Archive Page 161

OceanSODA-MDB: a standardised surface ocean carbonate system dataset for model-data intercomparisons

Published 11 August 2022 Science Closed
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In recent years, large datasets of in situ marine carbonate system parameters (partial pressure of CO2 (pCO2), total alkalinity, dissolved inorganic carbon and pH) have been collated, quality controlled and made publicly available. These carbonate system datasets have highly variable data density in both space and time, especially in the case of pCO2, which is routinely measured at high frequency using underway measuring systems. This variation in data density can create biases when the data are used, for example for algorithm assessment, favouring datasets or regions with high data density. A common way to overcome data density issues is to bin the data into cells of equal latitude and longitude extent. This leads to bins with spatial areas that are latitude and projection dependent (e. g. become smaller and more elongated as the poles are approached). Additionally, as bin boundaries are defined without reference to the spatial distribution of the data or to geographical features, data clusters may be divided sub-optimally (e. g. a bin covering a region with a strong gradient).

To overcome these problems and to provide a tool for matching surface in situ data with satellite, model and climatological data, which often have very different spatiotemporal scales both from the in situ data and from each other, a methodology has been created to group in situ data into ‘regions of interest’: spatiotemporal cylinders consisting of circles on the Earth’s surface extending over a period of time. These regions of interest are optimally adjusted to contain as many in situ measurements as possible. All surface in situ measurements of the same parameter contained in a region of interest are collated, including estimated uncertainties and regional summary statistics. The same grouping is applied to each of the non-in situ datasets in turn, producing a dataset of coincident matchups that are consistent in space and time. About 35 million in situ data points were matched with data from five satellite sources and five model and re-analysis datasets to produce a global matchup dataset of carbonate system data, consisting of ~286,000 regions of interest spanning 54 years from 1957 to 2020. Each region of interest is 100 km in diameter and 10 days in duration. An example application, the reparameterisation of a global total alkalinity algorithm, is shown. This matchup dataset can be updated as and when in situ and other datasets are updated, and similar datasets at finer spatiotemporal scale can be constructed, for example to enable regional studies. The matchup dataset provides users with a large multiparameter carbonate system dataset containing data from different sources, in one consistent, collated and standardised format suitable for model-data intercomparisons and model evaluations. The OceanSODA-MDB data can be downloaded from https://doi.org/10.12770/0dc16d62-05f6-4bbe-9dc4-6d47825a5931 (Land and Piollé, 2022).

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Physical-chemical factors influencing the vertical distribution of phototrophic pico-nanoplankton in the Oxygen Minimum Zone (OMZ) off Northern Chile: the relative influence of low pH/low O2 conditions

Published 11 August 2022 Science Closed
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Highlights

  • Pico-nano eukaryotes and phototrophic nanoflagellates showed high abundances in the upper layer decreasing in abundance down to the upper oxycline.
  • Temperature, oxygen, and carbonate chemistry parameters (pH and dissolved inorganic carbon, DIC) influenced significantly the vertical distribution of phototrophic pico-nanoplankton.
  • The phototrophic nanoflagellate Imantonia sp. upon an experimental treatment mimicking OMZ conditions, declined dramatically, suggesting this nanoflagellate did not survive upon such conditions.

