Archive for September, 2008

Chemostatic modes of the ocean-atmosphere-sediment system through Phanerozoic time

The essential state of the Phanerozoic ocean-atmosphere system with respect to major lithophile and organic components can be bounded by sedimentary observational data and relatively few model assumptions. The model assumptions are in turn sufficient to constrain and compute the remaining fluxes that result in a comprehensive model describing atmospheric and oceanic evolutionary history over the past 500 m.y. that is in accord with the sedimentary observational data. Two central themes emerge. First, there is a strong coupling of the state of various reservoirs throughout the entire system imposed mainly by negative physical, chemical and biological feedbacks. Second, there is a significant overprint of ‘physical’ processes, such as weathering, by biologically-mediated processes and ecosystem evolution. Ultimately, the Phanerozoic is characterized by two modes of sea water major-ion chemistry, pH and carbonate saturation state, and atmospheric CO2. Importantly, the transition between these two modes may result from the previous state of the system whose impacts lag by tens of millions of years. Thus, the instantaneous state of the system at any given point in time may reflect in part the ‘memory’ of a previous period when fluxes and processes were not in balance. The modern-day problem of ocean acidification mainly reflects the fact that human activities of fossil fuel burning and land use changes are resulting in geologically rapid releases of CO2 to the atmosphere and its absorption by the surface ocean and does not reflect the longer term processes and feedbacks that led to the acidic oceans of the past.
Continue reading ‘Chemostatic modes of the ocean-atmosphere-sediment system through Phanerozoic time’

Biocalcification by Emiliania huxleyi in batch culture experiments

Coccolithophores, among which Emiliania huxleyi is the most abundant and widespread species, are considered the most productive calcifying organism on earth. The export of organic carbon and calcification are the main drivers of the biological CO2 pump and are expected to change with oceanic acidification. Coccolithophores are further known to produce transparent exopolymer particles (TEP) that promote particle aggregation. As a result, the TEP and biogenic calcium carbonate (CaCO3) contribute to the export of carbon from the surface ocean to deep waters. In this context, we followed the development and the decline of E. huxleyi using batch experiments with monospecific cultures. We studied the link between different processes such as photosynthesis, calcification and the production of TEP. The onset of calcification was delayed in relation to photosynthesis. The timing and the general feature of the dynamics of calcification were closely related to the saturation state of seawater with respect to calcite, Ωcal. The production of TEP was enhanced after the decline of phytoplankton growth. After nutrient exhaustion, particulate organic carbon (POC) concentration increased linearly with increasing TEP concentration, suggesting that TEP contributes to the POC increase. The production of CaCO3 is also strongly correlated with that of TEP, suggesting that calcification may be considered as a source of TEP precursors.
Continue reading ‘Biocalcification by Emiliania huxleyi in batch culture experiments’

Impacts of changing ocean chemistry in a high-CO2 world

Over the last ∼200 years, since the start of the industrial revolution, the increase in the burning of fossil fuels, cement manufacturing and changes to land use has increased atmospheric CO2 concentrations from ∼280 to 385 ppm. These are the highest levels experienced on Earth for at least the last 800,000 years, possibly for the past 10’s of millions of years. The 2007 IPCC report on climate change predicts a continued rapid rise in atmospheric CO2 leading to significant temperature increases in the atmosphere and ocean in the coming decades, as well as other climate changes. The IPCC (2007) also reports, for the first time, that increasing anthropogenic CO2 will result in increased acidity of the world’s surface oceans. This process is already happening and further rapid decreases in ocean pH will occur this century, concomitantly with warming seas, creating multiple threats to the marine environment. The future addition of massive amounts of CO2 to surface waters will have a profound impact on ocean chemistry and could have an equally profound impact on biogeochemical cycles, marine organisms, ecosystems and the services they provide. ‘Ocean acidification’ is a strong additional argument to that of climate change for urgent and substantial reduction of CO2 emissions.
Continue reading ‘Impacts of changing ocean chemistry in a high-CO2 world’

