coupled Model Intercomparison Project (CMIP6) were evaluated with respect to climate-related stressors impacting Arctic marine ecosystems (temperature, sea ice, oxygen, ocean acidification). Stressors show regional differences and varying differences over time and space among models. Trend magnitudes increase over time and are highest by end-of-century for temperature and O2. Differences between scenarios SSP2-4.5 and SSP5-8.5 for these variables vary among models and regions, mainly driven by sea-ice retreat. Differences in biogeochemical parameterizations contribute to acidification differences. Projections indicate consistent ocean acidification until 2040 and faster progression for the higher emission scenario thereafter. For SSP5-8.5 all Arctic regions show aragonite undersaturation by 2080, and calcite undersaturation for all but two regions by 2100 for all models. Most regions can avoid calcite undersaturation with lower emissions (SSP2-4.5). All variables show increases in seasonal amplitude, most prominently for temperature and oxygen. Calcium carbonate saturation state (Ω) shows little change to the seasonal range and a suggestion of temporal shifts in extrema. Seasonal changes in Ω may be underestimated due to lacking carbon cycle processes within sea ice in CMIP6 models. The analysis emphasizes regionally varying threats from multiple stressors on Arctic marine ecosystems and highlights the propagation of uncertainties from sea ice to temperature and biogeochemical variables. Large model differences in seasonal cycles emphasize the need for improved model constraints, predominantly the representation of sea-ice decline, to enhance the applicability of CMIP models in multi-stressor impacts assessments.
Continue reading ‘Trends and projections in climate-related stressors impacting Arctic marine ecosystems – a CMIP6 model analysis’Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes
Published 2 January 2024 Science ClosedTags: Arctic, chemistry, field, Indian, North Atlantic, North Pacific, South Atlantic, South Pacific
Mangroves and saltmarshes are biogeochemical hotspots storing carbon in sediments and in the ocean following lateral carbon export (outwelling). Coastal seawater pH is modified by both uptake of anthropogenic carbon dioxide and natural biogeochemical processes, e.g., wetland inputs. Here, we investigate how mangroves and saltmarshes influence coastal carbonate chemistry and quantify the contribution of alkalinity and dissolved inorganic carbon (DIC) outwelling to blue carbon budgets. Observations from 45 mangroves and 16 saltmarshes worldwide revealed that >70% of intertidal wetlands export more DIC than alkalinity, potentially decreasing the pH of coastal waters. Porewater-derived DIC outwelling (81 ± 47 mmol m−2 d−1 in mangroves and 57 ± 104 mmol m−2 d−1 in saltmarshes) was the major term in blue carbon budgets. However, substantial amounts of fixed carbon remain unaccounted for. Concurrently, alkalinity outwelling was similar or higher than sediment carbon burial and is therefore a significant but often overlooked carbon sequestration mechanism.
Continue reading ‘Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes’Future warming stimulates growth and photosynthesis in an Arctic microalga more strongly than changes in light intensity or pCO2
Published 20 December 2023 Science ClosedTags: Arctic, biological response, growth, laboratory, light, multiple factors, photosynthesis, physiology, phytoplankton, primary production, temperature
We assessed the responses of solitary cells of Arctic Phaeocystis pouchetii grown under a matrix of temperature (2°C vs. 6°C), light intensity (55 vs. 160 μmol photons m−2 s−1) and pCO2 (400 vs. 1000 μatm CO2, i.e., 40.5 vs. 101.3 Pa). Next to acclimation parameters (growth rates, particulate and dissolved organic C and N, Chlorophyll a content), we measured physiological processes in vivo (electron transport rates and net photosynthesis) using fast-repetition rate fluorometry and membrane-inlet mass spectrometry. Within the applied driver ranges, elevated temperature had the most pronounced impacts, significantly increasing growth, elemental quotas and photosynthetic performance. Light stimulations manifested more prominently under 6°C, underlining temperature’s role as a “master-variable”. pCO2 was the least effective driver, exerting mostly insignificant effects. The obtained data were used for a simplistic upscaling simulation to investigate potential changes in P. pouchetii‘s bloom dynamics in the Fram Strait with increasing temperatures over the 21st century. Although solitary cells might not be fully representative of colonial cells commonly observed in the field, our results suggest that global warming accelerates bloom dynamics, with earlier onsets of blooms and higher peak biomasses. Such a temperature-induced acceleration in the phenology of Phaeocystis and likely other Arctic phytoplankton might cause temporal mismatches, e.g., with the development of grazers, and therefore substantially affect the biogeochemistry and ecology of the Arctic.
