Using multispectral imagery to predict microcystin toxicity in Iowa lakes

Cyanobacterial harmful algal blooms (cyano-HABs) negatively impact lake water quality, resulting in economic losses and public health risks from the toxins produced by cyano-HABs. Lakes in Iowa have frequent cyano-HABs because of the nutrients that runoff into lakes from fertilizer. Contact to toxins through recreation or consumption of contaminated drinking water can result in negative effects ranging from skin irritation to liver damage and even death. Therefore, it is important to understand and properly manage these blooms to protect the public and reduce negative impacts. Several strategies have been developed to monitor these systems, but current methods do not fully describe the variability and diversity of bloom events. We combined drone-based imaging with relationships between the pigment produced and the toxins released by cyanobacteria to try to capture the distribution and toxicity of a bloom event on Green Valley Lake in Iowa. We developed a new image processing procedure to improve the stitching of images over water. We also conducted a state-wide study to determine if a simple relationship between pigments and toxins exists and what lake characteristics may impact that relationship. As part of the state-wide study, we also characterized different forms of cyanotoxins and determined how the abundance of each toxin may change the overall risk associated with a bloom event. Cyano-HABs vary in space and time and the severity of bloom events are controlled by many factors. However, it is important to continue to improve bloom monitoring to protect the public and minimize economic impacts.