Land-based aquaculture systems expose fish to elevated dissolved CO2 levels, a factor that is correlated with reduced growth, feed conversion efficiency and body condition index. The physiological basis underlying the pathological effects of environmental hypercapnia is poorly understood, in particular for marine fish species. We investigated whether changes in energy expenditure and the specific dynamic action (SDA) of digestion and assimilation could account for the lower growth of adult Atlantic cod (Gadus morhua) under environmental hypercapnia. Fish acclimated to a partial pressure of 800 μatm CO2 (0.6 mmHg, 1.5 mg/L) and 9200 μatm CO2 (7 mmHg, 18.7 mg/L) exhibited no difference in maintenance metabolic rates, which concurs with previous research for this species and other fish species. At 9200 μatm CO2 Atlantic cod had a significantly diminished (14%) maximum aerobic capacity. While hypercapnia did not affect the amount of oxygen required for the SDA process, it did prolong the SDA duration by 23%. The longer SDA process time may offer an explanation for the observation of lower feed intake, growth and condition factor in long-term hypercapnia studies. Comparison of aerobic scope and cardiac performance during digestion suggested that reduced oxygen delivery capacity under hypercapnia could be one mechanism by which CO2 prolongs SDA, although our results could not definitively demonstrate this effect.
Archive for November, 2014
Prolonged SDA and reduced digestive efficiency under elevated CO2 may explain reduced growth in Atlantic cod (Gadus morhua)
Published 24 November 2014 Science ClosedTags: biological response, chemistry, fish, laboratory, North Atlantic, physiology, respiration
Long-term mesocosms study of the effects of ocean acidification on growth and physiology of the sea urchin Echinometra mathaei
Published 24 November 2014 Science ClosedTags: biological response, echinoderms, growth, Indian, laboratory, mesocosms, mortality, physiology, respiration
Recent research on the impact of ocean acidification (OA) has highlighted that it is important to conduct long-term experiments including ecosystem interactions in order to better predict the possible effects of elevated pCO2. The goal of the present study was to assess the long-term impact of OA on a suite of physiological parameters of the sea urchin Echinometra mathaei in more realistic food conditions. A long-term experiment was conducted in mesocosms provided with an artificial reef in which the urchins principally fed on algae attached to the reef calcareous substrate. Contrasted pH conditions (pH 7.7 vs control) were established gradually over six months and then maintained for seven more months. Acid-base parameters of the coelomic fluid, growth and respiration rate were monitored throughout the experiment. Results indicate that E. mathaei should be able to regulate its extracellular pH at long-term, through bicarbonate compensation. We suggest that, within sea urchins species, the ability to accumulate bicarbonates is related to their phylogeny but also on the quantity and quality of available food. Growth, respiration rate and mechanical properties of the test were not affected. This ability to resist OA levels expected for 2100 at long-term could determine the future of coral reefs, particularly reefs where E. mathaei is the major bioeroder.
Temporal changes in surface partial pressure of carbon dioxide and carbonate saturation state in the eastern equatorial Indian Ocean during the 1962–2012 period (update)
Published 24 November 2014 Science ClosedTags: chemistry
Information on changes in the oceanic carbon dioxide (CO2) concentration and air–sea CO2 flux as well as on ocean acidification in the Indian Ocean is very limited. In this study, temporal changes of the inorganic carbon system in the eastern equatorial Indian Ocean (EIO, 5° N–5° S, 90–95° E) are examined using partial pressure of carbon dioxide (pCO2) data collected in May 2012, historical pCO2 data since 1962, and total alkalinity (TA) data calculated from salinity. Results show that sea surface pCO2 in the equatorial belt (2° N–2° S, 90–95° E) increased from ∼307 μatm in April 1963 to ∼373 μatm in May 1999, ∼381 μatm in April 2007, and ∼385 μatm in May 2012. The mean rate of pCO2 increase in this area (∼1.56 μatm yr−1) was close to that in the atmosphere (∼1.46 μatm yr−1). Despite the steady pCO2 increase in this region, no significant change in air–sea CO2 fluxes was detected during this period. Ocean acidification as indicated by pH and saturation states for carbonate minerals has indeed taken place in this region. Surface water pH (total hydrogen scale) and saturation state for aragonite (Ωarag), calculated from pCO2 and TA, decreased significantly at rates of −0.0016 ± 0.0001 and −0.0095 ± 0.0005 yr−1, respectively. The respective contributions of temperature, salinity, TA, and dissolved inorganic carbon (DIC) to the increase in surface pCO2 and the decreases in pH and Ωarag are quantified. We find that the increase in DIC dominated these changes, while contributions from temperature, salinity, and TA were insignificant. The increase in DIC was most likely associated with the increasing atmospheric CO2 concentration, and the transport of accumulated anthropogenic CO2 from a CO2 sink region via basin-scale ocean circulations. These two processes may combine to drive oceanic DIC to follow atmospheric CO2 increase.
