The discovery suggests that the neurotoxin called anatoxin-a (ATX) has the potential to become airborne. The researchers have reported the discovery in a paper published Thursday, April 1, in Lake and Reservoir Management.
Harmful algal blooms appear when huge amounts of photosynthetic bacteria, known as cyanobacteria, grow on the surface of a pond or lake. These blooms are amplified by fertilizer runoff from wastewater or farm fields. ATX is a potent cyanotoxin produced by algal blooms. But ATX has never been detected in the air before.
To investigate, study lead author James Sutherland, an environmental scientist with the Nantucket Land Council, and his colleagues collected samples of airborne particles from around the edge of Capaum Pond from July to October, when the pond was regularly covered with algal blooms. They sampled the water as well.
They used a technique called liquid chromatography-tandem mass spectrometry to search for ATX in the water and air samples. ATX was consistently detected in the water at concentrations of up to 21 nanograms per milligram of water (ng/mg). Concentrations of ATX in the water were particularly high on Sept. 11, 2019.
The researchers also detected ATX in the air around the pond on that same day, which was especially foggy and windy. In particular, they found an average concentration of 0.87 ng per filter on their air sampling device, which would correspond to a potential airborne exposure of 0.16 ng per meter squared.
However, the researchers weren't sure how ATX became airborne. They surmised that the neurotoxin was blown from the surface of the water by strong winds the night before they collected air and water samples. ATX could have lingered in the air because of the foggy conditions on the day they collected samples.
It also remains unclear whether airborne ATX has adverse impacts on humans and animals. Nevertheless, they warned that the possibility of exposure is still a cause for concern and further investigation. They concluded that the emission of ATX molecules presents a potential human health exposure not previously analyzed.
People often have recreational activities around lakes or ponds with algal blooms unaware of the health problems the blooms may bring, said Sutherland. Direct contact or inhalation of ATX and other cyanotoxins released by algal blooms may present health risks for individuals.
Sutherland noted that algal blooms are emerging more frequently in recent years due to human activity. Farms treated with fertilizer, for instance, partly feed cyanobacteria that form algal blooms. Heavy rain can wash excess nutrients from fertilizers into bodies of water.
And while ATX was only detected in the air around a specific pond, Sutherland and his colleagues warned against hanging around still bodies of water with algal blooms. Further research is needed to test ponds around the world for airborne ATX particles.
Algal blooms, also known as pond scum, are notorious for their detrimental environmental effects. Thick layers of algae can block sunlight from reaching plants at the bottom of ponds or lakes. When those plants die, the entire food web and ecosystem can be severely impacted.
Algal blooms can also cause fish-kill events. Algae photosynthesize and produce oxygen during the day. But the aquatic organisms also use up oxygen at night, competing with fish. Eventually, algae can cause dissolved oxygen concentrations in the water to drop. Fish will inevitably die as a result. (Related: Thousands of dead fish wash up on Lake Michigan.)
Environ.news has more stories about algal blooms and their environmental impacts.