Continue reading ‘Future warming stimulates growth and photosynthesis in an Arctic microalga more strongly than changes in light intensity or pCO2’Planktonic foraminifers and shelled pteropods in the Barents Sea: seasonal distribution and contribution to the carbon pump of the living fauna, and foraminiferal development during the last three millennia
Published 30 November 2023 Science ClosedTags: abundance, Arctic, biological response, BRcommunity, community composition, field, morphology, otherprocess, paleo, protists, sediment
The Arctic Ocean in general and the Barents Sea specifically, are highly affected by the human induced carbon dioxide (CO2) emissions and increasing temperatures. Atlantification, caused by an increase in warm Atlantic Water inflow, and polar amplification, caused by a higher impact of the increasing temperatures at high latitudes, have already been observed. Moreover, the Barents Sea has been described as a hotspot for ocean acidification. Ocean acidification is the decrease of pH, calcium carbonate saturation state, and carbonate ion concentration due to an increase in CO2 uptake from the atmosphere by the ocean. This alteration of the carbonate chemistry of the water affects the marine biota, especially planktonic marine calcifiers. They are organisms living in the water column with a shell made of calcium carbonate (CaCO3). They contribute significantly to the carbon cycle by exporting mainly CaCO3 from the surface water to the seabed when they die. The main goal of this thesis is to study the distribution of marine calcifiers (planktonic foraminifers and shelled pteropods) in the Barents Sea and the adjacent Arctic Basin. We have (1) investigated their distribution patterns and contribution to carbon dynamics in the north Svalbard margin and in a seasonal basin in the northern Barents Sea; and (2) reconstructed the foraminiferal production and preservation patterns from the late Holocene in sediment cores from the northern and southern Barents Sea. The results from this thesis show that pteropods are important contributors to the carbon dynamics in all seasons in the northern Barents Sea and northern Svalbard margin. Due to the higher sensitivity of their shells compared to foraminifers, they are more likely to be affected by ocean acidification. Moreover, the abundance of foraminifers in the sediment suggests higher productivity in the southern than in the northern Barents Sea. The almost zero abundances observed in the northern Barents Sea core, combined with the seasonality of marine calcifiers, the water carbonate chemistry, and the presence of agglutinated foraminifers suggest dissolution of CaCO3 in the sediment. Due to the use of their shells in paleoceanography, further investigations of CaCO3 dissolution are needed to use them as proxies for the reconstruction of the paleoenvironmental and paleoclimatic conditions in the Barents Sea.
Continue reading ‘Planktonic foraminifers and shelled pteropods in the Barents Sea: seasonal distribution and contribution to the carbon pump of the living fauna, and foraminiferal development during the last three millennia’Editorial: the changing carbonate systems in coastal, estuarine, shelf areas and marginal seas
Published 23 November 2023 Science ClosedTags: Antarctic, Arctic, biogeochemistry, biological response, chemistry, corals, North Pacific, review
Editorial on the Research Topic
The changing carbonate systems in coastal, estuarine, shelf areas and marginal seas
Global atmospheric CO2 concentrations have increased from 320 ppm in the 1960s to the present-day value of 420 ppm, primarily due to anthropogenic activities. This increase influences the seawater carbonate system, impacting the marine ecosystem. There are still gaps that need to be resolved for predicting how these marine systems respond to current and future CO2 levels. Any actions to mitigate the change in pH will require adaptive management of multiple stressors across several spatial scales. Combined, these perspectives yield a more comprehensive picture of events during ocean acidification (OA).