Life on the edge: Is ocean acidification a threat to deep-sea life? (text & video)
Published 21 November 2014 Media coverage Closed
Even animals living in the deep ocean are affected by the increasing emissions of carbon dioxide into the atmosphere. The ocean naturally absorbs carbon dioxide from the atmosphere, resulting in a more acidic habitat for ocean life. Researchers at the Monterey Bay Aquarium Research Institute use a series of specially designed chambers to study how deep-sea animals will respond to this change in ocean chemistry. They also bring animals into the laboratory, where the animals can be observed as they are exposed to seawater resembling current and future carbon-dioxide levels. It is important to understand how deep-sea animals will respond to impending changes in ocean chemistry because a disturbance to one part of an ecosystem can have cascading effects throughout the entire ecosystem.
As CO2 acidifies the oceans, scientists develop a new way to measure its effect on marine ecosystems
Published 21 November 2014 Media coverage ClosedFollowing a 5,000 km long ocean survey, research published in the Proceedings of the National Academy of Sciences presents a new way to measure how the acidification of water is affecting marine ecosystems over an entire oceanic basin.
As a result of man-made emissions, the content of CO2 in the atmosphere and oceans has increased dramatically during recent decades. In the ocean, the accumulating CO2 is gradually acidifying the surface waters, making it harder for shelled organisms like corals and certain open sea plankton to build their calcium carbonate skeletons.
Since this process impacts the functioning of many marine ecosystems, it has been intensively studied in recent years. However, getting an accurate measure is complicated because the effect of ocean acidification on the rates of calcium produced by marine organisms is highly variable and species specific. Since scientists tend to use local and site-specific field measurements, treating reef environments and open sea environments separately, their measurements reflect the local response of individual organisms to elevated CO2 levels, and not the overall picture.
Basin-scale estimates of pelagic and coral reef calcification in the Red Sea and Western Indian Ocean
Published 21 November 2014 Science ClosedTags: biogeochemistry, biological response, calcification, chemistry, corals, field, Indian, modeling, phytoplankton, Red Sea, regionalmodeling
Basin-scale calcification rates are highly important in assessments of the global oceanic carbon cycle. Traditionally, such estimates were based on rates of sedimentation measured with sediment traps or in deep sea cores. Here we estimated CaCO3 precipitation rates in the surface water of the Red Sea from total alkalinity depletion along their axial flow using the water flux in the straits of Bab el Mandeb. The relative contribution of coral reefs and open sea plankton were calculated by fitting a Rayleigh distillation model to the increase in the strontium to calcium ratio. We estimate the net amount of CaCO3 precipitated in the Red Sea to be 7.3 ± 0.4·1010 kg·y−1 of which 80 ± 5% is by pelagic calcareous plankton and 20 ± 5% is by the flourishing coastal coral reefs. This estimate for pelagic calcification rate is up to 40% higher than published sedimentary CaCO3 accumulation rates for the region. The calcification rate of the Gulf of Aden was estimated by the Rayleigh model to be ∼1/2 of the Red Sea, and in the northwestern Indian Ocean, it was smaller than our detection limit. The results of this study suggest that variations of major ions on a basin scale may potentially help in assessing long-term effects of ocean acidification on carbonate deposition by marine organisms.
