Is a High Abundance of Spring Diatoms in the Photic Zone of Lake Baikal in July 2019 Due to an Upwelling Event?

Abstract

A high abundance of planktonic microalgae is typically thought to be related to their ‘bloom’, that is, to active population growth. Diatom blooms in the photic zone of Lake Baikal generally occur during hydrological spring (April–June); when the summer arrives and the surface water temperature increases, diatoms are replaced by other microalgae. In July 2019, we found a concentration of the diatom Fragilaria radians at a station in South Baikal that was extremely high for that season. This species generally blooms in spring, but in spring (May) of 2019, this alga was nearly absent from the phytoplankton population. Microscopic analysis of the sample taken in July 2019 revealed that the cells were in a dormant stage. The species composition of microalgae in phytoplankton samples from May 2018 and July 2019 was similar. According to the temperature profile analysis, a summer upwelling event from a depth of ca. 100 m occurred in 2019. We hypothesised that this event caused the resuspension of microalgae, including Fragilaria radians, which were deposited on the slopes of the lake in 2018. Hence, the high abundance is not always a ‘bloom’ or an active growth.

Combined Earth observations reveal the sequence of conditions leading to a large algal bloom in Lake Geneva

“…However, such coastal upwelling is common in Lake Geneva 36 – 38 and hence cannot solely explain the exceptional bloom observed in September 2021. Wind-induced upwelling events have been also reported in other large meso-oligotrophic lakes, e.g., Lake Baikal 39 , Lake Tahoe 40 , 41 , and Lake Constance 42 , with some of those events leading to amplified C chl-a 36 , 43 , 44 .…”

Fatty Acid Changes in Nearshore Phytoplankton under Anthropogenic Impact as a Biodiversity Risk Factor for the World’s Deepest Lake Baikal

“…In our investigation, water temperature ranged from 3.4-3.6 • C at almost all pelagic sampling sites and from 3.0-6.0 • C at almost all coastal sites. Nitrate, phosphate, and silica concentrations in Baikal water are constant throughout the year [10,19,66]. According to Popovskaya et al, there is no clear relationship between the concentration of nutrients and phytoplankton growth [44].…”

“…In coastal areas of oceans, the interaction of winds and currents generates vertical movement of cold, nutrient-rich deepwater towards the surface (upwelling). As in oceans, upwelling is a typical phenomenon for Lake Baikal [19,20]. Causes of vertical water movement include asymmetric depression and the presence of high-pressure thermal and cold-water springs through bottom cracks.…”

Изменения Климата И Цветение Арктического Озера Имандра

“…[66,80]. Водный столб и лед действуют как фильтры, определяя оптические режимы для первичных и вторичных продуцентов [21,37,40,52,75]. Было показано, что интенсивность и сроки цветения подледного фитопланктона контролируются ледяным и снежным покровами Они, помимо регулирования доступности света ими, играют важную роль в стратификации водной толщи, определяя удержание фитопланктона во взвешенном состоянии и ограничивая обмен питательными веществами, кислородом и другими газами между слоями воды.…”

“…К последствиям нарушения устойчивости пресноводных экосистем относится цветение водоемов, которое становится экологической проблемой, принимающей глобальные масштабы. Оно было названо одной из самых больших угроз качеству поверхностных вод, влияющих на здоровье населения и водных экосистем [40,63]. Только в США массовое развитие цианобактерий приводит к потере рекреационных, питьевых и сельскохозяйственных водных ресурсов на сумму более 2 миллиардов долларов в год [33].…”