Israel’s Desalination System Stunned by Massive Microalgae Bloom

A miles-long microalgae bloom in the Mediterranean Sea caused five of Israel’s six major coastal desalination plants to shut down on Sunday. The facilities, which use reverse-osmosis technology, have only partially resumed operation, and as of Thursday a single plant is running at full capacity. Mekorot, the national water company, reports that the interruption has not yet led to a drinking-water shortage.

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Desalination supplies at least 65 % of Israel’s drinking water, a critical lifeline for an arid nation lacking large rivers or abundant rainfall. Scientists trace the bloom to the Nile Delta, where it likely formed before drifting northward with prevailing currents. Associate professor Edo Bar-Zeev of Ben-Gurion University notes the bloom stretches “more than a dozen miles” and attributes its emergence to an “unusual combination of factors”: a sea storm that raised turbidity, sea-surface temperatures of 86 °F (30 °C) and above, and elevated nutrient loads. Marine ecologist Tamar Guy-Haim adds that the right mix of nutrients, light, temperature, currents and mixing enabled the rapid algae growth.

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Lior Gutman, spokesperson for Mekorot, called the incident “an extremely rare event” and emphasized that in roughly 99 % of cases Israel has avoided drinking-water shortages. Michael Christopher Low, director of the University of Utah’s Middle East Center, warned that suspended algae can foul reverse-osmosis membranes, exposing the system’s vulnerability. Both Gutman and Low said the timing—during summer, when water demand peaks—made the situation especially challenging.

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Experts argue the bloom signals a growing climate-driven threat to water security. Low predicts that similar events will become more frequent as ocean temperatures rise and storms intensify, potentially overwhelming desalination infrastructure. Bar-Zeev also highlighted non-climatic risks, noting that oil spills, cyber attacks, or military actions could disable plants for far longer periods than a transient algae bloom.

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• “An event of this kind has never occurred before in Israel … it was an extremely rare event,” — Lior Gutman

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• “It’s not if, it’s just when an oil spill in the vicinity of desalination facilities will occur,” — Ben-Zeev

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