Tiny shells indicate big changes to global carbon cycle

Experiments with tiny, shelled organisms in the ocean suggest big changes to the global carbon cycle are underway, according to a study from the University of California, Davis. For the study, published in the journal Scientific Reports, scientists raised foraminifera — single-celled organisms about the size of a grain of sand — at the UC Davis Bodega Marine Laboratory under future, high CO2 conditions. These tiny organisms, commonly called “forams,” are ubiquitous in marine environments and play a key role in food webs and the ocean carbon cycle.

Stressed Under Future Conditions

After exposing them to a range of acidity levels, UC Davis scientists found that under high CO2, or more acidic, conditions, the foraminifera had trouble building their shells and making spines, an important feature of their shells. They also showed signs of physiological stress, reducing their metabolism and slowing their respiration to undetectable levels.

This is the first study of its kind to show the combined impact of shell building, spine repair, and physiological stress in foraminifera under high CO2 conditions. The study suggests that stressed and impaired foraminifera could indicate a larger scale disruption of carbon cycling in the ocean.

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Enhancing global ocean acidification monitoring and research

The policy and scientific needs for coordinated, worldwide information-gathering on ocean acidification and its ecological impacts are now widely recognized. The importance of obtaining such measurements has been endorsed by the United Nations General Assembly, as well as by many other governmental and non-governmental bodies.

The Global Ocean Acidification Observing Network (GOA-ON), a collaborative international network of 367 members representing 66 nations, is committed to increasing global ocean acidification observing capacity in support of SDG target 14.3: Average marine acidity (pH) measured at agreed suite of representative sampling stations.

To achieve this commitment, GOA-ON and its partners are expected to continue to develop and nurture this global network. Importantly, we plan to work to build capacity in regions that currently have limited observation records and little ocean science capacity by conducting targeted training workshops on ocean acidification monitoring and experimentation best practices. We are committed to distributing sensor kits that will allow scientists in resource-poor countries to collect reliable data and so contribute to the global ocean acidification monitoring effort.

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It’s getting hot in here: how ocean acidification and warming affect shark hunting and behavior


Sharks have an advanced sensory system that allows for efficient foraging using various senses such as sight, hearing, smelling, and touch.  They can even detect movement, and differences in pressure! Because of this, some sharks are high in the food web. So, any changes in their physiology and behavior due to the changing climate is likely to trickle down into lower trophic levels and alter the structure of the marine food web. What causes such changes, though?  When we burn fossil fuels such as coal, oil and gas for energy or transportation, excess carbon dioxide (CO2) gets released into the atmosphere. This excess CO2 acts like a heat trapping blanket and the ocean absorbs much of this heat. The ocean also absorbs about quarter of this excess CO2 where it reacts with seawater and making the ocean more acidic. This is called ocean acidification.

Continue reading ‘It’s getting hot in here: how ocean acidification and warming affect shark hunting and behavior’

Ocean acidification compromises a planktic calcifier with implications for global carbon cycling

Anthropogenically-forced changes in ocean chemistry at both the global and regional scale have the potential to negatively impact calcifying plankton, which play a key role in ecosystem functioning and marine carbon cycling. We cultured a globally important calcifying marine plankter (the foraminifer, Globigerina bulloides) under an ecologically relevant range of seawater pH (7.5 to 8.3 total scale). Multiple metrics of calcification and physiological performance varied with pH. At pH > 8.0, increased calcification occurred without a concomitant rise in respiration rates. However, as pH declined from 8.0 to 7.5, calcification and oxygen consumption both decreased, suggesting a reduced ability to precipitate shell material accompanied by metabolic depression. Repair of spines, important for both buoyancy and feeding, was also reduced at pH < 7.7. The dependence of calcification, respiration, and spine repair on seawater pH suggests that foraminifera will likely be challenged by future ocean conditions. Furthermore, the nature of these effects has the potential to actuate changes in vertical transport of organic and inorganic carbon, perturbing feedbacks to regional and global marine carbon cycling. The biological impacts of seawater pH have additional, important implications for the use of foraminifera as paleoceanographic indicators.

