A British scientific institution marked World Ocean Day this week with a quiet boast. The Marine Biological Association in Plymouth [https://www.mba.ac.uk/] has been towing plankton recorders across the ocean since 1931, assembling one of the longest and most geographically extensive ecological records ever made. Tiny drifting organisms, sampled year upon year, become a ledger of the sea’s changing health. The point the Association makes is deceptively simple. A long record lets you see what a short one cannot.

That is a lesson the eastern Mediterranean is learning the hard way, and Israel sits at the centre of it.

The Levantine basin, the far corner of the sea bordered by Israel, Lebanon, Syria, Egypt and Turkey, is now among the fastest warming and most heavily invaded marine systems on earth. Since the Suez Canal opened in 1869, tropical species from the Red Sea have poured north through what scientists call Lessepsian migration, after Ferdinand de Lesseps, who built the canal. Warming water has turned that trickle into a flood. More than a thousand alien species have established themselves, most of them thermophilic newcomers thriving in seas their native competitors can no longer tolerate.

The marine biologist Bella Galil, who has studied these waters from Tel Aviv for over thirty years, puts it starkly. The seabed communities she catalogued in the 1970s simply no longer exist. They have been replaced. The commercially valuable fish her predecessors knew, such as the meagre once common in Levantine catches, have given way to Red Sea arrivals like the narrow barred Spanish mackerel.

Consider one newcomer in particular. The nomad jellyfish arrived through the canal in the 1970s and now swarms the Israeli coast every summer around the solstice, growing larger than a human head. It is more than a nuisance for bathers. Israel’s coastal power stations draw seawater to cool their generators, and the country’s desalination plants, which supply most of its drinking water, draw seawater to process it. When the swarms arrive they clog the intake screens of both. Engineers crate the creatures away by the tonne. Israel’s own State Comptroller put figures to the damage in 2022, estimating losses to desalination facilities in the tens of millions of shekels, alongside further losses to tourism and to coastal fishermen. A drifting animal that did not exist in these waters fifty years ago is now a recurring tax on the infrastructure that keeps the lights on and the taps running.

This is why the matter is strategic and not merely ecological.

Israel has built its modern existence on engineered relationships with the sea. Desalination supplies most of the nation’s water. The offshore fields of Leviathan and Tamar anchor both the economy and a web of regional diplomacy reaching to Egypt and beyond. Every one of these systems sits in a sea that is changing faster than almost anywhere on the planet, and changing in ways a country cannot manage if it does not measure.

This is where the British example earns its keep. You cannot tell a genuine shift from ordinary noise unless you hold a record long enough to know what ordinary looks like. A bad jellyfish summer in isolation means little. Set against ninety years of data it becomes a signal that the baseline itself has moved. Without the long series there is only surprise, and for a small state living on engineered margins, surprise is the one thing it cannot afford.

Israel is not starting from nothing. The Israel Oceanographic and Limnological Research Institute, founded in 1967 and headquartered at Haifa, monitors the eastern Mediterranean and the Gulf of Aqaba and archives the data through its marine data centre. A national programme tracks the biodiversity of the rocky shore. The Mediterranean Sea Research Center of Israel pulls the country’s universities and institutes into a single consortium. The instruments exist. What the British survey demonstrates is the value of patience, of keeping the record unbroken across decades and across changes of government, funding and fashion, so that a future scientist can ask a question no one today has thought to pose.

A regional dimension follows from the simple fact that the sea ignores borders. The same warming water laps Israeli, Lebanese, Egyptian and Cypriot shores, and the same jellyfish that tax Israel’s power stations now swarm the Egyptian coast hundreds of kilometres away. Whatever the politics, the organisms are a shared problem with a shared dataset, and data of that kind has at times moved between governments that agreed on little else. It is a thin thread, but in this region thin threads are worth noting.

The plankton recorder is a humble instrument, a box of silk towed behind a ship. Yet the institution behind it grasped something statecraft often forgets. The most valuable intelligence is rarely the dramatic snapshot. It is the patient and unglamorous record, kept long enough to reveal that the sea around you has shifted while your attention was elsewhere.

The eastern Mediterranean is shifting now. Israel would be wise to keep watching, and to keep the record.

Appendix

Table 1. Selected Lessepsian arrivals in the Levantine basin and their documented impact

Table 2. Israel’s principal marine monitoring and research bodies

Table 3. A compressed timeline of warming and invasion