An in situ assessment of local adaptation in a calcifying polychaete from a shallow CO2 vent system

Ocean acidification (OA) is likely to exert selective pressure on natural populations. Our ability to predict which marine species will adapt to OA, and what underlies this adaptive potential, are of high conservation and resource management priority. Using a naturally low pH vent site in the Mediterranean Sea (Castello Aragonese, Ischia) mirroring projected future OA conditions, we carried out a reciprocal transplant experiment to investigate the relative importance of phenotypic plasticity and local adaptation in two populations of the sessile, calcifying polychaete Simplaria sp. (Annelida, Serpulidae, Spirorbinae): one residing in low pH and the other from a nearby ambient (i.e. high) pH site. We measured a suite of fitness related traits (i.e. survival, reproductive output, maturation, population growth) and tube growth rates in laboratory-bred F2 generation individuals from both populations reciprocally transplanted back into both ambient and low pH in situ habitats. Both populations showed lower expression in all traits, but increased tube growth rates, when exposed to low pH compared to high pH conditions, regardless of their site of origin suggesting that local adaptation to low pH conditions has not occurred. We also found comparable levels of plasticity in the two populations investigated, suggesting no influence of long-term exposure to low pH on the ability of populations to adjust their phenotype. Despite high variation in trait values among sites and the relatively extreme conditions at sites close to the vents (pH < 7.36), response trends were consistent across traits. Hence, our data suggest that, for Simplaria and possibly other calcifiers, neither local adaptations nor sufficient phenotypic plasticity levels appear to suffice in order to compensate for the negative impacts of OA on long-term survival. Our work also underlines the utility of field experiments in natural environments subjected to high level of pCO2 for elucidating the potential for adaptation to future scenarios of OA.

Continue reading ‘An in situ assessment of local adaptation in a calcifying polychaete from a shallow CO2 vent system’

Ocean acidification reduces transfer of essential biomolecules in a natural plankton community

Ocean acidification (OA), a process of increasing seawater acidity caused by the uptake of anthropogenic carbon dioxide (CO2) by the ocean, is expected to change surface ocean pH to levels unprecedented for millions of years, affecting marine food web structures and trophic interactions. Using an in situ mesocosm approach we investigated effects of OA on community composition and trophic transfer of essential fatty acids (FA) in a natural plankton assemblage. Elevated pCO2 favored the smallest phytoplankton size class in terms of biomass, primarily picoeukaryotes, at the expense of chlorophyta and haptophyta in the nano-plankton size range. This shift in community composition and size structure was accompanied by a decline in the proportion of polyunsaturated FA (PUFA) to total FA content in the nano- and picophytoplankton size fractions. This decline was mirrored in a continuing reduction in the relative PUFA content of the dominant copepod, Calanus finmarchicus, which primarily fed on the nano-size class. Our results demonstrate that a shift in phytoplankton community composition and biochemical composition in response to rising CO2 can affect the transfer of essential compounds to higher trophic levels, which rely on their prey as a source for essential macromolecules.

Continue reading ‘Ocean acidification reduces transfer of essential biomolecules in a natural plankton community’

Thermal and pCO2 stress elicit divergent transcriptomic responses in a resilient coral

