‘Extremely rare event:’ Miles-long microalgae bloom knocks out most of Israel’s desalination plants

Israel Oceanographic and Limnological Research institute

A miles-long microalgae bloom in the Mediterranean Sea has been blamed for temporarily knocking offline many of Israel’s major desalination plants this week, threatening its main source of drinking water.

Five of the country’s six coastal desalination plants — which convert seawater into drinkable water — shut down on Sunday, according to Mekorot, Israel’s national water company. Since then, some of these facilities, which are privately owned and operated, have partially resumed operations, but only one was operating at full capacity on Thursday.

“An event of this kind has never occurred before in Israel … it was an extremely rare event,” said Lior Gutman, a spokesperson for Mekorot, although he stressed in roughly 99% of cases, there has been no drinking water shortage.

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Still, it’s an alarming situation given the country’s heavy dependence on desalination for drinking water. Israel is arid and has neither big rivers nor abundant rainfall, but its mastery of this technology has made it a water superpower. Desalination now provides at least 65% of its drinking water, with most plants located on the Mediterranean coast.

The problems started at the weekend, as a “ sporadic, vast event of contaminates occurred across the Israeli coastline,” said Edo Bar-Zeev, an associate professor in water research at Ben-Gurion University, in Israel. When he and other scientists looked closer, they discovered it was microalgae, tiny organisms that feed on sunlight, carbon dioxide and nutrients in the water — and which can grow rapidly.

The microalgae bloom — stretching more than a dozen miles at least, according to Bar-Zeev — is believed to have originated in the Nile Delta and traveled northward with the sea’s currents up Israel’s coast. This is “the first time I saw something in this extent,” said Bar-Zeev, who has been testing the coastal water for 20 years.

The country’s desalination facilities mostly use a technology called “reverse osmosis,” where water is pre-treated to remove larger contaminants, before it’s pushed through membranes which filter out salt, bacteria and other molecules to leave clean drinking water.

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Algae, and the substances they produce, can foul and damage the membranes, said Michael Christopher Low, director of the Middle East Center at the University of Utah. If there’s too much suspended material in the water, the treatment processes cannot keep up.

It’s happened before. A severe “red tide” — a harmful algae bloom — in the Gulf of Oman in 2008 and 2009 affected many desalination plants in that region.

In Israel, the government water system has “stepped in to close the gap” caused by the plant closures, Mekorot’s Gutman said. This has included pumping water from the Sea of Galilee, activating groundwater wells and using national water reserves.

Some cities have faced short-term local restrictions, including on garden irrigation and filling swimming pools, but the the main limitations affected farmers who use drinking water-quality water for irrigation, as opposed to those who use recycled water, Gutman said.

The timing compounded the problem. It happened in summer “when water demand in Israel is at its highest,” he said, adding “the situation has been challenging.”

Mostafa Alkharouf/Anadolu/Getty Images

A bloom occurs when the right combination of environmental factors in the water come together that allow the algae to grow rapidly, said Tamar Guy-Haim, a marine ecologist at the Israel Oceanographic and Limnological Research Institute. These include nutrients, temperature, light, currents and mixing.

Mekorot said this recent bloom was part of “very unusual combination of factors,” including a sea storm that increased turbidity — the amount of suspended matter in the water — and raised sea temperatures to 86 Fahrenheit (30 degrees Celsius) and above.

The extent of the disruption is striking. Desalination facilities have been forced to close before due to algae or jellyfish, “but multiple facilities over the large portion of our coast is something that is definitely abnormal,” Ben-Zeev said.

It’s something the country needs to figure out how to deal with — and will, he added. “It’s a fair estimation that this will not be a once-in-a-lifetime kind of event … you can assume that this will occur more and more through climate change.”

As the planet heats up, driven by humans burning fossil fuels, the oceans are changing. Temperatures are at record highs , currents are shifting and stronger storms wash more pollutants into the water, including sewage and fertilizers, which can trigger huge algae blooms.

Gil Cohen Magen/Xinhua/Getty Images

This temporary crisis also exposes a broader concern, experts say.

Desalination is becoming increasingly popular, especially as the climate crisis drives more severe heat and drought, undermining water security . But this growing dependence on a centralized, technical solution carries risks. “This event is causing considerable alarm and even some criticism that the system is too vulnerable to a dramatic disruption,” Low said.

This could be natural or climate change-driven events, but there’s also the possibility of military and cyber threats. Desalination plants in the Gulf have been targeted and damaged during the US-Iran war, raising significant alarm in a region that depends overwhelmingly on this technology. Hackers have also targeted water facilities, including in the US.

Oil spills are another big concern. “It’s not if, it’s just when an oil spill in the vicinity of desalination facilities will occur,” Ben-Zeev said. A lot of plants are in water-scarce countries that are also big oil producers, such as the Gulf states.

A spill could potentially take plants offline for a much longer time than this microalgae bloom, he added. “That to me is way more worrying.”

