Foraminifera are intruiging. They are animals, both planktonic and benthic forms exist, that, for the most part, have a 'shell' that is formed from calcarous minerals, called a test. Thus they are fora-minifera, mineral animals. This is shortened to "forams", which unfortunately looses and obscures the meaning of the latin.
An organism can be said to be planktonic if it resides in the water column and has no ability to swim against the ocean currents. However, a plankton, such as many forams, are infact active swimmers, its just that they swim to different positions up and down the water column, while at the same time being pushed along horizontally (and of course vertically at times) by the ocean currents.
I'll be specifically looking at a planktonic species called Neogloboquadrina pachyderma. This intersting creature's tests grow as a series of increasing ovate to spherical chambers that form a sworl. They tend to inhabit the higher lattitudes. If the organism grows in relatively cold water, the chambers form a left-handed sworl, in warmer waters, they form a right-handed sworl. Thus, by counting the percentage of right and left handed forms present, one can say something about the temperature of the surface water that they inhabit.
When alive, planktonic foraminifera can have all sorts of pseudo-podia and cytoplasmic projections stemming off of them, these things help them to stay afloat. They can also have pockets of gas or globs of fat inside of them that help them stay afloat also. They live out their lives and either die naturally or are ingested by other organisms, likesay, fish. Upon death, they slowly sink to the bottom of the ocean, where they collect on the floor as a portion of the ocean sediment. This sinking is aided by 'flocculation'. When the foram is ingested by a fish, it gets mixed with other materials and is eventually excreted. This mass then settles quickly, 'flocculating' other dead sinking forams and other organisms along the way. Thus, there is a "fish poop" express shuttle that gets them to the ocean bottom.
This is the overall process that has generated the sediments that make up the drilling core that I will be getting my forams from.
Because of the basic uniformitarian principle of superpositioning, the core sections further down are older and those closer to the top of the core are younger. Thus there is a time series. By examining the proportions of left and right coiling N. pachyderma at different sections of this series, I should be able to say something about the changing surface water conditions for that region, and thus can say something about the ocean currents that used to exist there.
The section was drilled from off of the coast of southern Africa. Thus it represents a region where there is movement of water from the Indian ocean and into the Atlantic, passing between the Antarctic and the Cape of Good Hope. Ultimately, this project will be looking at the formation of what is called the Circum-Polar current, which is the movement of water in a tight and uninterupted circle around Antarctica. Because this movement is unobstructed, it can get very stormy. Indeed, the tip of South Africa is euphemistically named the Cape of "Good Hope", because its an incredibly dangerous and stormy passage that sailors hope to get through.
The core isn't from off the cape itself however, its more north-east wards and is thoroughly a part of the Atlantic Ocean. In addition to the spin off of this circum-polar current, there is an input of water from the north. This is, infact, water that has made the global journey from the Carribean /Gulf of Mexico, up along the Atlantic Coast, over to the British Isles (where it represents an influx of heat and thus makes Britian warmer than Nova Scotia, which is at the same lattitude), and then travels down along the west coast of Africa to the region in which the core was sampled from. Along this long route, the water is giving up its heat and sinking, thus by the time it gets to the study region, it is Cold Deep Water. From there is moves back across the Atlantic and into the Gulf/Carribean region, to continue cycling.
It should be an interseting project.
Neogloboquadrina pachyderma fossil, left-coiling variety. The Bar represents a length of 1 mm:
Neogloboquadrina pachyderma fossil, right-coiling variety:
