Saxitoxin & Algal Blooms
Saxitoxin is an extremely dangerous neurotoxin produced in algal blooms. These blooms are caused by the accelerated growth of single cell organisms such as cyanobacteria or dinoflagellates. A “red tide” is simply one manifestation of this.
In freshwater systems, this can be triggered by farm fertilizers which runoff into lakes & rivers when it rains. Phosphates in particular are important triggers to algal blooms since it enhances ATP production, a molecule important to metabolism in both plants & animals.
In marine ecosystems, upwelling of deeper nutrient rich water has much the same effect. While this is a naturally occurring phenomenon, there are indications global warming may be contributing since algal blooms are now seen as far north as Alaska.
Why Are Algal Blooms Dangerous?
There are different levels of danger with some worse than others. In freshwater systems, it can be a simple matter of algal die off & decomposition. This consumes large amounts of dissolved oxygen which in turn can suffocate fish & other organisms.
Some algae or dinoflagellates can produce highly toxic substances which find their way into the food chain. Zooplankton, which are tiny marine invertebrates that feed on phytoplankton (the algae & dinoflagellates) concentrate these toxins further. They in turn are eaten by whales, turtles & other marine animals which are incapacitated & die.
How Do Algal Blooms Affect Humans?
Not all phytoplankton remain in the water column. Many sink to the bottom where they are consumed by filter feeders such as scallops, oysters, clams & mussels which are commercially important food sources. The toxins produced in the algal blooms become sufficiently concentrated as they make their way up the food chain to the point that even a small serving is lethal.
Saxitoxin is produced in some algal blooms & is a very potent neurotoxin. It has no known antidote. Even in minute quantities, it can block the normal functioning of nerves & the tissues they serve. Specifically, this leads to respiratory failure-the muscles that power our lungs stop working & you suffocate.