This Research Topic brings together articles from different regions, including coastal, estuarine, and shelf areas and marginal seas, all susceptible to changing atmospheric conditions, riverine inputs, air-sea CO2 exchanges, and multiple acid-base reactions that can alter carbonate chemistry. Articles on the long-term trends of CO2 system descriptors and the interactions with calcifying organisms were also sought. The present Research Topic is primarily based on original articles devoted to carbonate systems in the marginal seas, but it is a pity that some interesting papers dealing with freshwater inflows, estuaries, and related coastal areas were not accepted.
Fransson et al. examined the effects of glacial and sea-ice meltwater on ocean acidification in the waters near the 79 North Glacier (79 NG) and the northeast Greenland shelf. The researchers investigated various ocean acidification factors and the influence of freshening, primary production, and air-sea CO2 exchange. One of the key findings was that the biological removal of CO2 through primary production played a crucial role in offsetting the negative impact of freshwater dilution on the aragonite saturation state (ΩAr), which is a measure of ocean acidification. This compensation effect was most pronounced in 2012, especially in the vicinity of the 79 NG front, where there was a significant presence of glacial meltwater and surface stratification. In 2016, a different scenario was observed, with a more homogenized water column due to sea-ice meltwater. In this case, the compensation effect of biological CO2 removal on ΩAr was weaker compared to 2012. The study also suggests that in the future, with ongoing climate and ocean chemistry changes, the increasing influence of meltwater may surpass the mitigating effects of biological CO2 removal. This could lead to unfavorable conditions for organisms that rely on calcium carbonate for their shells and skeletons. Thus, all the proposed factors need to be closely monitored as they could have significant implications for marine ecosystems and calcifying organisms in the face of ongoing environmental changes.
Continue reading ‘Editorial: the changing carbonate systems in coastal, estuarine, shelf areas and marginal seas’Water structure and carbon dioxide flux over the Laptev Sea continental slope and in the Vilkitsky Strait in the autumn season
Published 17 November 2023 Science ClosedTags: Arctic, chemistry, field
Within the program “Ecosystems of the Siberian Arctic Seas,” carried out by Shirshov Institute of Oceanology, Russian Academy of Sciences since 2007, studies of the water structure and spatial variability of the parameters of the carbonate system have been performed, and the intensity and direction of the carbon dioxide flux over the continental slope of the Laptev Sea and in the Vilkitsky Strait in September 2018 have been calculated. The presence of several main water masses that govern the water structure in the study area is shown. A strong spatial variability of the parameters of the carbonate system of seawater, determined by complexes of physical and chemical–biological processes, has been revealed. The intensity and direction of the carbon dioxide flux at the water–atmosphere boundary were calculated, which range from –12 to 4 mmol m–2 day–1. It was revealed that the investigated area of the outer shelf and continental slope of the Laptev Sea is an emitter of carbon dioxide into the atmosphere as of September 2018. Conversely, the area of the Vilkitsky Strait, is a CO2 sink zone.
Continue reading ‘Water structure and carbon dioxide flux over the Laptev Sea continental slope and in the Vilkitsky Strait in the autumn season’Atlantic-origin water extension into the Pacific Arctic induced an anomalous biogeochemical event
Published 15 November 2023 Science ClosedTags: Arctic, biogeochemistry, chemistry, field, fisheries, modeling, multiple factors, nutrients, oxygen, policy, regionalmodeling, salinity
The Arctic Ocean is facing dramatic environmental and ecosystem changes. In this context, an international multiship survey project was undertaken in 2020 to obtain current baseline data. During the survey, unusually low dissolved oxygen and acidified water were found in a high-seas fishable area of the western (Pacific-side) Arctic Ocean. Herein, we show that the Beaufort Gyre shrinks to the east of an ocean ridge and forms a front between the water within the gyre and the water from the eastern (Atlantic-side) Arctic. That phenomenon triggers a frontal northward flow along the ocean ridge. This flow likely transports the low oxygen and acidified water toward the high-seas fishable area; similar biogeochemical properties had previously been observed only on the shelf-slope north of the East Siberian Sea.
