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Earthworm calcite

The importance of earthworms in a variety of soil processes is well established, e.g. mixing and aeration of soil, breakdown of organic matter. It is less well appreciated that many earthworm species produce millimetre sized aggregates of calcite crystals called granules.
Dr Denise Lambkin (NE/F009623/1, 2008-9) determined rates of granule production and dissolution and controls on these rates. She demonstrated that granule production decreased with decreasing pH but that under suitable conditions granules can last in soils for thousands of years playing an important part in the terrestrial calcium cycle.
We went on to investigate the incorporation of trace metals into the granules. in collaboration with Professor Fred Mosselmans (Diamond) and Paul Schofield (Natural History Museum) we investigated Pb (Anne Fraser, MSc project), Sr and Zn (Dr Loredana Brinza, Diamond, 2010-13)
In a NERC project Dr Emma Versteegh (NE/H021914/1, 2010-2013) has demonstrated the potential use of granule calcite as a palaeothermometer and we are presently applying our novel thermometer to palaeogranules.

We are also pursuing work investigating the mineralogical composition of the granules, most notably the occurrence of calcium carbonate phases other than calcite in the granules.
A granule of calcium carbonate secreted by the earthworm L. terrestris
CLose up of an earthworm calcium carbonate granule