Question

Red tides are caused by:

O a. Reddish seaweed that dominates near-surface waters.
O b. Phytoplankton tha release toxins harmful to humans
O c. Dead fish and shellfish that float to the water surface.
O d. Abnormally high tides that happen when the Earth is closest to the Moon

Answer 1

Red tides result from blooms of toxic dinoflagellates that can cause paralytic shellfish poisoning and harm marine life. These events necessitate careful monitoring of seafood for toxins to prevent human health risks.

Step-by-step explanation:

Red tides are caused by phytoplankton that release toxins harmful to humans, specifically a few different species of a class of plankton known as dinoflagellates. When conditions are favorable, these dinoflagellates can reproduce rapidly, leading to a dense population, also known as a bloom. Species such as Gonyaulax and Alexandrium produce toxins, leading to paralytic shellfish poisoning when their densities become high. Toxins produced by certain species, like Karenia brevis, affect not only marine life but can also cause severe symptoms if contaminated shellfish are consumed by humans. Regular monitoring of toxin levels in shellfish is crucial, as evidenced by practices such as those by the Division of Marine Fisheries in Massachusetts, which bans clam harvesting when toxin levels exceed safe thresholds.