…
Fig. 1: Schematic of the Arctic Ocean circulation and the study area with hydrographic stations.
a, b Maps of the Arctic Ocean and the study area. In a, yellow, blue, and red arrows represent flows from the shelf-slope at the north of the East Siberian Sea (ESS), and from the Pacific and Atlantic oceans in 2017–2020. Ocean circulation and water masses are abbreviated as follows: Beaufort Gyre (BG), Transpolar Drift (TPD), Pacific Water (PW), Lower Halocline Water (LHW), and Atlantic Water (AW). Geographical locations are abbreviated as follows: Canada Basin (CB), Chukchi Plateau (CP), Mendeleyev Ridge (MR), Makarov Basin (MB), and Lomonosov Ridge (LR). In b red, green, and blue dots denote the hydrographic stations conducted by the Research Vessel (R/V) Araon (Korea), R/V Mirai (Japan), and Canadian Coast Guard Ship Louis S. St-Laurent (Canada), under the 2020 Synoptic Arctic Survey project. Black dots indicate other hydrographic stations between 2002 and 2019 listed in Supplementary Table 1.
Continue reading ‘Atlantic-origin water extension into the Pacific Arctic induced an anomalous biogeochemical event’Global synthesis of the status and trends of ocean acidification impacts on shelled pteropods
Published 13 November 2023 Science ClosedTags: Antarctic, Arctic, biological response, chemistry, mollusks, morphology, North Pacific, physiology, zooplankton
The accumulation of anthropogenic CO₂ in the ocean has major ecological, socioeconomic, and biogeochemical impacts, with repercussions for the ocean as a critical carbon sink. Ocean acidification (OA) disproportionately affects marine calcifiers, among which pelagic zooplanktonic pteropods play a significant role in carbonate export. The pteropod, due to the susceptibility of its aragonite shell to rapid dissolution, is one of most vulnerable groups and a key indicator for OA regional monitoring, but its regional sensitivities have not yet been extrapolated over global scales. To delineate spatial and temporal changes in pteropod shell dissolution, global OA status and the OA rate of change were evaluated, based on gridded climatologies of observations and using a Regional Ocean Modeling System (ROMS) biogeochemical/ecosystem model. Pteropods, which dominate in the polar and subpolar regions, are characterized by low aragonite saturation state and low buffering capacity, where extended pteropod subsurface dissolution is projected. We show that pteropods are most susceptible to OA in the polar regions, subpolar North Pacific, and eastern boundary upwelling system regions, particularly the California and Humboldt Current Systems. Rates of acidification and corresponding increases in pteropod shell dissolution are projected to be the fastest in the North and South Equatorial Currents. These are the regions with the greatest impacts on pteropods and biogeochemical implications.
Continue reading ‘Global synthesis of the status and trends of ocean acidification impacts on shelled pteropods’Impacts of glacial and sea-ice meltwater, primary production, and ocean CO2 uptake on ocean acidification state of waters by the 79 North Glacier and northeast Greenland shelf
Published 20 October 2023 Science ClosedTags: Arctic, chemistry, field, North Atlantic
The waters adjacent to the Nioghalvfjerdsbræ (79 North Glacier, 79NG) are influenced by Greenland Ice Sheet (GrIS) melt, sea-ice meltwater, and waters on the adjacent northeast Greenland shelf (NEGS). We investigated ocean acidification (OA) variables and the role of freshening, primary production, and air-sea CO2 exchange in Dijmphna Sound (DS) and on the NEGS in the summers of 2012 and 2016. The upper 150 m consisted of Polar Water with Arctic origin that was divided into a fresh surface layer (SL<50 m) and a cold halocline layer (CHL, 50 to 150 m). The layer below 150 m was of Atlantic origin. The SL freshwater was larger in 2012 than in 2016, mainly originated from local 79NG (and GrIS) runoff in DS, whereas on the NEGS in both years, it was mainly from sea-ice melt. The lowest aragonite saturation state (ΩAr) of 1.13 was found in the SL in 2012. Biological CO2 drawdown at primary production caused increased ΩAr in SL, which compensated for most of the ΩAr decrease due to the freshwater dilution of carbonate ions reducing total alkalinity, hence preventing corrosive conditions. This was most pronounced near the 79NG front in 2012, where surface stratification was most pronounced coinciding with large glacial meltwater fractions. Freshening decreased ΩAr by 0.4 at the 79NG front was compensated by biological CO2 drawdown by ~0.5. In 2016, a well-mixed water column in DS and NEGS, with dilution by sea-ice meltwater, caused less compensation on ΩAr by biological CO2 drawdown than in 2012. In future with changing climate and changing ocean chemistry, the increased meltwater effects may overcome the alleviating effects of biological CO2 drawdown on OA with unfavorable conditions for calcifying organisms. However, our study also suggests that primary production may be stimulated by stratification from surface meltwater. In addition, Atlantification and subglacial discharge may result in upwelling of inorganic nutrients that could promote primary production.
