Modification of an algal culture medium for sustained growth of a saxitoxin-producing isolate of Alexandrium minutum

In order to study saxitoxin (STX) production by micro-algae in the laborato ry, a defined algal culture medium which supports optimum growth over a lon g time-period is a requirement. In the development of such a medium, a numb er of modifications were made to a standard algal culture medium (GP) and g rowth of a STX-producing isolate of Alexandrium minutum in the different fo rmulations was assessed by measuring maximum cell densities and mean genera tion times (MGT). All experiments were carried out under controlled conditi ons in an aerobic atmosphere with increased CO2. Whilst maximum cell densit ies in the different modifications were similar, the MGT was significantly shortened by the addition of Tris buffer and the trace metals strontium, se lenium and molybdenum. Replacement of natural with artificial seawater and removal of soil extract did not adversely affect algal growth. Five of the six media formulations supported the growth of A. minutum over a 9-month pe riod.