Abstract
The ecological and sanitary state of the littoral zone of Lake Ladoga is described according to the data from microbiological observations in 2006, 2010, 2014, and 2019. The total bacterial numbers (TBN) in different parts of the littoral zone varied from 1.10 million cells/ml (2006, Lyaskelya Village and Koionsaari Island) to 15.90 million cells/ml (2014, entrance to Impilahti Bay). It is shown that based on the average total bacterial numbers during the observation period the trophic status of most of the studied water area was typically mesotrophic. Some parts of the littoral have a mesotrophic-eutrophic status: entrance to Impilahti Bay; the area near Pitkyaranta in the channel opposite to the pulp and paper mill (northern region), and near the Voronovo Village (southern region). Correlation analysis revealed a positive relationship between TBN and water temperature. The development of bacterioplankton in the littoral zone was more intensive in the “warm years” (2010, 2014) compared to the “colder” ones (2006, 2019). The content of rod-shaped bacteria ranged from 30 % in the water area near the Lyaskelya Village and in Haukkalahti Bay in summer 2014 up to 73 % near Nazia Village in summer 2010. Based on the average quantitative ratios of saprophytic bacteria and TBN in 2019, the water masses in all the littoral areas were conventionally classified as “clean” and “very clean”. The main environmental risk spots, where a relatively high number of saprophytes and a growth of total coliform bacteria were detected (even if in small quantities), were the littoral part of the Rautalahti Peninsula; littoral zone near Pitkyaranta; water area near Priozersk, the mouth of the River Vuoksa; Shchuchiy Bay; waters at Cape Osinovets; Taipolovsky Bay; water areas near Nazia Village and the village Imeni Morozova.
Highlights
The ecological and sanitary state of the littoral zone of Lake Ladoga is described accor ding to the data from microbiological observations in 2006, 2010, 2014, and 2019
The total bacterial numbers (TBN) in different parts of the littoral zone varied from 1.10 million cells/ml (2006, Lyaskelya Village and Koionsaari Island) to 15.90 million cells/ml (2014, entrance to Impilahti Bay)
It is shown that based on the average total bacterial numbers during the observation period the trophic status of most of the studied water area was typically mesotrophic
Summary
Водосбор Ладожского озера находится в подзонах южной и средней тайги. Районирование литоральной зоны водоема проводилось по физико-географическим особенностям различных частей озера [Черняева, 1966, цит. по: Ладожское..., 2015]. Отбор микробиологических проб производился из поверхностного горизонта воды на станциях, расположенных по всему периметру Ладожского озера (рис.), в конце июля – начале августа 2006, 2010, 2014 и 2019 гг. Дополнительно производился отбор проб на литорали Волховской губы и вблизи пос. Определение общей численности бактериопланктона, как показателя качества воды и количественного соотношения палочковидных и кокковидных форм микроорганизмов, в качестве косвенного показателя антропогенного воздействия на водоем [Кожова, Дутова, 1989; Киреева, 2007] производили в течение всего периода исследований. Трофический статус различных районов литоральной зоны оценивался в соответствии с классификацией водоемов по общей численности бактериопланктона [Копылов, Косолапов, 2007]. Дополнительно определялась численность сапрофитных микроорганизмов методом глубинного посева на питательную среду ГРМ-агар [Кузнецов, Дубинина, 1989] и рассчитывалось соотношение количества сапрофитных бактерий и общего количества бактерий, которое обычно колеблется в водоемах в пределах от 0,0003 до 3 (редко более) [Романенко, 1979; Руководство..., 1982]. Оценка достоверности различий между значениями параметров проводилась по критерию Манна – Уитни
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