Mineralogical and geochemical study of carp otoliths from Baiyangdian Lake and Miyun Water Reservoir in China
Carp otoliths from two different freshwaters (Baiyangdian Lake and Miyun Water Reservoir) were mineralogically and chemically analyzed. The water quality standard of Miyun Water Reservoir is Grade 2 which is much better than the Grade 5 of Baiyangdian Lake. The aim of this study was to examine the differences in otoliths in mineralogy and chemistry from the two sites with quite different qualities. All the analyzed carps showed lapillus and sagitta otoliths made of aragonite, except for B-22 (from Baiyangdian Lake) whose lapillus consisted of vaterite and sagitta consisted of aragonite and vaterite; all asteriscus are composed of vaterite. It is inferred that the occurrence of vaterictic otoliths is linked to poor water quality. Chemical analysis showed that significant difference of Pb concentration between sites was tested by t-test of the compare means (t-test comparison: t = 2.043, P<0.05). While the sitespecific differences of the other metals were not significant. In addition, a significant difference of Sn concentration was tested as well (t-test comparison: t = 2.652, P<0.05). Average content of lapilli Pb is consistent with the water dissolved Pb measurement, with higher dissolved Pb concentration in Baiyangdian Lake relative to the Miyun Water Reservoir.
Key words: Carp otoliths, water quality, mineralogy, chemistry, Pb.