The oceans are becoming warmer and more acidic as a result of rising atmospheric pCO2. Transcriptome plasticity may facilitate marine organisms’ acclimation to thermal and acidification stress by tailoring gene expression to mitigate the impacts of these stressors. Here, we produce the first transcriptome of the abundant, ubiquitous, and resilient Caribbean reef-building coral Siderastrea siderea, and investigate this corals’ transcriptomic response to 95 days of thermal (T = 25, 28, 32°C) and CO2-induced acidification (324, 477, 604, 2553 µatm) stress. The S. siderea transcriptome was assembled using RNAseq and then Weighted Gene Correlation Network Analysis was employed to obtain systems-level insights into the coral’s stress response. Exposure of the coral to both elevated temperature and acidification elicited strong but divergent transcriptomic responses. Gene Ontology analysis suggests that long-term thermal stress disrupts homeostasis by increasing transcription of protein-coding genes associated with protein catabolism and suppressing transcription of genes involved in responding to environmental stimuli. Both next century (604 µatm) and extreme-high (2553 µatm) pCO2 stress increased transcription of genes associated with respiration, highlighting the potentially greater energetic requirements of maintaining calcification under high-pCO2 conditions. Under extreme-high-pCO2, increased transcription of H+-transporter genes was observed, consistent with the proposed role of proton transport in facilitating coral calcification under elevated pCO2. These results suggest that 95 days of exposure to 32°C seawater elicits a more adverse transcriptomic response (i.e., broad scale reductions in gene expression) than exposure to extreme-high acidification (2553 µatm; i.e., increased expression of genes associated with ion transport) within S. siderea—with the response to extreme warming suggesting cellular shutdown and the response to extreme acidification indicating capacity for acclimation. These results are consistent with the observation that rates of net calcification for the investigated corals were more negatively affected by the prescribed thermal stress than by the prescribed acidification stress. This study demonstrates how transcriptome plasticity may promote coral acclimation to these global change stressors, but that there are limits to the efficacy of this plasticity.
Continue reading ‘Thermal and pCO2 stress elicit divergent transcriptomic responses in a resilient coral’

The EPOCA information outlet morphs into the OA-ICC news stream

This news stream (also known as the “ocean acidification blog”) is going to change hands. I started this information outlet in July 2006 as a “one man” effort. From May 2008 to August 2012 it was a product of the European Project on Ocean Acidification (EPOCA), and has been endorsed by the IMBER and SOLAS projects in January 2010.

Here are a few numbers:

  • 5334 posts have been published since 2006
  • 654,159 views from 185 countries
  • 743 subscribers through RSS or email
  • 451 Twitter followers
  • an unknown number of FaceBook friends

Quite frankly, I did not anticipate such a tremendous success when I launched the blog. It obviously fulfils a need. However, it is time for me to move on to other challenges but I did not want to just pull the plug. I am happy that the perfect arrangement was found to continue this service.

This blog is going to be taken over and managed by the Ocean Acidification International Coordination Centre (OA-ICC), based at the Environmental Laboratories of the International Atomic Energy Agency (IAEA) in Monaco, with the goal to continue serving all ocean acidification actors and end-users, including the scientific community, decision-makers and the general public. I will remain involved in the editorial supervision but the day-to-day management will be in the very capable hands of Lina Hansson. SOLAS and IMBER will remain strongly involved through their close partnership with the OA-ICC.

In the following blog post, Lina Hansson will provide information on the, hopefully smooth, transition on WordPress, Twitter and FaceBook.

The past 7 years have been very fulfilling and I am very proud to have helped the research community by highlighting publications and disseminating news on ocean acidification. I am convinced that the new set-up will continue to provide a similar, or even better, service.

Thank you very much to the whole readership!

Jean-Pierre Gattuso
CNRS and Université Pierre et Marie Curie-Paris 6

Ocean acidification blog: 2012 in review

Dear Blog Addicts,

Lina Hansson and I wish all the best for 2013 to all readers of the EPOCA blog! We thank you all for your interest. Even though EPOCA came to an end in June 2012, we have been able to maintain this blog, partly thanks to support from the International Atomic Energy Agency (IAEA). The blog will soon be transferred to the Ocean Acidification International Coordination Centre and operated from IAEA. We hope that the transition will be smooth; stay tuned for more information.

Here are a few numbers:

  • 4584 posts have been published since 2006 (about 1198 in 2012)
  • 653 subscribers through RSS or email (up from 570 in 2011)
  • 376 Twitter followers (up from 270 in 2011)
  • an unknown number of FaceBook friends

The stats helper monkeys prepared a 2012 annual report for this blog: click here to see the complete report.

I remind you below the content of the “About” page and, also, that comments are always welcome. Just type your comment in the box located below each article. Note that comments are moderated.

Jean-Pierre Gattuso
EPOCA Scientific Coordinator (until June 2012)

Jean-Pierre Gattuso |

This blog was started in July 2006 as a “one man” effort. It is a product of EPOCA, the European Project on Ocean Acidification since May 2008 and it is sponsored by the IMBER and SOLAS projects since January 2010. Its only ambition is to centralize information available on ocean acidification and its consequences on marine organisms and ecosystems. By no means it is meant to be comprehensive but we are trying to provide an unbiased view of the literature and media articles. The owner of this blog, the European Commission and the sponsoring organizations do not endorse the information published.

