Misbar Tracks Algae Bloom From Egypt Behind Israeli Desalination Crisis

Misbar’s team at Al-Araby TV used Sentinel-2 satellite imagery to track a notable change in the color of Mediterranean waters along the eastern coast. The change was first observed off the Egyptian coast, followed by similar changes off North Sinai and the Gaza Strip before reaching the Israeli coast.

The phenomenon reached Israel’s coastline in late August and early September, coinciding with a near-unprecedented disruption to the country’s desalination system. Five of the six major desalination plants along the Mediterranean were shut down after a sharp increase in seawater turbidity.

The affected facilities included Ashkelon, Ashdod and Palmachim, as well as Sorek A and Sorek B. The Hadera plant farther north remained operational. Sources in the water sector said the shutdowns were a precautionary measure to protect sensitive filtration systems and membranes from clogging or damage.

Preliminary findings by researchers at the Israel Oceanographic and Limnological Research Institute suggest that the turbidity may be linked to a dense bloom of microalgae that could have originated in Egypt’s Nile Delta and was subsequently carried by water movement and currents through the eastern Mediterranean.

The hypothesis has not yet been confirmed. Researchers are continuing to analyze samples to identify the algae species and determine their precise origin, while experts have raised other possibilities regarding the source and movement of the phenomenon.

Satellite Images Track Sea Color Changes From Egypt to Israel’s Coast

Misbar’s team analyzed a series of Sentinel-2 images captured between July and early September to track changes in water color along the eastern Mediterranean coast.

Natural-color imagery cannot, by itself, identify the type of algae or establish whether the changes observed at different locations were part of the same water mass. However, it can help track changes in water color and turbidity over time and across different areas of the coastline.

The first notable signs appeared on July 6, when the waters off Port Said and parts of the Nile Delta coast took on a dark green hue that extended eastward toward Lake Bardawil.

By July 16 and 18, the phenomenon had become more pronounced, covering broad areas off Port Said and extending along the North Sinai coast.

At the end of July, similar changes were visible in the waters off Al-Arish and North Sinai, while the discoloration remained apparent near its initial point of emergence off Port Said.

On August 4, the waters off the Gaza Strip appeared clearer in the available imagery. By August 24, however, a limited change in water color had emerged off parts of southern Gaza.

On September 1, a widespread change in water color was visible off Ashkelon and Ashdod, coinciding with the turbidity crisis that prompted the shutdown of desalination plants.

The time-series comparison shows the area affected by the visible changes gradually shifting northeastward from the Egyptian coast over roughly six to eight weeks. However, determining whether the imagery tracks a single algae mass, rather than a series of successive or partially related phenomena, requires additional data on chlorophyll levels, turbidity and ocean currents, along with laboratory analysis of water samples.

Rough Seas and the Movement of Algae Toward Israel

The desalination plant crisis followed several days of rough sea conditions in the Mediterranean. On August 29, the Egyptian Meteorological Authority warned of disruptions to maritime navigation along the coast from Matrouh to North Sinai, with winds reaching 50 to 70 kilometers per hour and waves measuring 2.5 to 4.5 meters in height.

The rough conditions also extended to parts of the eastern Mediterranean during the same period. When five desalination plants were shut down, the Israeli Water Authority attributed the elevated turbidity to unusual weather conditions. Israeli reports also said authorities were investigating whether the turbulent sea conditions were contributing to the movement of large quantities of algae toward the coast.

Strong winds and waves can stir the water column, resuspend sediment and other suspended matter, and influence the movement of water masses. However, the timing of the rough sea conditions and the northeastward progression of the changes observed in satellite imagery are not, by themselves, sufficient to establish that the weather conditions transported the algae from the Egyptian coast to Israel.

How Microscopic Algae Can Disrupt Desalination Plants

Analysis of samples collected from desalination plant intakes revealed high concentrations of microscopic algae. Dr. Tamar Guy-Hayim, a researcher at the Israel Oceanographic and Limnological Research Institute, said these single-celled organisms can produce gelatinous substances when they multiply in large numbers. These substances can pass through some stages of the filtration process and reach the fine membranes used in reverse osmosis, increasing the risk of clogging and operational failures.

Seawater does not flow directly into reverse osmosis membranes. It first undergoes several stages of filtration and pretreatment. As concentrations of algae and organic matter increase, so does the risk of sediment buildup and biofouling, which can reduce plant efficiency and cause costly damage to membranes and pretreatment equipment.

Research by Guy-Hayim indicates that the gelatinous substances produced by algae during blooms can pass through conventional and sand filters before reaching and accumulating on the fine membranes. This helps explain why algal blooms can pose a significant threat to desalination plants that rely on reverse osmosis.

Prof. Jack Gellron, an expert at the Zuckerberg Institute for Water Research at Ben-Gurion University, said phosphate- and nitrogen-rich wastewater from the Gaza Strip may have provided an additional source of nutrients, potentially contributing to algae growth as the water moved northward.

Israeli desalination plants draw seawater through intake pipes that extend offshore to designated depths. Sensors at the intake points continuously monitor water quality and turbidity levels.

According to the operating protocols cited in the report, pumping is halted when turbidity exceeds 5 nephelometric turbidity units (NTU). The measure is intended to prevent biofouling of the fine membranes, which could result in prolonged shutdowns and high repair and operating costs.

Alon Zaszk, director of the Israel Oceanographic and Limnological Research Institute, described the scale and intensity of the phenomenon along the southern and central coasts as an exceptional event with no precedent in the region’s modern history.

Desalination Crisis Disrupts Water Supplies and Agriculture in Israel

As several desalination plants remained offline, the Water Authority and Mekorot moved to activate alternative water sources, increasing reliance on groundwater and other supplies to maintain household water supplies and limit the impact on the wider water network.

The crisis also affected agriculture and municipal services. Authorities suspended irrigation in public parks and green spaces and reduced water supplies to agricultural areas in southern Israel, raising concerns about damage to vegetable crops and orchards and potential losses for farmers.

The measures included suspending irrigation across about 20,000 dunams of farmland planted with water-intensive crops, including vegetables and orchards. Authorities warned that prolonged water shortages, particularly during heat waves, could damage seasonal crops and affect their market prices.

Several cities and regional councils, including Sderot, Jerusalem and Givatayim, also reported lower water pressure. Local authorities urged residents to limit nonessential water use.

The Tel Aviv municipality urged residents to conserve water and suspended water use in some public parks and beach facilities. In Jerusalem, the Gihon Company prepared emergency points for filling water tankers in case water supplies declined further.

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