The effect of severe drought on the disappearance of the brine shrimp Artemia from Urmia Lake

Urmia Lake has been suffered from continuous water withdrawal for more than ۲ decades. It is the largest habitat of a unique brine shrimp species, Artemia urmiana, first reported by Gϋnther. This study was performed to determine if harsh environmental conditions has eliminated the A. urmiana from the lake. Six sampling sites were selected in northern and southern parts of the lake. Two stations were not accessible through the sampling campaign due to drastic water withdrawal and marshy path. Samplings were performed monthly from March ۲۰۲۲ to February ۲۰۲۳. Electeric Conductivity (EC) and Total Dissolved Solids (TDS) were determined by EC-meter WTW model LF ۳۲۰ and multi-meter WTW model ۳۴۱۰, respectively. The water salinity was measured by refracto-meter ATAGO (Japan) model S-۲۸E. Water level, surface area and volume were extracted from East Azarbaijan water resources management company web site. The brine shrimp samples were collected by pulling a net (۲۵×۱۰۰cm - ۱۰۰ μ mesh size) in definite distance. The Artemia samples were studied under stereomicroscope Nikon. In this study, we did not observe any types of Artemia biomass (Nauplii, Meta-nauplii, young and adult Artemia). Only Artemia cysts was observed in Lake Urmia. In summer and autumn (dry season) cyst density were ۰.۰۰۲۱۶ ± ۰.۰۰۱۷ No/l and zero, respectively, whereas in spring and winter (wet season) were ۰.۳۶۴ ± ۰.۲۵۹ and ۰.۱۴۹ ± ۰.۰۸۴ No/l. In general, the results of this study show that the surface area, volume and level of the lake had the highest effects on the cyst density.

Keywords:

Artemia biomass , cyst density , Urmia Lake , water level , Drought