Quantification of bacteriochlorophylls d and e in water with green sulfur bacteria: spectroscopic approaches

Abstract

Optical characteristics of water in stratified lakes are important to study in connection with the observation of colored layers in their chemocline zone resulted from the massive development of anoxygenic phototrophic bacteria. Several water bodies on the coast of the Kandalaksha Bay of the White Sea are known as being at different stage of isolation from the Sea. The development of sulfur bacteria indicates the presence of hydrogen sulfide in deep water layers; therefore, it is important to have reliable and fast methods to assess concentration of phototrophic bacteria and their main pigments, bacteriochlorophylls (BChl). While chlorophyll (Chl a) optical properties have long been used for quantitative measurements of phytoplankton in aquatic ecosystems, methods for measuring the concentration of BChl are only being developed. We describe several spectral techniques for measuring BChl d and BChl e in extracts in organic solvents with preliminary concentration of bacteria using filtration, as well as methods for measuring pigments directly in water with microbial cells. Examples of BChl depth distribution in March and September 2021 for several reservoirs of the Kandalaksha Bay of the White Sea are given.
The work was performed using the financial support of the RFBR grant No. 19-05-00377 and the Theoretical Physics and Mathematics Advancement Foundation “BASIS


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Anna Zhiltsova
Lomonosov Moscow State University, Faculty of Physics
Moscow, Russia

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