Continue reading ‘Impacts of glacial and sea-ice meltwater, primary production, and ocean CO2 uptake on ocean acidification state of waters by the 79 North Glacier and northeast Greenland shelf’Seasonality of marine calcifiers in the northern Barents Sea: spatiotemporal distribution of planktonic foraminifers and shelled pteropods and their contribution to carbon dynamics
Published 22 September 2023 Science ClosedTags: abundance, Arctic, biological response, chemistry, field, mollusks, morphology, otherprocess, physiology, primary production, protists
Highlights
- In the northern Barents Sea there is a seasonal pattern of production and size distribution of planktonic foraminifers and pteropods, increasing from winter (March) to summer (July–August) and late autumn (December).
- In general, pteropods dominate over planktonic foraminifera in the Arctic influenced stations.
- In the study area, pteropods contribute the most (>80%) to carbon standing stocks and export production.
- The highest values of carbon standing stocks and export production were found in the seasonal ice zone during all seasons.
Abstract
The Barents Sea is presently undergoing rapid warming and the sea-ice edge and the productive zones are retreating northward at accelerating rates. Planktonic foraminifers and shelled pteropods are ubiquitous marine calcifiers that play an important role in the carbon budget and being particularly sensitive to ocean biogeochemical changes and ocean acidification. Their distribution at high latitudes have rarely been studied, and usually only for the summer season. Here we present results of their distribution patterns in the upper 300 m in the water column (individuals m−3), protein content and size distribution on a seasonal basis to estimate their inorganic and organic carbon standing stocks (µg m−3) and export production (mg m−2 d−1). The study area constitutes a latitudinal transect in the northern Barents Sea from 76˚ N to 82˚ N including seven stations through both Atlantic, Arctic, and Polar surface water regimes and the marginal and seasonal sea-ice zones. The transect was sampled in 2019 (August and December) and 2021 (March, May, and July). The highest carbon standing stocks and export production were found at the Polar seasonally sea-ice covered shelf stations with the contribution from shelled pteropods being significantly higher than planktonic foraminifers during all seasons. We recorded the highest production of foraminifers and pteropods in summer (August 2019 and July 2021) and autumn (December 2019) followed by spring (May 2021), and the lowest in winter (March 2021).
Continue reading ‘Seasonality of marine calcifiers in the northern Barents Sea: spatiotemporal distribution of planktonic foraminifers and shelled pteropods and their contribution to carbon dynamics’Rising snow line: Ocean acidification and the submergence of seafloor geomorphic features beneath a rising carbonate compensation depth
Published 22 August 2023 Science ClosedTags: Antarctic, Arctic, chemistry, Indian, modeling, North Atlantic, North Pacific, regionalmodeling, review, South Atlantic, South Pacific
Highlights
- Ocean acidification has caused the carbonate compensation depth (CCD) to rise by ~98 m.
- Seafloor area below the CCD has increased by 3.6% in the last 200 years.
- Risk of impact of rising CCD is greatest in the western equatorial Atlantic Ocean.
- Different geomorphic features impacted by rising CCD in different ocean areas.
