Archive for April, 2013



Establishing the scientific truth about ocean acidification and raising public awareness

The acidity of the oceans is increasing from absorption of the increasing amounts of CO2 being released into the atmosphere. We are now certain about this, but can we assess the impact on marine ecosystems? Peter Brewer, the scientist who initiated the FOCE* project at the Monterey Bay Aquarium Research Institute (MBARI) in California, explains why it is urgent to obtain solid scientific data in this regard.

Continue reading ‘Establishing the scientific truth about ocean acidification and raising public awareness’

Acidification des océans – établir la vérité scientifique et éveiller les consciences (in French)

Les océans s’acidifient avec l’augmentation du CO2 dans l’atmosphère. C’est aujourd’hui une certitude, mais peut-on en évaluer les conséquences sur les écosystèmes marins ? Peter Brewer, scientifique à l’origine du projet FOCE* au Monterey Bay Aquarium Research Institute (MBARI), en Californie, explique pourquoi il est urgent d’obtenir des données scientifiques solides en la matière.

Continue reading ‘Acidification des océans – établir la vérité scientifique et éveiller les consciences (in French)’

Ocean acidification top ranked in “Research Fronts 2013”

“Ocean acidification and marine ecosystems” is identified as #1 research front in Ecology and Environmental Sciences in “Research Fronts 2013: 100 top-ranked specialities in the sciences and social sciences”.

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A developmental and energetic basis linking larval oyster shell formation to acidification sensitivity

Acidified waters are impacting commercial oyster production in the U.S. Pacific Northwest and favorable carbonate chemistry conditions are predicted to become less frequent. Within 48 hours of fertilization, unshelled Pacific oyster (Crassostrea gigas) larvae precipitate roughly 90% of their body weight as calcium carbonate. We measured stable carbon isotopes in larval shell and tissue and in algal food and seawater dissolved inorganic carbon in a longitudinal study of larval development and growth. Using these data and measured biochemical composition of larvae we show that sensitivity of initial shell formation to ocean acidification results from diminished ability to isolate calcifying fluid from surrounding seawater, a limited energy budget dependent, and a strong kinetic demand for calcium carbonate precipitation. Our results highlight an important link between organism physiology and mineral kinetics in larval bivalves and suggest the consideration of mineral kinetics may improve understanding winners and losers in a high CO2 world.

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Certain species show potential resistance to acidic oceans: study

A recent study published in the journal Global Change Biology studies the effect of ocean acidification on the larvae of cobia, pelagic spawners that are mainly found in the tropical waters. This is the first study of its kind.

It was conducted by researchers Sean Bignami, Su Sponaugle and Robert Cowen.

For the study, researchers reared cobia in tanks that had different levels of CO2 saturation. They then examined the effect on growth, development, otolith formation, swimming ability and activity level when the cobias were in their larval stage.

Continue reading ‘Certain species show potential resistance to acidic oceans: study’

EPA faces ocean acidification legal challenge

The USA’s Clean Water Act could be used to combat the growing threat posed by ocean acidification, the San Francisco based Center for Biological Diversity (CBD) claims in a new petition.

The world’s seas have become 30% more acidic since the industrial revolution, and scientists says this figure is likely to increase as the oceans absorb more carbon dioxide.

Studies suggest sea life such as oysters, clams, sea urchins and corals will struggle to survive in increasingly acidic waters – affecting a variety of life further up the food chain.

The CBD’s 66-page submission calls on the Federal Environment Protection Agency (EPA) to: ‘publish information to provide guidance to states on ocean acidification, including the factors necessary to prevent deleterious changes in seawater chemistry due to anthropogenic carbon dioxide emissions and the factors necessary to prevent adverse impacts of ocean acidification on fish, shellfish, and wildlife.’

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Ocean acidification: science, law & governance conference

We cordially invite you to attend the conference on “Ocean Acidification: Science, Law, & Governance” as a guest of the “Toward a Sustainable 21st Century” initiative at the University of California, Irvine. The program will focus on issues surrounding ocean acidification and its major impact on the West Coast of the United States. The emphasis will be on options for preserving the precious aquatic habitat and the threatened shellfish industry. The problem is global, but the threats are compelling and urgent in the states of Washington, Oregon, and California.

