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........

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