Place: Tempe, Arizona, USA
Date: 28 August 2021
Background:
Cyanobacterial blooms (blue-green algae) are an increasingly occurring phenomenon worldwide that is considered a serious threat to animal and human health (4). Certain environmental conditions, exacerbated by human influence have led to widespread eutrophication of aquatic ecosystems-a phenomenon termed ‘algal bloom’ (4). The blooms often release biological toxins that impact the liver, digestive and nervous system of humans and animals (4). Furthermore, build up of noxious mats on the water surface, obstruct recreational activities, power generation and irrigation (1). Several chemical-based solutions have been attempted to combat algal blooms but have generally been targeted at the most common genera of cyanobacteria – Microcystis, while less common cyanobacteria, such as Lyngbya sp have rarely been treated (1). Lyngbya are large-celled mat forming cyanobacterium (blue-green alga) that occur in freshwater ecosystems. The mats can be several inches thick and cover large surface areas of water or form as benthic (bottom) mats (UF Center for Aquatic and Invasive Plants).
The Lake Guard® technology features a novel formulation that allows the active ingredient to float and time-release. This mode of delivery is the most effective targeted treatment against harmful algal blooms (HABs). The approved (EPA/NSF60) products present a novel application method to treat HABs in a timely and cost-effective manner.
Treatment setup and Methodology:
An artificial warm water lake in Tempe Arizona has suffered from recurring Lyngbya sp. algal blooms and previous attempts to eliminate the blooms were unsuccessful. Visible and noxious mats persisted on the surface of the lake which posed a negative impact on the health and quality of life of the resort’s residents.
On August 26th, 2021, a team from BlueGreen Water Technologies, applied a treatment dose of 30lb/acre of Lake Guard® Blue, a copper sulfate pentahydrate-based product, on the 1.3-acre artificial warm water lake. Water quality parameters were recorded before and after treatment using a YSI Sonde. Measurements included pH, temperature, chlorophyll-b, phycocyanin and percent of dissolved oxygen (DO). Additionally, water samples from two different sites on the lake were collected and analyzed for total algae and cyanobacteria cell count. These samples were collected over a course of 9 days. Water sample collection and cell count analysis were completed by Aquatic Consulting & Testing Inc., a consulting group based in Tempe Arizona.
Results and discussion:
Within 24-48 hours from the Lake Guard® Blue application, the green-brown scum was cleared from the water surface (Fig. 1 a & b). Chlorophyll biomass decreased post-treatment, while phycocyanin level remained at a very low value. No noticeable difference was observed in the DO content, and pH levels only slightly decreased. The cyanobacteria cell count decreased significantly within 24 hours post-treatment application, and continued to decrease over the course of the next 8 days (Fig. 2).
Fig. 1. Pictures of the lake before and after treatment. (a) Before treatment on Aug 26, 2021. (b) 48 hours after treatment on Aug 28, 2021.
Fig. 2. Cyanobacteria cell count over a course of 9 days. Aug. 26 value is from time zero, before the treatment application with the Lake Guard® technology. Cyanobacterial cell density decreased significantly 24 hours post-treatment, Aug. 27, and continued to decrease in the subsequent days after the application.
References:
1. Bishop, W.M., B.E. Willis, W. G. Cope, and R. J. Richardson, 2020. Biomass of the Cyanobacterium Lyngbya wollei Alters Copper Algaecide Exposure and Risks to a Non-target Organism. Bulletin of environmental contamination and toxicology, 104:228-234.
2. Center for Aquatic and Invasive Plants: University of Florida, IFAS. Center for Aquatic and Invasive Plants, University of Florida, IFAS, https://plants.ifas.ufl.edu/plant-directory/lyngbya-species/.
3. Descy, J. P., F. Leprieur, S. Pirlot, B. Leporcq, J. Van Wichelen, A. Peretyatko, S. Teissier, G. A. Codd, L. Triest, W. Vyverman, and A. Wilmotte, 2016. Identifying the factors determining blooms of cyanobacteria in a set of shallow lakes. Ecological Informatics, 34:129–138.
4. Huisman, J., G. A. Codd, H. W. Paerl, B. W. Ibelings, J. M. H. Verspagen, and P. M. Visser, 2018. Cyanobacterial blooms. Nature Reviews Microbiology, 16:471–483.
5. Paerl, H. W., and T. G. Otten. 2013, Harmful cyanobacterial blooms: causes, consequences, and controls.
