How can microorgan- isms, such as some green algae, affect
the health of organisms in aquatic
ecosystems?

Some algae produce toxic chemicals that pose a threat to fish, other aquatic organisms, wild and domestic animals, and humans. The toxins are released into the water when the algae die and decay. The most common and visible nuisance algae in fresh water, and the species that are often toxic, are the cyanobacteria.

Explanation:

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b is the best answer for this question.

b. heterotroph

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