Methods

We will conduct two cruises to the Ross Sea, one is summer and one in austral spring, and conduct both experimental and observational studies. We will sample regions where iron and carbon dioxide is high, as well as regions where both are low, and determine the irradiance regime in each. If possible, we will also sample regions with high iron and reduced CO2 levels, as well as low Fe and high CO2 concentrations (both are relatively unusual states). The observations should allow us to determine the most important factor in controlling phytoplankton composition, a major factor in controlling biogeochemical cycles in the ocean.
We also will sample water and manipulate CO2, Fe and irradiance levels within deck-board semi-continuous mesocosms. This will directly test the interactions among the three variables.

Measured Parameters

Many different measurements were made by the group and include the following:

Temperature, salinity, density
Nutrients (nitrate, nitrite, silicate, phosphate, ammonium)
Iron (dissolved, complexed, particulate), Cobalt, Cadmium
Chlorophyll (total and < 20 µm)
Particulate organic carbon, nitrogen and phosphorus
Biogenic silica
DMS, DMSP (all pools)
CO2, pH
Photosynthetic performance via fluorescence
Primary production via 14C
Phytoplankton pigments via HPLC
Phytoplankton composition via microscopy
Bacterial and viral abundance
Photosynthetic responses