Macroflora in Lake Ülemiste (Estonia) – changes and the impact of environmental factors

Abstract

The changes in the macroflora observed over the last 100 years in Lake Ulemiste in the vicinity of Tallinn and the impact of environmental factors are reported. Lake Ulemiste has supplied the city of Tallinn with water since the 14th century, but the treatment of water did not start until 1927. The macroflora of Lake Ulemiste has been studied four times during the 20th century: in 1908, 1968, 1979, and 2000, with additions in 2004. The extent of macrophyte cover and the maximum width of the zone of macrophytes have reduced in the course of 100 years. While the species composition has not changed in most of the lake, the relationships between dominating species have altered. In 2000, Phragmites australis was the predominant species in the lake, whereas Scolochloa festucacea was the main dominant in 1908. The widely fluctuating water level, as well as steadily increasing mean annual water level since the beginning of the 1960s, favoured a decline in the macrophyte community by the end of the 20th century.