Results of studies of the coastal zone of Lake Ladoga in the area of Valaam Archipelago (1998–2019) at RSHU

Abstract

Ecological monitoring data of pelagic communities and environmental factors for the coastal zone of the Valaam archipelago and also littoral and sublittoral samples analyses of contrasting hydrological conditions zones are generalized. Values ranges of the focused parameters have been identified for the unique coastal zone of Lake Ladoga with a significant biotopes diversity over than 20 years of research. Phyto- and zooplankton abundance relatively high indices are characteristic of water area closed from wind and wave mixing. This area is characterized by an active vegetation period of macrophytes and highly productive macrozoobenthos formation. According to the open water area temperature (conducted since 2013) continuous data (logger) observations, a significant average monthly temperature values interannual variability is shown, warm period duration with a surface water horizon temperature value more than 10 °C is equal to 100 days. In shallow closed areas, zooplankton biomass values differ strongly from another parts of the water area. However, in some cases, extremely high values of phytoplankton biomass (up to 29.5 mg / l) were observed in Lake Ladoga open areas, associated mostly with surges. In general, the phyto- and zooplankton biomass in the Valaam archipelago open areas coastal zone is comparable with the data for the northern Lake Ladoga deep-water area, for the closed areas biomass has been lower than the published earlier data for the coastal zone of the lake. Plankton quantitative development interannual differences are caused by the hydrological conditions of specific years. Despite the relatively small coastal zone area and macrophytesmosaic distribution, this community was characterized by a high species richness (more than half of the species recorded for Ladoga). In terms of quantitative characteristics, the invertebrates littoral communities are not less then to well-studied communities of the coastal area at depths up to a meter and significantly much bigger those observed in the open lake water area. The littoral fauna (including groups of larva insects, some crustaceans and molluscs) is observed in various conditions (10-12 m depth), thus, with macrophytes distribution data, it makes possible to expand the littoral boundary zone equals to 10 m depth, instead of the previously depth equals 8.5 m. The water area, for all studied biological communities, is classified as oligo-mesotrophic.

Macrophytes As Indicators Of The Ecological Status Of Valaam Island Small Lakes System

“…was identified. A predominance of hydrophytes (44 -73% of a total number of species, see Table 9) observed in 2020 is not recent, however, it increased compared to 2010 (Table 10) when values reported were within the range of 30 -50% (in the Konevsky Lakes and Nikonovskoe Lake) and 45% (in Krestovoe Lake) were reported (Zueva 2010;Stepanova et al 2021).…”

“…1). The five forest lakes are characterized by small areas (0,003 -0,022 km 2 ), low -medium depth (1,3 -4,5 m), humic -very humic (55 -212 °Pt-Co), and slightly acid -neutral pH (5,6 -8,6) (Stepanova et al 2016;Voyakina 2017, Stepanova et al 2021. The most important features of this group are given in Table 1 (Stepanova et al 2021).…”

“…The Valaam archipelago is located in the north of the Lake Ladoga and consists of more than 50 islands, of which the largest is Valaam Island, on which there are eleven small forest lakes characterized by low transparency (0,3 -4,6 mSD), medium -high chromaticity (40 -296°Pt-Co), medium -high content of organic matter (7,0 -58,2 mgO/L) (Rumyantsev and Kondratiev 2013;Stepanova et al 2016;Voyakina 2017).…”

“…The anthropogenic impact on the ecosystem has increased in recent years, especially since 2007, due to the construction of roads, new monastery hermitages, restoration and development of agricultural land, tourism, and recreational activities; further exacerbating concern about the disturbances of the natural environment, such as depletion of natural resources, change in the hydrological regime and the microclimate, accumulation of waste (municipal, agricultural, etc. ), disappearance or reduction of species, chemical alteration of water, soil and air composition, erosion processes, and others (Litovka and Samokhin 1991;Stepanova et al 2016). In the southern part of Ossievo and Chernoe lakes, pastureland improvement is developed; also, nearby is located the Valaam farm, which is expanding its production area.…”

“…In the southern part of Ossievo and Chernoe lakes, pastureland improvement is developed; also, nearby is located the Valaam farm, which is expanding its production area. Since 2007, 15% of the Nikonevsky Lakes basin has been taking place in the process of meadows reclamation, which has affected the decrease in lake transparency (Stepanova et al 2016).…”