Long-term spectroscopic observations on water samples with phototrophic microorganisms from the supralittoral zone of the Alaid Volcano, the Kuril Islands
The Alaid Volcano (the Kuril Islands) is the highest and one of the most active volcanoes of the Kuril Islands, the unique object for interdisciplinary research. In 2015 within the supralittoral zone of the island the several splash pools filled with colored marine water were discovered for the first time. Observation of water colored by photosynthetic microbes in different parts of the Atlasov island within several summer seasons in 2015-2017 allowed us to conclude that the development of the purple phototrophic bacteria in the splash baths above the littoral zone is not an accidental even, but the stable phenomenon. This work continues spectral studies of natural water sampled from the rock baths of the island-volcano Alaid during scientific expeditions performed in 2018-2019. The optical studies were conducted to determine the presence of photosynthetic pigments through extraction by organic solvents, to establish the presence of phototrophic bacterial and algal communities in natural water, and to compare the results with the spectra of bacteria isolated and cultivated from the samples. Fluorescence emission and excitation spectra were recorded in laboratory conditions with a Solar CM2203 luminescence spectrometer. The absorption spectra of natural water samples/extractions were measured with a Solar PB2201 spectrophotometer with respect to distilled water/acetone-methanol mixture. The measurements were carried out in quartz cuvettes with an optical path length of 1 or 3 cm. The absorption measurements of the bright purple-red color samples showed maxima at 380, 590, 806, 854 nm wavelengths and the shoulders at 510, 590 and 890 nm, which corresponded to presence of bacteriochlorophyll a, the main photosynthetic pigment of purple sulfur bacteria, For the samples of green colored water, we found absorption bands characteristic for chlorophyll-containing microorganisms (algae or cyanobacteria). This research allowed to identify the rock baths with massive development of phototrophic microorganisms in several locations of the island-volcano Alaid (Atlasov Island) and to conclude that this is not an accidental event, but a stable natural phenomenon for this island.
The work was performed with financial support of the Russian Foundation for Basic Research, projects No 18-05-00410, 18-05-0041 and 19-05-00377, and the Ministry of Science and Higher Education of Russian Federation. The author A.A. Zhiltsova was also supported by the Foundation for the advancement of theoretical physics “BASIS”.
Faculty of Physics, Lomonosov Moscow State University,GSP-1, 1-2 Leninskie Gory, Moscow,119991
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