Method Development for Unenclosed Mesoscale Iron Enrichment Experiments and Galapagos Plume Studies

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A study of the origin of the Galapagos plume is underway; the feature is documented through satellite ocean color images showing a marked plume of high phytoplankton pigments streaming off the Galapagos Islands. The phenomenon of enhanced phytoplankton abundance down current from the Galapagos Islands has also been observed via traditional shipboard studies. The high productivity zone in a region marked by low productivity, high nutrient waters may result from one of several hypothesized processes: 1. Introduction of a "seed" population from the Galapagos platform waters which then generates the observed bloom. 2. Disruption of an environmental balance dominated by zooplankton, and a bloom caused when flow of water over the platform causes zooplankton to lose control, and 3. Introduction of the scarce element Fe into the nutrient rich waters as they pass near the Galapagos Islands, allowing a previously inhibited bloom condition to develop. Measurements of nutrients, Fe and other trace elements, productivity, POC, DOC, PON, DON, phytoplankton and zooplankton growth rates and related parameters around and inside the plume are planned to test the hypotheses.