Nonspecific response of Lake Baikal phytoplankton to anthropogenic impact

In this study, we present the first results on oxidation stress in Lake Baikal phytoplankton and its adaptation to environmental changes under anthropogenic impact. As was shown, the changing of the dominant species of phytoplankton collected from the surface water layer (similar to 0.3 m) took place from February to June 2021. Phytoplankton were collected at a nearshore station (a littoral station at a distance of similar to 0.01 km from the shoreline, depth to bottom is similar to 5 m) and an offshore station (a pelagic station at a distance of similar to 1 km from the shoreline, depth to bottom is similar to 543 m). In February, dinoflagellates were dominant (similar to 40 %) as well as diatoms (<= 33 %) and green algae (<= 12 %). Their biomass was 100 mg center dot m(-3). In March, chrysophytes were dominant (up to 50 %) as well as cryptophytes (<= 43 %) and dinoflagellates (<= 30 %). Their biomass was 160-270 mg center dot m(-3). In April, biomass increased up to 700-3100 mg center dot m(-3) with the dominance of large cell dinoflagellates (up to 99 %), chrysophytes (up to 50 %), and cryptophytes (up to 35 %). By the end of the first decade of May, the percentage of dinoflagellates decreased and that of cryptophytes increased. In the second decade of May, the percentage of diatoms increased up to similar to 26-38 % but phytoplankton biomass was minimal (13-30 mg center dot m(-3)). By June, the percentage of diatoms in the samples reached 44-75 % at 60-550 mg center dot m(-3). The oxidation stress of phytoplankton as a nonspecific adaptive response to a prolonged, intensive, or recurrent effect of a stress factor was estimated from the content of thiobarbituric acid reactive substances ( TBARS). The mean content of these substances (markers of the lipid peroxidation) was determined spectrophotometrically. The oxidation stress of phytoplankton was revealed only when diatom algae dominated. It can be explained by adaptation of algae of other classes to the stress factor. The content of the lipid peroxidation markers in the coastal phytoplankton collected close to the settlement of Listvyanka known as a large touristic center was estimated from 100 to 500 mu g center dot g(-1) of dry weight of sample. During the period of diatom blooming in 2016 and 2018, oxidation stress of phytoplankton collected near large settlements was found. In phytoplankton from deep-water pelagic stations most remote from settlements, stress was not revealed. Using the method of gas chromatography, we showed a lower (up to 15 %) content of polyunsaturated fatty acids in phytoplankton characterized by stress occurrence. This confirms cell membrane damages. In Lake Baikal surface water, we found a higher content of synthetic anionic surfactants (sodium alkylbenzene sulfonates), which are components of detergents and cause oxidation stress of hydrobionts (up to 30 +/- 4 mu g center dot L-1). The presence of these substances in a water ecosystem can result in exhausting of phytoplankton cell resources, homeostasis imbalance, stress, pathological changes, and rearrangements in phytoplankton assemblage.