Red tides are caused by ________.

• A. green algae
• B. cyanobacteria
• C. diatoms
• D. dinoflagellates

Answer: (D)

Verified step by step guidance

1. Understand that red tides are a type of harmful algal bloom characterized by a reddish discoloration of seawater caused by the rapid growth of certain microorganisms.
2. Recall the main groups of microorganisms that can cause algal blooms: green algae, cyanobacteria, diatoms, and dinoflagellates.
3. Recognize that green algae and cyanobacteria are primarily freshwater organisms and are less commonly associated with marine red tides.
4. Know that diatoms are important marine phytoplankton but typically do not cause the red coloration characteristic of red tides.
5. Identify dinoflagellates as the group of marine plankton responsible for red tides due to their pigment composition and ability to multiply rapidly, producing the reddish color.