Algal Growth A Blooming Problem Space Station To Help Monitor
Jessica Nimon, International Space Station Program Science Office NASA’s Johnson Space Center
The green stuff that clouds up fish tanks – it’s not just an aesthetic annoyance. In fact, if you’ve been watching recent news of algal bloom concerns in Lake Erie, you know that the right conditions for algae can lead to contamination of local water sources, potentially impacting aquatic life and humans. What you might not have known is that among the resources to help study this problem you will find the International Space Station’s Hyperspectral Imager for the Coastal Ocean (HICO).
This instrument, mounted to the exterior of the orbiting laboratory, provides a way for researchers to see 90 wavelengths of light not visible to the human eye. This can help with research on harmful algal blooms (HABs) because they, along with other organic materials, have a “spectral signature.” The biological matter emits a unique wavelength as it absorbs and scatters solar energy, resulting in fluorescence and backscattering. Essentially the light reflects back to HICO, which reads the data like a fingerprint.
Researchers can use the information from HICO to “see” what they’re missing with their own senses. With it they study biological and chemical signatures for aquatic and terrestrial materials. This can reveal the presence of microscopic plants, organic compounds, suspended sediments and other factors controlling water quality.
HICO was first designed and built by the U.S. Naval Research Laboratory (NRL) for the Office of Naval Research to assess water quality in the coastal ocean. HICO continues to operate beyond its original one-year mission, having moved past the initial three-year mission when NASA took over the support of operations in January 2013. Researchers continue to use HICO for science around the world.
To address water quality issues, the Center for the Advancement of Science in Space (CASIS) partnered with the NRL at NASA’s Stennis Space Center (SSC) in Mississippi to enable the study of HABs, including those in Lake Erie.
“Historically, blooms have been visually observed by the naked eye due to the discoloration of the water,” said Ruhul Amin, Ph.D., principal investigator for the HICO CASIS-NRL project. “Now optical sensors can detect these changes in the color of the water and quantitatively measure the spectral radiance changes due to algae blooms.”
In the Lake Erie area researchers are looking at phytoplankton and algal blooms that occur regularly in summer months, often in the harmful quantities found this year. Of particular concern are blue-green algae Microcystis spp., which can cause health concerns in humans such as nausea, numbness or dizziness—potentially leading to liver damage. Once airborne in sea spray, the brevetoxin producing HAB Karenia brevis—known as red tide—can go beyond irritating the eyes and lungs of coastal visitors, according to Amin, as it is capable of killing fish, birds and marine mammals. No human fatalities are directly attributed to brevetoxins, he goes on to say, though it is possible to reach fatal toxin levels during K. brevis blooms.
“Unlike conventional multi-spectral images, the high spatial and spectral resolution afforded by HICO enables us to develop new approaches to more fully utilize hyperspectral data to distinguish HAB species from space,” said Amin. “Conventional multi-spectral ocean color imagery in general does not contain sufficient information to discriminate between bloom species, but HICO’s contiguous bands collect information that can enable us to identify the species.”