Authorities spent Thursday and Friday trying to ease concerns over chemicals released into the Mediterranean roughly a kilometer (0.6 miles) from Israel’s southern coastline. The substances were used in an effort to combat an algae outbreak that had previously brought five of the country’s six desalination facilities to a standstill.

According to Channel 13, the Water Authority initially carried out the operation without publicly announcing it, dispersing a mixture of substances, including substantial amounts of copper sulfate from the air over a roughly nine-kilometer (5.6-mile) section of coastline.

Following the disclosure, the Health Ministry ordered a temporary suspension of fishing in the affected area. Officials stressed, however, that no confirmed danger had been identified and said the restriction was being imposed strictly as a precaution while additional information was gathered. Authorities did not prohibit people from eating fish.

The Energy and Water Ministry said in a statement that “the targeted dispersion of authorized substances in the sea was carried out with the approval of the interministerial Committee [for granting permits to dump substances] led by the Environmental Protection Ministry and the Health Ministry. The substances do not endanger bathers; environmental monitoring is currently underway in the area, and results are expected soon.” The ministry also said that drinking water remained “completely safe for drinking and household use without any concern.”

The Environmental Protection Ministry said the Health Ministry had examined the substances both before and during deliberations by the interministerial committee. According to the ministry, the committee authorized “targeted activity, within a defined time and space, and subject to special and stringent conditions.”

It added: “The approval included restrictions on the location and method of substance dispersion, environmental monitoring and documentation, continuous tracking of current directions, and immediate cessation in the event of flow toward the shore or a risk of harm to wildlife.”

Officials said the substances had been released in carefully controlled amounts and were selected because they would rapidly disperse and break down in seawater. Any additional treatment, the ministry said, would be “professionally evaluated based on findings” and could only proceed after receiving a new permit.

But Prof. Nadav Davidovitch, who heads the School of Public Health at Ben-Gurion University, criticized the response, saying that “the revelation regarding the dispersion of toxic substances near Israel’s coasts as a response to the algae crisis is further testimony to ongoing helplessness and crisis management in a firefighting mode, rather than a broad, in-depth vision that must focus on prevention and preparedness. Our growing reliance on desalinated drinking water brings numerous challenges, both in routine times and emergencies, certainly in light of climate change and the need to account for various environmental impacts.”

Davidovitch also warned that “neglect of the marine environment and the failure to address the root causes of pollution come back to bite us like a boomerang.”

Desalination has become a central component of Israel’s water system, supplying approximately 80 percent of the country’s potable water.

The recent algae outbreak had forced five desalination facilities to close in an unprecedented shutdown. The algae was carried northward by ocean currents and waves originating near Egypt’s Nile Delta.

All of the affected facilities had returned to full operation by Thursday.

The shutdown had previously led local authorities to suspend irrigation and other nonessential public-space water uses across the country. Water supplies to agricultural communities in southern Israel were also temporarily curtailed as officials worked to manage the disruption.