NOAA, partners provide real-time ocean acidification data to Pacific coast shellfish growers
Published 21 November 2014 Media coverage ClosedNew portal builds on NOAA’s commitment to provide public access to data from observational network.
Shellfish farms and hatcheries along the Pacific U.S. coast can now get real-time, online ocean acidification data through the Integrated Ocean Observation System (IOOS), a NOAA-led national-regional partnership working to provide new tools and forecasts to improve safety, enhance the economy, and protect the environment. The data, ranging from carbon dioxide concentrations to salinity and water temperatures can be found through the IOOS Pacific Region Ocean Acidification Data Portal which began operations this month.
“This new portal provides critical environmental intelligence to researchers, coastal managers, and end users such as shellfish aquaculture farms,” said Libby Jewett, Ph.D., director of NOAA’s Ocean Acidification Program. “We hope that the data gathered through this system, combined with on-going research, can help NOAA and our partners provide information to support effective adaptation strategies and other coastal resource decision making.”
40 years of scratching reveals ocean acidification data
Published 21 November 2014 Media coverage ClosedAs carbon dioxide levels increase due largely to human emissions, the world’s oceans are becoming highly corrosive to a number of organisms that call it home. But the rate of acidification and related changes are anything but uniform. That’s why a new study aims to set a baseline for nearly every patch of saltwater from sea to acidifying sea so that future acidification and its impacts can be better monitored.
Taro Takahashi, a geochemist at Lamont-Doherty Earth Observatory who authored the new study in Marine Chemistry, said it has been a decades-long process to compile enough data about ocean acidification to effectively set a benchmark.
Think of the ocean as a giant scratch ticket and the ships and research stations in Bermuda, Hawaii, Iceland and elsewhere as a coin used to slowly scratch away at the surface, revealing just how much the ticket is worth. It took 40 years of scratching but now there’s finally enough data in Takahashi’s eyes to set an accurate baseline.
Continue reading ’40 years of scratching reveals ocean acidification data’
Quantifying the relative importance of transcellular and paracellular ion transports to coral polyp calcification
Published 21 November 2014 Science ClosedTags: biogeochemistry, biological response, calcification, corals, globalmodeling, laboratory, modeling, physiology
Ocean acidification due to rising atmospheric pCO2 slows down coral calcification and impedes reef formation, with deleterious consequences for the diversity of reef ecosystems. Such effects contrast with the capacity of corals to actively regulate the chemical composition of the calcifying fluid where calcification occurs. This regulation involves the active transport of calcium, bicarbonate, and hydrogen ions through epithelium cells, the transcellular pathway. Ions can also passively diffuse through intercellular spaces via the paracellular pathway, which directly exposes the calcifying fluid to changes in ocean chemistry. Although evidence exists for both pathways, their relative contribution to coral calcification remains unknown. Here we use a mathematical model to test the plausibility of different calcification mechanisms also in relation to ocean acidification. We find that the paracellular pathway generates an efflux of calcium and carbonate from the calcifying fluid, causing a leakage of ions that counteracts the concentration gradients maintained by the transcellular pathway. Increasing ocean acidity exacerbates this carbonate leakage and reduces the ability of corals to accrete calcium carbonate.
Ocean acidification crumbling the shells of the sea
Published 20 November 2014 Media coverage Closed
Photo by C. Vonderhaar
If there is one thing we know from the history of life on Earth, it is that the oceans are resilient and relentless. Nearly four billion years ago the first raindrops fell from our cooling planet, accumulating in low basins and forming the first oceans. It is from these oceans that the first forms of life emerged and then continued to grow, expand and evolve. Over four billion years, they endured centuries of change, differing compositions of gaseous atmospheres, and yet they still held the capacity to support the evolution of life – a process that created the most complex and conscious being to stand upright and walk this planet: the oceans gave rise to us.
