Polycyclic Aromatic Hydrocarbons in the Surface Microlayer of Lake Baikal during Wildfires and Naphthalene-degrading Str
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XPERIMENTAL ARTICLES
Polycyclic Aromatic Hydrocarbons in the Surface Microlayer of Lake Baikal during Wildfires and Naphthalene-Degrading Strains from the Bacterioneuston A. D. Galachyantsa, *, M. Yu. Suslovaa, I. I. Marinaytea, O. N. Izosimovaa, A. Yu. Krasnopeeva, Yu. R. Shtykovaa, I. V. Tikhonovaa, G. V. Podlesnayaa, and O. I. Belykha aLimnological
Institute, Siberian Branch of the Russian Academy of Sciences, Irkutsk, 664033 Russia *e-mail: [email protected] Received February 21, 2020; revised May 18, 2020; accepted May 29, 2020
Abstract —The summer of 2015 was characterized by a large number of forest fires along the coastline of Lake Baikal. The concentrations of all analyzed polycyclic aromatic hydrocarbons (PAHs) in the surface microlayer of Lake Baikal during wildfires in August 2015 were significantly increased compared to August 2017, when there were fewer fires. Among the PAHs, naphthalene, phenanthrene and pyrene dominated in the surface microlayer in August 2015, while in August 2017, only naphthalene and its derivatives were prevalent. To evaluate the PAH-degrading capacity of the strains Pseudomonas sp. P30, Microbacterium sp. NC4, Massilia sp. NC8, Flavobacterium sp. NC135, Pseudomonas sp. NC83, and Bacillus sp. P29.2.1 isolated from the Lake Baikal surface microlayer, a laboratory-based experiment was established. Suspension cell cultures in mineral medium were set up in flasks, and naphthalene was added as the only source of carbon. Flasks were incubated for 5–20 days at a temperature of 18°С. It was shown that the strains could effectively biodegrade naphthalene. Keywords: aquatic surface microlayer, polycyclic aromatic hydrocarbons, naphthalene-degrading bacteria, Lake Baikal, forest fires DOI: 10.1134/S0026261720050082
INTRODUCTION During the summer of 2015, a large number of forest fires were recorded in the area adjacent to Lake Baikal (https://worldview.earthdata.nasa.gov/). Lake Baikal is of unique natural significance, being the oldest lake in the world with an age of about 25 million years. It has a surface area of 31,500 km2 and a water volume of 23,000 km3. Prior studies of the impact of wildfires on surface water quality have mainly focused on nutrients, especially phosphate, nitrate and ammonium (Spencer and Hauer, 1991; Earl and Blinn, 2003). However, contamination by pyrolytic substances has increasingly received research attention, in particular polycyclic aromatic hydrocarbons (PAHs) (Olivella et al., 2006; Vila-Escalé et al., 2007; Schäfer et al., 2010; Campos et al., 2012). PAHs are organic compounds containing only carbon and hydrogen that are composed of multiple aromatic rings. They are known for their cytotoxic, mutagenic and cancerogenic potential, as well as their environmental persistence and tendency towards bioaccumulation (Bastiaens et al., 2000; Baboshin and Golovleva, 2012; Hassanshahian et al., 2015). The hydrophobic nature of PAHs causes them to accumu-
late in the surface microlayer of water (SML), at the boundary between the hydrosphere and the atmosphere.
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