Toxic Algae Blooms

Image by Lincoln Mackenzie, Cawthron Institute

Why oysters and mussels are sometimes poisonous

Key Ideas about Toxic Algae Blooms

Activities for investigating Toxic Algae Blooms

19KB JPEG Lesley RhodesSea Keeper Profile: Lesley Rhodes Cawthron Institute, Nelson

Hi.. I'm Lesley Rhodes, a research scientist at the Cawthron Institute, Nelson. I study marine toxic algal blooms.

If you come from the Hauraki Gulf or from near Caroline Bay, Timaru, and if you are observant, you might have seen brown patches discolouring the water during the summer. Those patches were blooms of a fish-killing micro-alga called Heterosigma.

Occasionally I have the fun job of visiting such blooms to collect samples, but mostly my work is based at the bench or microscope. If the micro-algae are particularly difficult to identify then I prepare samples for the electron microscope. This special microscope can let me look at scales on the surface of the cells. Some of these minute scales, less than 1/1000th of a millimetre, bear exquisite patterning and each view is a delightful surprise.

The scales help me identify the species and that is important to understanding exactly what forces are at work in the sea.

The ecology of these single celled plants is fascinating. They interact with one another as well as with other organisms in the water. They produce secretions that can actually control the ecology of the whole area, influencing the succession of different species of plankton throughout the seasons. Only a small proportion of the micro-algae are actually toxic, but I have found several kinds of poisonous ones here in New Zealand. Knowing when these species are present is extremely useful to shellfish and fin fish farmers, who can often predict whether a toxic bloom is likely to occur on the basis of the micro-algae present in the water combined with the current weather conditions.

My research keeps me incredibly busy. New Zealand's aquaculture industry is a large and growing - and important - activity. Shellfish eat plankton and if there are poisonous species in the water the oysters and mussels eat them and then THEY become poisonous to eat. That's why the people who farm the oysters and mussels need to know as soon as possible if there are any toxic algae around. We would not want poisonous oysters ruining our excellent reputation overseas.

My work is totally satisfying .. new discoveries are a tremendous buzz, the development of new methodologies is absorbing, and the links with other researchers around the world is stimulating, And I get paid for doing it .. who could want for more!