The ecological state of Lake Peipsi (Estonia/Russia): improvement, stabilization or deterioration?

[摘要] Lake Peipsi sensu lato consists of limnologically and hydrochemically different parts, Lake Peipsi sensu stricto, Lake Lämmijärv, and Lake Pihkva. The eutrophic L. Peipsi s.s. and the hypertrophic Lake Pihkva were studied. The aim was to find out if the ecological state of these lake parts has improved, stabilized or deteriorated during a ten-year period, 2003–2012. For this purpose, data on loadings, in-lake nutrient concentrations, water transparency, water level, chlorophyll a concen­tration, as well as phyto- and zooplankton were compared for two five-year sub-periods (2003–2007 and 2008–2012). Comparison demonstrated a decline in the loading of total phosphorus (TP) from rivers on the Estonian and Russian sides as well as in its mean concentration in both lake parts. Both phytoplankton biomass and cyanobacterial biomass decreased in response to the reduced nutrient content in the lake water. The responses of zooplankton were contradictory. Changes in the occurrence of indicator species and declining mean zooplankter weight reflected a continuous eutrophication process while changes in the abundance of rotifers and the genus Daphnia indicated a subtle shift towards recovery. Our results show a modest improvement in the ecological condition of both lake parts.

[学科分类] 化学（综合）

[关键词] lake recovery;eutrophic lake;hypertrophic lake;pollution load;nutrients;plankton response