ELEMENTAL COMPOSITION OF A TUSK OF A DUGONG, DUGONG DUGON, FROM EXMOUTH, WESTERN-AUSTRALIA

Element analysis of the annual increments in a longitudinal section fr om the tusk of a female dugong Dugong dugon (Muller) from Exmouth, Wes tern Australia, was carried out by X-ray fluorescence-imaging, inducti vely coupled plasma-atomic emission spectrometry (ICP-AES) and inducti vely coupled plasma-mass spectrometry (ICP-MS). Nine elements (Ba, Ca, Fe, Li, Mg, Na, P, Sr and Zn) were present in concentrations amenable to determination by these techniques. Most elements revealed both lon g-term trends and shorter, year-to-year, variations. For example, sodi um concentrations increased from 0.55 to 0.72% with the age of the dug ong. Strontium concentrations (mean 0.17%) were closely correlated (r = 0.86) with those of barium (mean 4.5 mg kg(-1)). Zinc concentrations increased from similar to 70 to 170 mg kg(-1) with dugong age, but al so showed shorter-term fluctuations of similar to 30 mg kg(-1) that we re correlated (r = 0.41) with mean annual Fremantle sea level (a measu re of the Southern Oscillation Index and strength of the Leeuwin Curre nt). The concentrations of the elements and correlations with year and between pairs of elements are discussed.