The combined effects of ocean acidification and respiration on habitat suitability for marine calcifiers along the West coast of North America

Published 24 April 2024 Science Leave a Comment
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Abstract

The California Current Ecosystem (CCE) is a natural laboratory for studying the chemical and ecological impacts of ocean acidification. Biogeochemical variability in the region is due primarily to wind-driven near-shore upwelling of cold waters that are rich in re-mineralized carbon and poor in oxygen. The coastal regions are exposed to surface waters with increasing concentrations of anthropogenic CO2 (Canth) from exchanges with the atmosphere and the shoreward transport and mixing of upwelled water. The upwelling drives intense cycling of organic matter that is created through photosynthesis in the surface ocean and degraded through biological respiration in subsurface habitats. We used an extended multiple linear-regression approach to determine the spatial and temporal concentrations of Canth and respired carbon (Cbio) in the CCE based on cruise data from 2007, 2011, 2012, 2013, 2016, and 2021. Over the region, the Canth accumulation rate increased from 0.8 ± 0.1 μmol kg−1 yr−1 in the northern latitudes to 1.1 ± 0.1 μmol kg−1 yr−1 further south. The rates decreased to values of about ∼0.3 μmol kg−1 yr−1 at depths near 300 m. These accumulation rates at the surface correspond to total pH decreases that averaged about 0.002 yr-1; whereas, decreases in aragonite saturation state ranged from 0.006 to 0.011 yr-1. The impact of the Canth uptake was to decrease the amount of oxygen consumption required to cross critical biological thresholds (i.e., calcification, dissolution) for marine calcifiers and are significantly lower in the recent cruises than in the pre-industrial period because of the addition of Canth.

Key Points

  • In the California Current Ecosystem the anthropogenic carbon (Canth) uptake rate at the surface ranges from 0.8 to 1.1 μmol kg−1 yr−1
  • This corresponds to a total pH decrease of about 0.002 yr−1, whereas the decrease in aragonite saturation ranges from 0.006 to 0.011 yr−1
  • Dissolved oxygen consumptions required to cross critical biological thresholds are significantly lower in 2021 than in the pre-industrial

Plain Language Summary

The combined effect of ocean acidification and respiration in the California Current Ecosystem is to reduce water column pH and aragonite saturation state, resulting in a compression of the overall size of suitable habitat for marine calcifiers. The addition of excess anthropogenic CO2 also makes it more likely that critical biological thresholds are crossed and shell dissolution begins to occur. Consequently, the addition of the excess CO2 also has the added effect of reducing the amount of biological consumption of oxygen that is required to drop the ecosystem below these thresholds.

Continue reading ‘The combined effects of ocean acidification and respiration on habitat suitability for marine calcifiers along the West coast of North America’

Climate change effects on aquaculture production and its sustainable management through climate-resilient adaptation strategies: a review

Published 24 April 2024 Science Leave a Comment
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Aquaculture witnessed a remarkable growth as one of the fastest-expanding sector in the food production industry; however, it faces serious threat from the unavoidable impacts of climate change. Understanding this threat, the present review explores the consequences of climate change on aquaculture production and provides need based strategies for its sustainable management, with a particular emphasis on climate-resilient approaches. The study examines the multi-dimensional impacts of climate change on aquaculture which includes the shifts in water temperature, sea-level rise, ocean acidification, harmful algal blooms, extreme weather events, and alterations in ecological dynamics. The review subsequently investigates innovative scientific interventions and climate-resilient aquaculture strategies aimed at strengthening the adaptive capacity of aquaculture practices. Some widely established solutions include selective breeding, species diversification, incorporation of ecosystem-based management practices, and the implementation of sustainable and advanced aquaculture systems (aquaponics and recirculating aquaculture systems (RAS). These strategies work towards fortifying aquaculture systems against climate-induced disturbances, thereby mitigating risks and ensuring sustained production. This review provides a detailed insight to the ongoing discourse on climate-resilient aquaculture, emphasizing an immediate need for prudent measures to secure the future sustainability of fish food production sector.