Abstract

The vertical distribution of phytoplankton is of fundamental importance in the structure, dynamic, and biogeochemical pathways in marine ecosystems. Nevertheless, what are the main factors determining this distribution remains as an open question. Here, we evaluated the relative influence of environmental factors that might control the coexistence and vertical distribution of pico-nanoplankton associated with the OMZ off northern Chile. Our results showed that in the upper layer Synechococcus-like cells were numerically important at all sampling stations. Pico-nano eukaryotes and phototrophic nanoflagellates (PNF) also showed high abundances in the upper layer decreasing in abundance down to the upper oxycline, while only Prochlorococcus showed high abundances under oxycline and within the oxygen-depleted layer. Statistical analyses evidenced that temperature, oxygen, and carbonate chemistry parameters (pH and dissolved inorganic carbon, DIC) influenced significantly the vertical distribution of phototrophic pico-nanoplankton. Additionally, we experimentally-evaluated the combined effect of low pH/low O2 conditions on a nanophytoplankton species, the haptophyte Imantonia sp. Under control conditions (pH = 8.1; O2 = 287.5 μM, light = 169.6 μEm−2s−1), Imantonia sp. in vivo fluorescence increased over fifty times, inducing supersaturated O2 conditions (900 μM) and an increasing pH (8.5), whereas upon an experimental treatment mimicking OMZ conditions (pH = 7.5; O2 = 55.6 μM; light = 169.6 μEm−2s−1), in vivo fluorescence declined dramatically, suggesting that Imantonia sp. did not survive. Although preliminary, our study provides evidence about the role of low pH/low O2 conditions on the vertical distribution of nanophytoplankton, which deserve future attention through both fieldwork and more extended experimental experiences.

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SOOS symposium “Southern Ocean in a changing world” August 2023

Published 11 August 2022 Events , Meetings Closed
soos symposium2023

Description: The Southern Ocean Observing System (SOOS) Symposium, “Southern Ocean in a Changing World”, will consist of plenary presentations, parallel sessions and workshops. These will be focused around the topics below and incorporate a wide spectrum of Southern Ocean research. 

Date: 14-18 August 2023 in Hobart, Australia

Links: SOOS Symposium 2023 Save-the-Date Flyer
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Long-term and short-term inorganic carbon reservoirs in Aegean seawater – an experimental study

Published 10 August 2022 Science Closed
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The relevant literature does not explicitly address the fact that there are two fundamentally different inorganic carbon (DIC) reservoirs in seawater; (1) a long-term “background” DIC reservoir that is not in net-transfer equilibrium with the atmosphere, and (2) a short-term “atmospheric” DIC reservoir that is fed by atmospheric pCO2. In addition, we may define a third “anthropogenic” DIC reservoir that quantifies the increase in DIC since industrialization.

We perform experiments to quantify these reservoirs. We equilibrate Aegean seawater with N2-O2 (79:21) gases with variable pCO2 from < 10 to 100,000 µatm, and pure CO2 gas. We quantify electrochemically the changes in pH and, by titration and IR spectroscopy, total alkalinity (TA) and dissolved inorganic carbon (DIC) that occur with variations in pCO2. About 78 % of the Aegean DIC is “background“, introduced into the Aegean sea by the long-term carbon cycle, i.e. riverine input, remineralization of organic carbon, and hydrothermal CO2. In terms of concentration and in the short term, this reservoir is independent of atmospheric pCO2. About 22 % of DIC is atmospheric in origin and is in exchange equilibrium with atmospheric pCO2. The anthropogenic contribution to the atmospheric DIC reservoir is derived by measuring the increase in DIC between 280 (pre-industrial) and 410 µatm (present-day) pCO2 and quantified at around 26 %.

Our experiments also allow projections into the future. It has been suspected that increasing atmospheric pCO2 lowers the CO2 absorption capacity of ocean surface water. Our data confirm this assessment. When the pCO2 increases, the pH and the CO32--concentration fall, and with them the ability of seawater to hydrolyze CO2. Without measures to limit anthropogenic CO2 emissions, the absorption capacity of Aegean seawater in the year 2100 will be only about one half of the absorption capacity of today.

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Higher survival but smaller size of juvenile Dungeness crab (Metacarcinus magister) in high CO2

Published 10 August 2022 Science Closed
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Highlights

  • Ocean acidification conditions do not affect Dungeness crab megalopae survival.
  • Dungeness crab juveniles reared in high CO2 have higher survival but are smaller.
  • Dungeness crab zoea more susceptible to ocean acidification than juveniles.

