Ehux lives! We think!
The journal Science last week published a paper that challenges several years of thinking about how an algal species pivotal to the oceans' health will fare under higher atmospheric, and therefore oceanic, carbon levels.
Many factors make coccolithophores intriguing. If nothing else, they are beautiful. Check out this micrograph of one species, Calcidiscus leptoporus:
They are storied little creatures -- plant flakes on the half-shell, basically. Thomas Henry Huxley, "Darwin's bulldog," wrote a memorable essay about their geological and evolutionary significance in 1868, giving credit to calcifying microorganisms for the great chalk chalk deposits of Eurasia, from Britain, south to Morocco, and east to Syria. Carbon cycle scientists in the second half of the 20th century acknowledged their importance to the healthy flow of carbon through the atmosphere and oceans, down to sediment -- a leg of the carbon cycle thought to be under some strain if coccolithophores fail to adjust well to ocean waters rendered more acidic by industrial CO2 pollution. For their size, coccolithophores have disproportionate influence on the global carbon cycle. They are one of three classes of organisms that together make up less than one percent of photosynthetic biomass, but fix carbon into about 45 percent of total biomass. Coccolithophores are shelled algae that take up carbon both for their soft cellular material, and the calcite coccoliths that shield them, spinning it into the ocean carbon cycle, and contributing significantly to the removal of carbon from the atmosphere-ocean system. Their blooms can cover millions of square kilometers of ocean -- they're one of the few organisms that an only be seen with either an electron microscope or a satellite.
A coccolithophore bloom off Newfoundland, satellite image taken July 21, 1999
Head-turning studies in the early 2000's dimmed the future of coccolithophores' prodigious carbon-munching, particularly that of their most abundant species, Emiliana huxleyi. A study published in Nature in 2000 revealed sickly growth patterns in Ehux populations living in waters more acidic than today's:
Emiliana huxleyi, healthy (left); under simulated acidic ocean conditions (right)
Ulf Riebesell et al wrote in 2000 that ocean acidification caused by industrial CO2 pollution would slow down these algae's ability to make their calcite shields. And given the importance of these shields to the oceanic carbon conveyer, a problem for Ehux could be a problem for the entire global carbon cycle.
The paper published last week sheds new hope on Darwin's Bulldog's chalk-makers. The new experiment takes a different approach to simulated ocean conditions under high CO2 scenarios. The Riebesell study in 2000 made the laboratory seawater more acidic by adding hydrochloric acid. The new study actually bubbled CO2 through the water to attain the desired levels of both alkalinity and carbon content.
The results are dramatically different the species studied. Ehux thrives under these new, more accurately simulated conditions. Between 280 parts CO2 per million parts of air to 490 ppm, Ehux calcifies and grows as expected. From 490 ppm to 750 ppm, Ehux dramatically steps up the amount of inorganic carbon (shell) and organic carbon (fruity interior) that it produces. What's more, ocean sediment samples correlate this simulated increase in carbon uptake among Ehux -- further evidence that researchers are on the right track.
This new study is an important piece of the coccolithophore/oceans puzzle -- and also an indicator of how many pieces remain to snap into place, particularly when we don't even really know how many "pieces" there are. One of the authors of the paper wrote me:
Many factors make coccolithophores intriguing. If nothing else, they are beautiful. Check out this micrograph of one species, Calcidiscus leptoporus:
They are storied little creatures -- plant flakes on the half-shell, basically. Thomas Henry Huxley, "Darwin's bulldog," wrote a memorable essay about their geological and evolutionary significance in 1868, giving credit to calcifying microorganisms for the great chalk chalk deposits of Eurasia, from Britain, south to Morocco, and east to Syria. Carbon cycle scientists in the second half of the 20th century acknowledged their importance to the healthy flow of carbon through the atmosphere and oceans, down to sediment -- a leg of the carbon cycle thought to be under some strain if coccolithophores fail to adjust well to ocean waters rendered more acidic by industrial CO2 pollution. For their size, coccolithophores have disproportionate influence on the global carbon cycle. They are one of three classes of organisms that together make up less than one percent of photosynthetic biomass, but fix carbon into about 45 percent of total biomass. Coccolithophores are shelled algae that take up carbon both for their soft cellular material, and the calcite coccoliths that shield them, spinning it into the ocean carbon cycle, and contributing significantly to the removal of carbon from the atmosphere-ocean system. Their blooms can cover millions of square kilometers of ocean -- they're one of the few organisms that an only be seen with either an electron microscope or a satellite.
A coccolithophore bloom off Newfoundland, satellite image taken July 21, 1999
Head-turning studies in the early 2000's dimmed the future of coccolithophores' prodigious carbon-munching, particularly that of their most abundant species, Emiliana huxleyi. A study published in Nature in 2000 revealed sickly growth patterns in Ehux populations living in waters more acidic than today's:
Emiliana huxleyi, healthy (left); under simulated acidic ocean conditions (right)
Ulf Riebesell et al wrote in 2000 that ocean acidification caused by industrial CO2 pollution would slow down these algae's ability to make their calcite shields. And given the importance of these shields to the oceanic carbon conveyer, a problem for Ehux could be a problem for the entire global carbon cycle.
The paper published last week sheds new hope on Darwin's Bulldog's chalk-makers. The new experiment takes a different approach to simulated ocean conditions under high CO2 scenarios. The Riebesell study in 2000 made the laboratory seawater more acidic by adding hydrochloric acid. The new study actually bubbled CO2 through the water to attain the desired levels of both alkalinity and carbon content.
The results are dramatically different the species studied. Ehux thrives under these new, more accurately simulated conditions. Between 280 parts CO2 per million parts of air to 490 ppm, Ehux calcifies and grows as expected. From 490 ppm to 750 ppm, Ehux dramatically steps up the amount of inorganic carbon (shell) and organic carbon (fruity interior) that it produces. What's more, ocean sediment samples correlate this simulated increase in carbon uptake among Ehux -- further evidence that researchers are on the right track.
This new study is an important piece of the coccolithophore/oceans puzzle -- and also an indicator of how many pieces remain to snap into place, particularly when we don't even really know how many "pieces" there are. One of the authors of the paper wrote me:
The evidence is not all unanimous for coccos, with some studies showing detrimental effects, others not. For instance, another large study was just published last week, and they found reduced calcification at high CO2, in line with the earlier work and contradictory to our study. And they bubbled with CO2 rather than adding acid, i.e. the 'correct' way.Let's just be relieved that I hedged this passage in The Carbon Age, in anticipation of a study like this coming out!
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