Continue reading ‘Climate change effects on aquaculture production and its sustainable management through climate-resilient adaptation strategies: a review’

East coast mussel shells are becoming more porous in warming waters

Published 24 April 2024 Press releases Leave a Comment

A selection of historic and modern mussel shells from the American Museum of Natural History’s collection used in the study. Credit: Daniel Kim/ AMNH

Researchers at the American Museum of Natural History have found that over the last 120 years, the porosity—or small-scale holes—in mussel shells along the East Coast of the United States has increased, potentially due to warming waters. The study, which analyzed modern mussel shells in comparison to specimens in the Museum’s historic collection, was published in the journal PLoS ONE.

“Mussels are important on so many levels: They provide habitats on reefs, they filter water, they protect coasts during storms, and they are important commercially as well—I love mussels and I know many other people do, too,” said Leanne Melbourne, a Kathryn W. Davis postdoctoral fellow in the Museum’s Master of Arts in Teaching program and the lead author on the study. “Human-caused environmental changes are threatening the ability of mussels and other mollusks to form their shells, and we need to better understand what risks will come from this in the future.”

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Sea-surface pCO2 maps for the Bay of Bengal based on advanced machine learning algorithms

Published 23 April 2024 Science Leave a Comment
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Lack of sufficient observations has been an impediment for understanding the spatial and temporal variability of sea-surface pCO2 for the Bay of Bengal (BoB). The limited number of observations into existing machine learning (ML) products from BoB often results in high prediction errors. This study develops climatological sea-surface pCO2 maps using a significant number of open and coastal ocean observations of pCO2 and associated variables regulating pCO2 variability in BoB. We employ four advanced ML algorithms to predict pCO2. We use the best ML model to produce a high-resolution climatological product (INCOIS-ReML). The comparison of INCOIS-ReML pCO2 with RAMA buoy-based sea-surface pCO2 observations indicates INCOIS-ReML’s satisfactory performance. Further, the comparison of INCOIS-ReML pCO2 with existing ML products establishes the superiority of INCOIS-ReML. The high-resolution INCOIS-ReML greatly captures the spatial variability of pCO2 and associated air-sea CO2 flux compared to other ML products in the coastal BoB and the northern BoB.

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Using museum collections to assess the impact of industrialization on mussel (Mytilus edulis) calcification

Published 23 April 2024 Science Leave a Comment
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Mytilus edulis is a commercially and ecologically important species found along the east coast of the United States. Ecologically, M. edulis improves water quality through filtration feeding and provides habitat formation and coastal protection through reef formation. Like many marine calcifiers, ocean warming, and acidification are a growing threat to these organisms—impacting their morphology and function. Museum collections are useful in assessing long-term environmental impacts on organisms in a natural multi-stressor environment, where acclimation and adaptation can be considered. Using the American Museum of Natural History collections ranging from the early 1900s until now, we show that shell porosity changes through time. Shells collected today are significantly more porous than shells collected in the 1960s and, at some sites, than shells collected from the early 1900s. The disparity between porosity changes matches well with the warming that occurred over the last 130 years in the north Atlantic suggesting that warming is causing porosity changes. However, more work is required to discern local environmental impacts and to fully identify porosity drivers. Since, porosity is known to affect structural integrity, porosity increasing through time could have negative consequences for mussel reef structural integrity and hence habitat formation and storm defenses.

Continue reading ‘Using museum collections to assess the impact of industrialization on mussel (Mytilus edulis) calcification’

Coral microbiome offers early warning signs of stress in coral reefs

Published 23 April 2024 Press releases Leave a Comment

Imagine a vibrant underwater metropolis, teeming with life and color. This is the coral reef, a complex ecosystem that supports a quarter of all marine life.

But beneath the dazzling surface lies a hidden world, a symphony of microbial life that plays a vital role in the reef’s health. Recent studies published shed light on this unseen orchestra, revealing how these tiny organisms conduct the health of the reef.

Microbial Maestros: Keeping the Coral in Tune

(Photo : DAVID GRAY/AFP via Getty Images)

Corals themselves are a marvel of nature – a partnership between a polyp, a soft-bodied animal, and microscopic algae called zooxanthellae.

These algae provide the coral with energy through photosynthesis, but the relationship is delicate. When stressed by environmental changes like rising water temperatures, corals can expel the algae, leading to coral bleaching – a sickly white appearance that signifies the breakdown of the coral-algae partnership. This is where the microbial community steps in.

Researchers have discovered that a diverse and healthy microbiome, the collection of microbes living within the coral, is essential for coral resilience.

