Tiny creatures at the bottom of the food chain called diatoms suck up nearly a quarter of the atmosphere's carbon dioxide, yet research by Michigan State University scientists suggests they could become less able to "sequester" that greenhouse gas as the climate warms. The microscopic algae are a major component of plankton living in puddles, lakes and oceans.
Zoology professor Elena Litchman, with MSU colleague Christopher Klausmeier and Kohei Yoshiyama of the University of Tokyo, explored how nutrient limitation affects the evolution of the size of diatoms in different environments. Their findings underscore potential consequences for aquatic food webs and climate shifts.
"They are globally important since they 'fix' a significant amount of carbon," Litchman explained of the single-cell diatoms. "When they die in the ocean, they sink to the bottom carrying the carbon from the atmosphere with them. They perform a tremendous service to the environment."
Carbon dioxide buildup, due to a significant extent to burning fossil fuels and deforestation, is identified as the leading cause of climate change. Carbon dioxide is at its highest level in at least 650,000 years and rising, according to The National Academies, and only half of the CO2 produced now can be absorbed by plant life.
Litchman analyzed data from lakes and oceans across the United States, Europe and Asia and found a striking difference between the size of diatoms in freshwater and in marine environments. In oceans, diatoms grow to be 10 times larger on average than in freshwater and have a wider range of sizes.
One factor that affects growth is nutrient availability, Litchman said. The research shows that limitations by nitrogen and phosphorus exert different selective pressures on cell size. The availability of these nutrients depends on the mixing of water from greater depths. Using a mathematical model, Litchman and her colleagues found that when those nutrients are constantly limited and mixing is shallow, smaller diatoms thrive.
But when nitrate comes and goes, as often happens in roiling oceans, diatoms evolve larger to store nutrients for lean times. Deep mixing also benefits large diatoms. Depending on how intermittent the nitrate supply is and how deep the ocean mixes, there can be a wide range of diatom sizes. Size matters for the creatures that eat them and also for carbon sequestration, as large diatoms are more likely to sink when they die.
Changing climate could alter the mixing depths and delivery of nutrients to diatoms and their subsequent sizes with a cascade of consequences, Litchman said.
"On a global scale, increased ocean temperatures could make the ocean more stratified," she explained. "This would cause less mixing and create stronger nutrient limitation and less frequent nutrient pulses. A change like this would select for different sizes of diatoms. If smaller sized diatoms dominate, then carbon sequestration becomes less efficient and there may be more CO2 remaining in the atmosphere, which would exacerbate global warming."
Litchman and colleagues' research was supported by the National Science Foundation and the J.S. McDonnell Foundation. Their findings were published recently in the Proceedings of the National Academy of Sciences.
Comments
the ideas.
The diatom is the most vital organism on the planet for it feeds the oceans and as it sequesters carbon through photosynthesis it gives off the critical core of the 60% of the earth's oxygen (the percentage attributed to the oceans.
Even more, where this oxygen would most logically be carried over land one finds the principal rains that water the core of the crops produced by the landmasses of the Northern Hemisphere.
In any case the triangular North Pacific would, most logically, pinch water movement into place and the S-shaped Atlantic lift.
The fact that the South Atlantic draws water from both the Indian and the South Pacific (around Cape Horn) when it should be slipping with the wind, makes this [Cape Horn] the roughest of waters on earth (due to the Atlantic's lifting).
As this foreign (trans-equatorial) jet enters the North Atlantic it draws the seed diatoms from the area around the Sargasso and at its convectional bend, southeast of George's Bank (a shoal documented as the primary reproductive section of the North Atlantic for fish) the sinking Gulf Stream creates great eddies known as Gulf Rings that carry seed diatoms on an arching path towards George's Bank in the same season the precise food for the triggering of the diatom bloom should be surfacing at Cape Cod (a deposit of silica) to be swept off shore to meet and be inhaled by the watery tornado-like Rings.
Most all the newly hatched fish (and shellfish) of George's Bank from cod, to flounder, to hake and herring depend for survival upon the diatom.
If one adult cod lays between 4 million and 7 million eggs and the two dozen other species that spawn here also depend upon diatoms. . . have the fish stocks in the North Atlantic have declining over the past 70 years been cause primarily by over-fishing as most everyone believes, or could it have to do with the extreme erosion of Cape Cod and Nantucket? It is my belief that this erosion has been mistakenly blamed on winter storms that sweep up this coast known as "Northeasters."
The truth is that the Labrador Current, the richest of cold water veins, is being ruptured. Without silica in this current, the Cape and Nantucket erode and the diatom bloom as a geometric progression, is being chopped before it begins.
Without diatoms, the newly hatched starve soon after taking life.
With a greatly reduced diatom count in the North Atlantic the fishing grounds from the Grand Banks, to the southern tip of Greenland, to the southern tip of Iceland, the British Isles, North Sea and even the North Pacific fed via the Bering Strait and Bering Sea. As this rich super-cooled flow passes out on the floor of the Bering Sea it creates the Alaskan "King" Crab (proof of this rich food).
Where the oxygen produced by the bloom would most logically be carried over land one finds the rains over the British Isles (that then drift over Northern Europe). Where it surfaces in the Northeastern Pacific it creates the nearly constant rains of the Pacific Northwest and Canadian West that then drift over North America (watering the farmlands of the Midwest, "breadbasket of thew world".
This means the rupture of the vein that triggers the diatom bloom is reducing fish stocks in the two most productive oceans on the planet.
If one were to repair this mechanism it would generate over a trillion dollars of revenue for the United Sates and the same for the rest of the world.
By repair the Bloom one could turn vast areas of these oceans into carbon dioxide-absorbing, oxygen emitting surfaces.
Richard Henkels (not verified) | 04/17/09 | 10:10 AM
At the Sargasso this is to beshown to draw seed diatoms. And a thousand miles to the north the sinking of the Gulf Stream in late autumn and winter stirs up turbulence, sewith diatoms amongst other microorganisms.
Due to the counterclockwise motion of theses eddies they are carried on an arching northwesterly course where, in the same season the precise food for triggering the diatom bloshould be surfacing at Cape Cod *(A deposit of silica).