Complex controls on the trace-element chemistry of non-marine ostracods: an example from Lake Pلtzcuaro, central Mexico

The calcitic shells of non-marine ostracods are sources of geochemical information that have the potential to record changes in the water chemistry of closed-basin lakes resulting from variations in the hydrological budget within the catchment. In particular the uptake of Sr and Mg into the shell has been shown to be a function of salinity, and salinity and temperature, respectively. This paper assesses the trace-element chemistry records from 4 short (1.5–2.8 m) cores from Lake Pátzcuaro, central Mexico, in the light of a detailed limnological study of the lake. The following three environmental factors are believed to have influenced the interpretation of the trace-element chemistry record: (i) salinity: the salinity of Lake Pátzcuaro lies close to the calcite branchpoint, below which the linear relationship between Mg/Ca or Sr/Ca and salinity has been lost in the fossil record; (ii) environmental stresses: e.g. low HCO3− concentrations, produced poorly calcified valves. This study found this had no significant effect on the trace-element chemistry results; and (iii) solute composition of the host water: changes in the solute concentration of inwash waters played a primary role in determining major water chemistry changes within the lake.