Algae blooms are a common phenomenon in many water bodies around the world. They occur when algae, microscopic organisms that use sunlight to produce their own food, grow rapidly and form dense mats on the water's surface.
Some algae blooms are harmless, but others can be harmful to humans, animals, and the environment.
These harmful algal blooms (HABs) can produce toxins that can cause illness, death, or ecological damage.
One of the most common and dangerous toxins is microcystin, a liver toxin and potential carcinogen that can contaminate drinking water and affect aquatic life.
Monitoring and managing HABs is a challenging task, as they can vary in size, duration, location, and toxicity.
Current methods for detecting microcystin in water involve collecting water samples and analyzing them in a laboratory using expensive and time-consuming techniques.
These methods are often not fast or accurate enough to provide timely information for decision-makers and stakeholders.
However, a team of researchers from Oregon State University has developed a novel technique for sniffing out toxic algae blooms: using volatile organic compounds (VOCs) as indicators of microcystin presence.
VOCs are gaseous molecules that are released by various sources, including algae. The researchers found that certain combinations of VOCs emitted by algae can reveal the level of microcystin in the water.
This technique could provide a faster, cheaper, and more reliable way to monitor HABs and protect public health and the environment.
How VOCs can reveal microcystin levels
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The researchers conducted their study on Upper Klamath Lake in Oregon, a large shallow lake that experiences frequent and severe HABs caused by cyanobacteria, also known as blue-green algae.
Cyanobacteria are a type of algae that can produce microcystin and other toxins. The researchers collected water samples from different locations and depths of the lake during two bloom events in 2018 and 2019. They also collected samples from irrigation canals that receive water from the lake.
The researchers measured the concentration of microcystin and the composition of VOCs in each sample using various analytical methods.
They identified 32 different VOCs that were emitted by cyanobacteria, including alcohols, aldehydes, ketones, esters, and terpenes.
They found that some VOCs were positively correlated with microcystin levels, meaning that they increased as microcystin increased.
These VOCs included 2-methyl-1-propanol, 3-methyl-1-butanol, hexanal, heptanal, octanal, nonanal, decanal, geraniol, and linalool.
The researchers also found that some VOCs were negatively correlated with microcystin levels, meaning that they decreased as microcystin increased.
These VOCs included acetone, 2-butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, 2-heptanone, 3-heptanone, 2-octanone, 3-octanone, 2-nonanone, 3-nonanone, 2-decanone, and 3-decanone.
The researchers used these correlations to develop a statistical model that could predict microcystin levels based on VOC profiles.
They tested their model on independent samples from the same lake and canal system and found that it performed well in estimating microcystin concentrations.
They also compared their model with other methods for detecting microcystin and found that it was more accurate and consistent than enzyme-linked immunosorbent assay (ELISA) kits or cell counts.
The potential applications and benefits of VOC-based monitoring
The study by Halsey et al. (2023) demonstrates the potential of using VOCs as indicators of microcystin levels in water. This technique could offer several advantages over existing methods for monitoring HABs. For example:
It could be faster and cheaper than laboratory-based methods that require sample collection and transportation.
It could be more reliable and sensitive than field-based methods that rely on visual inspection or colorimetric tests.
It could provide continuous and real-time information on HAB dynamics and toxicity.
It could cover larger spatial scales and depths than point measurements or remote sensing.
It could be integrated with existing sensor networks or drones to enhance spatial and temporal resolution.
The researchers suggest that their technique could be applied to other water bodies and other toxins produced by algae, such as domoic acid or saxitoxin.
They also suggest that their technique could be used to detect other environmental changes or disturbances, such as oxygen depletion, nutrient enrichment, or invasive species.
The study by Halsey et al. (2023) provides a valuable contribution to the understanding and management of HABs and their impacts. It also provides a novel tool for assessing water quality and ecosystem health using VOCs as biomarkers.
