Crystal phases of calcium carbonate within otoliths of CYPRINUS CARPIO. L. from Miyun Reservoir and Baiyangdian Lake, China

Abstract

Asteriscus (lagenar otolith) of CYPRINUS CARPIO. L. (Cyprinida, common carp) from the serious intermittent 
polluted Baiyangdian Lake and the little polluted Miyun Reservoir, all located in northern China, were 
chemically and mineralogically analyzed. All the analyzed fish showed that the composition of asterisci 
is dominated by calcium carbonate, with the minor elements As, Ba, Sr, and Zn; and the polymorph of 
CaCO3 in the asterisci is vaterite. Three different vaterite X-ray diffraction (XRD) patterns were found in 
the analyzed samples. For the 60% fish from both localities, two different vaterite XRD patterns coexist 
in the core area and the edge area in same asteriscus sample. Significant differences of the dimensions 
of crystalline cells of vaterites exist between these two localities, which reveals that crystal structure of 
vaterite polymorphs seem sensitive to water quality and water environment, its crystalline cell 
dimensions might be a potential proxy for monitoring the change of water quality.