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.