|Earthworm Calcite Granules|
A new method for determination of past climate data on land applied comparatively for the first time / Ice Age summers in Central Europe were at times warmer than previously known
Scientists from an international research project led by Johannes Gutenberg University Mainz (JGU) have applied a new method to reconstruct past climate. As they report in the current issue of Communications Earth & Environment, they have determined temperatures and precipitation during the last Ice Age, which peaked about 25,000 years ago, by analyzing earthworm granules. “The new method was discovered at Université Paris 1 Panthéon-Sorbonne and further developed at the Max Planck Institute for Chemistry,” said Dr. Peter Fischer of JGU’s Institute of Geography, who was the lead investigator of the TerraClime project funded by the German Research Foundation (DFG) in which the study is embedded. “In cooperation with other scientists, including researchers from the University of Lausanne and Römisch-Germanisches Zentralmuseum, we used the method to reconstruct the climate at Schwalbenberg near Remagen and Nußloch near Heidelberg.” The two sites form well-developed last-glacial dust deposits. The so-called loess contains sequences dating from 45,000 to 22,000 years before present, in which the earthworm granules with up to about only 2.5 millimeters in size can be found throughout. These calcitic granules, technically known as Earthworm Calcite Granules (ECGs), are secreted daily by earthworms. Using the so-called radiocarbon method, which is based on the decay of the naturally occurring radioactive carbon isotope (14C), researchers can precisely determine their age. Additionally, by analyzing the ratios of stable oxygen and carbon isotopes in the ECGs, it is then possible to reconstruct how warm or how humid it was at the time of their formation.
“Analysis of the data obtained from the ECGs shows that from 45,000 to 22,000 years before present it was much drier in Central Europe than it is today, with up to 70 percent less humidity,” said Dr. Charlotte Prud’homme from the University of Lausanne, the study’s lead author. “This allows us for the first time to quantify previous findings about this period.” The novelty in these investigations on ECGs is that summer temperatures at the time were significantly higher than previously thought. “Although summers during the cold maximum of the last glacial were about four to eleven degrees Celsius colder than today, they were only one to four degrees below the values of short milder climatic phases that occurred during the last glacial,” explained Fischer. “Given these summer temperatures, we cannot exclude that Ice Age human populations may have made a seasonal living in Central Europe during the cold maximum, at a time for which it is generally assumed that humans could not survive here,” added Dr. Olaf Jöris of Römisch-Germanisches-Zentralmuseum, who was also involved in the study.
|Heidi Klum dressed as an earthworm|
“Darwin observed that the crystals formed, but no one has looked closely at their mineralogical composition before,” says Mark Hodson, a geochemist at the University of Reading in England and co-author of a new study published in Geology. “We found the crystals are composed of finely zoned calcite wrapped around a central grain of quartz.”
Hodson and colleagues analyzed scanning-electron-microscope images and found that the calcite starts out in the worm as amorphous calcium carbonate and is then converted into crystalline calcium carbonate, or calcite, before it is excreted. “Amorphous calcium carbonate is thermodynamically unstable,” Hodson says. “So it’s not clear if the earthworm is intentionally converting the amorphous stuff to calcite or whether it’s just thermodynamics taking its toll. It all ties back into why this occurs in the first place, which we don’t yet know.”
“There are a number of theories,” Hodson says. “But each has proved unsatisfactory in one way or another.” Earthworms may use the calcium carbonate to regulate the pH or carbon dioxide levels in their intestines, or perhaps they inadvertently ingest large quantities of calcium carbonate as they move through the soil and the crystals are the most efficient way of getting rid of excess calcium, which can be toxic in high concentrations, he says.
What is known is that calcite granules are produced by most species of earthworms in many different soils. Laboratory studies have shown that an individual worm can produce 2.2 milligrams of calcite per day, or as many as 30,000 granules per year. And soil studies have recorded as much as 56 kilograms of earthworm-produced calcite per hectare of soil. “These worms produce a tremendous amount of calcite. It’s a wonder we’re not knee deep in the stuff,” says Matt Canti, a geoarchaeologist with the English Heritage Commission in England, who has investigated the possibility of using earthworm-derived calcite crystals to radiocarbon date ancient soils. Such techniques are possible, he says, but difficult and very expensive.
So, you get a lot of calcium from eating dirt, and you there's lots of CO2 in most soil, so yes, it make sense to help them to get together and get out of your system. Makes sense. It might even be true.