Just as life has changed in the past, the planet continues to change today. Yet there is vastly marked difference. No longer is the ocean changing on a scale of geological time – tens of millions of years; the ocean is changing at a rate faster than it has ever seen. This has a singularly human cause: our rapid increase in carbon dioxide emissions. These rising levels of carbon dioxide alter not only the temperature of the planet, shifting our climate in ways that scientists call climate change, but also the chemistry of the ocean in a process known as ocean acidification.
Continue reading ‘Ocean acidification crumbling the shells of the sea’
Evaluating the economic damage of climate change on global coral reefs
Published 20 November 2014 Science ClosedTags: biological response, corals, multiple factors, socio-economy, temperature
This paper evaluates the global economic damage arising from the effects of climate change and associated carbon dioxide concentrations on the loss of coral reefs. We do this by first estimating the effects of sea surface temperature and carbon dioxide concentrations on coral cover. We develop a statistical relationship between coral coverage and sea surface temperature that indicates that the effects are dependent on the temperature range. For example, we find that increasing sea surface temperature causes coral coverage to decrease when sea surface temperature is higher than 26.85 °C, with the estimated reduction being 2.3% when sea surface temperature increases by 1%. In addition, we find that a 1% carbon dioxide increase induces a 0.6% reduction in global coral coverage. We also estimate the resultant loss in economic value based on a meta-analysis of the recreational and commercial value of reef coverage and a crude proportional approach for other value factors. The meta-analysis shows that the coral reef value decreases by 3.8% when coral cover falls by 1%. By combining these two steps we find that the lost value in terms of the global coral reef value under climate change scenarios ranges from US$3.95 to US$23.78 billion annually.
Continue reading ‘Evaluating the economic damage of climate change on global coral reefs’
Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin
Published 20 November 2014 Science ClosedTags: biological response, BRcommunity, chemistry, field, multiple factors, North Atlantic, oxygen, physiology, primary production, respiration, sediment
Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification signal induced by increasing atmospheric pCO2. The development of eutrophication-induced hypoxia intensifies coastal acidification, since the CO2 produced during respiration decreases the buffering capacity of the hypoxic bottom water. To assess the combined ecosystem impacts of acidification and hypoxia, we quantified the seasonal variation in pH and oxygen dynamics in the water column of a seasonally stratified coastal basin (Lake Grevelingen, the Netherlands).
Monthly water column chemistry measurements were complemented with estimates of primary production and respiration using O2 light-dark incubations, in addition to sediment-water fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA). The resulting dataset was used to set up a proton budget on a seasonal scale.
Temperature-induced seasonal stratification combined with a high community respiration was responsible for the depletion of oxygen in the bottom water in summer. The surface water showed strong seasonal variation in process rates (primary production, CO2 air–sea exchange), but relatively small seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In contrast, the bottom water showed less seasonality in biogeochemical rates (respiration, sediment–water exchange), but stronger pH fluctuations (0.60 units). This marked difference in pH dynamics could be attributed to a substantial reduction in the acid-base buffering capacity of the hypoxic bottom water in the summer period. Our results highlight the importance of acid-base buffering in the pH dynamics of coastal systems and illustrate the increasing vulnerability of hypoxic, CO2-rich waters to any acidifying process.
Promoting international collaboration on ocean acidification data management
Published 20 November 2014 Meetings , Science ClosedOcean acidification, often referred to as “the other carbon dioxide problem,” is the progressive increase in ocean acidity that has taken place since the onset of the industrial revolution. Biological and ecological studies of ocean acidification impacts only began in the late 1990s, but the field has evolved rapidly, with exponential growth in the past decade. For example, 374 papers on this subject were published in 2013, compared with only 18 in 2004 (see http://tinyurl.com/oaicc-biblio).
