Israel Sprayed Algicides Off Ashkelon After a Microalgae Bloom Shut Desalination Plants—But How Much Entered the Sea?
An aerial operation off Ashkelon used approved algicide products as a microalgae bloom disrupted five desalination plants. Officials say drinking and bathing remained safe; critics want the missing dosage and monitoring data.
Five of Israel's six major coastal desalination facilities were disrupted this week by a dense microalgae bloom moving north through the Mediterranean. The emergency response then created a second controversy: aircraft dispersed algicide products off Ashkelon, prompting questions about copper exposure, ecological monitoring and why the public learned important details through television rather than a complete government disclosure.
The treatment took place on September 2, according to Israeli reporting, about one kilometre offshore along a roughly nine-kilometre strip near Ashkelon and Zikim. The Water Authority requested permission from an interministerial sea-dumping committee chaired by the Environmental Protection Ministry, with the Health Ministry represented. Officials said the purpose was to suppress the bloom and restore desalination capacity.
The bloom itself is not disputed. Ashkelon, Ashdod, Palmachim and the two Sorek plants were among the facilities affected, while Hadera continued operating. High concentrations of algae and organic matter can overwhelm pretreatment systems, clog filters and damage membranes. A country that obtains most of its domestic drinking water from desalination has little room for several plants to fail together.
Channel 13 aired a ministry table naming three BlueGreen Water Technologies product lines: Lake Guard Blue, Lake Guard Oxy and Lake Guard DEW. Company safety information identifies their principal active ingredients as copper sulfate pentahydrate, sodium percarbonate and aluminum sulfate. Blue releases copper as an algicide; Oxy produces an oxidizing effect; aluminum salts can help suspended particles aggregate.
That does not establish the exact contents of every aircraft load. No ministry page located for this report publishes a batch ticket, number of kilograms, flight-by-flight manifest or final concentration map. Social-media calculations based on the capacity of an Air Tractor are therefore estimates, not measurements. Claims of six, ten or fifty tonnes should not be repeated as facts without loading records.
The public argument centers on apparently conflicting official messages. Energy and water officials said the release was authorized, controlled and posed no danger to bathers or drinking water. Agriculture temporarily prohibited fishing from Ashkelon toward the Gaza boundary, extending offshore, while Health described the measure as precautionary and did not prohibit eating fish already marketed.
A restriction does not automatically prove poisoning. Regulators often impose buffers while sampling is incomplete. Yet reassurance is also more credible when accompanied by numbers. Channel 13 reported a planned upper-water copper concentration of approximately 0.13 milligrams per litre and a ministry comparison marked around 27 times a cited saltwater benchmark. Authorities should publish the source, legal meaning and sampling results behind that comparison.
Copper sulfate is widely used to control algae, and product literature includes freshwater, brackish and some saltwater applications. It is not chemically invisible after algae die. Copper dilutes, binds to organic material and particles, and may accumulate in sediments or filter-feeding organisms. Sodium percarbonate breaks down more rapidly, while aluminum behavior depends on pH and water chemistry. Open-sea currents make exposure less concentrated than in a pond but also harder to contain and measure.
Officials said the operation included current tracking, environmental monitoring and rules to stop if material moved shoreward or wildlife risks emerged. Those safeguards are relevant. The decisive evidence will be pre- and post-treatment samples for dissolved copper, sediment, plankton mortality, fish and desalination intake water—not the confidence of either press releases or viral posts.
The operation also raises an effectiveness question. Ashkelon and Ashdod reportedly remained offline after treatment, while Hadera, farther north, was operating. That does not prove failure: treatment may require time or may have been intended to protect other intakes as the bloom moved. It does mean officials should not imply that spraying immediately reopened Ashkelon unless operating data show it.
There is a second policy issue beyond toxicology: resilience. Israel's desalination network is geographically concentrated along one coastline, so a moving biological event can create correlated failures that planners may have treated as independent. Emergency chemical treatment may be a rational last line of defense, but it should not substitute for intake redesign, larger stored-water buffers, better bloom forecasting and coordination with Egyptian and regional marine scientists. Climate-driven warming may make some blooms more likely, while nutrients, currents and species composition determine whether any individual event occurs. Assigning this episode solely to climate change would be as premature as dismissing environmental change entirely.
The operator and manufacturer also have information to provide. Chim-Nir can identify flights, hopper loads and coordinates; BlueGreen can explain the intended marine dosage and environmental fate; plant operators can publish intake turbidity and membrane performance. Commercial confidentiality should not cover the quantities deliberately released into public waters. A single consolidated incident report would resolve more uncertainty than separate reassurances from ministries with different responsibilities.
What to watch next
Watch for the permit, product manifests, kilograms dispersed, monitoring locations, copper measurements and the exact dates each plant returns to service. Israel faced a real threat to its water supply and may have needed an emergency intervention. The unanswered question is whether a necessary response was conducted with enough transparency to let the public judge both its safety and its success.