Abstract

Dungeness crab (Metacarcinus magister) are the most valuable fishery on the U.S. West Coast and both larval and adult Dungeness crabs are important components of regional food webs. Previous experiments have shown decreased survival and a slower development rate for Dungeness crab zoea reared in water with high CO2, indicating a susceptibility to ocean acidification. In this study we reared late-stage megalopae and juvenile Dungeness crabs in both ambient and high CO2 conditions for over 300 days. Counter to expectations, crabs reared in high CO2 had a higher survival rate than those reared in ambient conditions and crabs in high CO2 transitioned more quickly in one of the stages (J5 to J6). However, crabs reared in high CO2 were generally smaller and had a higher resting metabolic rate than crabs in ambient CO2. We hypothesized that two separate mechanisms were in effect, with one process driving survival and a second process driving size and respiration rate. We further hypothesized that increased mortality in ambient CO2 could be caused by a CO2-sensitive microbial pathogen, but that size and respiration differences were caused by the direct effects of CO2 on the crabs themselves. Overall, the zoea stages seem more sensitive to CO2 than the megalopae and juvenile stages.

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Coral bleaching from a nutrient perspective is understudied: a bibliometric survey

Published 10 August 2022 Science Closed
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How coral–Symbiodiniaceae mutualistic symbiosis is established, maintained, and disrupted is arguably the most fundamental and central area of coral research. The breakdown of this symbiosis, and consequent coral bleaching, have been frequently attributed to thermal stress, although microbial attack and pollution have also been blamed. Despite the perceived intense and broad research, it is unclear whether all the potential causes have been given adequate attention and whether some important areas have been overlooked. This work aims to comprehensively review the literature on coral and Symbiodiniaceae research and provide a portrait of the current coral research landscape, hence identifying areas that require more research effort. Data of publication output were extracted from the Web of Science (WoS) from 1986 to 2022 by using the keywords “coral” and “Symbiodiniaceae.” A total of 43,089 and 3,191 papers in the coral and Symbiodiniaceae were identified, mostly published after 2002. The journal Coral Reefs was ranked first regarding the total number of publications on coral or Symbiodiniaceae. The USA, Australia, and China were the top three countries in the number of publications. The network co-occurrence analysis of all keywords in coral and Symbiodiniaceae using VOSviewer showed that biodiversity, climate change, nutrient, and survival were the central research areas in coral and Symbiodiniaceae. Among them, climate change was the most invested research field, as revealed by the high proportion of published literature, while nutrient was the most understudied area. Thematic evolution analysis revealed that nutrient enrichment combined with elevated temperature was an emerging research field about coral and Symbiodiniaceae. Besides, nitrogen is currently the most studied nutrient. The findings from this study shed light on the trends of coral and Symbiodiniaceae research in the past 36 years, current research hotspots in the field, and areas that need more research investment going forward.

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OA action plan toolkit & guide

Published 10 August 2022 Methods , Projects , Resources , Web sites and blogs Closed
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The International Alliance to Combat Ocean Acidification (OA Alliance) brings together governments and organizations from across the globe dedicated to taking urgent action to protect coastal communities and livelihoods from the threat of ocean acidification and other climate- ocean impacts.

Facilitated through the OA Alliance, national, subnational, regional and tribal governments are proactively responding to the impacts of ocean acidification as they create OA Action Plans to effectively promote solutions and advancing knowledge into action.

The OA Alliance has created this Action Plan Toolkit as a guide. The OA Action Toolkit contains both regulatory and non-regulatory actions that members might consider when crafting their own OA Action. Not all OA Action plans will have the same framework or structure, as there is no “one- size fits all” approach.

Some members may choose to write a stand-alone plan, while others may decide to integrate ocean acidification mitigation, adaptation and resiliency actions across existing Climate Action Plans, Ocean Action Plans, Biodiversity or Resilience Goals and Targets, Nationally Determined Contributions pursuant to the Paris Climate Agreement, or decide to integrate and strengthen actions across other applicable management tools.