This blog is coordinated by:

Jean-Pierre Gattuso, CNRS Senior Research Scientist
CNRS-Université Pierre et Marie Curie Paris 6, France
Email: gattuso at
Web site

Contributors are:

  • Jean-Pierre Gattuso, EPOCA coordinator (gattuso at
  • Lina Hansson, EPOCA Project Manager (hansson at
  • Anne-Marin Nisumaa (Until May 2012), EPOCA Information Technology Manager (nisumaa at

Acid ocean

Marine scientists across the world are hunting for clues to one of the greatest environmental catastrophes facing our planet. For years we’ve known the ocean absorbs about a third of the carbon dioxide (CO2) in the atmosphere – but as CO2 levels continue to rise the ocean’s chemistry is changing and becoming more acidic.

In increasingly acidic waters, marine animals can’t form the skeletons and shells vital for their survival. From the planet’s poles to the tropics, thousands of species are in danger.

Continue reading ‘Acid ocean’

Marine invertebrate skeleton size varies with latitude, temperature, and carbonate saturation: implications for global change and ocean acidification

There is great concern over the future effects of ocean acidification on marine organisms, especially for skeletal calcification, yet little is known of natural variation in skeleton size and composition across the globe, and this is a prerequisite for identifying factors currently controlling skeleton mass and thickness. Here taxonomically-controlled latitudinal variations in shell morphology and composition were investigated in bivalve and gastropod molluscs, brachiopods and echinoids. Total inorganic content, a proxy for skeletal CaCO3, decreased with latitude, decreasing seawater temperature and decreasing seawater carbonate saturation state (for CaCO3 as calcite (Ωcal)) in all taxa. Shell mass decreased with latitude in molluscs and shell inorganic content decreased with latitude in buccinid gastropods. Shell thickness decreased with latitude in buccinid gastropods (excepting the Australian temperate buccinid) and echinoids, but not brachiopods and laternulid clams. In the latter the polar species had the thickest shell. There was no latitudinal trend in shell thickness within brachiopods. The variation in trends in shell thickness by taxon suggests that in some circumstances ecological factors may override latitudinal trends. Latitudinal gradients may produce effects similar to those of future CO2-driven ocean acidification on CaCO3 saturation state. Responses to latitudinal trends in temperature and saturation state may therefore be useful in informing predictions of organism responses to ocean acidification over long-term adaptive timescales.

Continue reading ‘Marine invertebrate skeleton size varies with latitude, temperature, and carbonate saturation: implications for global change and ocean acidification’

Ocean acidification weakens the structural integrity of coralline algae

The uptake of anthropogenic emission of carbon dioxide is resulting in a lowering of the carbonate saturation state and a drop in ocean pH. Understanding how marine calcifying organisms such as coralline algae may acclimatize to ocean acidification is important to understand their survival over the coming century. We present the first long-term perturbation experiment on the cold-water coralline algae, which are important marine calcifiers in the benthic ecosystems particularly at the higher latitudes. Lithothamnion glaciale, after three months incubation, continued to calcify even in undersaturated conditions with a significant trend towards lower growth rates with increasing pCO2. However, the major changes in the ultra-structure occur by 589 μatm (i.e. in saturated waters). Finite element models of the algae grown at these heightened levels show an increase in the total strain energy of nearly an order of magnitude and an uneven distribution of the stress inside the skeleton when subjected to similar loads as algae grown at ambient levels. This weakening of the structure is likely to reduce the ability of the alga to resist boring by predators and wave energy with severe consequences to the benthic community structure in the immediate future (50 years).

Continue reading ‘Ocean acidification weakens the structural integrity of coralline algae’

Questionnaire, ocean acidification observing network

To document the status and progress of ocean acidification in open-ocean and coastal environments and to understand its drivers and impacts on marine ecosystems, it will be necessary to develop a coordinated multidisciplinary multinational approach for observations. In partnership with the NOAA Ocean Acidification Program, the International Ocean Carbon Coordination Project, and the Global Ocean Observing System, the University of Washington is hosting a workshop on June 2628th to take steps to develop a global ocean acidification monitoring network.

