Death of the seas from CO2 acidification

Summary:  The lastest scary stories from scientists.  Real data, reliable projections, but does that make the story plausible?  Part 1 of a  series.


  1. An introduction to the problem
  2. An introduction to ocean acidification
  3. Some journal articles about acidification
  4. Update: good news

(1)  An introduction to the problem

Atmospheric CO2 concentrations oscillated between 200 and 280 parts per million (ppm) over the 400,000 years before the industrial period. Current atmospheric concentrations are now approaching 380 ppm as a result of the industrial and land use activities of humankind. In the past few decades, only half of the CO2 released by human activity has remained in the atmosphere; of the remainder, about 30% has been taken up by the ocean and 20% by the terrestrial biosphere.  {Science, 2004}

A description of the threat:  “Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum“, James C. Zachos et al, Science, 10 June 2005 — Conclusion (red emphasis added);

Excessive carbonate undersaturation of the deep ocean would likely impede calcification by marine organisms and therefore is a potential contributing factor to the mass extinction of benthic foraminifera at the P-E boundary. Although most plankton species survived, carbonate ion changes in the surface ocean might have contributed to the brief appearance of weakly calcified planktonic foraminifera  and the dominance of heavily calcified forms of calcareous algae .

What, if any, implications might this have for the future? If combustion of the entire fossil fuel reservoir (~4500 gigatons of Carbon) is assumed, the impacts on deep-sea pH and biota will likely be similar to those in the PETM. However, because the anthropogenic carbon input will occur within just 300 years, which is less than the mixing time of the ocean, the impacts on surface ocean pH and biota will probably be more severe.

OK, that looks like logical cause and effect.  The commonly stated case:

  1. The atmosphere holds roughly 750 gigatonnes of carbon in the form of CO2. The ocean holds about 35-40 thousand gigatons.
  2. During the past 2 centuries CO2 levels have levels have increased from 280 to nearly 400 ppm. (However, this is misleading.  Warming in the 19th C had other causes, as almost all the CO2 rise is post-WWII. See the Mauna Loa graph.)
  3. Extrapolations of current industrial activity suggest CO2 levels of 600 ppm in 100 years, and 900 ppm in 200 years.

But is this scenario likely?

Three hundred years ago the fossil fuel age began when Thomas Newcomen built the first practical steam engine to pump water at the Conygree Coalworks  — in 1712, an arbitrary marker in an evolutionary process (Wikipedia).    Today we have nuclear power, solar cells — and a dozen fusion power systems under development.

Perhaps we’ll burn off the planet’s remaining coal and oil deposits over the next few centuries.  I doubt it.  And spending money on R&D for new power sources looks like a better use of money than “mitigating” hypothetical CO2 emissions.

As for saving the oceans, they face a severe and imminent threats — far more deserving of action:  pollution and over-fishing.  The first has been amply discussed.  The latter is more serious and easily stopped.  Here are a few articles about this topic.  Again we see urgent and obvious problems displaced by fears of future and hypothetical threats.  Here are some articles, as an introduction.

  1. Globalization, Roving Bandits, and Marine Resources“, Science, Boris Worm et al, 17 March 2006
  2. Impacts of Biodiversity Loss on Ocean Ecosystem Services“, Boris Worm et al, Science, 3 November 2006 – The author’s forecast that unless global policies change, 100% of seafood-producing species stocks will collapse by 2048.
  3. Can Catch Shares Prevent Fisheries Collapse?“, Costello et al, Science 19 September 2008
  4. Ecologists fear Antarctic krill crisis“, Nature, 1 September 2010 — “Fishing industry threatens to destabilize stocks.”

(2)  An introduction to ocean acidification

Note it is misleading to say the ocean is becoming “more acidic.”  The oceans’ pH varies over time and space, but is roughly 8.1 — and would require thousands of years at current rates to become acidic (pH < 7).

Here are some brief introductions to the topic:

  1. The Ocean in a High-CO2 World“, Oceanography, September 2004  (7 pages)
  2. Ocean Acidification Home Page, Pacific Marine Environmental Laboratory (NOAA) — Rich resource of information
  3. Ocean Acidification Unprecedented, Unsettling“, Richard A. Kerr, Science, 18 June 2010 — Nice 2 page intro; subscription only.
  4. Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers: A Guide for Future Research“, A report from a workshop sponsored by the National Science Foundation, the National Oceanic and Atmospheric Administration, and the U.S. Geological Survey (June 2006, 96 pages)

(3)  Some journal articles about acidification

Note there is broad agreement about the likelihood of acidification, but some dispute about its effects.  Red emphasis added.

(a) Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans“, Richard A. Feely et al, Science 16 July 2004

(b) Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum“, James C. Zachos et al, Science, 10 June 2005 — A horrifying scenario.

