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Sharks indicate ocean change

Friday, 08 July 2011 18:23
Basking shark
Basking shark
(c) Nigel Moyer

The Inishowen based basking shark study group have detected dramatic changes in 2011 throughout the Atlantic Ocean. The team of scientists who started out tracking basking shark movements became interested in plankton (basking shark food) due to the unusual lack of shark sightings.

Plankton is the basis of all life in the ocean and if you know what the plankton is doing you have a very good idea what everything else is going to do explained Donal Griffin a student with Queens University Belfast and a researcher with the IBSSG. The project which is supported by the Inishowen Development Partnership started out investigating the secrets behind the movement of basking sharks in Inishowen and Atlantic waters but the research team quickly realised that 2011 was going to be different. "We've had allot of ups and downs this year; we had really dense aggregations of sharks in April a whole month earlier than usual, then pretty much no large groupings throughout May and June and now we are seeing jellyfish species and Sunfish in Inishowen waters 4-6 weeks before any previous records", says Emmett Johnston coordinator of the project. He added "We have always advocated the basking shark as a fantastic indicator species for monitoring global climate and ocean change and this year we have proven it".

Although initially disappointed with the lack of shark activity the scientists quickly understood that the strange goings on offered a perfect comparison to previous 'normal' year's records. Preliminary results show the key to the shark's movements is the distribution and density of their food; plankton, which at the surface is determined by sunshine and wind speeds. Emmett went on to say "Having a good hunch or theory is one thing but being able to robustly prove it to the scientific world is another, obviously we hoped for hundreds of sharks but in hindsight we should have actually been wishing for what we got this year, which was little or no activity, because that has provided us with a robust set of figures to prove what marine biologist's have been discussing for the last 50 years". 

There is allot of unknown variables when it comes to the ocean not least the changes in temperature at different depths. This year's research has shown that the unseasonably rough weather was really a bit of a red herring when it comes to oceanographic changes. Researcher Donal Griffen summed it up like this "It sounds complicated but if you can imagine a cross section of the ocean like a sandwich of layers, each layer has a different density and different temperature. Normally we get a higher temperature at the surface than the underlying main body of water but this year the surface of the ocean has been cooler than normal but the Atlantic as a whole has been warmer and it's this difference that has given rise to the 4- 6 week difference in animal's movements". The team believe the ongoing studies on the basking shark are vital to discovering and monitoring the links between Irish waters and the wider Atlantic Ocean.