Andrea VanderWoude studies Great Lakes conditions from the window of a plane. A hyperspectral camera on the aircraft also comes in handy.
VanderWoude, a remote sensing specialist, has spent the past four years looking for harmful algal blooms and an algae called Cladophora from the skies above Lake Erie, Lake Huron and Lake Ontario.
She’s up in the air a handful of times each year, and reviews images multiple times a week from the camera, which captures detailed color bands at a higher resolution than those taken by satellites. The extra bands can be used to detect different types of algal groups.
Vanderwoude is able to figure out what the pictures mean by using post-processing software and an experienced eye.
“Who would think that scum is such a beautiful thing?” VanderWoude said.
The photo below, for instance, shows a scum feature of cyanobacteria at different levels in the water column over the western arm of Lake Erie on July 30, 2018. Brighter green is scum near the water surface, which has been disrupted by boat and ship tracks.
As part of ongoing research for the Great Lakes Environmental Research Lab out of Ann Arbor, Michigan, she flies every week during the summer, from May through mid-October or early November. A pilot takes photos with a conventional camera and the hyperspectral sensor.
VanderWoude describes the images as “fascinating.”
The photos are useful in helping people like drinking water managers know when an algal bloom is headed for a city’s water intake, so they can adjust treatment methods as necessary. A bloom can contain blue-green algae that produces cyanotoxins and harms humans and wildlife. Cladophora is a nuisance algae, but it can be a site for botulism growth that kills birds.
“We can fly anywhere,” VanderWoude said. “We can fly underneath the clouds and capture areas close to the shoreline, where drinking water intakes are at.”
The Great Lakes Environmental Research Lab is an arm of the US National Oceanic and Atmospheric Administration and also known as NOAA-GLERL. VanderWoude is a contractor.
On Nov. 7, 2016, NOAA-GLERL flew over the Sleeping Bear Dunes National Lakeshore to map Cladophora (the bottom blue image). Submerged aquatic vegetation appears as darker shaded regions that are verified with shipboard surveys and image processing by the Michigan Technological Research Institute. The second image (right-hand side) shows an example of a sampling site on North Manitou Island on Aug. 14, 2018.
Two hyperspectral images below, from Sept. 22, 2016, show a prevalent cyanobacteria harmful algal bloom at the lake surface just east of Point Pelee on Lake Erie.
Vanderwoude is an oceanographer by trade, and lives in West Olive, Michigan, across the street from Lake Michigan. In her spare time, she likes to draw and create multimedia art from items found on the beach.
She processes about half a terrabyte of data (500,000 megabytes) per week while the flights are going on.
Rip currents are next on her to-do list.
“Since I’ve lived on the west side of the state, I’ve come to understand how many drownings happen due to rip currents,” she said.
She hopes to use future flights to map how sandbars are moved around after storms to create troughs that can result in rip currents and drownings. This could create a way to alert the public at certain beaches.