Abstract
Due to burning of fossil fuels, carbon dioxide is being absorbed by the ocean where its chemical conversion to carbonic acid has already caused the surface ocean to become more acidic than it has been for at least the last 2 million years. Global ocean modeling suggests that the carbonate compensation depth (CCD) has already risen by nearly 100 m on average since pre-industrial times and will likely rise further by several hundred meters more this century. Potentially millions of square kilometres of ocean floor will undergo a rapid transition in terms of the overlying water chemistry whereby calcareous sediment will become unstable causing the carbonate “snow line” to rise.We carried out a spatial analysis of seafloor geomorphology to assess the area newly submerged below the rising CCD. We found that shoaling of the CCD since the industrial revolution has submerged 12,432,096 km2 of ocean floor (3.60% of total ocean area) below the CCD. Further hypothetical shoaling of the CCD by 100 m increments illustrated that the surface area of seafloor submerged below the CCD has risen by 14% with 300 m of shoaling, such that 51% of the ocean area will be below the CCD. All categories of geomorphic feature mapped in one global database intersect the lysocline and will be (or already are) submerged below the CCD with much regional variation since the rise in CCD depth during the last 150 years varies significantly between different ocean regions. For seamounts, the highest percentages of increase in area submerged below the CCD occurred in the Southern Indian Ocean and the South West Atlantic regions (6.3% and 5.9%, respectively). For submarine canyons we found the South West Atlantic increased from 3.9% in pre-industrial times to 8.0% at the present time, the highest percentage of canyons found below the CCD in any ocean region.We also carried out a relative risk assessment for future submergence of ocean floor below the CCD in 17 ocean regions. In our assessment we assumed that the change in CCD from pre-industrial times to the present is an indicator of the likelihood and the change in percentage of seafloor submerged below the CCD due to a hypothetical 300 m rise in the CCD is an indicator of the consequences. We found that the western equatorial Atlantic is at high risk and 9 other Ocean Regions are at moderate risk. Overall, geomorphic features in the Atlantic Ocean and southern Indian Ocean are at greater risk of impact from a rising CCD than Pacific and other Indian Ocean regions.A separate analysis of the Arctic Ocean points to the possible submergence of glacial troughs incised on the continental shelf within a mid-depth (400–800 m) acidified water mass. We also found that the area of national Exclusive Economic Zones submerged below the rising CCD exhibits extreme variability; with 300 m of CCD shoaling we found a > 12% increase in area submerged below the CCD for 23 national EEZs, whereas there was virtually no change for other countries.
Continue reading ‘Rising snow line: Ocean acidification and the submergence of seafloor geomorphic features beneath a rising carbonate compensation depth’Large-scale culturing of Neogloboquadrina pachyderma, its growth in, and tolerance of, variable environmental conditions
Published 18 August 2023 Science ClosedTags: Arctic, biological response, laboratory, morphology, mortality, performance, phytoplankton, protists
The planktic foraminifera Neogloboquadrina pachyderma is a calcifying marine protist and the dominant planktic foraminifera species in the polar oceans, making it a key species in marine polar ecosystems. The calcium carbonate shells of foraminifera are widely used in palaeoclimate studies because their chemical composition reflects the seawater conditions in which they grow. This species provides unique proxy data for past surface ocean hydrography, which can provide valuable insight to future climate scenarios. However, little is known about the response of N. pachyderma to variable and changing environmental conditions.Here, we present observations from large-scale culturing experiments where temperature, salinity and carbonate chemistry were altered independently. We observed overall low mortality, calcification of new chambers and addition of secondary calcite crust in all our treatments. In-culture asexual reproduction events also allowed us to monitor the variable growth of N. pachyderma’s offspring. Several specimens had extended periods of dormancy or inactivity after which they recovered. These observations suggest that N. pachyderma can tolerate, adapt to and calcify within a wide range of environmental conditions. This has implications for the species-level response to ocean warming and acidification, for future studies aiming to culture N. pachyderma and use in palaeoenvironmental reconstruction.
