Response of Aquatic Organisms Communities to Global Climate Changes and Anthropogenic Impact: Evidence from Listvennichny Bay of Lake Baikal

Abstract

Recent studies have revealed how the freshwater biota of Lake Baikal responds to climate change and anthropogenic impacts. We studied phyto- and zooplankton, as well as phyto- and zoobenthos, in the open coastal waters of the southern basin of the lake and of Listvennichny Bay. A total of 180 aquatic organism taxa were recorded. The response of the Baikal ecosystem to climate change can be traced by changes in the species composition of planktonic communities of the lake's open coasts in summer. The key species were thermophilic the Anabaena lemmermannii P. Richt. (F_ij = +0.7) blue-green algae, the Asplanchna priodonta Gosse (F_ij = +0.6) rotifers in 2016, the Rhodomonas pusilla (Bachm.) Javorn. (F_ij = +0.5) cold-loving algae, and the Cyclops kolensis Lilljeborg (F_ij = +0.9) copepods in the past century. The proportion of Chlorophyta decreased from 63% to 17%; the Cyanophyta increased from 3% to 11% in the total biomass of phytoplankton; and the proportion of Cladocera and Rotifera increased to 26% and 11% in the biomass of zooplankton, respectively. Human activity makes an additional contribution to the eutrophication of coastal waters. The Dinobryon species, the cosmopolitan Asterionella formosa Hass. and Fragilaria radians Kütz., dominated phytoplankton, and filamentous algae, Spirogyra, dominated at the bottom in the area with anthropogenic impact. The trophic level was higher than at the unaffected background site: the saprobity index varied from 1.45 to 2.17; the ratio of eutrophic species to oligotrophic species ranged from 1:2 to 3:1, and the ratio of mesosaprobiont biomass to endemics biomass ranged from 2:1 to 7:1. Currently, the boundaries of eutrophication zones of shallow waters in Lake Baikal are expanding, and its coastal zone has acquired features typical of freshwater bodies of the eutrophic type.

Keywords: Lake Baikal; benthos; community composition; diversity; eutrophication; plankton.

Figure 1

Ambient temperature trends for the territory of Russia and the Baikal region, and sampling map of Lake Baikal: (A) Averaged anomalies of the mean annual temperature at the earth’s surface for the territory of Russia from 1901 to 2018 (according to the Y.A. Izrael Institute for Global Climate and Ecology; the data is free available from http://climatechange.igce.ru (accessed on 6 September 2021)). (B) Averaged air temperatures in the Baikal region. (C) Averaged surface water temperatures of Lake Baikal (according to [15]). (D) Sampling station. Plankton sampling at two sites at depths from 0 to 15 m of the water layer. The background Site 1 included stations that are outside the zone with the impact of human activity: I—opposite Tolsty Cape in the open part of the southern basin 14 km in a southwestern direction from Listvennichny Cape (N 51°47′309; E 104°36′736); II—open part of the southern basin 7 km off the shore in direction to Listvennichny Cape-Tankhoy settlement (N 51°48′718; E 104°53′126); III—opposite Emelyanovka Valley in northwestern direction 5 km off Listvennichny Cape (N 51°51′529; E 104°56′463). Site 2 with anthropogenic impact included stations located in the coastal zone of Listvennichny Bay adjacent to the Listvyanka settlement at a distance of 50–100 m off the shore opposite the shipyard (IV) (N 51°50′479; E 104°52′772), Krestovka Valley (V) (N 51°51′236; E 104°51′595), and Baikal Museum (VI) (N 51°52′021; E 104°49′683). Benthos samples were collected from stones at the transects from the 0 to 5 m depth range opposite Emelyanovka Valley (Tr. 1) (N 51°51′529; E 104°56′463) and Krestovka Valley (Tr. 2) (N 51°51′236; E 104°51′595). Light circles are plankton sampling stations and water sampling stations for hydrochemical analysis in the Baikal coastal zone; dark circles—water sampling stations for nutrient determination in rivers and groundwater on the beach; the dotted line indicates the boundaries between the southern, central, and northern basins of Lake Baikal.

Figure 2

Plankton community structure and spatial distribution of dominant species in the coastal zone of Lake Baikal. (A) Species composition of plankton communities (a, b, and c) extracted by Ward’s cluster analysis using Euclidean distances. (B) Locations of the identified plankton communities in the plane of the first two principal components (PCA). RD—reference data, including samples collected in the southern basin of Lake Baikal in the past century; Site 1 included stations I, II, and III of the background area in 2016; Site 2 included stations IV, V, and VI of the area with human activity in 2016 (see Figure 1D).

Figure 3

Benthic community structure and spatial distribution of dominant species in the coastal zone of Lake Baikal. (A) Species composition of benthic communities (d, e, and f) extracted by Ward’s cluster analysis using Euclidean distances. (B) Locations of the identified benthic communities in the plane of the first two principal components (PCA). RD—reference data, including samples collected on the stones from 0 to 5 m depth range in north-western direction 5 and 17 km off Listvennichny Cape in the past century; Site 1 included stations at transect 1 of the background area in 2016; Site 2 included stations at transect 2 of the area with human activity in 2016 (see Figure 1D).

Figure 4

The proportion of higher taxa in the formation of the total plankton biomass in the studied areas of the Baikal coastal zone. (A) Percentage ratio of biomass of phytoplankton higher taxa; (B) percentage ratio of biomass of zooplankton higher taxa. RD—reference data, including samples collected in the southern basin of Lake Baikal in the past century; Site 1 included stations I, II, and III of the background area in 2016; Site 2 included stations IV, V, and VI of the area with human activity in 2016 (see Figure 1D).

Figure 5

The k-dominance curves characterising the state of the zooplankton community in the coastal zone of Lake Baikal: RD—zooplankton community characterised as stable in the early period; Site 1—zooplankton community characterised as stable in the background area; Site 2—zooplankton community characterised as moderately disturbed in the area with human activity. The ordinate axis is the cumulative % of biomass (1) and abundance (2) of species, and the abscissa axis is the sequence of zooplankton species ranked in descending order.

Figure 6

The proportion of higher taxa in the formation of the total benthic biomass in the studied areas of the Baikal coastal zone. (A) Percentage ratio of the biomass of macroalgae higher taxa; (B) percentage ratio of the biomass of macrozoobenthos higher taxa. RD—reference data include samples collected on the stones from 0 to 5 m depth range in the north-western direction 5 and 17 km off Listvennichny Cape in the past century. Site 1 included stations at transect 1 of the background area in 2016; site 2 included stations at transect 2 of the area with human activity in 2016 (see Figure 1D).