| Description: |
We have performed an in situ test of the iron limitation hypothesis in the subarctic North Pacific Ocean. A single enrichment of
dissolved iron caused a large increase in phytoplankton standing stock and decreases in macronutrients and dissolved
carbon dioxide. The dominant phytoplankton species shifted after the iron addition from pennate diatoms to a centric diatom,
Chaetoceros debilis, that showed a very high growth rate, 2.6 doublings per day. We conclude that the bioavailability of iron
regulates the magnitude of the phytoplankton biomass and the key phytoplankton species that determine the biogeochemical
sensitivity to iron supply of high-nitrate, low-chlorophyll waters.
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