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GOA-ON webinar: ocean acidification monitoring and scientific research in the the PI-TOA region

Published 10 August 2022 Events , Presentations Closed

Topic: GOA-ON Webinar: Ocean Acidification Monitoring and Scientific Research in the the PI-TOA Region

Description: Please join GOA-ON for this month’s webinar, “Ocean Acidification Monitoring and Scientific Research in the PI-TOA Region” on August 25 11am Fiji. The webinar will be moderated by Dr Kim Currie with presentations by Dr Antoine De Ramon N’Yeurt, Associate Professor Patila Amosa and Ms Luia Taise. The three speakers will span topics such as establishing a pH time-series on the Suva reef, the effects of ocean acidification on organismal calcification such as corals and bryozoans, and the impacts on the photosynthetic physiology of a green seaweed. These research topics are important in understanding the impact of ocean acidification on coastal ecosystems of the Pacific.

Time: Aug 25, 2022 23:00 UTC

Registration: Webinar Registration – Zoom

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OA-ICC bibliographic database updated

Published 9 August 2022 Science Closed

An updated version of the OA-ICC bibliographic database is available online.

The database currently contains 9,688 references and includes citations, abstracts and assigned keywords. Updates are made every month.

The database is available as a group on Zotero. Subscribe online or, for a better user experience, download the Zotero desktop application and sync with the group OA-ICC in Zotero. Please see the “User instructions” for further details.

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pH trends and seasonal cycle in the coastal Balearic Sea reconstructed through machine learning

Published 9 August 2022 Science Closed
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The decreasing seawater pH trend associated with increasing atmospheric carbon dioxide levels is an issue of concern due to possible negative consequences for marine organisms, especially calcifiers. Globally, coastal areas represent important transitional land-ocean zones with complex interactions between biological, physical and chemical processes. Here, we evaluated the pH variability at two sites in the coastal area of the Balearic Sea (Western Mediterranean). High resolution pH data along with temperature, salinity, and also dissolved oxygen were obtained with autonomous sensors from 2018 to 2021 in order to determine the temporal pH variability and the principal drivers involved. By using environmental datasets of temperature, salinity and dissolved oxygen, Recurrent Neural Networks were trained to predict pH and fill data gaps. Longer environmental time series (2012–2021) were used to obtain the pH trend using reconstructed data. The best predictions show a rate of  −0.0020 ± 0.00054 − 0.0020 ± 0.00054 pH units year−1, which is in good agreement with other observations of pH rates in coastal areas. The methodology presented here opens the possibility to obtain pH trends when only limited pH observations are available, if other variables are accessible. Potentially, this could be a way to reliably fill the unavoidable gaps present in time series data provided by sensors.

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Impacts of ocean warming and acidification on the energy budget of three commercially important fish species

Published 9 August 2022 Science Closed
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Using experimental data of three commercially important marine fish species (Diplodus sargus, Diplodus cervinus and Solea senegalensis), a model based on Dynamic Energy Budget theory was parametrized. The model was used to produce projections of growth and reproduction for these species, under different scenarios of ocean warming and acidification.

A mechanistic model based on Dynamic Energy Budget (DEB) theory was developed to predict the combined effects of ocean warming, acidification and decreased food availability on growth and reproduction of three commercially important marine fish species: white seabream (Diplodus sargus), zebra seabream (Diplodus cervinus) and Senegalese sole (Solea senegalensis). Model simulations used a parameter set for each species, estimated by the Add-my-Pet method using data from laboratory experiments complemented with bibliographic sources. An acidification stress factor was added as a modifier of the somatic maintenance costs and estimated for each species to quantify the effect of a decrease in pH from 8.0 to 7.4 (white seabream) or 7.7 (zebra seabream and Senegalese sole). The model was used to project total length of individuals along their usual lifespan and number of eggs produced by an adult individual within one year, under different climate change scenarios for the end of the 21st century. For the Intergovernmental Panel on Climate Change SSP5-8.5, ocean warming led to higher growth rates during the first years of development, as well as an increase of 32-34% in egg production, for the three species. Ocean acidification contributed to reduced growth for white seabream and Senegalese sole and a small increase for zebra seabream, as well as a decrease in egg production of 48-52% and 14-33% for white seabream and Senegalese sole, respectively, and an increase of 4-5% for zebra seabream. The combined effect of ocean warming and acidification is strongly dependent on the decrease of food availability, which leads to significant reduction in growth and egg production. This is the first study to assess the combined effects of ocean warming and acidification using DEB models on fish, therefore, further research is needed for a better understanding of these climate change-related effects among different taxonomic groups and species.