Continue reading ‘Coral microbiome offers early warning signs of stress in coral reefs’

Decline of a distinct coral reef holobiont community under ocean acidification

Published 22 April 2024 Science Leave a Comment
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Background

Microbes play vital roles across coral reefs both in the environment and inside and upon macrobes (holobionts), where they support critical functions such as nutrition and immune system modulation. These roles highlight the potential ecosystem-level importance of microbes, yet most knowledge of microbial functions on reefs is derived from a small set of holobionts such as corals and sponges. Declining seawater pH — an important global coral reef stressor — can cause ecosystem-level change on coral reefs, providing an opportunity to study the role of microbes at this scale. We use an in situ experimental approach to test the hypothesis that under such ocean acidification (OA), known shifts among macrobe trophic and functional groups may drive a general ecosystem-level response extending across macrobes and microbes, leading to reduced distinctness between the benthic holobiont community microbiome and the environmental microbiome.

Results

We test this hypothesis using genetic and chemical data from benthic coral reef community holobionts sampled across a pH gradient from CO2 seeps in Papua New Guinea. We find support for our hypothesis; under OA, the microbiome and metabolome of the benthic holobiont community become less compositionally distinct from the sediment microbiome and metabolome, suggesting that benthic macrobe communities are colonised by environmental microbes to a higher degree under OA conditions. We also find a simplification and homogenisation of the benthic photosynthetic community, and an increased abundance of fleshy macroalgae, consistent with previously observed reef microbialisation.

Conclusions

We demonstrate a novel structural shift in coral reefs involving macrobes and microbes: that the microbiome of the benthic holobiont community becomes less distinct from the sediment microbiome under OA. Our findings suggest that microbialisation and the disruption of macrobe trophic networks are interwoven general responses to environmental stress, pointing towards a universal, undesirable, and measurable form of ecosystem change.

Continue reading ‘Decline of a distinct coral reef holobiont community under ocean acidification’

Ocean acidification: what are the causes, effects, & solutions?

Published 22 April 2024 Web sites and blogs Leave a Comment

In this blog post, the process of ocean acidification and how it relates to human and marine life will be explained in hopes of spreading more information on this topic to the public.

What is Ocean Acidification?

There are many different types of global change. Deforestation and pollution of our land and sea are the most well-known global changes. However, ocean acidification is an impactful global change that many people are unaware of, and it tends to go unnoticed. Ocean acidification is the ongoing decrease in the pH of the Earth’s oceans. The acidity of water is based on a pH scale. A pH level less than 7 is considered acidic, while pHs greater than 7 are considered basic or alkaline. The oceans absorb 94% of carbon dioxide (CO2) from the atmosphere. Ocean acidification is primarily caused by the increase in CO2 levels in the atmosphere, which leads to higher levels of CO2 being absorbed by the oceans.

According to the Encyclopedia of the Anthropocene, “The vast majority, 94% of the planet’s CO2, is held in the world’s oceans. The carbon cycle moves CO2 between the atmosphere, oceans, and biosphere.” (Increased Acidity of Ocean Waters).

The world’s carbon cycle is constantly changing, affecting the pH of our oceans. The oceans act as a significant carbon sink, absorbing CO2 from the atmosphere. However, increased atmospheric CO2 levels can lead to ocean acidification, negatively impacting marine ecosystems and the organisms within them. Over the years, the pH of the ocean has decreased due to many ongoing factors.

According to the Encyclopedia of Ocean Sciences, “Overall, the increase in atmospheric CO2 concentrations from anthropogenic emissions has subsequently resulted in the acidification of the world’s surface ocean on the order of 0.1pH units since preindustrial times.” (Coastal Ocean Acidification: Carbonate Chemistry and Ecosystem Effects).

Continue reading ‘Ocean acidification: what are the causes, effects, & solutions?’

Interactive effects of chronic ocean acidification and warming on the growth, survival, and physiological responses of adults of the temperate sea urchin Strongylocentrotus intermedius

Published 19 April 2024 Science Leave a Comment
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Highlights

  • Ocean acidification and warming (OAW) repressed the survival and growth of Strongylocentrotus intermedius.
  • OAW altered the relative expression and activities of key metabolic enzymes of S. intermedius.
  • OAW attenuated the ATP production and antioxidant capability of S. intermedius.
  • Interactive effects of OAW on S. intermedius were analyzed in detail.

