Limnology and Freshwater Biology 2020 (3): 433-438 DOI:10.31951/2658-3518-2020-A-3-433 Original Article Mass development of periphyton ciliates in the coastal zone of Southern Baikal in 2019-2020 Khanaev I.V.*, Obolkina L.A., Belykh O.I., Nebesnykh I.A., Sukhanova E.V., Fedotov A.P. Limnological Institute, Siberian Branch of the Russian Academy of Sciences, Ulan-Batorskaya Str., 3, Irkutsk, 664033, Russia ABSTRACT. Changes in biocenoses of the shallow water zone of open Lake Baikal continue. In the autumn of 2019 during scuba dives, we recorded abundant fouling of macrophytes in the littoral zone by ciliates of the subclass Peritrichia, the genus Vorticella, at the Listvyanka settlement – Bolshiye Koty settlement section (west coast of Southern Baikal). Despite the fact the Vorticella are the permanent component of the Bailak periphyton, such mass development of Peritrichia in the littoral zone of open Baikal has not been previously recorded. Increasing anthropogenic pressure in the littoral zone of the lake can be one of the main causes of this outbreak in the abundance of Vorticella cf. campanula, the main species of this fouling. Keywords: ciliate, Vorticella, bacteria, Lake Baikal, abundance 1. Introduction Periphyton serves as one of the important indicators of the ecological state in aquatic ecosystems The open littoral zone (i.e. the littoral zone of (Abakumov et al., 1983). Underwater observations indigenous Lake Baikal except for warm bays) of Lake that were carried out from October to December 2019 Baikal occupies approximately 7% of its area. The indicated the continuing changes in the composition landscape of the underwater slope on the western side and distribution of benthic biocenoses in the open of Southern Baikal composed of crystalline bedrocks of littoral zone of the lake, in particular, the periphyton. Archean and Proterozoic complexes has large bottom Thus, ciliates of the genus Vorticella have become the slopes of 30-35 degrees and a stepped structure with an main component of abundant fouling of macrophytes. insignificant layer of loose sediments: rock fragments, Despite the rich fauna of ciliates (93 species) inhabiting pebbles, gravel, grus, and sand (Karabanov et al., microphytes in the open littoral zone (Gajewskaja, 1990). L.A. Izhboldina (1970 and 2007) identified and 1933), such a massive development of ciliates has not described five vegetation belts in the open littoral zone, been previously observed in open Baikal. which were located parallel to the coast at different Aquatic protozoa are the important intermediate depths: the first Ulotrix zonata belt started from the in the transfer of organic matter from the nanoplankton water edge to a depth of 1-1.5 m; the second and third level to higher trophic chains of the water body. In belts predominated by Tetraspora and Draparnaldioides this regard, this abnormal outbreak of the ciliate – to depths of 2-2.5 m and 10-12 m, respectively; population may be a signal of significant changes in the the fourth and fifth belts – to depths of 20-35 m and picoplankton community of Southern Baikal. 60-78 m or more. The population of biotopes in the open littoral zone was one of the richest and the most 2. Materials and methods diverse in the lake (Kozhov, 1962). In recent years, the composition of macrophytes and population of these To assess the current state of bottom biocenoses belts have changed significantly. Since 2008, there in the open littoral zone of Lake Baikal, underwater has been a violation of vertical zonation and massive observations were carried out at several stations along development of the Spirogyra algae that is untypical the west coast of the southern basin of the lake (Fig. 1) for open coasts of Lake Baikal (Kravtsova et al., 2012; from 25 October 2019 to 2 January 2020. 2014). Since 2011, a ubiquitous disease and death of Below, there are the areas and dates of the endemic sponges have been recorded (Bormotov, 2011; fieldworks: Khanaev et al., 2018, etc.). *Corresponding author. E-mail address: [email protected] (I.V. Khanaev) © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. 433 Khanaev I.V. et al. / Limnology and Freshwater Biology 2020 (3): 433-438 Fig.1. Schematic map of sites of underwater observations and sampling; figures in circles are numbers of stations (sites). • the Listvyanka settlement, the Angara River source To determine hygiene indicator microorganisms, (opposite Baikal Museum), Site 1, the water edge water samples were inoculated according to the SanPin coordinates: N 51°52´03,7´´; E 104°49´52,4´´, 2.1.5.980-00 standards and the MUK 4.2.1884-04 dates: 25 and 29 October 2019, and 2 January guidelines. Total bacterial count and thermotolerant 2020; coliform bacteria (TBC and TCB), as well as enterococci, were taken into account. To determine the number of • the Listvyanka settlement (opposite Sennushka cultured