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Fluctuating pH simulating natural variability modulates larval growth for Strongylocentrotus droebachiensis

Published 9 August 2022 Science Closed
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Ocean acidification (OA) is the downward trend of ocean pH mainly resulting from the absorption of carbon dioxide (CO2) emissions from anthropogenic sources. pH of the open ocean is expected to drop to 7.7 by the end of the century. Previous experiments investigating biological response to OA often use this open ocean prediction to assess response and neglect the potential modulating effects of a dynamic, fluctuating coastal ecosystem. pH in the Gullmar Fjord on the west coast of Sweden experiences natural fluctuations of pH as a result of biological processes that exceed the end-of-the century predictions, and as such these natural fluctuations need to be considered. The aim of this study was to investigate which part of the natural variability cycle, minimum pH experienced or duration of exposure under fluctuating conditions, drives the biological response of green sea urchin larvae (Strongylocentrotus droebachiensis), which are residents in the Gullmar Fjord. It was hypothesized that both intensity and duration of different pH exposures contributes to the stress experienced by an organism and further that (1) the level of stress is dependent on both intensity and duration of exposure in a cumulative manner (intensity*time); (2) for a given intensity, the negative effect on sea urchin larvae will increase with the duration of exposure; and (3) for a given duration of exposure, the negative effect on sea urchin larvae will increase with the intensity. The main results were that overall fluctuating conditions were beneficial to growth relative to constant conditions, intensity*time predicted stress response for body length growth, ignoring the role of modulating effects on pH can overestimate biological response to OA, and an overall change in shape was observed under fluctuating conditions. Future studies should further investigate this change in shape and also assess biological response in the context of natural fluctuations combined with other global change stressors.

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Ocean acidification in the western Pacific: boron isotopic composition recorded in a tropical massive coral core from Lanyu Islet SE Taiwan

Published 8 August 2022 Science Closed
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Boron (B) and B isotopic compositions (δ11B) in biogenic carbonates are useful proxies for pH reconstruction in the ocean. However, high-resolution archives are scarce due to associated sampling and analytical difficulty. In this study, a modern long-lived massive coral skeleton (Porites lobata) from Lanyu Islet off southeast Taiwan was drilled and used for high-resolution major/trace element analyses, including trace elements B and δ11B, as well as oxygen and carbon isotopes, to investigate the associated environmental changes during 1991–1997. To avoid complicated biological influence, the top-most tissue layer was excluded in this study. The coralline records show a clear temporal trend in metal/Ca-based sea surface temperatures (SSTs) on annual and monthly timescales. In particular, the Mg/Ca-SSTs, the most sensitive temperature proxy at the site, show a significant warming trend (+0.2°C year−1) during the study period. On the other hand, subtle changes in the annual δ11B record were identified, corresponding to ~0.2 pH unit, which is comparable with other coral records in the Pacific, e.g., the South China Sea (SCS), Guam Island, Flinders, and Arlington Reef, as well as the in-situ seawater pH measurement at Hawaii station. This corresponds to an acidification rate of ~0.25 pH unit 100 year−1, similar to other coralline data, in-situ pH/pCO2 measurement, or model predictions, and emphasizes the importance of ocean acidification due to anthropogenic activities. Combined with the Mg/Ca-SST, the intra-annual data show a clear seasonal cycle with higher pH in winter, consistent with the pCO2 at the oceanic surface. These chemical and isotopic results in corals conclude that marine biogenic carbonates are informative for oceanic pH reconstruction and can provide new insights into the relationships between climate changes and environmental responses on the coast of Taiwan.

