Copper algicide treatments may require multiple applications because

• A. Copper algicide treatments are not repeated.
• B. Copper algicides are illegal in most water bodies.
• C. The effects can be shortlived, so multiple treatments may be necessary.
• D. Copper algicides permanently remove all aquatic plants.

Answer: (C)

Copper algicides suppress algae by releasing copper ions, but their effect in natural waters is usually temporary. Several factors limit how long copper remains effective: it can bind to sediments and organic matter, reducing the amount of free copper that can affect algae; water hardness and pH can cause copper to precipitate or become less available; dilution from water movement or inflows can wash copper away; and sunlight or other chemical processes can change its activity. Algae can persist or regrow from remaining fragments or spores, so the initial reduction may fade over time. Because of these factors, a single application often isn’t enough to achieve lasting control, making multiple treatments necessary. The other statements aren’t accurate because copper treatments aren’t inherently one-and-done, aren’t illegal in most water bodies, and don’t permanently remove all aquatic plants.