Photosynthesis and growth of Spirulina platensis (Cyanophyta) in an equatorial lake (Lake Simbi, Kenya)1

A unialgal population of Spirulina platensis (Cyanophyta) was discovered and studied in Lake Simbi (Kenya), a volcanic crater soda lake. Photosynthetic rates of bottled phytoplankton reached 12,900 mg O2·m−3·h−1 and areal rates ranged from 620 to 5,220 mg O2·m−2·h1. Free water changes in dissolved oxygen varied from 2,800 to 12,000 mg O2·m−2·h−1. A principal reason for these exceptionally high rates of photosynthesis was the extraordinary chlorophyll a content of the euphotic zone—200–650 mg Chl a · m−2. Growth rate measurements based on actual weight changes yielded turnover times of 8.9–18.9 h.