A number of marine Dinoflagellates, Alexandrium tamarense being one of them, are known to produce toxins that kill many fish and cause illness and even death to humans. This toxin is called saxitoxin. Saxitoxin is the toxin produced by Alexandrium tamarenseSaxitoxin Chemical Composition species. The chemical make up of this toxin is presented to the right. The illness saxitoxin causes is most commonly known as Paralytic Shellfish Poisoning. Alexandrium tamarense is a poisonous algae and when the toxin gets out into the marine environments it gets eaten up by filter feeders and other small fish. Filter feeders pump water into their systems to eat up algae and other food particles. Sometimes PSP can get into their systems causing them to become poisoned. Once poisoned these filter feeders, or in this case shellfish and fish, can be harvested for human uses. When humans eat a poisoned shellfish (clams, oysters, mussels, etc) or fish they can experience a variety of different symptoms but if the concentrations of PSP are great enough humans can also experience death.

Symptoms include:

1.      Tingling of the lips and tongue

2.      Tingling of fingers and toes

3.      Arm and leg control loss

4.      Difficulty breathing

5.      Muscles in the chest and abdomen become paralyzed

6.      Suffocation/death

(Washington State Department of Health)

All of these symptoms depend on the concentrations of PSP. As already discussed in the reproduction section, A. tamarense can have a cystic stage in its life cycle. According to a study during this cystic stage the organism can still harbor this poisonous toxin and the cysts are ten times more toxic then when in their motile stages (Dale et. al, 1978). This encystment stage is a major reason why it persists in areas across the globe.


Red Tide is a contributor to Paralytic Shellfish Poisoning. They go hand in hand because Red Tide is often the reason for outbreaks of PSP in marine environments. Red Tide is an algal bloom that happens in marine systems. These blooms can be either toxic or not harmful at all. During theseRed Tide blooms saxitoxin can be released into the water for other organisms to consume. It got its name Red Tide from the fact that sometimes these algal blooms can turn water red. The effect it can have on marine habitats can be severe. Zooplankton grazes on algal blooms and if these blooms are poisoned with Alexandrium tamarense it can cause the deaths of many zooplankton. This is important because zooplankton play an important role as filter feeders in marine ecosystems.

Wikipedia Commons: PJS Franks


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