Molecular investigation of harmful cyanobacteria reveals hidden risks and niche partitioning in Kenyan Lakes

• Published in: Harmful algae 2024-12, Vol.140, p.102757-102757, Article 102757
• Main Authors: Zepernick, Brittany N., Hart, Lauren N., Chase, Emily E., Natwora, Kaela E., Obuya, Julia A., Olokotum, Mark, Houghton, Katelyn A., Kiledal, E. Anders, Achieng, Dorine, Barker, Katelyn B., Basweti, George M., Beal, Max, Brown, Katelyn M., Byrne, Aidan, Drouillard, Ken G., Getabu, Albert, Kiteresi, Linet I., Lawrence, Theodore, Lomeo, Davide, Miruka, Jared B., Mohney, Samantha, Njiru, James, Okutoyi, Pamela, Omondi, Reuben, Otieno, Dennis, Owino, Omondi A., Owoko, Winnie, Owuor, Bethwell, Shitandi, Anakalo, Stoll, Jordyn, Swaleh, Miriam, Tebbs, Emma, Varga, Emily, Wagner, Ryan S., Sheik, Cody S., Sherman, David H., Dick, Gregory J., Wilhelm, Steven W., Sitoki, Lewis, Otiso, Kefa M., McKay, R. Michael L., Bullerjahn, George S.
• Format: Article
• Language: English
• Subjects: Cyanobacteria - genetics; Dolichospermum; freshwater; Harmful Algal Bloom; Kenya; Lake Naivasha; Lake Simbi; Lake Victoria; lakes; Lakes - microbiology; Metabarcoding; metabolism; Metagenomics; methane; Methane metabolism; Microcystis; poisonous algae; risk assessment process; stakeholders; sulfur; Sulfur limitation; surface area; surveys; Synechococcus; toxicity; watersheds
• ISSN: 1568-9883; 1878-1470; 1878-1470
• DOI: 10.1016/j.hal.2024.102757

•Dolichospermum and Microcystis spp. populations of Lake Victoria's Winam Gulf suggest an underappreciated role of sulfur dynamics in competition between diazotrophic and non-diazotrophic cHABs.•A subdominant cHAB community in Lake Naivasha represents an incipient risk in the face of ongoing eutrophication and anthropogenic influence.•Methane metabolism may shape Lake Naivasha's cyanobacterial community with Synechococcus spp. serving as a potential methane source and sink.•Lake Simbi supported a Limnospira spp. bloom lacking cyanotoxin biosynthetic gene clusters, thus representing a low cHAB risk.•We provide a risk assessment framework and primer candidates for targeted PCR screening of lakes deemed as moderate to high cHAB risk level by local authorities. Despite the global expansion of cyanobacterial harmful algal blooms (cHABs), research is biased to temperate systems within the global north, such as the Laurentian Great Lakes. This lack of diversity represents a significant gap in the field and jeopardizes the health of those who reside along at-risk watersheds in the global south. The African Great Lake, Lake Victoria, is understudied despite serving as the second largest lake by surface area and demonstrating year-round cHABs. Here, we address this knowledge gap by performing a molecular survey of cHAB communities in three anthropogenically and ecologically important freshwater systems of Victoria's Kenyan watershed: Winam Gulf (Lake Victoria), Lake Simbi and Lake Naivasha. We identified a bloom of non-toxic Dolichospermum and toxic Microcystis in the Winam Gulf, with data suggesting sulfur limitation shapes competition dynamics between these two bloom-formers. Though we did not detect a bloom in Naivasha, it contained the largest diversity of cHAB genera amongst the three lakes. In turn, our results indicated methane metabolism may allow non-toxic picoplankton to outcompete cHAB genera, while suggesting Synechococcus spp. serves as a methane source and sink in this system. Lake Simbi exhibited a non-toxic Limnospira bloom at the time of sampling with very low abundances of cHAB genera present. Subsequently, these results were employed to design a cHAB screening and risk assessment framework for local stakeholders. Cumulatively, this work serves to increase cHAB research efforts on the international scale while serving as an impetus for cHAB monitoring on the local scale.