(c) Preindustrial to Modern Interdecadal Variability in Coral Reef pH“, Carles Pelejero et al, Science, 30 September 2005 — Conclusion:

…  the next rise in the 50-year cycle of reef-water pH should counteract the lowering of pH values at Flinders Reef until 2035 A.D. Conversely, the subsequent fall in the reef-water pH cycle will lead to an abrupt shift toward low pH reef water. The extent to which corals and other calcifying reef organisms can adapt to such rapid decreases in pH is largely unknown. … Although the relatively large variations in seawater pH at Flinders Reef suggest that coral reefs may be resilient to the shorter term effects of ocean acidification, in the coming decades many reefs are likely to experience reduced pH that is unprecedented relative to “natural” levels.

(d) Modern-age buildup of CO2 and its effects on seawater acidity and salinity“, Hugo A. Loáiciga, Geophysical Research Letters, 26 May 2006 — Abstract:

“This paper’s results concerning average seawater salinity and acidity show that, on a global scale and over the time scales considered (hundreds of years), there would not be accentuated changes in either seawater salinity or acidity from the observed or hypothesized rises in atmospheric CO2 concentrations.

(e) Phytoplankton Calcification in a High-CO2 World“, M. Debora Iglesias-Rodriguez et al, Science, 18 April 2008 — Abstract:

Ocean acidification in response to rising atmospheric CO2 partial pressures is widely expected to reduce calcification by marine organisms. From the mid-Mesozoic, coccolithophores have been major calcium carbonate producers in the world’s oceans, today accounting for about a third of the total marine CaCO3 production. Here, we present laboratory evidence that calcification and net primary production in the coccolithophore species Emiliania huxleyi are significantly increased by high CO2 partial pressures. Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over the past 220 years there has been a 40% increase in average coccolith mass. Our findings show that coccolithophores are already responding and will probably continue to respond to rising atmospheric CO2 partial pressures …

(f) Dynamic patterns and ecological impacts of declining ocean pH in a high-resolution multi-year dataset“, J. Timothy Wootton et al, Proceedings of the National Academy of Sciences (PNAS), 2 December 2008

(g) Marine calcifiers exhibit mixed responses to CO2-induced ocean acidification“, Justin B. Ries et al, Geology, December 2009 — Some animals can adapt to changing Ph.  ScienceDaily describes the results:  “In Carbon Dioxide-Rich Environment, Some Ocean Dwellers Increase Shell Production

(h) Direct observations of basin-wide acidification of the North Pacific Ocean“, Robert H. Byrne et al, Geophysical Research Letters, 20 January 2010

(i) Calcareous Nannoplankton Response to Surface-Water Acidification Around Oceanic Anoxic Event 1a“, Elisabetta Erba et al, Science, 23 July 2010 — Looking 120 million years into the past.

(j) Especially note this:  “Global phytoplankton decline over the past century“, Nature, Daniel G. Boyton, Marlon R. Lewis & Boris Worm, 29 July 2010 — Press release here.  According to the HadISST dataset, the global ocean surface temperature has only increased by 0.4 C in the last century years.  The authors state that this has caused “a global rate of decline of ~1% of the global median per year” since 1899.  A decline of 1/2!  And nobody noticed? Not likely.

(4)  Update: good news

Pacific coral happy as acidity of the ocean rises“, New Scientist, 1 January 2014 — Article for a general audience about “Diverse coral communities in naturally acidified waters of a Western Pacific reef”, Kathryn E. F. Shamberger, Geophysical Research Letters, 28 January 2014 — Abstract:

Anthropogenic carbon dioxide emissions are acidifying the oceans, reducing the concentration of carbonate ions ([CO32−]) that calcifying organisms need to build and cement coral reefs. To date, studies of a handful of naturally acidified reef systems reveal depauperate communities, sometimes with reduced coral cover and calcification rates, consistent with results of laboratory-based studies. Here we report the existence of highly diverse, coral-dominated reef communities under chronically low pH and aragonite saturation state (Ωar).

Biological and hydrographic processes change the chemistry of the seawater moving across the barrier reefs and into Palau’s Rock Island bays, where levels of acidification approach those projected for the western tropical Pacific open ocean by 2100. Nevertheless, coral diversity, cover, and calcification rates are maintained across this natural acidification gradient. Identifying the combination of biological and environmental factors that enable these communities to persist could provide important insights into the future of coral reefs under anthropogenic acidification.




One thought on “Death of the seas from CO2 acidification

  • Scripps blockbuster: Ocean acidification happens all the time — naturally“, Jo Nova, 9 January 2012 — Opening:

    There goes another scare campaign.

    Until recently we had very little data about real time changes in ocean pH around the world. Finally autonomous sensors placed in a variety of ecosystems “from tropical to polar, open-ocean to coastal, kelp forest to coral reef” give us the information we needed.

    It turns out that far from being a stable pH, spots all over the world are constantly changing. One spot in the ocean varied by an astonishing 1.4 pH units regularly. All our human emissions are projected by models to change the world’s oceans by about 0.3 pH units over the next 90 years, and that’s referred to as “catastrophic”, yet we now know that fish and some calcifying critters adapt naturally to changes far larger than that every year, sometimes in just a month, and in extreme cases, in just a day.


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