The Mediterranean Sea represents less than one percent of the world's ocean, yet it is home to almost a quarter of a million different marine species - a fifth of which can only be found in the Med (endemic species). Global warming is altering the ecosystem 'beyond recognition'.
The Mediterranean Sea
An atlas makes the med look like a big lake with a narrow opening to the Atlantic through the Straits of Gibraltar, and one could be forgiven for assuming that it is just an ordinary bit of the sea. Nothing could be further from the truth:
- evaporation from the surface is greater than the inflow from the rivers (if the Straits of Gibraltar were blocked then the Med would eventually dry up) - so the salinity is higher than that of the water coming in from the Atlantic, and this salinity increases the further one moves East, (as does water temperature)
- underwater ridges divide the Med into an number of different bodies of water - each with its own peculiar characteristics
- nutrient levels are relatively low, so there is low primary production (phytoplankton growth)
- in most places the tides are very small - less than 2m in most places (a notable exception being the Venice Lagoon where it can reach 4m)
Marine Life Studies in the Med
There are many academic institutions close to the Med, and interested in its fauna. These studies have been going on for a long time, and records are extensive. Since the opening of the Suez Canal (in 1869) tropical species have been able to make their way into the eastern end of the med, and this influx has been closely watched.
In 1935 Bodenheimer (an Israeli Zoologist) said: 'It is almost certain that the Indo-Pacific influx is still under way...', and the rate at which new species successfully colonise the Med seems to be on the increase recently. Water temperature records show that the Med is warming up - the water leaving through the Straits of Gibraltar is 0.3 C warmer now than ten years ago. This might not seem much of an increase, but it is obviously enough to change ecosystems.
Climate Change and the Mediterranean Sea
A major report by the Mediterranean Science Commission in 2008 stated that: 'global warming is changing the Mediterranean beyond recognition'.
One of the most obvious changes is the way that jellyfish numbers are increasing - there are regular annual reports of huge swarms causing problems. (A good example would be the incident in 2010 when swarms of jellyfish stung bathers in Spain.) This has led some (Deidun, writing in The Biologist in 2011) to declare that: 'the Mediterranean Sea is currently undergoing a paradigm shift, mutating from a fish to a jellyfish sea.'
So - the Med is a very complicated and well studied body of water, and things seem to be changing rapidly. As Deidun suggests: 'it is the ideal testing chamber to assess the impacts of sea warming on marine biota'.
Source
'A Miniature Ocean: the toll of climate change in the Med', Dr. Alan Deidun - The Biologist - June 2011.
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