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Inventory of water masses and carbonate system from Brazilian’s northeast coast: monitoring ocean acidification

Published 8 August 2022 Science Closed
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This manuscript presents an inventory of the carbonate system from the main water masses comprising the marine current system on Brazil’s northeast coast (South Atlantic Ocean). For this purpose, four transects were conducted with an approximate length of 357 km (each one) through the platform and continental slope of the Sergipe–Alagoas sedimentary basin. Water samples were then collected in vertical profiles measuring from 5 to 1,799 meters depth, totaling 34 stations. Total alkalinity, calcium, and total boron were obtained analytically from these samples and by relationships with salinity. Speciation and concentration of the carbonate system were obtained by means of thermodynamic modeling. The results revealed that the empirical models used to calculate the concentrations of TA, calcium and total boron showed relevant variation when compared to the analytical values (TA: 5.0–6.5%; Ca: 0.4–4.8%; BT: 7.0–18.9%). However, the speciation and concentration of the carbonate system (CA, DIC, CO32-, CO2(aq), ΩCalc, and ΩArag) obtained from the empirical values of TA, calcium and total boron did not differ significantly from those obtained analytically (0.0–6.1%). On the other hand, the parameters of pH, HCO3– , CO32-(aq), CO2(aq), ρCO2, ΩCalc, and ΩArag varied significantly within the different water masses (p < 0.05). This study supports and encourages acidification monitoring projects in the South Atlantic Ocean, based on modeling the carbonate system parameters generated in real-time.

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The impacts of climate change on blackeye goby, Rhinogobiops nicholsii, stress responses, reproduction, and offspring fitness

Published 8 August 2022 Science Closed
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Along with warming and sea level rise, the increasing intensity of ocean acidification (OA) and hypoxia events in coastal environments is of large concern as climate change progresses. Weakened immune function, altered reproductive output, reduced aerobic scope, and hyperventilation are just some of the ways OA and hypoxia negatively affect fish. Under stress, such as OA or hypoxia, fish will produce the hormone cortisol to maintain homeostasis, so cortisol concentration can be used to determine the relative stress an animal is experiencing. This study evaluated the stress response of adult female blackeye gobies under both acute and chronic exposure to environmental stressors by measuring muscular cortisol concentrations at specific time points from fish placed in one of four different treatments: control (8.1 pH; ~9 mg/L O2), low DO (8.1 pH; 2.0 mg/L O2), low pH (7.3 pH; ~9 mg/L O2), and a combination of low DO and low pH (7.3 pH; 2.0 mg/L O2). Additionally, some larval fish rely entirely on maternally derived hormones supplied by the yolk sac immediately after hatching. An increase in cortisol in the yolk supply may cause developmental disadvantages, but there is also evidence that it can better equip offspring to face the stressors experienced by their mothers. Therefore, the relationship between maternal muscular and whole egg cortisol concentrations was investigated with females laying clutches under each of the four treatments. After spawning, clutches were split to be incubated under the same conditions their mothers experienced or the control treatment. At 1 day post hatch, offspring physiological fitness was evaluated based on morphometric characteristics and standard metabolic rate. This study observed that adult female blackeye gobies experiencing acute stress tend to have higher cortisol concentrations than those under chronic stress. While under acute stress, blackeye gobies had the strongest stress response under the low pH treatment, followed by the combined stressors, with the response to the low DO treatment being the weakest. While under chronic stress, blackeye gobies had the highest sustained cortisol values while under the combined treatment, then the low pH treatment, with the lowest values under the low DO treatment. Low DO and low pH were also found to act antagonistically on the blackeye goby stress response. When evaluating how stress is translated generationally, a positive relationship between maternal and egg cortisol concentrations was found across the four treatments. However, blackeye gobies were not able to successfully fertilize eggs under the low pH or combined treatment. In addition, clutches with higher initial cortisol concentrations showed trends of increased time to hatching and standard metabolic rate and decreased length and weight at 1 day post hatch. The results of this study suggest decreased pH and dissolved oxygen are harmful to both adult and larval blackeye gobies. Due to the disruption of successful reproduction under low pH and the developmental and physiological disadvantages under low DO, future populations of blackeye gobies could suffer greatly as anthropogenic climate change progresses.