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The role of preconditioning in ocean acidification experiments: a test with the intertidal isopod Paradella dianae

Environmental alterations are accelerating worldwide and the rate of change in ocean chemistry is predicted to happen so rapidly that it is unclear how marine ecosystems will respond. It is hypothesized that the phenotypic plasticity or acclimation capacity of an individual provides a buffer against environmental change; however, this plasticity depends on the speed at which the change occurs. Ocean acidification studies have found direct and acute responses from organisms exposed to elevated CO2 levels. Now, the challenge lies in integrating acclimation into experimental design in short-term studies, requiring proper preconditioning setups. Here we experimentally show that different preconditioning approaches produce different physiological and behavioral responses in the intertidal isopod Paradella dianae. Isopods were impaired when immediately exposed to elevated CO2 levels relative to individuals that were gradually acclimated to high CO2 concentrations. Abruptly introducing organisms to severe changes in CO2 conditions can produce confounding effects of short-term stress with acclimated responses to long-term shifts in ocean chemistry. By exposing organisms to sudden changes in CO2 concentrations, we are forcing immediate physiological stress reactions that could be independent of exposure to specific CO2 levels. We discuss how integrating acclimation in experimental design can help provide more accurate predictions about the impact of ocean acidification on marine ecosystems.

Continue reading ‘The role of preconditioning in ocean acidification experiments: a test with the intertidal isopod Paradella dianae’

Interactive effects of ocean acidification and warming on sediment-dwelling marine calcifiers

The increase in human activities, such as the burning of fossil fuels, has elevated the concentration of atmospheric carbon dioxide and warmed the planet through the greenhouse effect. In addition, approximately 30% of the CO2 produced by human activities has dissolved into the oceans, lowering pH and reducing the abundance, and hence the availability, of carbonate ions (CO3 2-), which are essential for calcium carbonate deposition. Of great concern is the impact to photosynthetic marine calcifiers, elevated CO2 and temperature is expected to have a negative impact on the health and survivorship of calcifying marine organisms. This thesis explores the effects of elevated CO2 and temperature on the microenvironment, photosynthetic efficiency, calcification and biomechanical properties in important sediment producers on coral reefs. The reef-building and sedimentdwelling organisms, Halimeda and symbiont-bearing foraminifera are prominent, coexisting taxa in shallow coral reefs and play a vital role in tropical and subtropical ecosystems as producers of sediment and habitats and food sources for other marine organisms. However, there is limited evidence of the effects of ocean warming and acidification in these two keystone species. Irradiance alone was not found to influence photosynthetic efficiency, photoprotective mechanisms and calcification in Halimeda macroloba, Halimeda cylindracea and Halimeda opuntia (Chapter 2). There is also limited knowledge of foraminiferal biology on coral reefs, especially the symbiotic relationship between the protest host and algal symbionts. Marginopora vertebralis, the dominant tropical foraminifera, shows phototactic behavior, which is a unique mechanism for ensuring symbionts experience an ideal light environment. The diurnal photosynthetic responses of in hospite symbiont photosynthesis was linked to host movement and aided in preventing photoinhibition and bleaching by moving away from over-saturating irradiance, to more optimal light fields (Chapter 3). With this greater understanding of Halimeda and foraminiferan biology and photosynthesis, the impacts of ocean warming and acidification on photosynthesis and calcification were then tested (Chapter 4, 5 and 6). Impacts of ocean acidification and warming were investigated through exposure to a combination of four temperature (28, 30, 32, 34°C) and four pCO2 levels (380, 600, 1000, 2000 µatm; equivalent to future climate change scenarios for the current and the years 2065, 2100 and 2200 and simulating the IPCC A1F1 predictions) (Chapter 4). Elevated CO2 and temperature caused a decline in photosynthetic efficiency (FV/FM), calcification and growth in all species. After five weeks at 34°C under all CO2 levels, all species died. The elevated CO2 and temperature greatly affect the CaCO3 crystal formation with reductions in density and width. M. vertebralis experienced the greatest inhibition to crystal formation, suggesting that this high Mg-calcite depositing species is more sensitive to lower pH and higher temperature than aragonite-forming Halimeda species. Exposure to elevated temperature alone or reduced pH alone decreased photosynthesis and calcification in these species. However, there was a strong synergistic effect of elevated temperature and reduced pH, with dramatic reductions in photosynthesis and calcification in all three species. This study suggested that the elevated temperature of 32°C and the pCO2 concentration of 1000 µatm are the upper limit for survival of these species art our site of collection (Heron Island on the Great Barrier Reef, Australia). Microsensors enabled the detection of O2 surrounding specimens at high spatial and temporal resolutions and revealed a 70-80% in decrease in O2 production under elevated CO2 and temperature (1200 µatm 32°C) in Halimeda (Chapter 5) and foraminifera (Chapter 6). The results from O2 microprofiles support the photosynthetic pigment and chlorophyll fluorescence data, showing decreasing O2 production with declining chlorophyll a and b concentrations and a decrease in photosynthetic efficiency under ocean acidification and/or temperature stress. This revealed that photosynthesis and calcification are closely coupled with reductions in photosynthetic efficiency leading to reductions in calcification. Reductions in carbonate availability reduced calcification and that can lead to weakened calcified structures. Elevations in water temperature is expected to augment this weakening, resulting in decreased mechanical integrity and increased susceptibility to storm- and herbivory-induced mortality in Halimeda sp. The morphological and biomechanical properties in H. macroloba and H. cylindracea at different wave exposures were then investigated in their natural reef habitats (Chapter 7). The results showed that both species have morphological (e.g. blade surface area, holdfast volume) and biomechanical (e.g. force required to uproot, force required to break thalli) adaptations to different levels of hydrodynamic exposure. The mechanical integrity and skeletal mineralogy of Halimeda was then investigated in response to future climate change scenarios (Chapter 7). The biomechanical properties (shear strength and punch strength) significantly declined in the more heavily calcified H. cylindracea at 32ºC and 1000 µatm, whereas were variable in less heavily calcified H. macroloba, indicating different responses between Halimeda species. An increase in less-soluble low Mgcalcite was observed under elevated CO2 conditions. Significant changes in Mg:Ca and Sr:Ca ratios under elevated CO2 and temperature conditions suggested that calcification was affected at the ionic level. It is concluded that Halimeda is biomechanically sensitive to elevated temperature and more acidic oceans and may lead to increasing susceptibility to herbivory and higher risk of thallus breakage or removal from the substrate. Experimental results throughout the thesis revealed that ocean acidification and warming have negative impacts on photosynthetic efficiency, productivity, calcification and mechanical integrity, which is likely to lead to increased mortality in these species under a changing climate. A loss of these calcifying keystone species will have a dramatic impact on carbonate accumulation, sediment turnover, and coral reef community and habitat structure.