Continue reading ‘Large-scale culturing of Neogloboquadrina pachyderma, its growth in, and tolerance of, variable environmental conditions’Dynamics of the seawater carbonate system in the East Siberian Sea: the diversity of driving forces
Published 15 August 2023 Science ClosedTags: Arctic, chemistry, field
The East Siberian Sea (ESS) is a large and the shallowest part of the Arctic Ocean. It is characterized by high biogeochemical activity, but the seawater carbonate system remains understudied, especially during the late autumn season. Data from the research vessel (RV) “Professor Multanovsky” cruise were used to assess the dynamics of the seawater carbonate system, air–sea CO2 fluxes, and the calcium carbonate corrosive waters in the two biogeochemical provinces of the ESS shortly before freeze-up. The ESS waters were mainly a sink for atmospheric CO2 due to the limited dispersion of river waters, autumn water cooling, and phytoplankton blooms in its eastern autotrophic province. The mean value of the CO2 air–sea flux was 11.2 mmol m−2 day−1. The rate of CO2 uptake in the eastern ESS was an order of magnitude larger than that in the western ESS. The specific waters and ice cover dynamics determined intensive photosynthesis processes identified on the eastern shelf and in the northern deep oligotrophic waters. A part of the surface and most of the bottom ESS waters were corrosive with respect to calcium carbonate, with the lowest saturation state of aragonite (0.22) in the bottom layer of the eastern ESS. The eastern ESS was the main source of these waters into the deep basin. The observed export of corrosive shelf waters to the deep sea can have a potential impact on the ocean water ecosystem in the case of mixing with layers inhabited by calcifying organisms.
Continue reading ‘Dynamics of the seawater carbonate system in the East Siberian Sea: the diversity of driving forces’Canada’s marine carbon sink: an early career perspective on the state of research and existing knowledge gaps
Published 26 July 2023 Science ClosedTags: Arctic, biogeochemistry, North Atlantic, North Pacific, review
Improving our understanding of how the ocean absorbs carbon dioxide is critical to climate change mitigation efforts. We, a group of early career ocean professionals working in Canada, summarize current research and identify steps forward to improve our understanding of the marine carbon sink in Canadian national and offshore waters. We have compiled an extensive collection of reported surface ocean air–sea carbon dioxide exchange values within each of Canada’s three adjacent ocean basins. We review the current understanding of air–sea carbon fluxes and identify major challenges limiting our understanding in the Pacific, the Arctic, and the Atlantic Ocean. We focus on ways of reducing uncertainty to inform Canada’s carbon stocktake, establish baselines for marine carbon dioxide removal projects, and support efforts to mitigate and adapt to ocean acidification. Future directions recommended by this group include investing in maturing and building capacity in the use of marine carbon sensors, improving ocean biogeochemical models fit-for-purpose in regional and ocean carbon dioxide removal applications, creating transparent and robust monitoring, verification, and reporting protocols for marine carbon dioxide removal, tailoring community-specific approaches to co-generate knowledge with First Nations, and advancing training opportunities for early career ocean professionals in marine carbon science and technology.
Continue reading ‘Canada’s marine carbon sink: an early career perspective on the state of research and existing knowledge gaps’Sea ice loss translates into major shifts in the carbonate environmental conditions in Arctic Shelf Sea
Published 19 July 2023 Science ClosedTags: Arctic, chemistry, field
Healthy Arctic marine ecosystems are essential to the food security and sovereignty, culture and wellbeing of Indigenous Peoples in the Arctic. At the same time, Arctic marine ecosystems are highly susceptible to impacts of climate change and ocean acidification. While increasing ocean and air temperatures and melting sea ice act as direct stressors on the ecosystem, they also indirectly enhance ocean acidification, accelerating the associated changes in the inorganic carbon system. Yet, much is to be learned about the current state and variability of the inorganic carbon system in remote places. Here, we present pH and pCO2 time-series (2016–2020) from the Chukchi Ecosystem Observatory. The subsurface observatory is located in the midst of a biological hotspot with high primary productivity and a rich benthic food web that support coastal Iñupiat, whales, ice seals, walrus (Odobenus rosmarus), and Arctic cod (Boreogadus saida). Our observations suggest that near-bottom waters (33 m depth, 13 m above the seafloor) are a high carbon dioxide and low pH and aragonite saturation state environment in summer and fall, when organic material from the highly productive summer remineralizes. During this time, the aragonite saturation state can be as low as 0.4, triggering free CaCO3 dissolution. During the sea ice covered winter period, pH was < 8 and aragonite remained undersaturated under the sea ice. There are only two short seasonal periods with relatively higher pH and Ωarag, which we term ocean acidification relaxation events. In spring, high primary production from sea ice algae and phytoplankton blooms and ikaite dissolution lead to spikes in pH (pH > 8) and aragonite oversaturation. In late fall, strong wind driven mixing events that bring CO2 depleted surface water to the shelf also lead to events with elevated pH and Ωarag. Given the recent observations of high rates of ocean acidification, and sudden and dramatic shift of the physical, biogeochemical, and ecosystem conditions in the Chukchi Sea, it is possible that the observed extreme conditions at the Chukchi Ecosystem Observatory are significantly deviating from the carbonate conditions to which many species are adapted and may have negative impacts on the ecosystem.
