Archive for April, 2015

The Oceans 2015 Initiative, Part I: An updated synthesis of the observed and projected impacts of climate change on physical and biological processes in the oceans


The oceans have absorbed approximately 93% of the excess heat caused by global warming. Warming increases stratification, limiting the circulation of nutrients from deep waters to the surface. There is evidence that enhanced stratification and increasing temperature are causing a decline in dissolved oxygen concentration and expanding existing oxygen minimum zones (OMZs). Approximately 26% of anthropogenic CO2 is absorbed by the oceans, resulting in a reduction in pH and carbonate ion concentration, termed ocean acidification. Anthropogenic CO2 has caused global ocean pH to decrease by 0.1 units since the start of the Industrial Revolution.

Continue reading ‘The Oceans 2015 Initiative, Part I: An updated synthesis of the observed and projected impacts of climate change on physical and biological processes in the oceans’

The effects of elevated-CO2 on physiological performance of Bryopsis plumosa

An increase in the level of atmospheric carbon dioxide (CO2) and the resultant rise in CO2 in seawater alter the inorganic carbon concentrations of seawater. This change, known as ocean acidification, causes lower pH in seawater and may affect the physiology of seaweed species. Accordingly, the main goal of the current study was to determine the physiological responses of Bryopsis plumosa to elevated-CO2. The results indicated that photosynthesis of B. plumosa was insignificantly affected to elevated-CO2, but photosynthetic pigment contents and phenolics were significantly decreased. The results obtained from the research reveal that B. plumosa may become physiologically advanced when exposed to CO2-induced ocean acidification. In particular, B. plumosa may be more able to compete with calcifying algae when it will become future predicted CO2 scenario.

Continue reading ‘The effects of elevated-CO2 on physiological performance of Bryopsis plumosa’

Effects of seawater acidification on a coral reef meiofauna community

Despite the increasing risk that ocean acidification will modify benthic communities, great uncertainty remains about how this impact will affect the lower trophic levels, such as members of the meiofauna. A mesocosm experiment was conducted to investigate the effects of water acidification on a phytal meiofauna community from a coral reef. Community samples collected from the coral reef subtidal zone (Recife de Fora Municipal Marine Park, Porto Seguro, Bahia, Brazil), using artificial substrate units, were exposed to a control pH (ambient seawater) and to three levels of seawater acidification (pH reductions of 0.3, 0.6, and 0.9 units below ambient) and collected after 15 and 30 d. After 30 d of exposure, major changes in the structure of the meiofauna community were observed in response to reduced pH. The major meiofauna groups showed divergent responses to acidification. Harpacticoida and Polychaeta densities did not show significant differences due to pH. Nematoda, Ostracoda, Turbellaria, and Tardigrada exhibited their highest densities in low-pH treatments (especially at the pH reduction of 0.6 units, pH 7.5), while harpacticoid nauplii were strongly negatively affected by low pH. This community-based mesocosm study supports previous suggestions that ocean acidification induces important changes in the structure of marine benthic communities. Considering the importance of meiofauna in the food web of coral reef ecosystems, the results presented here demonstrate that the trophic functioning of coral reefs is seriously threatened by ocean acidification.

Continue reading ‘Effects of seawater acidification on a coral reef meiofauna community’

Public meeting: “Ocean acidification: What’s it all about?”, 4-5 June 2015, Royal Society, London

Registration closes on 20 May 2015!

A two-day public meeting at the Royal Society, London on 4-5 June will discuss the latest scientific findings arising from the UK Ocean Acidification (UKOA) research programme, co-funded by NERC, Defra and DECC, and the German partnership programme, Biological Impacts of Ocean Acidification (BIOACID).

The chemistry of the global ocean is rapidly changing as a result of the unprecedented increase of carbon dioxide in the atmosphere. This process of ocean acidification threatens marine organisms, ecosystems, and the services they provide to society.

Day 1: On 4 June, the questions addressed will be:

  • What is ocean acidification?
  • Why should we care about ocean acidification?
  • What can we do about ocean acidification?

Continue reading ‘Public meeting: “Ocean acidification: What’s it all about?”, 4-5 June 2015, Royal Society, London’

Threatened Caribbean coral is able to mitigate the adverse effects of ocean acidification on calcification by increasing feeding rate

Global climate change threatens coral growth and reef ecosystem health via ocean warming and ocean acidification (OA). Whereas the negative impacts of these stressors are increasingly well-documented, studies identifying pathways to resilience are still poorly understood. Heterotrophy has been shown to help corals experiencing decreases in growth due to either thermal or OA stress; however, the mechanism by which it mitigates these decreases remains unclear. This study tested the ability of coral heterotrophy to mitigate reductions in growth due to climate change stress in the critically endangered Caribbean coral Acropora cervicornis via changes in feeding rate and lipid content. Corals were either fed or unfed and exposed to elevated temperature (30°C), enriched pCO2 (800 ppm), or both (30°C/800 ppm) as compared to a control (26°C/390 ppm) for 8 weeks. Feeding rate and lipid content both increased in corals experiencing OA vs. present-day conditions, and were significantly correlated. Fed corals were able to maintain ambient growth rates at both elevated temperature and elevated CO2, while unfed corals experienced significant decreases in growth with respect to fed conspecifics. Our results show for the first time that a threatened coral species can buffer OA-reduced calcification by increasing feeding rates and lipid content.

Continue reading ‘Threatened Caribbean coral is able to mitigate the adverse effects of ocean acidification on calcification by increasing feeding rate’

Research divers go below Antarctic sea ice to investigate the effect of rising sea levels on sea bed

Researchers have battled minus-2-degree water and the distraction of seals to complete a world-first study on the ocean floor.

