The toxins causing this destruction are coming from Pfiesteria, a dinoflagellate. It has a 24-stage life cycle and can photosynthesize if it has stolen the green organelles called chloroplasts from true algal cells. It can subsist this way but when fish are nearby it turns into a predator. It emits one compound that seems to kill the fish and another that opens the fish s skin and feeds upon the tissue inside. It is both plant and animal like in nature.
Red tides are also dinoflagellates but behave more like plants.
Their pigments they use in photosynthesis can tint the water red during a bloom. They also emit airborne toxins that can sting the insides of the noses and throats of humans. The red tide can devastate shellfish and kill large animals such as the manatee. Other dinoflagellates that live in association with seaweed on coral reefs produce ciguatoxin. Small reef-dwelling fish ingest the toxin, which becomes concentrated in large predators, such as barracuda, further up the food chain.