Continue reading ‘Sea ice loss translates into major shifts in the carbonate environmental conditions in Arctic Shelf Sea’Ocean acidification altered microbial functional potential in the Arctic Ocean
Published 30 June 2023 Science ClosedTags: abundance, Arctic, biological response, BRcommunity, community composition, field, mesocosms, molecular biology, otherprocess, physiology, prokaryotes
Ocean acidification (OA) has considerably changed the metabolism and structure of plankton communities in the ocean. Evaluation of the response of the marine bacterioplankton community to OA is critical for understanding the future direction of bacterioplankton-mediated biogeochemical processes in the ocean. Understanding the diversity of functional genes is important for linking the microbial community to ecological and biogeochemical processes. However, the influence of OA on the functional diversity of bacterioplankton remains unclear. Using high-throughput functional gene microarray technology (GeoChip 4), we investigated the functional gene structure and diversity of bacterioplankton under three different pCO2 levels (control: 175 μatm, medium: 675 μatm, and high: 1085 μatm) in a large Arctic Ocean mesocosm experiment. We observed a higher evenness of microbial functional genes under elevated pCO2 compared with under low pCO2. OA induced a more stable community as evaluated by decreased dissimilarity of functional gene structure with increased pCO2. Molecular ecological networks under elevated pCO2 became more complex and stable, supporting the central ecological tenet that complexity begets stability. In particular, increased average abundances were found under elevated pCO2 for many genes involved in key metabolic processes, including carbon degradation, methane oxidization, nitrogen fixation, dissimilatory nitrite/nitrate reduction, and sulfide reduction processes. Altogether, these results indicate a significant influence of OA on the metabolism potential of bacterioplankton in the Arctic Ocean. Consequently, our study suggests that biogeochemical cycling mediated by these microbes may be altered by the OA in the future.
Continue reading ‘Ocean acidification altered microbial functional potential in the Arctic Ocean’Planktic foraminiferal resilience to environmental change associated with the PETM
Published 28 June 2023 Science ClosedTags: abundance, Arctic, biological response, chemistry, community composition, communitymodeling, modeling, North Pacific, otherprocess, paleo, protists, South Pacific
Carbonate-forming organisms play an integral role in the marine inorganic carbon cycle, yet the links 21 between carbonate production and the environment are insufficiently understood. Carbonate production is driven by the abundance of calcifiers, and the amount of calcite produced by each individual (their size and weight). Here we investigate how foraminiferal carbonate production changes in the Atlantic, Pacific and Southern Ocean in response to a 4-5°C warming and a 0.3 surface ocean pH reduction during the Palaeocene-Eocene Thermal Maximum (PETM). To put these local data into a global context, we apply a trait-based plankton model (ForamEcoGEnIE) to the geologic record for the first time. Our data illustrates negligible change in the assemblage test size and abundance of foraminifers. ForamEcoGEnIE resolves small reductions in size and biomass, but these are short-lived. The response of foraminifersshowsspatial variability linked to a warming-induced poleward migration and suggested differences in nutrient availability between open-ocean and shelf locations. Despite low calcite saturation at high latitudes, we reconstruct stable foraminiferal size-normalised weight. Based on these findings, we postulate that sea surface warming had a greater impact on foraminiferal carbonate production during the PETM than ocean acidification. Changes in the composition of bulk carbonate suggest a higher sensitivity of coccolithophores to environmental change during the PETM than foraminifers.
Continue reading ‘Planktic foraminiferal resilience to environmental change associated with the PETM’