以色列海洋与湖沼研究所

本周，地中海绵延数英里的微藻水华导致以色列许多主要海水淡化厂暂时停产，威胁到该国的主要饮用水源。

据以色列国家水务公司Mekorot称，该国六座沿海海水淡化厂中的五座于周日关闭，这些淡化厂负责将海水转化为饮用水。此后，这些私营海水淡化厂中的一些已部分恢复运营，但截至周四，只有一座工厂满负荷运转。

“以色列以前从未发生过此类事件……这是一起极其罕见的事件，”以色列水务公司 Mekorot 的发言人利奥尔·古特曼 (Lior Gutman) 说，但他强调，在约 99% 的情况下，并没有出现饮用水短缺。

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尽管如此，考虑到以色列对海水淡化饮用水的严重依赖，这种情况仍然令人担忧。以色列气候干旱，既没有大河也没有充沛的降雨，但它对海水淡化技术的掌握使其成为水资源强国。目前，以色列至少65%的饮用水来自海水淡化，其中大部分海水淡化厂都位于地中海沿岸。

问题始于周末，以色列本-古里安大学水资源研究副教授埃多·巴尔-泽夫表示，当时“以色列海岸线发生了一次零星的大范围污染事件”。他和一些科学家进一步研究后发现，污染源是微藻，这种微小的生物以阳光、二氧化碳和水中的营养物质为食，并且生长迅速。

据巴尔-泽夫称，这片微藻水华至少绵延十几英里，据信起源于尼罗河三角洲，并随着海流向北蔓延至以色列海岸。巴尔-泽夫从事沿海水质检测已有20年，他说：“这是我第一次见到如此大规模的微藻水华。”

该国的海水淡化设施大多采用一种称为“反渗透”的技术，即先对水进行预处理以去除较大的污染物，然后再将水推过膜，膜会过滤掉盐、细菌和其他分子，从而得到干净的饮用水。

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犹他大学中东研究中心主任迈克尔·克里斯托弗·洛表示，藻类及其产生的物质会污染并损坏膜。如果水中悬浮物过多，处理过程就无法跟上。

这种情况以前也发生过。2008 年和 2009 年，阿曼湾爆发了严重的“赤潮”（一种有害藻类大量繁殖），影响了该地区的许多海水淡化厂。

以色列国家供水公司（Mekorot）的古特曼表示，由于水厂关闭，政府供水系统已“介入填补缺口”。这包括从加利利海抽水、启用地下水井以及动用国家水资源储备。

古特曼表示，一些城市面临短期的地方性限制，包括限制花园灌溉和游泳池注水，但主要的限制影响的是使用饮用水级水进行灌溉的农民，而不是使用再生水的农民。

时机加剧了问题。他说，这件事发生在夏季，“以色列用水需求量最高的时候”，并补充说，“情况非常棘手”。

穆斯塔法·阿尔卡鲁夫/阿纳多卢/盖蒂图片社

以色列海洋与湖沼研究所的海洋生态学家塔玛尔·盖伊-海姆表示，当水中各种环境因素恰好结合在一起，使藻类能够迅速生长时，就会发生藻华现象。这些因素包括营养物质、温度、光照、水流和混合。

墨西哥国家水产养殖研究所 (Mekorot) 表示，最近这种藻类爆发是“非常不寻常的多种因素共同作用”的结果，其中包括一场海啸，这场海啸增加了浑浊度（水中悬浮物质的量），并将海水温度升高到华氏 86 度（摄氏 30 度）及以上。

此次中断的程度令人震惊。本-泽夫表示，海水淡化设施此前也曾因藻类或水母等原因被迫关闭，“但沿海大片区域的多个设施同时停产，这绝对是异常情况。”

这是国家需要想办法应对的问题——而且国家也一定会想办法应对，他补充道。“可以合理估计，这不会是百年一遇的事件……你可以预见，由于气候变化，这种情况会越来越频繁地发生。”

随着人类燃烧化石燃料导致地球变暖，海洋正在发生变化。气温达到历史新高，洋流发生改变，更强的风暴将更多污染物（包括污水和化肥）冲入水中，这些污染物可能引发大规模藻类爆发。

吉尔·科恩·马根/新华社/盖蒂图片社

专家表示，这场暂时的危机也暴露出一个更广泛的问题。

海水淡化正变得越来越普及，尤其是在气候危机导致高温和干旱加剧，威胁水资源安全的情况下。但这种对集中式技术解决方案日益增长的依赖也存在风险。“这次事件引发了相当大的担忧，甚至有人批评该系统过于脆弱，容易受到剧烈干扰，”洛说道。

这可能是自然灾害或气候变化引发的事件，但也可能源于军事和网络威胁。在美伊战争期间，海湾地区的海水淡化厂遭到袭击和破坏，这在高度依赖海水淡化技术的地区引起了严重警觉。黑客也曾攻击过包括美国在内的水务设施。

石油泄漏是另一个令人担忧的问题。“海水淡化设施附近发生石油泄漏不是会不会发生的问题，而是什么时候发生的问题，”本-泽夫说。许多海水淡化厂都位于缺水且石油产量巨大的国家，例如海湾国家。

他补充说，泄漏事故可能会导致工厂停工的时间比这次微藻爆发要长得多。“对我来说，那才是更令人担忧的事情。”