Answers – Pumping Iron

1) During upwelling events, the wind direction often completely reverses and the wind speed increases to twice the speed during regular or "relaxation" events.

2) Water temperature is lower during upwelling because cooler waters are being brought up from the bottom of the seafloor, and nitrate is higher during upwelling because the bottom waters are nitrogen-rich.

3) There is more iron present at the surface during the relaxation event; therefore, it appears that it is not being brought to the surface during upwelling; but rather it is being transported on the surface.

4) There is a delay in the primary productivity of phytoplankton due to the turbulence during upwelling events.

5) During the second upwelling event, water temperature is warmer because the water column is better mixed, nitrate is low because it was consumed during the relaxation event, and iron is higher than it was during the first upwelling and during the relaxation event.  During the first upwelling event, the waters are iron-limited, and during the second upwelling event the waters are nitrogen-limited.

6) In sample A, the addition of iron increased the chlorophyll concentration.

7) In sample B, iron enrichment had very little effect on chlorophyll concentration.  After day 3, when nitrate was added, chlorophyll concentrations increased.

8) Based on these data, one could say that at certain times, iron fertilization of the waters in this area would increase primary productivity, and at certain times it would not.

9) Consider assessing species of phytoplankton, how long blooms last, levels of CO_2, oxygen levels at depth, cost.