Continue reading ‘Questionnaire, ocean acidification observing network’

Expert review, Working Group of IPCC 5th Assessment Report

Working Group II (WGII) of the Intergovernmental Panel on Climate Change (IPCC) is pleased to announce that the first-order drafts of its contribution to the IPCC Fifth Assessment Report (AR5), Climate Change 2013: Impacts, Adaptation, and Vulnerability, will be available for formal review from 11 June to 6 August 2012. The WGII Technical Support Unit (TSU) is accepting pre-registrations for the Expert Review until 10 June 2012.

Continue reading ‘Expert review, Working Group of IPCC 5th Assessment Report’

Growth of cultured giant clams (Tridacna spp.) in low pH, high-nutrient seawater: species-specific effects of substrate and supplemental feeding under acidification

Four species of giant clams, Tridacna maxima, T. squamosa, T. derasa and T. crocea, were cultured in outdoor raceways for 364 days at the Waikīkī Aquarium and the Oceanic Institute on the island of O‘ahu, Hawai‘i, USA.  Growth of each species was compared among individuals grown with and without supplemental phytoplankton feeding, and directly on the substrate or mounted on concrete plugs in low pH, high nutrient seawater.  Among clams cultured with and without supplemental phytoplankton (Chaetoceros spp.), feeding resulted in significantly lower mortality in all species but T. deresa, whereas growth was significantly higher among fed clams for all species except T. squamosa. Tridacna derasa showed roughly a three-fold increase in growth when fed (88.5 g ± 4.4 SD) than when unfed (26.0 g ± 2.1 SD), whereas T. maxima growth was substantially lower, but nearly 10-fold greater in response to feeding (9.0 g ± 1.9 SD). The overall mortality rate of juvenile clams was significantly lower in the fed (44.4 ± 10.0%) than the unfed (71.8 ± 9.6%) trials, with the greatest effect observed in mortality of T. maxima (fed 15% versus unfed 80%) and T. squamosa (fed 65% versus unfed 95%). None of the T. squamosa remained on concrete plugs for the duration of the experiment. Among the remaining three species, there was no difference in either wet weight or shell length for T. maxima and for wet weight only in T. derasa on (186.5 g ± 16.1 SD) and off (147.0 g ± 6.0 SD) the concrete plugs.  In contrast, T. crocea had significantly greater shell growth off the plugs (14.3 mm ± 1.0 SD versus 8.5 mm ± 1.7 SD) but significantly greater gain in wet weight on the concrete plugs (26.3 g ± 1.5 SD versus 58.5 g ± 2.5 SD).  The seawater wells used for this study are well characterized with elevated levels of inorganic nutrients and higher pCO2 relative to tropical ocean waters, roughly approximating predictions for future oceanic conditions under IPCC IS92a emission scenarios. In comparison to previous studies in natural seawater, T. derasa had a significantly higher shell growth rate in the high-nutrient, low-pH well water.  In contrast, T. maxima and T. squamosa had significantly lower growth rates in low pH, whereas growth of T. crocea was not significantly different between low pH and ambient seawater.  These experiments demonstrate species-specific differences with each treatment, which cautions against making broad generalizations regarding the effects of substrate type, feeding effects, nutrient enrichment, and ocean acidification on tridacnid culture and survival.

Continue reading ‘Growth of cultured giant clams (Tridacna spp.) in low pH, high-nutrient seawater: species-specific effects of substrate and supplemental feeding under acidification’

Productivity response of calcareous nannoplankton to Eocene Thermal Maximum 2 (ETM2)

