By Sean B. Carroll, New York Times. An article relevant to GSS Climate Change chapter 8, Life and Climate chapter 9, and A Changing Cosmos chapter 1. Excerpt: GUBBIO, Italy — …Limestone is composed largely of crystallized calcium carbonate. Some of it comes from the skeletal remains of well-known creatures like corals, but much of the rest comes from less appreciated but truly remarkable organisms called foraminifera, or forams for short. Forams have been called “nature’s masons,” … these single-celled protists construct surprisingly complex, ornate and beautiful shells to protect their bodies. After forams die, their shells settle in ocean sediments…. While tiny relative to ourselves …, forams are extremely large for single-celled organisms, … largest forams can reach a few centimeters. … forams are particularly valuable to geologists and paleontologists in telling us about Earth’s history. The forams in the limestone just outside Gubbio provided the first clues to … an asteroid that struck earth at the end of the Cretaceous period, 65 million years ago…about the size of Mount Everest and traveling at about 50,000 miles an hour when it hit the earth, drilling a 120-mile-wide crater and ejecting so much material into (and even out of) the atmosphere that food chains on land and in the oceans were disrupted for thousands of years. The impact caused one of the greatest mass extinctions in history, from the largest animals to tiny forams.
...Forams are a vital part of a “biological pump” that removes carbon dioxide from the atmosphere. When carbon dioxide dissolves in seawater, one reaction product is carbonate. In making their calcium carbonate shells, the large mass of so-called planktonic forams floating in the upper levels of the oceans sequester about one quarter of all carbonate produced in the oceans each year.
The increasing levels of carbon dioxide in our planet’s atmosphere, now at a greater level than at any time in the past 400,000 years, threaten to overwhelm this biological pump by inhibiting the formation of calcium carbonate shells. As more carbon dioxide dissolves in the ocean, the waters acidify, decreasing the concentration of carbonate and making it more difficult for these organisms to form calcium carbonate shells…. Read the full article: http://www.nytimes.com/2012/06/26/science/natures-masons-do-double-duty-as-earths-storytellers.html?_r=1&emc=eta1
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