Carbon emissions are making the big blue ocean noisier

The big blue ocean is getting noisier, thanks to carbon emissions that have made the oceans more acidic.
Researchers have known for some time that acidity can influence how far sound travels in seawater. In the 1970s, acoustic measurements showed that the reach of low-frequency sounds varies between oceans.
A whale’’s call, for example, travels further in the north Pacific than in the north Atlantic, due to differences in pH.
Continue reading ‘Carbon emissions are making the big blue ocean noisier’

Reef madness: Warming could devastate world’s coral

Rising levels of carbon dioxide (CO2) in the Earth’s atmosphere from the burning of fossil fuels will likely devastate the world’s coral reefs in upcoming decades, report scientists Ken Caldeira and Long Cao of the Carnegie Institution for Science’s Department of Global Ecology in Stanford, Calif., this week. Ocean water absorbs the additional CO2, causing chemical reactions that are extremely harmful to coral.

“If current trends in CO2 emissions continue unabated,” says Caldeira, “in the next few decades, we will produce chemical conditions in the oceans that have not been seen for tens of millions of years. Ecosystems like coral reefs…just won’t be able to cope with the change.”
Continue reading ‘Reef madness: Warming could devastate world’s coral’

Acidifying oceans are brewing up an underwater din

The big blue ocean is getting noisier. Sound can now travel further than it did a century ago, thanks to carbon emissions that have made the oceans more acidic.

Researchers have known for some time that acidity can influence how far sound travels in seawater. In the 1970s, acoustic measurements showed that the reach of low-frequency sounds varies between oceans. A whale’s call, for example, travels further in the north Pacific than in the north Atlantic, due to differences in pH.
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Saving Climate Could Doom Coral

Carbon Dioxide Make Oceans Acidic, And Corals are On the Brink

U.N. Goals for reducing greenhouse gas emissions enough to stabilize the climate may not be aggressive enough to solve another thorny issue associated with carbon dioxide: ocean acidification.
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Modest CO2 cutbacks may be too little, too late for coral reefs

Stanford, CA—How much carbon dioxide is too much? According to United Nations Framework Convention on Climate Change (UNFCCC) greenhouse gases in the atmosphere need to be stabilized at levels low enough to “prevent dangerous anthropogenic interference with the climate system.” But scientists have come to realize that an even more acute danger than climate change is lurking in the world’s oceans—one that is likely to be triggered by CO2 levels that are modest by climate standards.
Continue reading ‘Modest CO2 cutbacks may be too little, too late for coral reefs’

Carbon dioxide emissions could mean trouble for ocean species

The mysterious cold water coral reefs could remain a mystery if the world’s carbon dioxide output stays the same.

The species, which has only been studied for the last 15 years and about which little information known, is highly affected by the depletion of carbonate ions, said Jeff Short, a National Oceanic and Atmospheric Administration research scientist.
Continue reading ‘Carbon dioxide emissions could mean trouble for ocean species’

Unanticipated consequences of ocean acidification: a noisier ocean at lower pH

We show that ocean acidification from fossil fuel CO2 invasion and reduced ventilation  will result in significant decreases in ocean sound absorption for frequencies lower than  about 10 kHz. This effect is due to known pH-dependent chemical relaxations in the B(OH)3/B(OH)4- and HCO3-/CO32- systems. The scale of surface ocean pH change today  from the + 105 ppmv change in atmospheric CO2 is about -0.12 pH, resulting in  frequency dependant decreases in sound absorption (α = dB/km) exceeding 12%. Under reasonable projections of future fossil fuel CO2 emissions and other sources a pH change  of 0.3 units or more can be anticipated by mid-century, resulting in a decrease in α by almost 40%. Ambient noise levels in the ocean within the auditory range critical for environmental, military, and economic interests are set to increase significantly due to the combined effects of decreased absorption and increasing sources from mankind’s activities.

Continue reading ‘Unanticipated consequences of ocean acidification: a noisier ocean at lower pH’


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