Abstract

To investigate the interactive effects of chronic ocean acidification and warming (OAW) on the growth, survival, and physiological responses of sea urchins, adults of the temperate sea urchin Strongylocentrotus intermedius were incubated separately/jointly in acidic (ΔpHNBS = −0.5 units) and thermal (ΔT = +3.0 °C) seawater for 120 days under lab-controlled conditions based on the projected ocean pH and temperature for 2100 put forward by the Intergovernmental Panel on Climate Change (IPCC). Survival rate (SR), average food consumption rate (FCR), gut index (GuI), specific growth rate (SGR), digestive capability, energy production, and antioxidant capability were subsequently determined. The results showed that 1) the SR, FCR, GuI and SGR decreased sharply under OAW conditions. Significant interactive effects of OAW on SR and SGR were observed at 120 days post-incubation (dpi), and on FCR this occurred at 90 dpi. 2) OAW altered the activities of both digestive and antioxidant enzymes. There were significant interaction effects of OAW on the activities of amylase, trehalase, and superoxide dismutase. 3) The relative gene expression levels and activities of key enzymes involved in glycometabolism pathways (i.e., glycolysis and the tricarboxylic acid cycle) were significantly affected by OAW, resulting in an alteration of the total ATP content in the sea urchins. Interaction effects of OAW were observed in both relative gene expression and the activity of enzymes involved in glycolysis (hexokinase), the transformation of glycolysis end-products (lactate dehydrogenase), the tricarboxylic acid cycle (citrate synthetase), and ATP production (Na+/K+-ATPase). The data from this study will enrich our knowledge concerning the combined effects of global climate change on the survival, growth, and physiological responses of echinoderms.

Continue reading ‘Interactive effects of chronic ocean acidification and warming on the growth, survival, and physiological responses of adults of the temperate sea urchin Strongylocentrotus intermedius’

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 Comment
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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’

Oregon could place limits on river trash, ocean acidification

Published 19 April 2024 Web sites and blogs Leave a Comment

…

In this September 2021 photo provided by Willamette Riverkeeper, volunteers help remove trash from the Upper Willamette River outside Eugene.

In addition to aquatic trash, DEQ added two additional types of water pollution to its report this year: ocean acidification and hypoxia, and PFOS, which is a subset of “forever chemicals” widely known as PFAS.

“All three of these kind of particular issues are very different and much harder to solve,” compared to water temperature pollution, DEQ spokesperson Lauren Wirtis said. “It’s not [from] a single entity or person or facility.”

In addition to the Willamette River, DEQ proposes the Columbia Slough — the 31-mile stretch of waterways between Fairview Lake and the Willamette River — be listed as impaired for PFOS based on the Oregon Health Authority’s fish consumption advisory.

DEQ is also proposing parts of the Oregon Coast be listed as impaired due to ocean acidification and hypoxia, which is linked to a changing climate. The ocean absorbs carbon dioxide, increasing acidity and depleting oxygen. DEQ based its findings on three years of data submissions, as well as a workgroup it formed.

The agency is proposing to list the stretch of coast from Cape Foulweather (south of Depoe Bay) to the Siltcoos River (north of Winchester Bay) as impaired for acidification and hypoxia. It’s also proposing the stretch of coast from the Columbia River to Cape Lookout (southwest of Tillamook) be listed for ocean acidification only. If approved by the EPA, Oregon would become the first state to have marine waters listed as impaired for ocean acidification.

April Erlich, OPB, 18 April 2024. Article.

Water pollution is fueling ocean acidification. Environmentalists urge California to act

Published 19 April 2024 Press releases Leave a Comment
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The Hyperion Water Reclamation Plant in Playa del Rey is one of a number of wastewater treatment plants that send treated effluent into the waters off California’s coast. (Gary Coronado / Los Angeles Times)

…

As the burning of fossil fuels and other human activities continue to increase the levels of carbon dioxide in the atmosphere, the ocean is absorbing a large portion of the CO2, which is making seawater more acidic.

The changing water chemistry in the ocean has far-reaching effects for plankton, shellfish and the entire marine food web.

And here’s one important fact about ocean acidification: It’s not happening at the same rate everywhere.

