Some recent trends regarding Lake Baikal phytoplankton and zooplankton

Abstract

Plankton sampling data from the period of 1951-2010 for Lake Baikal were used in this study. Data have been collected at least monthly, generally every 7-10 days, in depth profiles from the surface to 250 m at a single offshore sampling site in the southern basin, where the water depth is approximately 800 m. Measurements of abiotic variables and phytoplankton sampling were made at discrete water depths. The data for the top 50 m of the lake were averaged for temperature and biological characteristics, noting this is the water layer in the lake exhibiting most of the lake's photosynthetic production, as well as containing the most plankton organisms. Zooplankton samples were collected with a closing plankton net and enumerated at the species level and also identified by age class. Under-ice phytoplankton demonstrated the presence of some succession in spring phytoplankton, including a decreased proportion of endemic algal species. The openwater complex of the alga species demonstrated that some non-endemic species exhibited positive trends. The zooplankton analyses demonstrated a noticeable increasing trend for total zooplankton, the main zooplankton components being Epischura baicalensis, as well as increased Cladoceran numbers. These trends can be hypothetically explained by the following: (i) global climate change (although Lake Baikal also exhibits long-term temperature oscillations); (ii) regional warming (due to construction of reservoir systems during the 1950s-1970s period); (iii) local chemical pollution attributable to increased industrial and agricultural activity in the lake's watershed and airshed basins; and/or (iv) the natural oscillating behaviour of the lake's plankton components.

Diatom evidence of 20th century ecosystem change in Lake Baikal, Siberia

“…Concordant with recent warming, summer surface lake water temperatures have increased by over 2°C over the past 60 years [9, 23, 24], alongside seasonal changes to ice cover dynamics [25, 26]. Shorter ice cover and warmer water temperatures have led to marked increases in chlorophyll- a concentrations and summer plankton biomass in the south basin of Lake Baikal over the past 60 years [9, 23, 24, 27–29].…”

Hot and sick? Impacts of warming and a parasite on the dominant zooplankter of Lake Baikal

“…S1) in the southern basin of Lake Baikal between 1945 and 2003 at a submonthly frequency. Samples were collected with a closing zooplankton net; typical depth intervals for sampling were 0-10, 10-25, 25-50, 50-100, 100-150, 150-250, and 250-500 m. These rich data have recently been used to examine long-term trends in the ecology of the lake (Hampton et al 2008;Izmest'eva et al 2011Izmest'eva et al , 2016Silow et al 2016) and additional information about sampling and data is available in those papers.…”

Diatom evidence of 20th Century ecosystem change in Lake Baikal, Siberia

“…Phytoplankton monitoring studies from the south basin show major changes in the diatom flora consistent with those observed in the stratigraphic record. For example, within phytoplankton samples from the south basin, A. baicalensis concentrations have declined from c. 5 to 3 cells L -1 between 1950-2010 CE [29]. These changes are likely related to ice cover dynamics and increasing surface water stratification [27].…”

“…Concordant with recent warming, summer surface lake water temperatures have increased by over 2˚C over the past 60 years [9,23,24], alongside seasonal changes to ice cover dynamics [25,26]. Shorter ice cover and warmer water temperatures have led to marked increases in chlorophyll-a concentrations and summer plankton biomass in the south basin of Lake Baikal over the past 60 years [9,23,24,[27][28][29].…”

“…To date, these predictions at Lake Baikal have largely been made from diatom records collected in the early 1990's [31,33]. More recent diatom changes are examined here, as Lake Baikal has experienced limnological and biological changes with rising lake water temperatures and reductions in ice cover duration [9,24,25,[27][28][29]. Furthermore, it has become increasingly apparent that over the past decade cultural eutrophication from shoreline settlements has also impacted littoral regions of the lake [36,37], giving rise to the potential for multiple stressors impacting its ecological resilience.…”