Join Midwest Glacial Lakes Partnership for a webinar on HABs. Harmful algal blooms (HABs) are often linked to external nutrient inputs from anthropogenic phosphorus (P) pollution or atmospheric nitrogen deposition. However, the increasing occurrence of blooms without these inputs has shifted attention to internal drivers. Recent research highlights internal P loading from sediments, driven by changing stratification patterns, as a key trigger. We present examples from wilderness to hypereutrophic lakes, where HABs occur or intensify due to anoximixis. Using high-frequency sensors and traditional monitoring, we compare bloom timing and intensity with factors such as hypolimnetic P accumulation, mixing frequency, and cyanotoxin production. Our findings emphasize the need to understand anoximixis as climate change alters lake stratification and accelerates oxygen depletion. These changes may lead to more toxic blooms in affected systems and trigger blooms in lakes previously thought to be resistant. Register for the webinar here: Webinar Registration - Zoom