The California coast is one of the regions of the world where ocean acidification is occurring the fastest. And researchers have found that local sources of pollution are part of the problem.

In particular, effluent discharged from coastal sewage treatment plants, which has high nitrogen levels from human waste, has been shown to significantly contribute to ocean acidification off the Southern California coast. These nitrogen-filled discharges also periodically contribute to algae blooms, leading to hypoxia, or oxygen-deprived water that is inhospitable for marine life.

Continue reading ‘Water pollution is fueling ocean acidification. Environmentalists urge California to act’

Effect of ocean outfall discharge volume and dissolved inorganic nitrogen load on urban eutrophication outcomes in the Southern California Bight

Published 18 April 2024 Science Leave a Comment
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Climate change is increasing drought severity worldwide. Ocean discharges of municipal wastewater are a target for potable water recycling. Potable water recycling would reduce wastewater volume; however, the effect on mass nitrogen loading is dependent on treatment. In cases where nitrogen mass loading is not altered or altered minimally, this practice has the potential to influence spatial patterns in coastal eutrophication. We apply a physical-biogeochemical numerical ocean model to understand the influence of nitrogen management and potable wastewater recycling on net primary productivity (NPP), pH, and oxygen. We model several theoretical management scenarios by combining dissolved inorganic nitrogen (DIN) reductions from 50 to 85% and recycling from 0 to 90%, applied to 19 generalized wastewater outfalls in the Southern California Bight. Under no recycling, NPP, acidification, and oxygen loss decline with DIN reductions, which simulated habitat volume expansion for pelagic calcifiers and aerobic taxa. Recycling scenarios under intermediate DIN reduction show patchier areas of pH and oxygen loss with steeper vertical declines relative to a “no recycling” scenario. These patches are diminished under 85% DIN reduction across all recycling levels, suggesting nitrogen management lowers eutrophication risk even with concentrated discharges. These findings represent a novel application of ocean numerical models to investigate the regional effects of idealized outfall management on eutrophication. Additional work is needed to investigate more realistic outfall-specific water recycling and nutrient management scenarios and to contextualize the benefit of these management actions, given accelerating acidification and hypoxia from climate change.

Continue reading ‘Effect of ocean outfall discharge volume and dissolved inorganic nitrogen load on urban eutrophication outcomes in the Southern California Bight’

Biological response of eelgrass epifauna, Taylor’s sea hare (Phyllaplysia taylori) and eelgrass isopod (Idotea resecata), to elevated ocean alkalinity

Published 18 April 2024 Science Leave a Comment
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Marine carbon dioxide removal (mCDR) approaches are under development to mitigate the effects of climate change with potential co-benefits of local reduction of ocean acidification impacts. One such method is ocean alkalinity enhancement (OAE). A specific OAE method that avoids issues of solid dissolution kinetics and the release of impurities into the ocean is the generation of aqueous alkalinity via electrochemistry to enhance the alkalinity of the surrounding water and extract acid from seawater. While electrochemical acid extraction is a promising method for increasing the carbon dioxide sequestration potential of the ocean, the biological effects of this method are relatively unknown. This study aims to address this knowledge gap by testing the effects of increased pH and alkalinity, delivered in the form of aqueous base, on two ecologically important eelgrass epifauna in the U.S. Pacific Northwest, Taylor’s sea hare (Phyllaplysia taylori) and eelgrass isopod (Idotea resecata), across pH treatments ranging from 7.8 to 9.3. Four-day experiments were conducted in closed bottles to allow measurements of the evolution of carbonate species throughout the experiment with water refreshed twice daily to maintain elevated pH. Sea hares experienced mortality in all pH treatments, ranging from 40 % mortality at pH 7.8 to 100 % mortality at pH 9.3. Isopods experienced lower mortality rates in all treatment groups, which did not significantly increase with higher pH treatments. Different invertebrate species will likely have different responses to increased pH and alkalinity, depending on their physiological vulnerabilities. Investigation of the potential vulnerabilities of local marine species will help inform the decision-making process regarding mCDR planning and permitting.

Continue reading ‘Biological response of eelgrass epifauna, Taylor’s sea hare (Phyllaplysia taylori) and eelgrass isopod (Idotea resecata), to elevated ocean alkalinity’

How can China’s offshore fisheries handle climate change?

