Place: Safari National Zoo – Ramat Gan, Israel
Date: August-September 2016
Rationale
A growing number of publications indicates that cyanotoxins accumulate in the tissues of organisms living in infested waters and can be transferred through the food chain to preying animals or humans. These findings are putting the entire aquaculture industry, for example, in jeopardy, turning cyanobacteria-associated damages from taste and color issues into a health hazard altogether.
This trial is the first of a series of trials in the aquaculture sphere, conducted in Israel’s “Safari” National Zoo at its request and in an attempt to suppress a massive bloom that was interrupting the regular operation of the zoo as well as presenting a real health risk to the vast number of animals relying on the affected water body. It was conducted under the supervision of Dr. Orr Shapiro from the Volcani Institute – Israel’s National Agriculture Research Center.
Trial Setup
The trial was conducted in a 2,000 m2 freshwater pond heavily infested primarily with Microcystis sp., with a cell density of ~108-109 cells/ml and an initial Microcystins concentration of ~6µg/L.
Trial Protocol
Given the magnitude of the infestation, it was decided to begin with a treatment regime of 5g/m2 Lake Guard™ White to be repeated as needed according to real-time conditions in the pond.
Measurements were taken periodically, followed by an immediate decision on whether to treat again or not. When treatment was applied, a second measurement was taken within 24 hours after application.
Treatments were applied on day 0, day 1, day 8, and on day 20.
Trial Results
Each of the four treatments resulted in an immediate sharp decline in phycocyanin (a direct proxy for cyanobacterial biomass) and in chlorophyll-a as well as in microcystin levels, indicating an immediate improvement in water quality.
Each subsequent treatment resulted in a longer effect, with the last one, coming shortly after a heat wave, lasting until the end of the trial, some 2.5 months later.
Animals living in and around the pond were observed throughout the trial period. None was harmed by the treatment (albeit in high doses) or registered any discomfort. The reason for that lies with the Lake Guard’s autonomic distribution mechanism (winds and currents), limiting active ingredients vertically - to the upper layers of the water column; and spatially, allowing living organisms to move to lower layers or upwind in order to easily avoid contact.
