PARENT SESSION
Oral Session #27: Aquatic Ecology: Lake structure and function. Presiding: L.A. Hansson.
Tuesday, August 7, 2001. 8:00 AM to 11:30 AM. Hall of Ideas I.

The importance of viscosity in saline waters: Urmia Lake, northwest of Iran.

GHASSEMZADEH, FERESHTEH¹, ¹

ABSTRACT- Fluids differ in their ability to flow under a set of given environmental conditions. For water, two important environmental parameters in determining viscosity are temperature and salinity. Although the viscosity of water is a universal factor of any aquatic ecosystem, little research has been done to partition the biology and consequences of the changes in viscosity. The purpose of this paper is to evaluate the effect of viscosity on density of zooplanktonic organisms in the Urmia Lake which is a permanent saline lake in northwest of Iran. The viscosity, temperature and salinity of water as well as the density of zooplanktonic organisms was measured in sets of samples from the studied area. The results show that viscosity decreases rapidly with increasing temperature and increases slowly with increasing salinity. Statistical analysis of the data by ANOVA show that the relative viscosity is higher in the conditions of high salinity as well as where samples collected from polluted sites. The density of zooplanktonic organisms is low when the viscosity is high because the viscosity is important in locomotion and feeding of small organisms. It is concluded that the density of organisms in saline waters are low not only for high salinity but also of high viscosity. In addition, the viscosity measurement indicated the polluted sites in the Urmia Lake and it may also be used as a tool to find polluted areas in similar environments.

KEY WORDS: Salinity, Viscosity, Zooplankton