A crew of 15 scientists and divers conducted the first investigation of the effect of carbon dioxide on the ocean floor in Antarctica.

Continue reading ‘Research divers go below Antarctic sea ice to investigate the effect of rising sea levels on sea bed’

SOCAN webinar: “Crumbling Coral: Cold-water Reefs in the Acidic Northeast Pacific and their Implications for Other Regions of the USA”, 5 May 2015

Date & time: Tuesday, 5 May 2015, 12:00 pm ET
Speaker: Leslie Wickes and Peter Etnoyer, NOAA National Centers for Coastal Ocean Science Center for Coastal Environmental Health and Biomolecular Research
Cold-water reefs are fragile, complex ecosystems that extend into the bathyal depths of the ocean, creating three-dimensional structure and habitat for deep-water invertebrates and fishes.  The most prolific cold-water reef-building coral is Lophelia pertusa, which occurs at depths where aragonite saturation is three to four times lower than their shallow-water reef counterparts.  The current study employed an unprecedented number of ROV dives (n=564, 2003-2014) to document the widespread distribution of a reef-building coral on the U.S. West Coast for the first time, providing empirical evidence of species survival but loss of reef integrity in the naturally acidified conditions.  The study found that while Lophelia can persist in the corrosive waters, framework extent, linear extension and skeletal densities were greatly reduced relative to regions such as the North Atlantic and US South Atlantic Bight, where the coral forms more expansive reefs of robust skeleton. Preliminary findings in the South Atlantic Bight suggest corrosive water will also be impinging on Lophelia reefs in this region.  The future health of these SAB reefs may depend on both the degree and rate of change, necessitating new monitoring efforts to evaluate carbonate chemistry with respect to cold-water reefs in the Southeast region.

Continue reading ‘SOCAN webinar: “Crumbling Coral: Cold-water Reefs in the Acidic Northeast Pacific and their Implications for Other Regions of the USA”, 5 May 2015’

Ocean wealth valued at US$24 trillion, but sinking fast

The value of the ocean’s riches rivals the size of the world’s leading economies, but its resources are rapidly eroding, according to a report released by WWF today. The report, Reviving the Ocean Economy: The case for action – 2015, analyses the ocean’s role as an economic powerhouse and outlines the threats that are moving it toward collapse.

The value of key ocean assets is conservatively estimated in the report to be at least US$24 trillion. If compared to the world’s top 10 economies, the ocean would rank seventh with an annual value of goods and services of US$2.5 trillion.

Continue reading ‘Ocean wealth valued at US$24 trillion, but sinking fast’

Quantifying the influence of CO2 seasonality on future ocean acidification

Ocean acidification is a predictable consequence of rising atmospheric carbon dioxide (CO2), and is highly likely to impact the entire marine ecosystem – from plankton at the base to fish at the top. Factors which are expected to be impacted include reproductive health, organism growth and species composition and distribution. Predicting when critical threshold values will be reached is crucial for projecting the future health of marine ecosystems and for marine resources planning and management. The impacts of ocean acidification will be first felt at the seasonal scale, however our understanding how seasonal variability will influence rates of future ocean acidification remains poorly constrained due to current model and data limitations. To address this issue, we first quantified the seasonal cycle of aragonite saturation state utilizing new data-based estimates of global ocean surface dissolved inorganic carbon and alkalinity. This seasonality was then combined with earth system model projections under different emissions scenarios (RCPs 2.6, 4.5 and 8.5) to provide new insights into future aragonite under-saturation onset. Under a high emissions scenario (RCP 8.5), our results suggest accounting for seasonality will bring forward the initial onset of month-long under-saturation by 17 years compared to annual-mean estimates, with differences extending up to 35 ± 17 years in the North Pacific due to strong regional seasonality. Our results also show large-scale under-saturation once atmospheric CO2 reaches 486 ppm in the North Pacific and 511 ppm in the Southern Ocean independent of emission scenario. Our results suggest that accounting for seasonality is critical to projecting the future impacts of ocean acidification on the marine environment.

Continue reading ‘Quantifying the influence of CO2 seasonality on future ocean acidification’

Optimising methodology for determining the effect of ocean acidification on bacterial extracellular enzymes

To fully understand the impact of ocean acidification on biogeochemical cycles, the response of bacterial extracellular enzymes needs to be considered as they play a central role in the degradation and distribution of labile organic matter. This study investigates the methodology, and potential artefacts involved in determining the response of bacterial extracellular glucosidase and protease to ocean acidification. The effect of pH on artificial fluorophores and substrates was examined, as well as the impact of three different acidification methods. The results indicate that pH has a significant effect on the fluorescence of the artificial fluorophore 4-methylumbeliferone for glucosidase activity, and 7-amino-4-methylcoumarin for protease activity, while artificial aminopeptidase substrate alters the pH of seawater, confirming previous observations. Before use in ocean acidification research these enzyme assay components must be buffered in order to stabilise sample pH. Reduction of coastal seawater pH to 7.8 was shown to increase β-glucosidase activity rapidly (0.5 h), while no significant response was detected for leucine aminopeptidase, highlighting the need for short-term direct effects of pH on enzyme activities. Bubbling with CO2 gas resulted in higher β-glucosidase activity when compared to acidification using gas-permeable silicon tubing and acidification with HCl. Although bubbling showed variable effects between two experiments conducted at different times of the year. In addition, bacterial cell numbers were 15–40% higher with bubbling relative to seawater acidified with gas-permeable silicon tubing and HCl. Artefacts associated with bubbling may lead to the overestimation of extracellular enzyme activities, and interpretation of the impacts of ocean acidification on organic matter cycling.

Continue reading ‘Optimising methodology for determining the effect of ocean acidification on bacterial extracellular enzymes’

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Ocean acidification in the IPCC AR5 WG II

OUP book