Some factors afecting the abundance of phytoplankton in an unproductive alkaline lake (Lake Hazar, Turkey)

Abstract

Tis study aimed to explain the seasonal and vertical distribution of phytoplankton in the pelagic zone of a deep alkalinelake that is characterized by low phytoplankton abundance. Phytoplankton and water samples were collected seasonally from 9 pointsand 7 depths between the surface and 20 m from December 2004 to September 2005. Planktolyngbya contorta was the dominant orsubdominant species in all seasons and depths. Te dominance of Gomphonema species was observed in December, but they weresubdominant in September. Cyclotella meneghiniana was dominant at 20 m and subdominant in the upper depths during March, June,and September. Melosira sp. and Meridion circulare were the dominant taxa of the surface phytoplankton in March and June, respectively.A nonparametric test showed the prevalence of cyanobacteria and green algae at a depth of 10 m. Principal component analysis showedthe efect of temperature, pH, dissolved solids, nitrate, and silica on the abundance and distribution of phytoplankton. Te generalizedlinear model revealed that high pH and high dissolved solids content seemed to afect the abundance of phytoplankton via limitingnutrient availability.