Archive for May, 2012

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 http://www.arcticoacruise.org/?cat=1.

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’

The Legacy Project: ocean acidification (video)

Ocean acidification is the name given to the ongoing decrease in the pH of the Earth’s oceans, caused by the uptake of anthropogenic carbon dioxide (CO2) from the atmosphere. About a quarter of the carbon dioxide in the atmosphere goes into the oceans, where it forms carbonic acid.

Continue reading ‘The Legacy Project: ocean acidification (video)’

Ocean acidification by the Alliance for Climate Education (video)

A short video on ocean acidification by Ocean Acidification by the Alliance for Climate Education.

Continue reading ‘Ocean acidification by the Alliance for Climate Education (video)’


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