SOIREE Vertical Fe GoFlo Data

During the cruise we had the following three objectives:

(1) Undertake continuous sampling of the infused patch for dissolved/total iron

(2) Obtain samples from vertical profiles, using Go-Flo bottles, to examine the

partitioning between dissolved and particulate iron within the water column, both

inside and outside the patch.

(3) Undertake measurements to determine iron speciation within the water column.

Go-Flo casts were taken both inside and outside the patch during the course

of the experiment. Typically, water samples were obtained from four standard

depths (20, 40, 60 and 80 m) throughout the water column at each station. Deeper

samples (> 80 m) were obtained at some stations to examine the concentration of

iron below the mixed layer. Both filtered (0.2 um) and unfiltered samples were

collected. These samples will be analysed for Fe and other trace metals (Zn, Cd, Mn, Cu)

back in the clean laboratory at the University of Otago.

The speciation of iron was measured using competitive ligand exchange cathodic stripping

voltammetry (CLE CSV) on samples from 40 m depth from stations both inside and outside the

patch. This technique determines the total concentration of iron binding ligands present

in the sample and their relative binding strengths. From the data generated an estimation

of the inorganic iron concentration, Fe`, can also be made, this value can be used to

approximate the amount of iron that may be available for uptake by the phytoplankton.

References

Bowie, A.R., Maldonado, M.T., Frew, R.D., Croot P.L., Achterberg, E.A., Mantoura, R.F.C.,

Worsfold, P.J., Law, C.S., Boyd P.W., The Fate of Added Iron during a Mesoscale Fertilisation

Experiment in the Southern Ocean, Deep-Sea Research II (2001), SOIREE special issue, in the press.

Bruland, K.W., Franks, R.P., Knauer, G.A., Martin, J.H., 1979. Sampling and analytical methods for

the determination of copper, cadmium, zinc and nickel at the nanogram per litre level in seawater.

Analytica Chimica Acta 105, 233-245.

Danielsson, L.G., Magnusson, B., Westerlund, S., Zhang, K., 1982. Trace-metal determinations

in estuarine waters by electrothermal atomic-absorption spectrometry after extraction of

dithiocarbamate complexes into freon. Analytica Chimica Acta 144, 183-188.

VerticalFe.csv