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CCMAR on board of Iberian scientific campaign on acidification of marine organisms

Published 8 August 2022 Web sites and blogs Closed

Our researchers Emília Salgueiro, Lélia Matos, Andreia Rebotim are participating in the CARBO-ACID – Eurofleets a scientific campaign onboard RV Ramon Margalef,that takes place in August 

This cruise establishes the bases for the investigation of the potential effects of ocean acidification on carbonate marine organisms (coccolithophores, pteropods, planktonic and benthic foraminifera, and corals) along the Iberian coast.

On board there will be collect multi-samples from the water column, plankton, corals and sediments to evaluate, for the first time along the Iberian margin, the acidification effects into the entire water column for the pre / post-industrial transition.
For that, oceanographic data and water, plankton, cold-water corals, and sediment samples will be collect during an upwelling season, along two transects coinciding with the two prominent upwelling filaments of the Iberia coast: the Cape Finisterra and Estremadura Spur filaments.

This study will focus on seawater pH variations in this seasonal coastal upwelling region during the pre- and post-industrial transition (centennial-to-decade time resolution) and interglacial/ glacial climatic cycles.

The expected results of this cruise will allow to compare variations at different time-scales and under different forcings (natural vs. anthropogenic), and to estimate the amplitude of future changes in the ocean in terms of CO2.

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Limits and CO2 equilibration of near-coast alkalinity enhancement

Published 5 August 2022 Science Closed
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Ocean Alkalinity Enhancement (OAE) has recently gained attention as a potential method for negative emissions at gigatonne scale, with near-coast OAE operations being economically favorable due to proximity to mineral and energy sources. In this paper we study critical questions which determine the scale and viability of OAE: Which coastal locations are able to sustain a large flux of alkalinity at minimal pH and ΩArag (aragonite saturation) changes? What is the interference distance between adjacent OAE projects? How much CO2 is absorbed per unit of alkalinity added? How quickly does the induced CO2 deficiency equilibrate with the atmosphere?

Using the LLC270 (0.3deg) ECCO global circulation model we find that the steady-state OAE rate varies over 1–2 orders of magnitude between different coasts and exhibits complex patterns and non-local dependencies which vary from region to region. In general, OAE in areas of strong coastal currents allow the largest fluxes and depending on the direction of coastal currents, neighboring OAE sites can exhibit dependencies as far as 400 km or more. We found that within relatively conservative constraints set on ∆pH or ∆Omega, most regional stretches of coastline are able to accommodate on the order of tens to hundreds of megatonnes of negative emissions within 300 km of the coast. We conclude that near-coastal OAE has the potential to scale globally to several GtCO2/yr of drawdown with conservative pH constraints, if the effort is spread over the majority of available coastlines.

Depending on the location, we find a diverse set of equilibration kinetics, determined by the interplay of gas exchange and surface residence time. Most locations reach an uptake-efficiency plateau of 0.6–0.8mol CO2 per mol of alkalinity after 3–4 years, after which there is little further CO2 uptake. The most ideal locations, reaching an uptake of around 0.8 include north Madagascar, San Francisco, Brazil, Peru and locations close to the southern ocean such as Tasmania, Kerguelen and Patagonia, where the gas exchange appears to occur faster than the surface residence time. Some locations (e.g. Hawaii) take significantly longer to equilibrate (up to 8–10 years), though can still eventually achieve high uptake. If the alkalinity released advects into regions of significant downwelling (e.g. around Iceland) up to half of the OAE potential can be lost to bottom waters.

