Question

What is the phenomenon known as the “red tide”? What environmental damage can it cause?

Answer 1

Red tide is a phenomenon caused by harmful algal blooms during which algae become so numerous that they discolor coastal waters. The algal bloom may also deplete oxygen in the water and / or release toxins that may cause illness in humans and other animals. Some harmful species are Alexandrium fundyense, Alexandrium catenella and Karenia brevis. Sometime the term red tide specifically refers to the blooms of a species of dinoflagellate known as Karenia brevis. It is sometimes used to refer more broadly to other types of algal blooms as well. K.brevis produces potent neurotoxin known as brevetoxin which can cause illness and mortalities in fish, seabirds and marine mammals. Humans are susceptible to the effects of exposure to brevetoxins as well, as public health surveillance documented human intoxication from eating seafood.

How are red tides harmful?

Red tide algae make potent natural toxins, some can be hazardous to larger organisms through the process of biomagnification and bioaccumulation.Large fish kills and several mammalian diseases and deaths have been attributed to consumption of shellfish during red tide algal blooms. K.brevis blooms can kill marine animals including dolphins and endangered manatees.

Paralytic Shellfish Poisoning (PSP)

This disease caused by the production of saxtoxin by the Alexandrium species. Poisoning occurs when one ingests shellfish contaminated with PSP toxins causing disruption of nerve function and paralysis. Extreme cases may result in death by asphyxiation by respiratory paralysis.

Diarrhetic Shellfish Poisoning(DSP)

This disease is caused by the Dinophysis species . Symptoms of DSP include diarrhea, nausea, vomiting , abdominal pain and cramps. DSP is not lethal.