Hydroecological State of the Small Upland Armenian Lakes

Abstract

During summer-autumn 2023 hydrophysical, hydrochemical, and hydrobiological measurements had been done on six small upland Armenian lakes. For the first time colored dissolved organic matter (CDOM) and methane (CH4) � emission were observed. Studied lakes are on 1479-3312 m a.s., has maximal depth up to 12 m with groundwater springs input. Anoxic conditions were noticed on the lake bottom in August but changed to oxygen in October. Conductivity range was 0-231 ?S cm-1, TDS - 3-102 mg l-1, pH � 6.4-9.4 for surfaces of all lakes. Main part of nutrients was silicates Si, phosphates PO4 and ammonium NH4. CH4 flux was quite high � reached 13 gCH4 m-2 d-1. Colored dissolved organic matter changes in 12 times range for the lakes, shows allochthonous and autochthonous source of organic matter, ecosystems have low ability to photo degradation. Ecosystems of lakes depends on altitudes. Thus, pelagic zooplankton of Shushanalich (1552 m a.s.) presented Rotifera, Cladocera and Cyclopoida mostly, whereas Lessing lake (3312 m a.s.) had only Copepoda (Calanus sp.). Numerous diatoms were in plankton and sediments.