Cristal Clear Water on the Turkish Coast with the ever present Gulets
Was always fascinated by the crystal clear, turquoise waters of the Mediterranean. But it is only recently - after diving in the Philippines and the Caribbean - that I started wondering as to why the water has a turquoise color. The sea in other parts of the world is equally warm but darker, greener, less transparent and sometimes even murky.
The Mediterranean as seen from an European Satellite
The Mediterranean is unique. Rather a landlocked lake than a sea. Surrounded by land on all sides except for the Straits of Gibraltar and the Bosporus, it loses three times more water from evaporation than It receives from rain and its contributary rivers. The rivers emptying into the Mediterranean are small for its size: Nile, Po, Ebro and Rhone are the biggest.
The small number of rivers is a function of the Mediterranean’s position between the Atlantic weather system and the Sahara. During summer time, the dry Sahara climate pushes the wet Atlantic system north, leaving the Mediterranean basin for months without rain. The four rivers mentioned above originate from the Pyrenees, the Alps and the mountains of Ethiopia in West Africa, where it rains during the summer months and even more during the long winters.
There is little Life in the Southern Mediterranean: green = a lot of chlorophyll; blue = none
The lack of rivers flowing into the Mediterranean has another, not often mentioned consequence. Fewer nutrients are swept into the sea. Rivers carry not only mud and sand, but also biomass which sea bacteria then decompose. The waste of this bacterial “breakfast” feeds algae (phytoplankton) which in turn feed fish. Scientists label the Mediterranean oligotrophic – oligo = few and trophi = food. It is a sea with little food, thus fewer & smaller fish which results in fewer & smaller predators. A white shark would not come to the Mediterranean unless it has to go on a strict diet. Just kidding. There are no white sharks.
Algae are small organism and cannot be seen with the naked eye. But when more abundant, the green chlorophyll, the part that uses light and CO2 to make sugar, becomes visible and colours the sea. Higher algae concentration makes the nutrition rich Atlantic Ocean look green. The giant rivers from the Americas (Mississippi, Amazon, Rio Grande) and Africa (Niger, Congo) carry vast amounts of biomass into the Atlantic.
Salt Concentration in the World's Oceans. Blue is 30 grams, dark red 40 grams per liter
Nutrients in the Mediterranean are further depleted due to its high salinity. On average, the world’s oceans carry about 34 – 35 grams of salt per liter of water. In the Mediterranean, the level increases to 38 – 39 grams. This is still well within the tolerance of phytoplankton. But the higher salinity powers a Mediterranean conveyer belt. As heavier salt water sinks to the bottom, fresh and lighter Atlantic water gushes in through the Straits of Gibraltar to replace the evaporated water. On its way in, it pushes out the heavier bottom water rich in nutrients – biomass sinks to the floor. Not only does the Mediterranean get les nutrients than other seas, it also loses a big amount to the Atlantic.
The Mediterranean Conbeyer Belt
The result is the crystal, turquois water that we tourists love so much. Saltier water is also better in retaining heat because it has more molecules than fresh water. And our buoyancy increases. Anybody swimming in the Eastern Mediterranean must have noticed. Of course, fishermen are less pleased. The relative poverty of sea life in the Mediterranean may be one of the reasons why Greek people had to emigrate and found colonies 3’000 years ago. Not only were they living in a place with little arable land (less than 20%), their surrounding ocean was not specifically rich in fish either.
Thera on Santorini, one of the most popular Tourist Destinations. We arrive there Week 3
Tourism has outgrown the fishing industry by a fat margin. Visitors come for the spectacularly clean, turquoise water. Today, the nutrient poor sea creates lots of jobs for the locals. Visitors coming from colder, though nutrient rich parts of Europe, are happy to pay for the privilege.
We will enjoy the pristine Waters all along the Turkish Aegean Coast and the Greek Islands this summer. Easy visible on this Photo from Space are Turkish Cesme, Greek Chios & Samos
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