Published 18 April 2024 Press releases Leave a Comment

Hairtail landed in Fujian. The impact of climate change on China’s fisheries is alarming scientists, and research gaps need addressing. Professor Tian Yongjun says: “We’re still not certain where the spawning grounds of the ‘big four’ families of fish are,” referring to hairtail, large and small yellow croakers, and cuttlefish. (Image: Zhang Guojun / Alamy)

As climate change brings warmer, more acidic waters to China, its offshore fish stocks are coming under pressure.

A number of fish populations – including the large yellow croaker, sea bream and sandlance – are at risk, according to a study by researchers based in the US and China, and published in the Proceedings of the National Academy of Sciences (PNAS).

Ocean warming has been more pronounced in China’s offshore waters than almost anywhere else. Winter surface temperatures in the Bohai, Yellow and East China seas, off the country’s eastern seaboard, rose by nearly 2C from 1958 to 2014 – well above the global average. And with concentrations of atmospheric CO2 rising, more of the gas is absorbed into the ocean, resulting in acidification of surface water. The trend is particularly evident in the coastal waters of southern Jiangsu, the Yangtze estuary and Hangzhou Bay.

Continue reading ‘How can China’s offshore fisheries handle climate change?’

Ocean acidification significantly alters the trace element content of the kelp, Saccharina latissima

Published 17 April 2024 Science Leave a Comment
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Highlights

  • Exposure of S. latissima to higher concentrations of pCO2 caused a significant increase in the content and subcellular heterogeneity of iodine and arsenic in kelp.
  • The iodine-to‑calcium and bromine-to‑calcium ratios of kelp increased significantly under high CO2.
  • High CO2 significantly reduced levels of copper and cadmium in kelp tissue.
  • The elemental content of seaweeds used as food should be carefully monitored as climate change accelerates this century.

Abstract

Seaweeds are ecosystem engineers that can serve as habitat, sequester carbon, buffer ecosystems against acidification, and, in an aquaculture setting, represent an important food source. One health issue regarding the consumption of seaweeds and specifically, kelp, is the accumulation of some trace elements of concern within tissues. As atmospheric CO2 concentrations rise, and global oceans acidify, the concentrations of elements in seawater and kelp may change. Here, we cultivated the sugar kelp, Saccharina latissima under ambient (~400 μatm) and elevated pCO2 (600–2400 μatm) conditions and examined the accumulation of trace elements using x-ray powder diffraction, sub-micron resolution x-ray imaging, and inductively coupled plasma mass spectrometry. Exposure of S. latissima to higher concentrations of pCO2 and lower pH caused a significant increase (p < 0.05) in the iodine and arsenic content of kelp along with increased subcellular heterogeneity of these two elements as well as bromine. The iodine-to‑calcium and bromine-to‑calcium ratios of kelp also increased significantly under high CO2/low pH (p < 0.05). In contrast, high CO2/low pH significantly reduced levels of copper and cadmium in kelp tissue (p < 0.05) and there were significant inverse correlations between concentrations of pCO2 and concentrations of cadmium and copper in kelp (p < 0.05). Changes in copper and cadmium levels in kelp were counter to expected changes in their free ionic concentrations in seawater, suggesting that the influence of low pH on algal physiology was an important control on the elemental content of kelp. Collectively, these findings reveal the complex effects of ocean acidification on the elemental composition of seaweeds and indicate that the elemental content of seaweeds used as food must be carefully monitored as climate change accelerates this century.

Continue reading ‘Ocean acidification significantly alters the trace element content of the kelp, Saccharina latissima’

Seasonal variability of coastal pH and CO2 using an oceanographic buoy in the Canary Islands