Continue reading ‘Interactive effects of ocean acidification and warming on sediment-dwelling marine calcifiers’

pH alters the swimming behaviors of the raphidophyte Heterosigma akashiwo: implications for bloom formation in an acidified ocean

We investigated the effects of pH on movement behaviors of the harmful algal bloom causing raphidophyte Heterosigma akashiwo. Motility parameters from >8000 swimming tracks of individual cells were quantified using 3D digital video analysis over a 6-h period in 3 pH treatments reflecting marine carbonate chemistry during the pre-industrial era, currently, and the year 2100. Movement behaviors were investigated in two different acclimation-to-target-pH conditions: instantaneous exposure and acclimation of cells for at least 11 generations. There was no negative impairment of cell motility when exposed to elevated PCO2 (i.e., low pH) conditions but there were significant behavioral responses. Irrespective of acclimation condition, lower pH significantly increased downward velocity and frequency of downward swimming cells (p < 0.001). Rapid exposure to lower pH resulted in 9% faster downward vertical velocity and up to 19% more cells swimming downwards (p < 0.001). Compared to pH-shock experiments, pre-acclimation of cells to target pH resulted in ~30% faster swimming speed and up to 46% faster downward velocities (all p < 0.001). The effect of year 2100 PCO2 levels on population diffusivity in pre-acclimated cultures was >2-fold greater than in pH-shock treatments (2.2 × 105 μm2 s−1 vs. 8.4 × 104 μm2 s−1). Predictions from an advection-diffusion model, suggest that as PCO2 increased the fraction of the population aggregated at the surface declined, and moved deeper in the water column. Enhanced downward swimming of H. akashiwo at low pH suggests that these behavioral responses to elevated PCO2 could reduce the likelihood of dense surface slick formation of H. akashiwo through reductions in light exposure or growth independent surface aggregations. We hypothesize that the HAB alga’s response to higher PCO2 may exploit the signaling function of high PCO2 as indicative of net heterotrophy in the system, thus indicative of high predation rates or depletion of nutrients.

Continue reading ‘pH alters the swimming behaviors of the raphidophyte Heterosigma akashiwo: implications for bloom formation in an acidified ocean’


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Ocean acidification in the IPCC AR5 WG II

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