سال انتشار: ۱۳۸۶

محل انتشار: بیست و ششمین گردهمایی علوم زمین

تعداد صفحات: ۱۹

نویسنده(ها):

Habib Alimohammadian – Palaeomagnetic Magnetism Laboratory, Geological Survey of iran

چکیده:

On the course of environmental geology of the lakes and their distributors and their relation to changing of climate during Quaternary- Holocene, diatom species Didymosphenia geminata which from ecological point of view is considered as a nuisance diatom, for the first time is reported from high elevation of abut 2800 m(f.m.s.l) of Central Alburz Mountains range of Northern Iran. Didymosphenia geminata now has a broad distribution around the world, a condition that appears to have developed in the recent decades. This diatom was known to produce larg masses since the earliest historical records, but now the blooms are over a greater area in the Northern Hemisphere and spreading across rivers in the Southem Hemisphere While D. geminata was formerly considered to have narrow ecological tolerances, it is now present in streams exhibiting a wide range of chemical characteristics. It is capable of growing throughout most of the year in streams with low to high NO3 concentrations (<1mg/l->8 mg/l), low to high temperatures (4-27C), and within a broad range of light exposure. The experiences of European and American countries involved in control and minimizing of spreading of this species, suggest us to be very restrict in gathering more and precise information about D.geminata in affected rivers in state and national leve and possible necessay actions have to be taken in order to confine this nuisance species to its reported environment and minimize its faster growth and spread.