• Research on this cruise is a follow-up to the studies begun on the 2004 summer cruise. Waters in areas of the Southern Ocean were tested to determine if they were iron limited or not. Areas in the blue water zone (see illustration Chlorophyll Concentrations: Antarctic Circumpolar Current) of the Antarctic Circumpolar Current were determined to be iron limited. The shelf waters were not limited in iron. Our purpose is to continue our investigations on iron as an explanation for this transition.

• Iron comes off the continent and is deposited in the sediments in the shallow shelf waters. When mixing of the shelf waters with the deeper current waters occurs, the iron becomes available to the phytoplankton.

• First, we get our water samples from the trace metal CTD. The trace metal CTD has Teflon coated bottles and the CTD has a special coating to avoid contamination of the samples. The water is then put into bottles for incubation.

Incubation is:

a) processing for use

b) making something cube-like 

c) maintaining conditions promoting development

• Next, iron is added to the bottles. . We added large quantities of iron prior to incubation to show that iron was needed for plankton growth. On this cruise, we want to know how much iron needs to be added to ocean water to create conditions for phytoplankton blooms.  
  
  

• The water in this area has plenty of macronutrients such as nitrogen, phosphorus, and potassium. All are needed for phytoplankton growth.

• We can use radioactive iron to find out how much is left on the bottle, precipitated out, or was taken up by the phytoplankton. We measure the amount of light emitted as the radioactive iron decays in order to trace it.

• In order to understand the climate on earth, we need to understand the processes that take place in the ocean. Animals ingest chemicals, and some of their skeletons get buried in the sediment in the sea floor. These skeletons buried in the sediment provide a record of the distribution of specific types of elements.  Trace elements, those found in parts per billion, are the ones that provide clues to changes in the ocean.