EEB Tuesday Seminar Series - Elucidating How Intraspecific Variation Sustains Freshwater Harmful Cyanobacterial Blooms

Microbial population dynamics are regulated by bottom-up (resource availability) and top-down (predation) forces. However, within-species variation may prompt differential responses to these ecological factors, helping populations persist through fluctuating environments. Thus, treating a species as a single entity and using a single trait value to represent population responses cannot entirely capture the specific ecological drivers of population dynamics. Employing strain-level resolution is particularly impactful for studying cyanobacterial bloom dynamics due to the significant genetic diversity within the harmful cyanobacterium Microcystis, which often dominates these blooms across the globe. Microcystis exhibits optimal growth in high-temperature waters, explaining why they dominate blooms in the summer. Additionally, it is aided by anthropogenic nutrient loading and increased resistance to predation relative to other phytoplankton species. However, within these blooms, there are spatial and temporal variations in strain composition. What drivers and traits underpin these patterns is not well understood, yet can impact toxin production and likely both the rise and demise of these blooms. My research aims to parameterize strain-level responses to changing nutrient availability and predatory pressure in Microcystis and test whether these ecological drivers explain strain dynamics in natural contexts. In addition, arguably the highest intraspecific variation within Microcystis exists in its CRISPR-Cas anti-viral defense system. Yet, lab assays similar to those I performed for nutrient competition and predator defense are less available for studying virus-Microcystis interactions. Hence, I will use the coevolutionary history documented in the CRIPSR-Cas system to investigate how and why Microcystis-virus pairs change through time and space. This will help explain how host-virus coevolution occurs when ecological factors constrain host populations. Ultimately, this research will enhance our understanding of biotic interactions under the influence of nutrient inputs, improving our capacity to predict and manage harmful cyanobacterial blooms.