Toxic Algae Activities

Look up newspaper and magazine articles about toxic algal blooms. Discuss the fact that they were never seen in New Zealand before 1987.
Write a report on a local toxic algae bloom and how it effected the people in your community.
Collect some shellfish - oysters, cockles, pipi or mussels - without harming them and put them into a small aquarium or clear plastic food containers. Use two to three shellfish per litre of aquarium. A small air-stone with an air pump will assure their water has enough oxygen. Observe their behaviour after they have rested.
Most shellfish that live between the tides open their valves to feed about two hours before high tide. Those that live buried in the sand, like Cockles and Pipi, will open their shells and extend two siphons. They pump water in through one siphon and out through the other. Mussels and Oysters simply open their shells and begin pumping water through siphons that do not extend from their shells. Sometimes they release wastes through the excurrent siphon.
When the shells are open or siphons extended, carefully add drops of carmine solution to the water. Observe the shellfish pumping water. They will eventually clear all of the red particles from the water. Time them and see how long it takes them to clear the water. If you add more shellfish to the container do they clear the water faster? If you add more drops to the water does it take them longer?
If the tiny red particles of the carmine solution were toxic algae, where would they wind up?
After they have fed for a time, transfer the shellfish to a clean aquarium and let them rest. After awhile, perhaps overnight, look for the red matter coming out of their siphon or out of the opening in their shells. They cannot actually digest the red carmine particles and so they clean them out of their system. How does this compare to shellfish cleaning their system of poisons from toxic algae?
Why do shellfish like cockles and pipis have long siphons compared to mussels and oysters? Carefully add a drop of food colouring to the water near the siphons (if you move too fast, what happens?). The dye will be sucked into the incurrent siphon and ejected from the excurrent siphon. Which one is which and how can you tell them apart?
Where do people collect shellfish? Interview older people in a community near the sea to talk about shellfish populations today compared to when they were young.
Where do people farm shellfish? What kinds of shellfish are farmed in New Zealand and how is this done? Perhaps you can arrange a field trip to a shellfish farm or ask a shellfish farmer to talk to your school and demonstrate the process.
Where have there been outbreaks of shellfish poisoning? Research this in the library by looking up newspaper articles since 1992.
The species of toxic dinoflagellates are about 0.03 millimetres in diameter. How big is that? If one of these creatures was on your thumbnail and was enlarged to the size of a marble (say 18 millimetres) how big would your thumbnail be? How many dinoflagellates would fit on the head of a pin? On the full stop at the end of a sentence?
Observe the base of the food web. Obtain some brine shrimp eggs at a pet store (sea monkeys) and a species of algae used in aquaculture (Tetraselmis). Observe the development of the green "bloom" of the microalgae in flasks or plastic bags. Hatch the "sea monkeys" or brine shrimps and observe them feeding and growing under a stereo microscope. Cawthron Institute can provide small capsules of Tetraselmis with a media recipe and instruction sheet.
If a microscope is available, collect some water from a river or the sea and look for microalgae and microscopic animals.
To identify New Zealand's toxic dinoflagellates, click HERE.