Battling Algal Blooms: How Rotifers Keep Microcystis in Check

Overview

Harmful Algae Blooms (HABs) are growths of microalgae that produce harmful toxins. Microcystis aeruginosa is the cyanobacterium commonly found in HABs. Microcystis produces the cyanotoxin microcystin, a hepatotoxin that has caused death in livestock as well as humans. Native to Arkansas, rotifer Brachionus calyciflorus is an omnivorous holoplankton that digests microalgae and is known for its resistance to environmental pressures. This project researches rotifer Brachionus calyciflorus and how it could possibly reduce Microcystis HAB concentrations effectively. The cultures of Microcystis were grown under an LED growth light over the course of the experiment, then diluted to the desired concentration (100,000 or 1,000,000 cells/mL), with three trials per concentration. Each trial included Microcystis alone, Brachionus alone, and Microcystis & Brachionus together, which were each placed into three tubes with freshwater medium. The samples were placed under the LED light and regularly measured for Microcystis concentrations using a hemocytometer. The weekly percentage change of Microcystis cultured with Brachionus, on average, trends downward over time. Every trial's Microcystis growth significantly decreased (ANCOVA test, all p < 0.05) in comparison to the control group. A 2-sample t-test was performed between Microcystis with and without Brachionus per trial, showing a significant difference (all p-values < 0.05). Though the reduction in Microcystis was significant, it did not last, so the rotifers may need to be re-implemented after a few weeks for a constant effect. This study is an important opportunity for helping treat or even prevent blooms, especially in vulnerable locations.

Competition history

• ISEF 2026 Microbiology · Entry MCRO041T

Resources

• ISEF abstract page ↗

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