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Studentship: Carbonate chemistry, ocean acidification and CO2 exchange in the Canadian Arctic, McGill University, Canada
Published 20 November 2014 Jobs ClosedThe Department of Earth and Planetary Sciences of the McGill University seeks Ph.D. and M.Sc. students to participate in a large-scale study of processes that modulate the spatial and temporal variability of the pCO2 gradient at the air-sea interface and exchange of CO2 with sub-thermocline waters and across oceanic basins. The project will be part of the NSERC Canadian Climate Change and Atmospheric Research program GEOTRACES (http://www.geotraces.org/) and the ArcticNet Network of Centers of Excellence (http://www.arcticnet.ulaval.ca/).
The student(s) will receive a minimum of $17,000CAN per year in living expenses for the prescribed period of residency (4 years at the Ph.D., 2 years at the M.Sc.)) and will have the opportunity to participate to international conferences to present results of the project. Knowledge of the Ocean Data View software, MATLAB and the optimum multi-parameter algorithm (OMP) would be an asset.
Photo by G. Bould
It has long been suspected that rising temperatures and ocean acidification are making it harder for crabs to reproduce and survive. However, aside from weakening exoskeletons, it was unclear exactly why this was happening. Now, a new study suggests it comes down to these crustaceans’ own biology.
That’s at least according to a new study published in The Journal of Experimental Biology, which details how the vulnerable porcelain crab (Petrolisthes cinctipes) has recently had to put a great deal more energy into basic survival functions than it used to, leaving less energy for other behavior.
And when we say “basic functions,” we mean extremely basic. The crab, which lives in rocky shorelines along the Indian and Pacific Oceans, was observed laboring to just eat and breathe from day to day, often too tired to hide from predators or reproduce.
Continue reading ‘Changing oceans put crabs into ‘survival mode’’
According to the results of a major new national survey published by the University, the majority of the British public has a very low awareness of the issue of ocean acidification, with around only one-in-five participants stating they had even heard of the issue.
The oceans are currently absorbing large quantities of the carbon dioxide which has been emitted into the atmosphere from human activities. This absorption of CO2 is leading to a reduction in the pH of seawater – termed ‘ocean acidification’. According to the recent Intergovernmental Panel on Climate Change, ocean acidification is the hidden face of increasing global carbon emissions and poses a future threat to a range of marine ecosystems and the societies which depend upon them.
Although many other aspects of global climate change are readily recognised by the general public, we know far less about how they view ocean acidification. Researchers from the School of Psychology have conducted the first comprehensive survey of the British public’s views on this topic, interviewing over 2,500 people across the country.
Public perceptions of ocean acidification: summary findings of two nationally representative surveys of the British public, October 2014
Published 18 November 2014 Newsletters and reports ClosedThe oceans are absorbing large quantities of the carbon dioxide (CO2) which has been emitted into the atmosphere from human activities. This absorption of CO2 is leading to a reduction in the pH of seawater – termed ‘ocean acidification’ (OA) – with consequences for marine ecosystems and the societies which depend upon them. Ocean acidification and climate change are closely related phenomena, however to date OA has received far less attention as a subject of policy and public concern.
We currently know very little about how the British public perceives the problem of ocean acidification. We report the findings of two online representative surveys of the British public (aged 18-80 years) on this topic conducted pre- and then post- the recent round of Inter-Governmental Panel on Climate Change (IPCC) 5th assessment reporting.
