Thursday, 7 July 2011


Foraminiferids are microscopic, single-celled organisms which secrete shells composed of calcium carbonate. They are also the organisms which I attempted to pronounce (and if you are in my EPQ group will realise that I failed to do so) the name of today!!! I only mentioned them in passing today and so, as they are really quite interesting, I thought I would write a short post about them and why they are important to my EPQ.

There are two main species of Foraminiferids - the planktonic foraminiferids which live on the sea surface and the benthic foraminiferids which live on the ocean floor in the deepest oceans. I am only really concerned with the planktonic species as they very cleverly alter their body architecture in relation to changes in sea temperature. The planktonic species (if you are interested their proper name is Neogloboquadrina pachyderma - a name which I am not even going to attempt to say!) live in the oceans located in high latitudes and can be found in two varieties. The prinicpal difference between the two varities is the way in which they coil and, the direction in which they do so is determined by sea temperatures. The variety that coils to the right live in ice-free water whereas the variety that coil to the left reside in waters where sea ice is common. Therefore there distribution in cores of ocean-floor sediments can be used to show when, in the North Atlantic Ocean, there were periods when it was covered in sea ice and wasn't. Not only do Foraminiferid studies provide an insight into past sea ice conditions of the high latitude oceans but they also enable for the construction of sea surface temperature maps to occur. This is thanks to studies of a collection of species of modern Foraminiferids which show that their distribution across all the Earth's oceans is determined by ocean temperatures. For example, of the 16 most common planktonic foraminiferids, 1 is limited to high latitudes, 5 to middle latitudes, 5 in middle and lower and the remaining 5 in solely low latitudes. This allows for assemblages of Foraminiferids to be indentified that characterise polar, subpolar, tropical and subtropical waters, both today and in ocean-floor sediment cores. These studies have enabled a north-south profile of the Atlanitc to be drawn which summarises the changes through time in the planktonic foraminiferids. These profiles show many things including the fact that hardly any change, if any, occured in temperature  in the south of Spain whilst the high latitudes were affected by incursions of polar waters during both the last and penultimate glacial period. By looking into the abundance of the varieties that seasonally flourish, surface-water isotherms can also be plotted. These are really useful as, by comparing the temperature distribution around 18ka ago with present day conditions, it becomes apparent that the warm-water currents of the Gulf Stream and North Atlantic Drift (which are play a dictatorial role in determining the climate of western Europe) were not operating, 18ka ago, to warm the north-east Atlantic as they do today.

By gaining an understanding into the past climates, provided by the insight into past ocean conditions gained via the distribution of this tiny organism, more educated predictions into both future atmospheric circulations and ocean ciruclations will be able to be developed.

No comments:

Post a Comment