Published 17 April 2024 Science Leave a Comment
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Ocean acidification, caused by the absorption of carbon dioxide (CO2) from the atmosphere into the ocean, ranks among the most critical consequences of climate change for marine ecosystems. Most studies have examined pH and CO2 trends in the open ocean through oceanic time-series research. The analysis in coastal waters, particularly in island environments, remains relatively underexplored. This gap in our understanding is particularly important given the profound implications of these changes for coastal ecosystems and the blue economy. The present study focuses on the ongoing monitoring effort that started in March 2020 along the east coast of Gran Canaria, within the Gando Bay, by the CanOA-1 buoy. This monitoring initiative focuses on the systematic collection of multiple variables within the CO2 system, such as CO2 fugacity (fCO2), pH (in total scale, pHT), total inorganic carbon (CT), and other hydrographic variables including sea surface salinity (SSS), sea surface temperature (SST) and wind intensity and direction. Accordingly, the study allows the computation of the CO2 flux (FCO2) between the surface waters and the atmosphere. During the study period, stational (warm and cold periods) behavior was found for all the variables. The lowest SST values were recorded in March, with a range of 18.8-19.3°C, while the highest SST were observed in September and October, ranging from 24.5-24.8°C. SST exhibited an annual increase with a rate of 0.007°C yr-1. Warmer months increased SSS, while colder periods, influenced by extreme events like tropical storms, led to lower salinity (SSS=34.02). The predominant Trade Winds facilitated the arrival of deeper water, replenishing seawater. The study provided insights into atmospheric CO2. Atmospheric fCO2 averaged 415 ± 4 µatm (2020-2023). Surface water fCO2sw presented variability, with the highest values recorded in September and October, peaking at 437 µatm in September 2021. The lowest values for fCO2sw were found in February 2021 (368 µatm). From 2020 to 2023, surface water fCO2sw values displayed an increasing rate of 1.9 µatm yr-1 in the study area. The assessment of fCO2sw decomposition into thermal and non-thermal processes revealed the importance of SST on the fCO2sw. Nevertheless, in the present study, it is crucial to remark the impact of non-thermal factors on near-shallow coastal regions. Our findings highlight the influence of physical factors such as tides, and wind effect to horizontal mixing in these areas. The CT showed a mean concentration of 2113 ± 8 μmol kg-1 and pH at in-situ temperature (pHT,IS) has a mean value of 8.05 ± 0.02. The mean FCO2 from 2020 to 2023 was 0.34 ± 0.04 mmol m-2 d-1 (126 ± 13 mmol m-2 yr-1) acting as a slight CO2 source. In general, between May and December were the months when the area was a source of CO2. Extrapolating to the entire 6 km2 of Gando Bay, the region sourced 33 ± 4 Tons of CO2 yr-1.

Continue reading ‘Seasonal variability of coastal pH and CO2 using an oceanographic buoy in the Canary Islands’

Understanding how acidification impacts the ocean (video)

Published 17 April 2024 Presentations Leave a Comment

Valenti Sallares, director of the Spanish National Research Council’s Institute of Marine Sciences, explains to us how acidification is impacting our oceans.

Continue reading ‘Understanding how acidification impacts the ocean (video)’

Is there a quick fix for ocean acidification?

Published 17 April 2024 Educational Materials , Resources Leave a Comment
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The ocean is getting more and more acidic. Can we solve it by emptying a giant bottle of antacid into the ocean? No… but the idea of lowering the ocean’s acidity in order to decrease global carbon dioxide levels isn’t all bad. Let’s dive into the science behind ocean alkalinization, and how it could be one part of a larger solution to our global climate crisis.

Continue reading ‘Is there a quick fix for ocean acidification?’

Ocean acidification offsets the effect of warming on sediment denitrification and associated nitrous oxide production

Published 16 April 2024 Science Leave a Comment
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Rates of denitrification and associated nitrous oxide (N2O) production are expected to increase with global warming, leading to positive climate feedback. However, previous studies have not considered the combined effect of ocean acidification (OA, pCO2 ~ 900 µatm) and warming on denitrification rates and N2O production. Here we used a series of whole core incubation studies to assess the combined impact of warming and OA on estuarine sediment denitrification rates and N2O production. Strong warming (+5 °C over mean in situ conditions) increased N2O production by ~4.2 µmol-N m−2 d−1 and denitrification by ~43 µmol-N m−2 d−1, fuelled by water column nitrate (Dw), but decreased rates of nitrification-coupled denitrification in the sediment (Dn) by ~82 µmol-N m−2 d−1. While Dn was not affected by OA, Dw decreased significantly by 51 µmol-N m−2 d−1 when OA was coupled with warmer temperatures. We estimate that OA may offset the increase in estuarine sediment denitrification and N2O production expected from warming alone by up to 64% and reduce a potential positive climate feedback loop by inhibiting denitrification pathways.

Continue reading ‘Ocean acidification offsets the effect of warming on sediment denitrification and associated nitrous oxide production’

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