Work

Using an Ultraviolet-Enabled Boat to Reduce Microcystin and Suppress Cyanobacterial Growth in Harmful Algal Bloom-Impacted Surface Waters

Year: 2025

Type: article

Abstract: Numerous remediation strategies exist for cyanobacterial harmful algal blooms (cyanoHABs), however most are limited by challenges of scalability and adverse off-target effects on the surrounding ecosystem. Germicidal ultraviolet light (UV-C) has emerged as a promising method for suppressing cyanoHABs in a sustainable, chemical-free manner that is both scalable and results in limited off-target ecological effects. In this study, the US Army Engineer Research and Development Center’s (ERDC) CyanoSTUNTM (Cyanobacterial Suppression Through Ultraviolet-Light-C Neutralization) vessel was deployed to a cyanoHAB as part of a field trial to determine whether UV-C could effectively suppress cellular growth, degrade associated cyanotoxins, and inhibit harmful phytoplankton species more readily than beneficial species without the use of chemicals. Results of the field trial showed that the CyanoSTUN UV-C treatment effectively suppressed the growth of the cyanobacteria community for approximately two days at the three tested UV-C doses. The CyanoSTUN UV-C treatment also demonstrated a sustained, dose-dependent effect on microcystin concentration; the average reduction in microcystin concentration for 15, 30, and 45 mJ/cm2 treatment doses was 31.6% (1.3 µg/L reduced), 45.7% (1.9 µg/L reduced), and 49.9% (1.7 µg/L reduced), respectively. Non-cyanobacteria were too scarce in this CyanoHAB to conclude whether the CyanoSTUN UV-C inhibits harmful phytoplankton species more readily than beneficial species. The CyanoSTUN UV-C treatment reduced chlorophyll a concentration at a statistically significant level for some of the regrowth period, but had no significant effect on phycocyanin or optical density. Further field studies with the CyanoSTUNTM are required to validate performance under more severe cyanoHAB conditions, however the results reported herein from the first field trial with the CyanoSTUNTM suggest that this treatment method may offer water managers confronted with a CyanoHAB the ability to rapidly and safely pause a bloom for multiple days and reduce the risks posed by its associated cyanotoxins without using chemicals.

Source: Applied Sciences

DOI: 10.3390/app15126765

Authors: Taylor Rycroft, Brianna Fernando, Michael Mayo

Institutions: United States Army, U.S. Army Engineer Research and Development Center

Language: English

Topic: Aquatic Ecosystems and Phytoplankton Dynamics

Subfield: Environmental Chemistry

Field: Environmental Science

Domain: Physical Sciences

SDGs: Clean water and sanitation, Good health and well-being

Open Access status: gold

Estimated APC paid: $2,896