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 laboratory, a defined algal culture medium which supports optimum growth over a long time-period is a requirement. In the development of such a medium, a number of modifications were made to a standard algal culture medium (GP) and growth of a STX-producing isolate of Alexandrium minutum in the different formulations was assessed by measuring maximum cell densities and mean generation times (MGT). All experiments were carried out under controlled conditions in an aerobic atmosphere with increased CO sub(2). Whilst maximum cell densities in the different modifications were similar, the MGT was significantly shortened by the addition of Tris buffer and the trace metals strontium, selenium 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 period.