The effects of algaecides on Spirulina major and non-target organism Daphnia magna

(1) The Harker School, San Jose, California, (2) Schmahl Science Workshops, San Jose, California
Cover photo for The effects of algaecides on <i>Spirulina major</i> and non-target organism <i>Daphnia magna</i>
Image credit: The authors

Overpopulation of algae, whether in oceans, lakes, or ponds, can heavily disrupt ecosystems. However, when combating this issue, it is easy to forget the overarching effect that algaecides can have on not only the algae population, but also on other species that inhabit the body of water where the problem exists. When used against toxic algal blooms, do algaecides create harm for non-target organisms, ending one problem but creating a new one? In this experiment, we hypothesized that if the cyanobacterium, or blue-green algae, Spirulina major, and the common water flea that lives alongside S. major, Daphnia magna, were grown together in the presence of various algaecide treatment methods, then both organisms would die because the treatment methods would destroy both the S. major and the D. magna. We investigated three algaecides: copper sulfate, hydrogen peroxide, and bentonite clay. Temperature, pH, and lighting were constantly monitored throughout the experiment, and untreated samples of both S. major and D. magna served as controls. Our results showed that when the two species were grown in the presence of an algaecide treatment, they both perished, while the two species in the control group jars (grown in the absence of a treatment) survived longer. The results of this study supported the hypothesis that all three algaecide treatments had negative effects on the non-target organisms while treating the algae.

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