The Early Eocene Thermal Maximum 2 (ETM2) at ~53.7 Ma is one of multiple hyperthermal events that followed the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma). The negative carbon excursion and deep ocean carbonate dissolution which occurred during the event imply that a substantial amount (103 Gt) of carbon (C) was added to the ocean-atmosphere system, consequently increasing atmospheric CO2 (pCO2). This makes the event relevant to the current scenario of anthropogenic CO2 additions and global change. Resulting changes in ocean stratification and pH, as well as changes in exogenic cycles which supply nutrients to the ocean, may have affected the productivity of marine phytoplankton, especially calcifying phytoplankton. Changes in productivity, in turn, may affect the rate of sequestration of excess CO2 in the deep ocean and sediments. In order to reconstruct the productivity response by calcareous nannoplankton to ETM2 in the South Atlantic (Site 1265) and North Pacific (Site 1209), we employ the coccolith Sr/Ca productivity proxy with analysis of well-preserved picked monogeneric populations by ion probe supplemented by analysis of various size fractions of nannofossil sediments by ICP-AES. The former technique of measuring Sr/Ca in selected nannofossil populations using the ion probe circumvents possible contamination with secondary calcite. Avoiding such contamination is important for an accurate interpretation of the nannoplankton productivity record, since diagenetic processes can bias the productivity signal, as we demonstrate for Sr/Ca measurements in the fine (

Continue reading ‘Productivity response of calcareous nannoplankton to Eocene Thermal Maximum 2 (ETM2)’

The effect of chronic and acute low pH on the intracellular DMSP production and epithelial cell morphology of red coralline algae

The release of dimethylsulphoniopropionate (DMSP) by marine algae has major impacts on the global sulphur cycle and may influence local climate through the formation of dimethylsulphide (DMS). However, the effect of global change on DMSP/DMS (DMS(P)) production by algae is not well understood. This study examined the effect of low pH on DMS(P) production and epithelial cell morphology of the free-living red coralline alga Lithothamnion glaciale. Three pH treatments were used in the 80-day experiment: (1) current pH level (8.18, control), (2) low, chronic pH representing a 2100 ocean acidification (OA) scenario (7.70) and (3) low, acute pH (7.75, with a 3-day spike to 6.47), representing acute variable conditions that might be associated with leaks from carbon capture and storage infrastructure, at CO2 vent sites or in areas of upwelling. DMS(P) production was not significantly enhanced under low, stable pH conditions, indicating that red coralline algae may have some resilience to OA. However, intracellular and water column DMS(P) concentrations were significantly higher than the control when pH was acutely spiked. Cracks were observed between the cell walls of the algal skeleton in both low pH treatments. It is proposed that this structural change may cause membrane damage that allows DMS(P) to leak from the cells into the water column, with subsequent implications for the cycling of DMS(P) in coralline algae habitats.

Continue reading ‘The effect of chronic and acute low pH on the intracellular DMSP production and epithelial cell morphology of red coralline algae’

Arctic study of ocean acidification impacts

As the UK approaches summer with high hopes of good weather, a team of adventurous scientists will be setting sail for far chillier climes. Thirty researchers from eight laboratories will leave the UK on 1st June 2012 to study the effect of ocean acidification on the Norwegian, Barents and Greenland Seas.

They will travel as far north as polar ice will allow, collecting seawater samples from both the open water and gaps in the sea-ice. This study is the largest ever to examine the effects of altering carbon dioxide (CO2) levels in “real world” seawater samples directly after they are collected at sea.

Polar seas are expected to be especially sensitive to the effects of ocean acidification, since more CO2 dissolves in cold water, making Arctic waters a valuable natural example of how the marine environment will respond to a high CO2 world. Also, the chemical sensitivity of surface seawater in the Arctic means that it will become corrosive to calcium carbonate before anywhere else in the world. This could pose a serious problem for marine plankton and other organisms that use calcium carbonate for theirshells or skeletons.

During the expedition, the scientists will study the impact of the changing chemistry on marine organisms and ecosystems, the cycling of carbon and nutrients in the sea and how the sea interacts with the atmosphere to influence climate.

Two approaches will be used in this study. Firstly, the researchers will look at how ecosystems vary between areas where the chemistry of seawater is naturally more acidic or alkaline. By contrasting the observations over a range of different conditions, insights researchers will discover how acidification may affect organisms living in their natural environment, where natural selection and adaptation have had time to play out.

