Microbial degradation of biomass of Lyngbya aestuariі (Mertens) liebmann in hyperhaline brine from peloid deposits

Abstract

Microbial degradation of organic matter of benthic macroscopic growths of Lyngbya aestuariі in brine from peloid deposits on the Arabat and Berdyansk spits was studied through laboratory experiments measuring the biomass of L. aestuarii and the quantity of different physiological groups of destructive microorganisms. The biomass of L. aestuarii was dried, placed in brine-filled flasks, and exposed to different temperatures for 300 days, with the mass loss measured every 30 days. It was found that 1/4 part of biomass decomposes in 8–10 months depending on the temperature regime. Degradation is not uniform and is divided into two phases: in the first (120–150 days) biomass loss does not exceed 2%; in the second stage – the degradation rate increases significantly, causing a decrease in algal biomass over the next 120–150 days for 20–40%. The study estimated the quantity of various destructive microorganisms (their colony-forming units) using different nutrient media: starch agar, meat-peptone agar, and pork lard agar. It was found that the initial degradation of L. aestuarii involves proteolytic and lipolytic bacteria. It is shown that the degradation of L. aestuariі is accompanied by a decrease in the amount of dissolved oxygen. Anaerobic conditions developed starting from the 30th day. The duration of degradation of prokaryotic mats and anaerobic conditions in the brine indicate that these benthic growths can serve as a substrate for microbial transformation and also as a preservative agent that retains the products of organic matter decomposition from oxidation for a long period. Such properties may indicate deposits of high-quality black silty sulfide peloids or they can be used in the production of artificial medical mud with properties that are close to natural ones.