engleski

Physicochemical characteristics of the marine Lake Rogoznica and its connection with the atmosphere and the outer sea

Lake Rogoznica (also known as "Dragon's Eye" lake) is a karstic, marine lake situated on the peninsula Gradina, 100 meters from the sea at 43° 32’ N and 15° 58’ E. Most of the time the lake is stratified with a top oxic layer, an anoxic bottom layer, and a chemocline layer in between (1). Every few years the stratification suddenly breaks down and the whole water column becomes mixed, anoxic, and euxinic (with HS- presence throughout the entire water column). This causes mass mortality of aerobic organisms in the lake and it takes time before flora and fauna recover (2). In the last 30 years, four anoxic mixing events were recorded: September 1997, October 2011, October 2016, and October 2020. In this work, we present the physicochemical characteristics of the lake water column (σT stratification, dissolved oxygen concentration) and the influence of the atmosphere and outer sea on it. The atmospheric impact mostly manifests through precipitation and evaporation caused by daily and seasonal temperature changes. This is especially shown in the surface salinity changes. Daily water circulation (exchange) has been noticed by tides in the lake because of the connection with the outer sea through the surrounding karst. However, recent physicochemical measurements indicate that this circulating water is not strictly fresh seawater or lake water.

Lake Rogoznica ; sigma-T stratification ; water column mixing ; atmospheric precipitation ; circulation through karst

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