The second approach is experimental, using tanks of natural seawater collected from the upper ocean and brought into controlled conditions on deck. This natural seawater will be subjected to various levels of CO2 that are likely to occur in the future. The expedition, aboard the RRS James Clark Ross, will end on 4th July in Reykjavik, Iceland and members of the team will be blogging about their progress at

Dr Ray Leakey, Arctic Research Theme Leader at the Scottish Association for Marine Science (SAMS) and the leader of the current expedition says, “Few studies have investigated the effects of ocean acidification on the marine food web of the remote Arctic seas, and most have focused on laboratory cultures or natural communities from a limited number of relatively accessible coastal locations. By contrast our expedition will be by ship in both ice-covered and ice-free oceanic waters far from land. This will allow us to undertake the most comprehensive study to date of the ways in which the plants and animals living in the surface waters of the Arctic ocean respond to acidification.”

Dr Toby Tyrrell from the National Oceanography Centre and coordinator of the Sea Surface consortium added, “Following our cruise last year to the northwest European shelf (for more information please see Notes to Editors), this second cruise will visit the more remote Arctic Ocean which may well be more seriously affected by ocean acidification. The data collected will improve our understanding of future impacts, providing important information about the consequences of continuing to burn fossil fuels in enormous quantities (atmospheric CO2 is already 40% above its preindustrial level, and still climbing). Our final cruise, in 6 months time, will visit the other polar ocean, the Southern Ocean.”

The global ocean has absorbed about a third of the total CO2 produced by human activities in the past 200 years. This uptake of CO2 has greatly slowed the rate of human-driven climate change. It is also responsible for major changes to ocean chemistry, known as ocean acidification, with potentially serious implications for marine life.

The research is part of the UK Ocean Acidification Research Programme (UKOA), funded by the Natural Environment Research Council (NERC), the Department of Environment, Food and Rural Affairs (Defra) and the Department of Energy and Climate Change (DECC).
Continue reading ‘Arctic study of ocean acidification impacts’

Gene transcripts encoding hypoxia-inducible factor (HIF) exhibit tissue- and muscle fiber type-dependent responses to hypoxia and hypercapnic hypoxia in the Atlantic blue crab, Callinectes sapidus

Hypoxia inducible factor (HIF) is a transcription factor that under low environmental oxygen regulates the expression of suites of genes involved in metabolism, angiogenesis, erythropoiesis, immune function, and growth. Here, we isolated and sequenced partial cDNAs encoding hif-α and arnt/hif-β from the Atlantic blue crab, Callinectes sapidus, an estuarine species that frequently encounters concurrent hypoxia (low O2) and hypercapnia (elevated CO2). We then examined the effects of acute exposure (1 hr) to hypoxia (H) and hypercapnic hypoxia (HH) on relative transcript abundance for hif-α and arnt/hif-β in different tissues (glycolytic muscle, oxidative muscle, hepatopancreas, gill, and gonads) using quantitative real-time RT-PCR. Our results indicate that hif-α and arnt/hif-β mRNAs were constitutively present under well-aerated normoxia (N) conditions in all tissues examined. Further, H and HH exposure resulted in both tissue-specific and muscle fiber type-specific effects on relative hif-α transcript abundance. In the gill and glycolytic muscle, relative hif-α mRNA levels were significantly lower under H and HH, compared to N, while no change (or a slight increase) was detected in oxidative muscle, hepatopancreas and gonadal tissues. H and HH did not affect relative transcript abundance for arnt/hif-β in any tissue or muscle fiber type. Thus, in crustaceans the HIF response to H and HH appears to involve changes in hif transcript abundance, with variation in hif-α and arnt/hif-β transcriptional dynamics occurring in both a tissue- and muscle fiber type-dependent manner.
Continue reading ‘Gene transcripts encoding hypoxia-inducible factor (HIF) exhibit tissue- and muscle fiber type-dependent responses to hypoxia and hypercapnic hypoxia in the Atlantic blue crab, Callinectes sapidus’

Effect of carbonate chemistry manipulations on calcification, respiration, and excretion of a Mediterranean pteropod

