No abstract

1. This study considers whether the availability of iron and boron are important influences on the development of the cyanobacterium Gloeotrichia echinulata in Lake Erken, Sweden. 2. In an in situ experiment, phosphate and nitrate were added to all enclosures, but pelagic colonies of G. echinulata only increased in abundance in enclosures to which iron had also been added. 3. An even greater increase in the abundance of G. echinulata occured in enclosures in which the additions of phosphate, nitrate and iron were complemented by additions of boron. 4. Boron additions, together with phosphate and nitrate but without iron, did not stimulate the growth of G. echinulata.