When in doubt, stay out! Investigating harmful algal blooms

Faculty of Science
Hebah Mejbel
Have you ever been to a lake where you were warned not to swim? Was the water green and slimy, and did it have an unpleasant smell? If so, the water was likely contaminated by Harmful Algal Blooms (HABs).

HABs are overgrowths of algae produced by cyanobacteria that can be observed in lakes, rivers and coastal marine areas. They typically occur due to excess nutrients caused by pollution from agricultural run-off and wastewater. Furthermore, longer summers, occurring as a result of climate change, provide the ideal conditions for their growth.        

Most existing freshwater studies count cyanobacteria using traditional techniques such as microscopy. Since these techniques are expensive and labor intensive, Hebah Mejbel – a PhD graduate under the supervision of Professor Frances Pick – made it her goal to find more efficient and cheaper testing methods. Hebah utilized a molecular approach to study the concentration and toxicity of cyanobacteria in four different manipulated lakes, namely a lake fertilized with phosphorus and nitrogen, an acidified lake, and two controls. She collected large sediment samples from the various lakes and divided them into subsections that were analysed using molecular tools, including droplet digital Polymerase Chain Reaction (ddPCR) and high-throughput sequencing. Using sediments instead of water proved essential since they act as a time-capsule, making it possible to track long-term cyanobacterial trends in the lakes. Hebah’s results showed a dramatic increase in the concentration and toxicity of cyanobacteria in the fertilized and acidified lakes compared to the controls. In other words, if lakes continue to be polluted, cyanobacteria concentrations will increase and become more toxic, leading to more HABs.

Hebah won numerous awards in recognition of her impressive work in the emerging research field of HABs, including Best Student Paper at the 2022 Interdisciplinary Freshwater Harmful Algal Blooms conference, Antoine Morin Memorial Scholarship, Don E. McAllister Memorial Scholarship, and most recently, a post-doctoral Mitacs Canadian Science Policy Fellowship at Environment and Climate Change Canada.

In addition to her research, Hebah participated in the Skype a Scientist youth outreach program, presented at numerous aquatic sciences meetings (e.g., North American Lake Management Society, Paleolimnology Symposium, Phycological Society of America) and was a member of the uOttawa Biology Grad Student Equity, Diversity, and Inclusion committee where she advised on undergraduate student surveys and hiring processes.

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