Although shelled pteropods are expected to be particularly sensitive to ocean acidification, the few available studies have mostly focused on polar species and have not allowed determining which parameter of the carbonate system controls their calcification. Specimens of the temperate Mediterranean species Creseis acicula were maintained under seven different conditions of the carbonate chemistry, obtained by manipulating pH and total alkalinity, with the goal to disentangle the effects of the pH and the saturation state with respect to aragonite (Ωa). Our results tend to show that respiration, excretion as well as rates of net and gross calcification were not directly affected by a decrease in pH but decreased significantly with a decrease in Ωa. Due to the difficulties in maintaining pteropods in the laboratory and the important variability in their abundances in our study site, long-term acclimation as well as replication of the experiment was not possible. However, we strongly believe that these results represent an important step in the mechanistic understanding of the effect of ocean acidification on pteropods physiology.

Continue reading ‘Effect of carbonate chemistry manipulations on calcification, respiration, and excretion of a Mediterranean pteropod’

Biochemical, metabolic and morphological responses of the intertidal gastropod Littorina littorea to ocean acidification and increase temperature

Future changes to the pH and temperature of the oceans are predicted to impact the biodiversity of marine ecosystems, particularly those animals that rely on the process of calcification. The marine intertidal gastropod Littorina littorea can be used as a model of intertidal organism for investigating the effects of ocean acidification and high temperature, alone and in combination because its ability to be quickly adapt against environmental stressor. In the first study a single species population of L. littorea was used to test for physiological and biochemical effects underpinning organismal responses to climate change and ocean acidification. Compared with control conditions, snails decreased metabolic rates by 31% in response to elevated pCO2 while by 15% in response to combined pCO2 and temperature. Decreased metabolic rates were associated with metabolic depression, a strategy to match oxygen demand and availability, and an increase in end-product metabolites in the tissue under acidified treatments, indicating an increased reliance on anaerobic metabolism. This study also showed that anthropogenic alteration of CO2 and temperature may also lead to plastic responses, a fundamental mechanism of many marine gastropods to cope environmental variability. At low pH and elevated temperature in isolation or combined showing lower shell growth than individuals kept under control conditions. Percentage change in shell length and thicknesses was also lower under acidified and temperature in isolation or combined than control condition, making shells were more globular and desiccation rates were higher. Further studies to broader latitudinal ranges for six populations of L. littorea showed that shell growth decreased in all six populations under elevated pCO2 compared to control snails particularly those at range edges. Elevated pCO2 also affected to the reduction of shell length and width that causing shell aspect ratio to increase across latitudinal gradients except individuals from Millport, UK. Percentage changes of aperture width and aperture area were also decrease under elevated pCO2 with greater reduction of aperture area were found at populations in the mid-ranges which is assumed this response might be linked to local adaptation of the individual to microclimatic conditions. This study also showed that metabolic rates were negatively affected by high pCO2 and show non-linear trend across latitudinal gradients in compared to individual kept under normal pCO2 conditions. Metabolomic analysis showed that two northern populations of Trondheim and TromsØ were distinct from other populations when exposed to low temperature (15 °C) with elevated pCO2 due to, in part, high concentrations of thymine, uracil, valine and lysine. A similar separation also occurred under medium (25 °C) and high (35 °C) temperature exposure in which one of northern population (Trondheim) was distinct from other populations and had lower concentrations of alanine, betaine and taurine while higher of valine. These results suggest that populations at northern latitudes may apply different ionic transport mechanisms under elevated pCO2 and elevated temperatures and those populations are likely to vary in terms of their physiological responses to this environmental challenge.

Continue reading ‘Biochemical, metabolic and morphological responses of the intertidal gastropod Littorina littorea to ocean acidification and increase temperature’

Marine bivalve shell geochemistry and ultrastructure from modern low pH environments: environmental effect versus experimental bias (update)

Bivalve shells can provide excellent archives of past environmental change but have not been used to interpret ocean acidification events. We investigated carbon, oxygen and trace element records from different shell layers in the mussels Mytilus galloprovincialis combined with detailed investigations of the shell ultrastructure. Mussels from the harbour of Ischia (Mediterranean, Italy) were transplanted and grown in water with mean pHT 7.3 and mean pHT 8.1 near CO2 vents on the east coast of the island. Most prominently, the shells recorded the shock of transplantation, both in their shell ultrastructure, textural and geochemical record. Shell calcite, precipitated subsequently under acidified seawater responded to the pH gradient by an in part disturbed ultrastructure. Geochemical data from all test sites show a strong metabolic effect that exceeds the influence of the low-pH environment. These field experiments showed that care is needed when interpreting potential ocean acidification signals because various parameters affect shell chemistry and ultrastructure. Besides metabolic processes, seawater pH, factors such as salinity, water temperature, food availability and population density all affect the biogenic carbonate shell archive.