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Gaining insights into the seawater carbonate system using discrete fCO2 measurements

Published 5 August 2022 Science Closed
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Understanding the ocean carbon sink and its future acidification-derived changes requires accurate and precise measurements with good spatiotemporal coverage. In addition, a deep knowledge of the thermodynamics of the seawater carbonate system is key to interconverting between measured and calculated variables. To gain insights into the remaining inconsistencies in the seawater carbonate system, we assess discrete water column measurements of carbon dioxide fugacity (fCO2), dissolved inorganic carbon (DIC), total alkalinity (TA), and pH measured with unpurified indicators, from hydrographic cruises in the Atlantic, Pacific, and Southern Oceans included in GLODAPv2.2020 (19,013 samples). An agreement of better than ± 3% between fCO2 measured and calculated from DIC and pH is obtained for 94% of the compiled dataset, while when considering fCO2 measured and calculated from DIC and TA, the agreement is better than ± 4% for 88% of the compiled dataset, with a poorer internal consistency for high-CO2 waters. Inspecting all likely sources of uncertainty from measured and calculated variables, we conclude that the seawater carbonate system community needs to (i) further refine the thermodynamic model of the seawater carbonate system, especially K2, including the impact of organic compounds and other acid-base systems on TA; (ii) update the standard operating procedures for the seawater carbonate system measurements following current technological and analytical advances, paying particular attention to the pH methodology that is the one that evolved the most; (iii) encourage measuring discrete water column fCO2 to further check the internal consistency of the seawater carbonate system, especially given the new era of sensor-based seawater measurements; and (iv) develop seawater Certified Reference Materials (CRMs) for fCO2 and pH together with seawater CRMs for TA and DIC over the range of values encountered in the global ocean. Our conclusions also suggest the need for a re-evaluation of the adjustments applied by GLODAPv2 to pH, which were based on DIC and TA consistency checks but not supported by fCO2 and DIC consistency.

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How coastal seas help the ocean absorb carbon dioxide from the atmosphere

Published 5 August 2022 Web sites and blogs Closed

The biologically productive North Sea impacts the global climate through exchange of carbon and nutrients with the Atlantic Ocean. A Dutch consortium of scientists will investigate how big this role of the North Sea really is. Under the leadership of the Royal Netherlands Institute for Sea Research (NIOZ), a combination of field studies and computer model simulations will be conducted over the next four years to address this question. NWO has awarded approximately 3 million euros for this project.

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The North Sea is under pressure from overfishing, ocean acidification, eutrophication and in parts a shortage of oxygen. It is crucial to better understand how these human influences affect carbon and nutrient cycling. Such insight will help to understand and project the effects of ongoing environmental change on the North Sea. It may also help to better understand and predict changing biogeochemical interactions between other coastal seas and the global ocean in the future. 

The consortium expects that the NoSE project will strengthen existing collaborations in the marine research community in the Netherlands and internationally and will stimulate new collaborations and inspire future work on the large-scale impact of anthropogenic influences on the ocean.

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Diurnal fluctuations in seawater pCO2 amplify the negative effects of ocean acidification on the biotic performance of the calcifying macroalga Halimeda opuntia

Published 4 August 2022 Science Closed
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Although the adverse effects of increasing atmospheric CO2-induced ocean acidification (OA) on marine calcifying macroalgae have been widely reported, there are limited studies on how daily fluctuations in pCO2 (pH) within shallow ecosystems influence the growth and physiological performance of these calcifiers. Therefore, a 42-day laboratory mimetic experiment to determine how growth, biological performance and related carbon and nitrogen metabolic products of the calcifying macroalga, Halimeda opuntia are generated in response to fluctuating pCO2 under OA conditions (1200 ppmv) was performed. The results of present study showed that the adverse effects of OA were more determined by the adverse influence of elevated acidity (H+) on growth rates, calcification, photosynthesis and the related biotic performance of H. opuntia compared with the positive effects that higher CO2 provided. Moreover, diurnal fluctuations in pCO2 levels [with higher (nearly 8.10) and lower pH (nearly 7.40) values during day and night times, respectively] have amplified these negative influences on H. opuntia. To mitigate elevated pCO2-related stress, higher contents of free amino acids and proline were highly secreted and likely linked to protecting the integrity of algal cellular structures. The above results contribute to increasing our understanding of the biological consequences of pCO2 (pH) variability on calcifying Halimeda species and their physiological plasticity in response to further oceanic pCO2 changes.

Continue reading ‘Diurnal fluctuations in seawater pCO2 amplify the negative effects of ocean acidification on the biotic performance of the calcifying macroalga Halimeda opuntia’

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