Ecology of Cyclotella spp. from Chia-Nan stream (Taiwan)

Abstract

The ecology of dominant Cyclotella s pp. were studied at four sampling sites during 2000-2001, and eight sampling sites during 2002, in southwestern Taiwan. During the study in 2000-2001, the cell density of Cyclotella was compared with the variation of environmental factors by Pearson correlation analysis. The result showed significant positive correlation with nitrate (r=0.37, p=0.01) and negative correlation with water temperature (r=-0.255, p=0.05). Whereas, other factors such as ammonium, nitrite, orthophosphate, organic phosphate, dissolved oxygen concentration, pH, conductivity and salinity did not reveal any significant correlation. However, the especially high cell density of Cyclotella occurring in 2000-2001 could not be explained solely by nitrate and water temperature. Hence, further study was carried out at eight sampling sites during 2002. The result showed that high cell density correlated significantly with electric conductivity (r= -0.45, p =0.01). It was presumed that electric conductivity was a more important factor reflecting the cell density of Cyclotella. Apart from ecological studies, this paper also investigated the morphology of the dominant Cyclotella spp. and confirmed by using scanning electron microscopy that the local species are mainly Cyclotella meneghiniana Kiitz. mixed with Cyclotella sp.