Toxic cyanobacteria cause major problems in the production of drinking water and in recreational and agricultural water use. National suveys of several hundred cyanobacterial blooms in the UK, Finland, Denmark, Norway, the Netherlands and Germany, have revealed that more than 50 % of the blooms examined were hepatotoxic. Toxicity levels can vary widely and rapidly, non-toxic blooms also occur. Morphological analyses cannot distinguish between toxic and non-toxic blooms and present-day physiological knowledge is not able to predict toxin synthesis. Invertebrates are sensitive to the different components but the influence of the toxins on the different components of the food webs is not clear. By introducing genetic analytical methods into ecological and ecophysiological studies, a breakthrough can be obtained in identifying the conditions which indicate and stimulate toxin production in nature, and where influences on the aquatic food web can be expected

The programme contains 3 work packages:

I. Molecular biology:

• To provide sequence data of microcystin synthetase genes from hepatotoxic strains and bloom-forming cyanobacteria, to reveal differences between species/strains.
• To develop DNA probes and primers to study genetic variation in natural populations.
• To help to discriminate between toxic and non-toxic cells and to determine species.

II. Physiology and growth kinetics:

• To quantify the influence of chemical and physical actors on the production and pool size of microcystins.
• To quantify the influence of environmental factors on the competition between toxic and non-toxic strains.

III. Ecology:

• To understand and assess the environmental consequences of microcystin in aquatic food webs
• To investigate the persistence of microcystins in aquatic environments
• To understand the mechanism(s) which lead to the dominance of toxic Microcystis in aquatic environments.