Continue reading ‘Marine bivalve shell geochemistry and ultrastructure from modern low pH environments: environmental effect versus experimental bias (update)’

Combined effects of inorganic carbon and light on Phaeocystis globosa Scherffel (Prymnesiophyceae)(update)

Phaeocystis globosa (Prymnesiophyceae) is an ecologically dominating phytoplankton species in many areas around the world. It plays an important role in both the global sulfur and carbon cycles, by the production of dimethylsulfide (DMS) and the drawdown of inorganic carbon. Phaeocystis globosa has a polymorphic life cycle and is considered to be a harmful algal bloom (HAB) forming species. All these aspects make this an interesting species to study the effects of increasing carbon dioxide (CO2) concentrations, due to anthropogenic carbon emissions.

Here, the combined effects of three different dissolved carbon dioxide concentrations (CO2(aq)) (low: 4 μmol kg−1, intermediate: 6–10 μmol kg−1 and high CO2(aq): 21–24 μmol kg−1) and two different light intensities (low light, suboptimal: 80 μmol photons m−2 s−1 and high light, light saturated: 240 μmol photons m−2 s−1) are reported.

The experiments demonstrated that the specific growth rate of P. globosa in the high light cultures decreased with increasing CO2(aq) from 1.4 to 1.1 d−1 in the low and high CO2 cultures, respectively. Concurrently, the photosynthetic efficiency (FV/FM) increased with increasing CO2(aq) from 0.56 to 0.66. The different light conditions affected photosynthetic efficiency and cellular chlorophyll a concentrations, both of which were lower in the high light cultures as compared to the low light cultures. These results suggest that in future inorganic carbon enriched oceans, P. globosa will become less competitive and feedback mechanisms to global change may decrease in strength.

Continue reading ‘Combined effects of inorganic carbon and light on Phaeocystis globosa Scherffel (Prymnesiophyceae)(update)’

Light and temperature effect on δ11B and B/Ca ratios of the zooxanthellate coral Acropora sp.: results from culturing experiments

The boron isotopic composition (δ11B) of marine carbonates (e.g. corals) has been established as a reliable proxy for paleo-pH, with the strong correlation between δ11B of marine calcifiers and seawater pH being now well documented. However, further investigations are needed in order to better quantify other environmental parameters potentially impacting boron isotopic composition and boron concentration into coral aragonite. To achieve this goal the tropical scleractinian coral Acropora sp. was cultured under 3 different temperature (22, 25 and 28 °C) and two light conditions (200 and 400 μmol photon m−2 s−1). The δ11B indicates an internal increase in pH from ambient seawater under both light conditions. Changes in light intensities from 200 to 400 μmol photon m−2 s−1 could bias pH reconstructions by about 0.05 units. For both light conditions, a significant impact of temperature on δ11B can be observed between 22 and 25 °C corresponding to enhancements of about 0.02 pH-units, while no further δ11B increase can be observed between 25 and 28 °C. This non-linear temperature effect complicates the determination of a correcting factor. B/Ca ratios decrease with increasing light, confirming the decrease in pH at the site of calcification under enhanced light intensities. When all the other parameters are maintained constant, boron concentrations in Acropora sp. increase with increasing temperature and increasing carbonate ions concentrations. These observations contradict previous studies where B/Ca in corals was found to vary inversely with temperature suggesting that the controlling factors driving boron concentrations have not yet been adequately identified and might be influenced by other seawater variables and species specific responses.
Continue reading ‘Light and temperature effect on δ11B and B/Ca ratios of the zooxanthellate coral Acropora sp.: results from culturing experiments’

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