REHS EPH Program Week Four Practice Test

Why can algicides worsen HABs?

They lyse bacterial cells and release toxins into the water They kill all bacteria They instantly improve water clarity They are always effective

Correct Answer:

They lyse bacterial cells and release toxins into the water

Explanation:

The main idea is that destroying algal cells can release toxins stored inside them into the water. When an algicide lyses bloom cells, any toxins they contain (for example, microcystins from cyanobacteria) spill out into the surrounding water. This can raise toxin levels even as the visible bloom is reduced, making the water more dangerous for people, wildlife, and aquatic life and potentially triggering secondary ecological problems. That’s why a treatment can seem to “improve” visibility or kill the bloom on contact, yet still worsen overall HAB impacts by releasing toxins. The other statements aren’t accurate: algicides don’t magically remove toxins, they don’t kill all bacteria, and their effectiveness isn’t guaranteed or permanent.

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