heterotrophic bacteria, 0.5 and 1ml of samples Valley), Site 2, the water edge coordinates: N were inoculated on the nutrient media of meat peptone 51°51´51,7´´; E 104°50´37,9´´, dates: 28 October, agar (MPA), fish peptone agar/10 (FPA/10) and 1 and 10 November 2019; R2A agar as well as Hissa medium with glucose and • the Listvyanka settlement (between the Sennushka incubated at 22°С (room temperature). The cultivation and Banovka valleys), Site 3, the water edge on MPA was carried out at 37°С and on R2A – at 10°С. coordinates: N 51°51´46,2´´; E 104°50´51,2´´, 10 For microscopic examination, samples were November 2019; fixed with formalin (4% final concentration). Species identification of ciliates, algae and cyanobacteria were • Zhilische Valley (opposite the research station of carried out using an Axio Imager light microscope (Zeiss, Limnological Institute SB RAS), Site 4, the water Germany) equipped with an HBO 100W mercury lamp edge coordinates: N 51°53´59,5´´; E 105°03´50,1´´, and an AxioCam camera according to the key-guides 4 December 2019; (Komárek and Anagnostidis, 1999; 2005; Pomazkina • the Bolshiye Koty settlement (opposite the and Shcherbakova, 2010; Komárek, 2013). Bolshaya Kotinka River), Site 5, the water edge During fluorescent microscopy, algae were coordinates: N 51°54´11,1´´; E 105°04´19,8´´, 12 observed under blue filter (wavelength 480 nm) by November 2019; chlorophyll autofluorescence; cyanobacteria were • Chyortov Most Rock or Chayachiy Cliff (coast of detected by phycobilin autofluorescence under green open Baikal between the Sobolev and Kadilny filter (wavelength 540 nm). capes), Site 6, the water edge coordinates N 51°53´54,8´´; E 105°07´50,2´´, 12 November 2019. 3. Results and discussion The fieldworks were carried out using the On 25 October 2019 (Listvennichny Bay, the autonomous scuba diving equipment. Underwater Angara River source, the littoral zone opposite Baikal photo and video recordings were carried out with a Museum, Site 1), there were small Ulotrix zonata colonies Sony A7 photo camera and a GoPro HERO 3+ camera. in the near-water edge zone, which consisted of young Samples for quantitative and qualitative analysis were filaments and numerous spores of these algae. Among taken from different depths and substrates using a filaments, there were various ciliates and rotifers, scraper and dive knife. The samples were placed in except for Peritrichia, cyclops and harpacticides. At individual vials and plastic hermetic boxes. distance from the water edge, at depths of 3 m and The counting and detection of ciliates were carried deeper, the Peritrichia colonies occupied various out with living material under a LOMO microscope at substrates. On rocks, small stones, crustaceous sponges, a magnification of 20X-40X under laboratory conditions. 434 Khanaev I.V. et al. / Limnology and Freshwater Biology 2020 (3): 433-438 Fig.2. Colonies of Vorticella cf. campanula on different substrates: A – thickets of charophytes; B – individual enlarged colonies; C - molluscs covered with Vorticella; D – cyanobacteria; E – branching sponges Lubomirskia baikalensis; F – thickets of hornwort, Ceratophyllum sp., and elodea, Elodea canadensis. molluscs, amphipods, etc., Peritrichia were located Based on visual estimates, after a week and a singly or in small groups (patches), up to 15-20 or half (7 and 10 November 2019), in the littoral zone 35-50 cells/cm2. Macrophytes had the most abundant of Listvennichny Bay (Sites 2 and 3), the total number fouling of the Vorticella spp. ciliates: the Myriophyllum of the Peritrichia colonies increased at least twofold. sp. parrot feather, the Ceratophyllum sp. hornwort and The colonies were found everywhere in the depth range charophytes (Fig. 2). The poor presence of the Vorticella from 3.5 to 40 m. The water temperature at that time spp. ciliates in the 0-3m zone can be due to intense was 4-5°С, depending on the depth. hydrological impact from surf wave activity. On 2 January 2020, at the ice-free site of the The tips of hornwort’s branches had the fouling lake, near the Angara River source, (Site 1), with the by diatoms of the genera Cymbella, Gomphonema, water temperature of 1-2°С, the situation with the Nitzchia, and Cocconeis. These algae are found together Vorticella spp. colonies on macrophytes did not change: with Peritrichia on pondweed leaves and damaged their abundance remained very high. crustaceous sponges, and small Cocconeis densely Vorticella campanula is a eurythermal species cover the surface of dying charophytes. Vorticella cf. widespread in freshwater bodies. It is an epibiont that campanula dominated on all studied macrophytes prefers to live on algae and aquatic plants but can (approximately 90%). Its number was from 3-4 х 103 also inhabit other substrates, including invertebrates cells/cm2 on pondweed leaves to 7-8.5 х 103 cells/cm² (Banina, 1984).