Twenty
milligram CWM were digested in a triacid solution (HNO3:H2-
SO4:HClO4, 5:1:1, v/v/v) at 80 C until a red vapor was detected,
then the temperature increased to 150 C for more than 7 h until
a clear residue was produced. Calcium content was assayed by
atomic absorption using a Perkin–Elmer 5100 spectrophotometer
at 422.7 nm and expressed as lg g1 dry weight (DW).