Drastic changes in lake ecosystem development as a consequence of flax retting: a multiproxy palaeolimnological study of Lake Kooraste Linajärv, Estonia

This study demonstrates the power of multiproxy palaeolimnological analyses in investigating environmental changes in the Lake Kooraste Linajarv ecosystem through historical time in response to flax retting. Flax retting history was proven by applying pollen and macrofossil evidence and by using several biotic and geochemical proxies on a sediment core. Continuous findings of flax pollen and macrofossil remains in lake sediments were considered as strong evidence for the occurrence of retting. Analyses of the well-dated sediment core show the consequences of flax retting in the lake. As a result, the once clear soft water oligotrophic endorheic lake with limited sedimentation has turned into a hypertrophic high-sedimentation lake with anoxic bottom water, strong stratification and intense water blooms. Despite the fact that flax retting was forbidden in Estonia around ad 1950s and retting has not occurred over the last six decades, anthropogenic alterations were so pervasive in the past, that they have prevented any lake water improvements until the present-day.