GROWTH PHYSIOLOGY OF A MARINE NITROGEN-FIXING CYANOBACTERIUM (NODULARIA-HARVEYANA) IN OUTDOOR CULTURE

The performance of Nodularia harveyana, a N-2-fixing cyanobacterium is olated from seawater, has been studied outdoors in two different cultu re systems: open pond (OP) and tubular photobioreactor (TPR). The prod uctivity in both devices was influenced by areal density. The maximum yield obtained was 12.0 g (d.wt) m(-2) day(-1) in OP and 14.0 g (d.wt) m(-2) day(-1) in TPR in August, corresponding to the highest solar ra diation received. In a month-long experiment with the cyanobacterium c ultivated in TPR at high circulation speed, a net increase in producti vity was obtained over that at low circulation speed. The influence of temperature on the productivity of the cultures grown in open ponds a nd tubular photobioreactors has been investigated. The higher producti vity obtained in TPR compared to OP was attributed to its better contr olled temperature conditions. In outdoor culture the maximum nitrogena se activity did not coincide with the maximum light intensity, but occ urred in early afternoon. The amount of carbohydrate accumulated durin g the day probably influenced the rate of dark nitrogenase activity an d its duration in the night.