Without pH information, temperature reconstruction from magnesium to calcium ratios of such algae could be rather misleading», Dr. Jan Fietzke points out. (oceanacidification.de)
She took 10 to 20 samples from each annual band of each core and analyzed the samples for the strontium / calcium ratio using atomic emission spectrometry. (sciencedaily.com)
Sufficient vitamin D is needed for calcium absorption as is a proper potassium / calcium ratio in the blood. (westonaprice.org)