An unanticipated harmful algal bloom (HAB) appeared in Lake Anna, Virginia in early August, 2019. Lake Anna is one of the largest freshwater reservoirs in VA. Research is needed to understand threats, manage risks, mitigate incidents, develop capabilities, and strengthen collaborations for our water safety and security. Aerial and aquatic robots will work alongside health and water quality experts from VDH and DEQ to (1) help inform their regular sampling efforts, and (2) provide critical and timely information to guide regulatory decisions. The HAB is still going at Lake Anna, and it is expected to continue until the first freeze at the Lake. Once the first freeze occurs, most of the cyanobacteria will explode and unload a large amount of toxins, requiring further analysis.<br/><br/>Since the first report of the harmful algal boom (HAB) on Lake Anna, the bloom has reportedly intensified, and the Virginia Department of Health (VDH) has issued multiple advisories. The most recent VDH advisory (issued on Sept 20, 2019) showed the HAB extending down both northern branches of the lake. The VDH advisories are based in part on water quality data from the VA Department of Environmental Quality (DEQ), which collects samples from a series of stations (GPS waypoints where a manned boat is used to collect samples by hand) across the lake. The research team will work alongside water quality experts (DEQ and VDH) to make targeted collections of the HAB at Lake Anna using aerial robots (a drone equipped with multispectral sensors to image the bloom and a device to sample the water) and aquatic robots (a remotely operated underwater vehicle equipped with underwater GPS, sensors to track the plume in situ, and a device to collect underwater samples). These samples will be analyzed for toxins and nutrients, and the data will be shared with water quality experts and members of the Lake Anna Civic Association. Based on 10 years of seasonal toxin data for Grand Lake St. Marys in Ohio, the research team hypothesize that (1) the HAB at Lake Anna, VA will continue to progress and produce high toxin levels through the coming winter months and (2) aerial and aquatic robots can identify, localize, and sample targeted areas of the HAB in the lake. The specific objectives of this project are to (1) use aerial and aquatic robots to target the HAB in Lake Anna, VA and collect samples at strategic locations; and (2) determine toxin concentrations and nutrient loads in samples collected by robots working alongside humans. This information is critical for determining time-sensitive health advisories, and for the communities of people that live in and around the lake. This work will also show the value of unmanned systems to assist stakeholders in tracking HABs in the water; resulting field-tested technology will provide decision-makers with co-robots that can provide rapid and detailed information on the dispersal of HABs in the environment. The HAB is still going at Lake Anna, and it is expected to continue until the first freeze at the Lake. Once the first freeze occurs, most of the cyanobacteria will lyse and unload a copious amount of cyanotoxins.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.