When the phytoplankton species, Karenia brevis, experiences an algal bloom, it is known as a red tide. During a red tide, the concentration of toxins released by the plankton reaches levels that can kill fish. Filter feeders such as oysters can become contaminated with these toxins during the process of filtering water for food. People who eat the contaminated oysters can become seriously ill.
Which statement is the MOST accurate about red tides?