The diatom algae from sediments of a paleolake serve as records of changes to environments over the last 7500 cal yr. The lagoon lake formed when the sea level approximately corresponded to the present-day position. Evolution of the paleolake was controlled by sea-level oscillations and humidity changes. Eight stages have been distinguished. During a dry episode in 7330-7090 cal yr BP the lake size decreased. The salinity reached maximal values at the Holocene transgression peak. Three stages of a higher salinity are recognized (6750-6500, 6080-5830, 5420-5090 cal yr BP). A severe flood occurred in 6080-6000 cal yr BP. The brackish-water lake existed in ∼5090 cal yr BP and the freshwater lake in ∼4090 cal yr BP. A prolonged phase of decreasing humidity, associated with a weakening of summer monsoons, led to a drop in sedimentation rates in ∼3510 cal yr BP. Peat accumulation started at the Little Ice Age. The lake was transformed into a swamp during drop in precipitations in ∼270 cal yr BP. Presence of marine diatoms typical in bay and deep-water forms are evidence of influence of extreme storms and tsunami. The age of the paleotsunami coincides well with the regional data.