Continue reading ‘Ocean acidification compromises a planktic calcifier with implications for global carbon cycling’

Carbon assimilation and losses during an ocean acidification mesocosm experiment, with special reference to algal blooms

A mesocosm experiment was conducted in Wuyuan Bay (Xiamen), China, to investigate the effects of elevated pCO2 on bloom formation by phytoplankton species previously studied in laboratory-based ocean acidification experiments, to determine if the indoor-grown species performed similarly in mesocosms under more realistic environmental conditions. We measured biomass, primary productivity and particulate organic carbon (POC) as well as particulate organic nitrogen (PON). Phaeodactylum tricornutum outcompeted Thalassiosira weissflogii and Emiliania huxleyi, comprising more than 99% of the final biomass. Mainly through a capacity to tolerate nutrient-limited situations, P. tricornutum showed a powerful sustained presence during the plateau phase of growth. Significant differences between high and low CO2 treatments were found in cell concentration, cumulative primary productivity and POC in the plateau phase but not during the exponential phase of growth. Compared to the low pCO2 (LC) treatment, POC increased by 45.8–101.9% in the high pCO2 (HC) treated cells during the bloom period. Furthermore, respiratory carbon losses of gross primary productivity were found to comprise 39–64% for the LC and 31–41% for the HC mesocosms (daytime C fixation) in phase II. Our results suggest that the duration and characteristics of a diatom bloom can be affected by elevated pCO2. Effects of elevated pCO2 observed in the laboratory cannot be reliably extrapolated to large scale mesocosms with multiple influencing factors, especially during intense algal blooms.

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Ocean acidification: Pacific conversations with SPREP

In June this year, the Pacific islands are amplifying their voice at the United Nations Ocean Conference at the UN Headquarters in New York, focusing on Sustainable Development Goal 14 – Life Below Water.

This Pacific Conversation discusses ocean acidification and its impacts on Pacific species, providing you with more information to help make a difference in our region.

Did you know that a lower pH, the potential of hydrogen, makes the ocean a louder place? By 2050, under conservative projections of ocean acidification, sounds could travel as much as 70% farther in some ocean areas. This means ocean acidification affects whales and other animals, not just coral reefs and shellfish.

The ocean absorbs about 25% of the CO2 that we emit. If we had to pay for it, the value of this ‘ocean service’ to the global economy is USD 60 to 400 billion annually (EPOCA).

By taking up our extra CO2, the ocean has acidified by 30% since the start of the Industrial Revolution. The current rate of decrease is 0.02 units per decade, faster than any rate in the past 300 million years. Projections show that by 2060, seawater acidity could have increased by 120%.

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Net community metabolism and seawater carbonate chemistry scale non-intuitively with coral cover

Coral cover and reef health have been declining globally as reefs face local and global stressors including higher temperature and ocean acidification (OA). Ocean warming and acidification will alter rates of benthic reef metabolism (i.e., primary production, respiration, calcification, and CaCO3 dissolution), but our understanding of community and ecosystem level responses is limited in terms of functional, spatial, and temporal scales. Furthermore, dramatic changes in coral cover and benthic metabolism could alter seawater carbonate chemistry on coral reefs, locally alleviating or exacerbating OA. This study examines how benthic metabolic rates scale with changing coral cover (0-100%), and the subsequent influence of these coral communities on seawater carbonate chemistry based on mesocosm experiments in Bermuda and Hawaii. In Bermuda, no significant differences in benthic metabolism or seawater carbonate chemistry were observed for low (40%) and high (80%) coral cover due to large variability within treatments. In contrast, significant differences were detected between treatments in Hawaii with benthic metabolic rates increasing with increasing coral cover. Observed increases in daily net community calcification and nighttime net respiration scaled proportionally with coral cover. This was not true for daytime net community organic carbon production rates, which increased the most between 0 to 20% coral cover and then less so between 20% to 100%. These differences in scaling resulted in larger diel variability in seawater carbonate chemistry as coral cover increased. To place the results of the mesocosm experiments into a broader context, in situ seawater carbon dioxide (CO2) at three reef sites in Bermuda and Hawaii were also evaluated; reefs with higher coral cover experienced a greater range of diel CO2 levels, complementing the mesocosm results. The results from this study highlight the need to consider the natural complexity of reefs and additional biological and physical factors that influence seawater carbonate chemistry on larger spatial and longer temporal scales. Coordinated efforts combining various research approaches (e.g. experiments, field studies, and models) will be required to better understand how benthic metabolism integrates across functional, spatial, and temporal scales, and for making predictions on how coral reefs will respond to climate change.

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Ocean acidification in the IPCC AR5 WG II

OUP book