THE RELATIVE IMPORTANCE OF VARIOUS ENVIRONMENTAL FACTORS ON THE VERTICAL DISTRIBUTION OF THE AQUATIC PROTOZOAN COLEPS SPIRALIS

Abstract— The vertical distribution of Coleps spiralis in a tertiary lagoon system was observed over a period of 18 months. Water samples were taken from the surface, middle and bottom of the lagoons and examined to determine the number of Coleps present. Various external and internal environmental factors (i.e. light, temperature, wind, etc) were investigated to determine which might be important in influencing the vertical positioning of Coleps in nature. Irradiance factors (both total solar irradiance and the UV-B component (λ= 320–280 nm) of sunlight showed the highest correlation with the location of the animals. When irradiance was high, the animals were usually found near the bottom of the lagoon; when irradiance was low the animals were located more randomly throughout the water column. On the other hand, wind, cloud cover, temperature gradients and bacterial (food) gradients showed low correlation with location of the protozoan in the water.