Lake Sevan: Evolution, Biotic Variability and Ecological Degradation

Abstract

Lacustrine conditions in the Sevan Basin, Armenia, have a history that extends back to the late Miocene (Pontian), although the modern morphology of Lake Sevan was established after volcanic activity during the Pleistocene and Holocene. A diverse fauna and flora was established in this high-altitude lake during the Holocene, but profound anthropogenic pressures commenced in the mid-twentieth century. The model of ecological degradation predicts a phase of inception, followed by a phase of accelerated degradation which reaches an apogee. In some circumstances, this is followed by a phase of recovery. In Lake Sevan, the phase of inception was relatively short lived, confined to the 1930s, with the phase of acceleration commencing in the 1940s and continuing through the 1950s and 1960s resulting in significant changes in water depth, temperature, sedimentation, pellucidity and water quality, causing profound changes in the trophic structure and diversity. The phase of recovery was initiated in 2002 and it remains to be seen whether this will return the lake to its former condition and the biota to its former diversity.