The first fieldwork (Phase 1) took place during September 2013 (n= 1,001) and the second (Phase 2) during May 2014 (n= 1,500). This research was funded as part of the UK Ocean Acidification Research Programme (UKOA) of the Natural Environment Research Council. (…)
Synergistic effects of acute warming and low pH on cellular stress responses of the gilthead seabream Sparus aurata
Published 18 November 2014 Science ClosedTags: biological response, fish, laboratory, Mediterranean, mortality, multiple factors, physiology, temperature
The present study assesses the resilience of the Mediterranean gilthead seabream (Sparus aurata) to acute warming and water acidification, using cellular indicators of systemic to molecular responses to various temperatures and CO2 concentrations. Tissue metabolic capacity derived from enzyme measurements, citrate synthase, 3-hydroxyacyl CoA dehydrogenase (HOAD), as well as lactate dehydrogenase. Cellular stress and signaling responses were identified from expression patterns of Hsp70 and Hsp90, the phosphorylation of p38 MAPK, JNKs and ERKs, from protein ubiquitylation and finally from the levels of transcription factor Hif-1α as an indicator of systemic hypoxemia. Exposure to elevated CO2 levels at temperatures higher than 24 °C generally caused an increase in fish mortality above the rate caused by warming alone, indicating effects of the two factors and a failure of acclimation and thus the limits of phenotypic plasticity to be reached. As a potential reason, tissue-dependent induction and stabilization of Hif-1α indicate hypoxemic conditions. Their exacerbation by enhanced CO2 levels is linked to the persistent expression of Hsp70 and Hsp90, oxidative stress and activation of MAPK and ubiquitin pathways. Antioxidant defence is enhanced by expression of catalase and glutathione reductase, however, leaving superoxide dismutase suppressed by elevated CO2 levels. On longer timescales in specimens surviving warming and CO2 exposures, various metabolic adjustments initiate a preference to oxidize lipid via HOAD for energy supply. These processes indicate significant acclimation up to a limit and a time-limited capacity to survive extreme conditions passively by exploiting mechanisms of cellular resilience.
Coral macrobioerosion is accelerated by ocean acidification and nutrients
Published 18 November 2014 Science ClosedTags: biological response, chemistry, corals, dissolution, laboratory, multiple factors, nutrients
Coral reefs exist in a delicate balance between calcium carbonate (CaCO3) production and CaCO3 loss. Ocean acidification (OA), the CO2-driven decline in seawater pH and CaCO3 saturation state (Ω), threatens to tip this balance by decreasing calcification and increasing erosion and dissolution. While multiple CO2 manipulation experiments show coral calcification declines under OA, the sensitivity of bioerosion to OA is less well understood. Previous work suggests that coral and coral-reef bioerosion increase with decreasing seawater Ω. However, in the surface ocean, Ω and nutrient concentrations often covary, making their relative influence difficult to resolve. Here, we exploit unique natural gradients in Ω and nutrients across the Pacific basin to quantify the impact of these factors, together and independently, on macrobioerosion rates of coral skeletons. Using an automated program to quantify macrobioerosion in three-dimensional computerized tomography (CT) scans of coral cores, we show that macrobioerosion rates of live Porites colonies in both low-nutrient (oligotrophic) and high-nutrient (>1 μM nitrate) waters increase significantly as Ω decreases. However, the sensitivity of macrobioerosion to Ω is ten times greater under high-nutrient conditions. Our results demonstrate that OA (decreased Ω) alone can increase coral macrobioerosion rates, but the interaction of OA with local stressors exacerbates its impact, accelerating a shift toward net CaCO3 removal from coral reefs.
Continue reading ‘Coral macrobioerosion is accelerated by ocean acidification and nutrients’
The combined effect of temperature and pH on embryonic development of obscure puffer Takifuguobscurus and its ecological implications
Published 18 November 2014 Science ClosedTags: biological response, fish, laboratory, multiple factors, performance, reproduction, temperature
Rising temperature and decreasing pH caused by climate change may affect the development of fish. The objective of this study was to determine the combined effects of temperature (19, 22, 25, 28 °C) and pH (5, 6, 7, 8) on incubation time, total hatch rate, abnormal rate, and viability of newly hatched larvae 24 h post-hatch of obscure puffer Takifugu obscurus fertilized eggs. The results showed that incubation time was significantly shortened with increase in temperature and delayed at low pH. Significant interaction was detected between temperature and pH on incubation time. Both temperature and pH significantly affected the total hatch rate, abnormal rate, and the viability of newly hatched larvae, but no significant interaction was detected. Such results indicated that fluctuations in temperature and decreasing pH in waters during the spawning season of this anadromous species may have substantially negative impacts on its population recruitment and persistence.
