Comparative analysis of spectral methods for detection of the concentration of bacteriochlorophyll d of green sulfur bacteria in water
A.A. Zhiltsova1, O.A. Filippova1, E.D. Krasnova1, D.A. Voronov2, S.V. Patsaeva1
1Lomonosov Moscow State University, Moscow, Russia
2Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), Moscow, Russia
Keywords: bacteriochlorophyll, fluorescence, absorption spectrum, anoxygenic phototrophic bacteria, green sulfur, stratified reservoirs, the White Sea
Abstract
An important characteristic of a natural reservoir is the distribution of the pigment composition of various groups of photosynthetic organisms over depth and its changes in different seasons. Optical methods are widely used to monitor the concentration of chlorophylls of algae or cyanobacteria in aquatic ecosystems, but they are very limited used to monitor the bacteriochlorophyll (BChl) concentration of phototrophic bacteria. The paper describes in detail three methods of quantitative analysis of the photosynthetic pigment of BChl d of green sulfur bacteria using spectral measurements both in initial samples of natural water (optical density spectra) and in pigment extracts in organic solvents (absorption and fluorescence spectra). A comparative analysis of the results of different methods is carried out on the example of natural water from the chemocline region of the lake Trekhtzvetnoe, one of the meromictic reservoirs of the Kandalaksha Bay of the White Sea (water from different depths was selected in March 2021). The conclusions about the conditions of applicability of different methods, their advantages and limitations were made. All three methods for estimating the BChl concentration have proved their applicability on the samples of natural water with BChl concentrations differing by orders of magnitude, from 5 to 5000 mg/m3.
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