Investigation of flora and fauna species of Lake Baikal by electron-probe microanalysis

Complete text of publication follows. Baikal is an ancient unique lake. The sweet water of Baikal is crystal clean; it concentrates oxygen and contains scarce silicon. This feature is provoked very particular interest for scientists and poses some awkward questions concerning the preservation of Baikal's ecosystem. A profound investigation of fish otholiths, animal teeth, sponges, valves of mollusks and diatom algae provides chronological information, possibility to reconstruct the events proceeding in the environment based on variations of their chemical composition. Because these study objects are small-sized, and some of them are micron-size, application of the electron-probe microanalysis turns to be quite productive. The goal of this study is to disclose performance capabilities of this method while investigating the Baikal flora and fauna. Investigations were performed by devices JCXA-733 and JXA-8200 using the electron microscope and x-ray microprobe modes. Measurements of intensities were carried out by wave spectrometers and energy-dispersive spectrometers Sahara (Prinston Gamma-Tech Ltd) and EX-84055MU. Samples were prepared differently for every species: sponges, diatom valves and mollusk shells were saturated with epoxy resin, fish otholiths and seal teeth were cut across and length-wise and sealed with epoxy resin. Examination of obtained surfaces using back scattering and secondary electrons and x-rays recognized the pattern of element distribution in fish otholiths, seal teeth, sponge spicules, and mollusk and diatom valves. The results of such investigations are provided as maps and curves of distribution of element contents through the sections selected. The chemical composition of omul and golomyanka otholiths, seal teeth, sponge spicules, mollusk and diatom valves are tabulated. Some distinctions have been identified in the concentrations of sodium and calcium in different parts of otholiths. The teeth tissue of seal has a layered structure, and its porosity depends on the animal age. The content of silicon in spicules of different sponges varies essentially, and the distinctions are obvious between the upper and lower parts of a sponge. The valves of diatoms from sediments contain silica and aluminum. Aluminum content increases with increasing age of sediments. The author thanks Drs L. F. Paradina, I. V. Levina, P. N. Anoshko, E. V. Pastukov for sharing sample collections.