The Mediterranean and the Red Seas are some of the most historical, geographical and anthropologically important landmarks that this magnificent planet holds. Fed primarily by the Atlantic and Indian Oceans respectively, together these two bodies of water tell an opulent story dating back to the eons. In this article, we take a brief look at the history, geography and development of the Suez Canal that bridges the two seas, and how it affects the reef organisms that we’ve come to know and love.
The Mediterranean Sea is a largely landlocked body of water surrounded by various countries from three continents. It is bordered by Southern Europe and Asia minor to its north, and Africa at its southern limits. The Mediterranean Sea and its subdivisions (Straits of Gibraltar, Alboran, Balearic, Ligurian, Tyrrhenian, Ionian, Adriatic and the Aegean Seas) are fed by the Atlantic Ocean to the west through the Gibraltar straits. Just south-east of the Mediterranean Sea lies the Red Sea. Like the former, this water body is largely landlocked (surrounded by the Middle East), and is fed by the Indian Ocean at its southern limits via the Gulf of Aden and the Bab el Mandeb straits. It contains two major gulfs, the Gulf of Suez and the Gulf of Aqaba, both of which form the left and right arm of the Sinai Peninsular.
About five million years ago, the Mediterranean Sea and the Red Sea were connected. Throughout the passing of time and geological movements, land levels began to rise and the connection between the two seas were ultimately severed. Because of the disjunct connection between the two seas, the Red Sea essentially became a giant evaporation pan, increasing in its the salt concentration as evaporation took place.
It was only sometime later when the Straits of Perim to the south opened up, allowing an influx of water and various fish species from the Indian Ocean to mix. Fifteen thousand years ago during the last ice age however, a significant portion of the water was locked up in the form of glacial ice caps, thereby effectively reducing the water levels once more. Due to the now shallow and narrow anastomosis with the Indian Ocean, the Red Sea, to this day, maintains a precarious homogeneity with the former, setting the stage for speciation and evolution of its many endemic fauna. However despite this new connection with the Indian Ocean, the Red Sea was never able to reconnect with the Mediterranean.
17 November 1869. This date marks the historical reconnection of the two seas through the successful completion of the man-made Suez Canal. The conception of this ten year project aims to dramatically reduce the trade route distance between Europe and South Asia, eliminating the need to navigate the dangerous waters of Africa completely. Prior to the construction of this canal, trade routes from Europe to South Asia consisted of long voyages to the East of the Mediterranean, South along the margins of the African continent, and then U-turning back up on its eastern border. With the implementation of the Suez Canal route, traders need only cross the canal and out via the Horn of Africa.
Being such an important landmark and the heart of the Europe-Asian trade success, the Suez Canal was the subject of many historical and anthropologically important events during a two hundred year time line. The canal was a crucial focal point during the British invasion of 1882 and the Suez crisis, and during this period, has changed sovereignty numerous times.
But how does this all relate to us, the marine aquarist? The reconnection of two previously isolated water bodies will no doubt lead to the influence of exotic marine species, many of which were never sympatric to begin with. Red Sea immigrants into the Mediterranean via the artificially constructed Suez Canal are known specifically as Lessepsian migrants (the term Lessepsian originated from Ferdinand de Lesseps, a French diplomat in charge of the canal’s construction). This migration is currently on-going, with numerous species breaking through the boundary now made pervious by the Suez Canal.
The Suez Canal is 193 km (120 mi) long, 24 m (79 ft) deep and 205 metres (673 ft) wide. To its north at the Mediterranean confluence lies Port Said, which opens up the canal all the way to its southern counterpart, Port Tewfik. Two greater bodies of water sit in-between the ports, and these are Lake Timah and the Great Bitter Lake, the latter playing an important role in leading up to the events of the Lessepsian migration. The lack of any locks or barriers throughout the canal enables water to flow freely along its entirety, and the canal drains into the Gulf of Suez before reaching the Red Sea.
Prior to the construction of the Suez Canal, the Great Bitter Lake was dominated by dry salt valleys, a remnant of the once landlocked evaporated seas that connected the Mediterranean to the Red Sea. This hypersaline natural valley created inhospitable environments for many marine organisms, preventing the crossover into the Mediterranean post completion of the Suez Canal for many decades. Seeing as water is free flowing throughout the canal, it was only a matter of time before the salinity of the Bitter Lake equalized with that of the Red Sea. This removed the barrier preventing cross over, and catalysed the start of the Lessepsian migration. North of the lakes the current reverses seasonally, being north-going in winter and south-going in summer. South of the lakes, the current is tidal, reversing with the tides in the Red Sea. The Red Sea is slightly higher than the Eastern Mediterranean, so the canal serves as a tidal strait that pours Red Sea water into the Mediterranean.
The general northwardly flow of water along the Suez Canal has aided the Lessepsian migration in favour of the Red Sea fauna. In addition, these fauna are used to living in nutrient poor, higher salinity environments of the Red Sea, and therefore are able to flourish in the relatively nutrient rich and lower saline waters of the Mediterranean. To date, about 300 species of Lessepsian migrants have been documented in the Eastern Mediterranean, and more are expected to be found. Conversely, only three have been observed crossing the barrier from the Mediterranean side into the Red Sea, and these are mostly gobies.
The Suez Canal serves as an important reminder that although alien species may not be intentionally introduced into foreign habitats, the implementation and construction of certain geographical altering landmarks may produce repercussions such as this. The extent of the impact brought about by the Mediterranean-Red Sea Lessepsian migration is not yet fully understood, but as they say, prevention is always better than cure.
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