Response of the cyanobacterium Gloeotrichia echinulata to iron and boron additions - an experiment from Lake Erken

1. This study considers whether the availability of iron and boron are impo rtant influences on the development of the cyanobacterium Gloeotrichia echi nulata in Lake Erken, Sweden. 2. In an in situ experiment, phosphate and nitrate were added to all enclos ures, 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 en closures in which the additions of phosphate, nitrate and iron were complem ented by additions of boron. 4. Boron additions, together with phosphate and nitrate but without iron, d id not stimulate the growth of G. echinulata.