Possible implications of sea level changes for species migration through the Suez Canal

The Mediterranean and Red Sea, which were connected via the Suez Canal during the 19th century after eons of separation, host two distinctive ecosystems. Species invasion through the Suez Canal from the Red Sea vastly influences the ecology of the Mediterranean, but the level of reverse migration is assumed to be negligible. We present the first reconstructed flow transport record through the canal during the period 1923–2016. According to this reconstruction, the flow intensity and direction through the canal are strongly influenced by seasonal and long-term sea-level changes, which could also play a role in the characteristics of species migration through it. Our record not only supports previous observations of the unidirectional invasion until the 1980s and the accelerated species migration rates to the Mediterranean ever since, but also suggest that southward migration could have become possible since the early 1980s. The southward flow was primarily enhanced by Indian Ocean cooling and the Eastern Mediterranean Transition in deep water formation during the period 1980–2000. It was then gradually reduced by accelerated sea-level rise in the northern Indian Ocean.