A quantitative study of the phytoplankton of the River Avon, Bristol

Quantitative studies of the seasonal changes in composition and cell densities of phytoplankton of the River Avon, from June 1972 to August 1973 have been made. Phytoplankton of the river comprised three main algal groups; Centric diatoms, Chlorophyceae and Cryptophyceae. Centric diatoms increased in numbers in spring and autumn whilst Chlorophyceae were abundant in summer months. Total amount of phytoplankton increased downstream. In general, phytoplankton numbers were high in mid-spring and summer, decreasing gradually towards the end of autumn. In winter, numbers were low. Nutrients did not appear to limit the algal growth in the river.