Assessing the vulnerability of endemic diatom species in Lake Baikal to predicted future climate change: a multivariate approach

Abstract

Diatoms in Lake Baikal exhibit significant spatial variation, related to prevailing climate, lake morphology and fluvial input into the lake. Here we have assessed the threats to endemic planktonic diatom species (through the development of empirical models), which form a major component of primary production within the lake. Multivariate techniques employed include redundancy analysis (RDA) and Huisman-Olff-Fresco (HOF) models. Our analyses suggest that eight environmental variables were significant in explaining diatom distribution across the lake, and in order of importance these are snow thickness on the ice, water depth, duration of days with white ice, suspended matter in the lake, days of total ice duration, temperature of the water surface in July, concentration of zooplankton and suspended organic matter. Impacts on dominant phytoplankton diatom species are highlighted using t-value biplots. Predictions of future climate change on Lake Baikal are likely to result in shorter periods of ice cover, decreased snow cover across the lake in spring, increased fluvial input into the lake, and an increase in the intensification of surface water stratification during summer months. All these factors are likely to impact negatively on the slow-growing, cold-water endemics such as Aulacoseira baicalensis and Cyclotella minuta, which currently dominate diatom assemblages. Instead, taxa that are only intermittently abundant, at present, in offshore areas (e.g. Stephanodiscus meyerii) are likely to become more frequent. However, given the climatic gradient across the lake, the timing and extent of changes in community structure are likely to vary. Moreover, palaeolimnological records show that Lake Baikal diatom assemblages have been dynamic throughout the Holocene, with both endemic and cosmopolitan species exhibiting periods of dominance. Effects of climate change on the entire lake ecosystem may yet be profound as the structure of the pelagic food web may change from one based on endemic diatom taxa to one dominated by nondiatom picoplankton, and as limnological functioning (e.g. stratification and mixing) affects deepwater oxygen availability, nutrient cycling and trophic linkages.

Sixty years of environmental change in the world's largest freshwater lake – Lake Baikal, Siberia

“…Snow on ice strongly affects the light environment for algal growth (Mackay et al , 2006); we were able to obtain snow depth data at an Irkutsk station from the Historical Soviet Snow Depth dataset (Armstrong, 2001). The Irkutsk station was the available location in closest proximity to the main Baikal limnological station.…”

Ice and Snow Cover of Continental Water Bodies from Simultaneous Radar Altimetry and Radiometry Observations

“…Snow cover, together with the timing of ice formation and break up are affecting substantially the functioning of the ecosystems in lakes and seas. For example, for lake Baikal the interannual variability of the spring bloom intensity of diatoms is also associated with the character of the snow and ice cover during the wintertime (Kozhova and Izmest'eva 1998; Granin et al 1999;Mackay et al 2003Mackay et al , 2006. The transmission of incident solar radiation through different types of ice and snow cover can differ by almost an order of magnitude.…”

The Structure of Microbial Community and Degradation of Diatoms in the Deep Near-Bottom Layer of Lake Baikal

“…Moreover, some diatom species fail to descend to the lake bottom [22]–[24]. For example, Synedra acus is a member of the dominant assemblage of recent Baikal phytoplankton, but its remains in the upper layer of bottom sediments can be found not in all regions of the lake [24]–[26], because this diatom is subject to considerable degradation both in the water column [27] and in the surface sediment layer [23]. On the other hand, diatom records from Postglacial [28], [29] and Pleistocene sediments [30]–[33] are characterized by “ Synedra peaks”, or aggregations of siliceous frustules of this diatom, which are used for biostratigraphic correlation of core samples [28].…”