Search

This study is the first attempt at the European scale to make an inventory of ecosystem services (ESS) of a large lake. We analysed a set of ESS indicators against the annual mean values of environmental parameters for 2006–2013. According to principal component analysis, the trophic state- and hydrology-related factors explained about 70% of the environmental variability of the lake and showed strong relationships with some ESS. Among the provisioning ESS, the annual eel catch and the total fish catch were positively related to different eutrophication indicators while the catches of pike, bream, and burbot depended rather on hydrological factors. Reed harvesting efficiency was related to the lake’s water level. The indicators of regulating, maintenance, and cultural ESS showed very high variability in different years, the latter depending on socio-economic conditions rather than environmental factors. We discovered numerous trade-offs between ESS benefitting from higher trophic state or regulated water level of the lake and the goals of good ecological status of the lake. Our analysis showed a clear need for rules prioritizing life supporting regulatory services against other ESS.

The material for the present phytoplankton study was collected from 427 reaches of 162 Estonian rivers during the period of 1991–1997. Sampling was carried out at the end of June and in July. A total of 402 taxa of algae were identified in phytoplankton. The most numerous were diatoms (180), followed by green algae (125) and cyanobacteria (45). The phytoplankton of the Estonian rivers is sparse and heterogenous: only 13 species of algae were recorded in more than 50% of streams. Pennate diatoms dominate most frequently in phytoplankton biomass, while tiny flagellates dominate in phytoplankton abundance. The nonparametric means (medians) of phytoplankton biomass, abundance and number of taxa per sample in the lower reaches of the Estonian streams were 0.2 mg l−1, 0.4×106 cells l−1 and 19, respectively; the highest mean values (0.3 mg l−1, 0.6×106 cells l−1 and 23, respectively) were observed in the rivers of the drainage basin of Peipsi-Vortsjarv and the lowest ones (0.1 mg l−1, 0.2×106 cells l−1 and 13, respectively), in the streams of Hiiumaa. Phytoplankton biomass was correlated with content of chlorophyll a according to Lorenzen (L chl a) (Spearman r=0.72) and Jeffrey & Humphrey (JH chl a) (Spearman r=0.70) at the confidence level P