Effect of dumped chemical weapon on the Baltic Sea microbiota

Seawater contamination with mustard gas and its derivatives substantially affects marine microorganisms. The mustard gas hydrolysis products (MGHPs) cause depletion of the species composition of microbiocenosis, as suggested by decreases in the Shannon and Pielou indices and the increase in the dominance index. Significant ecological shifts manifested as the decrease in the similarity indices. Decreased bacterial diversity suggests growth of a tolerant opportunistic species. From among bacterial cultures tolerant to mustard gas hydrolysis products the MGHPs-degrading microorganisms were isolated. The isolates were identified as Flavobacterium, Alcaligenes, Bacillus, or Pseudomonas spp. The main properties of these microorganisms are the tolerance to MGHPs, and the ability to utilize thiodiglycol. MGHPs-degrading bacteria can use mustard gas hydrolysis products as the sole source of carbon and energy at the organochlorine substances and thiodiglycol concentrations up to 240 mg/l and 6 g/l, respectively. The results suggest a potential for MGHPs biodegradation by natural occurring populations of near-bottom water and sediment microorganisms. Reduction in the species diversity of the marine microbiota suggests a decrease in the stability of the biosystem as a whole.