9321336 Muller Karger There are several areas in the ocean where conditions appear to be optimal for phytoplankton growth. However, chlorophyll concentrations remain low in spite of persistently high major nutrient levels. One of the oldest explanations for this condition concerns iron deficiency. With the development and use of "clean" techniques, evidence supporting the "iron" hypothesis has been obtained in bottle experiments performed in several independent investigations. Nevertheless, many question the validity of these experiments because of various adverse bottle containment effects. Thus it has become apparent that the next step in testing the iron hypothesis should involve the performance of unenclosed mesoscale (10 100 km2) iron fertilization experiments. However adding a missing essential element to a way to proceed is unclear. Through OCE 9297518 and OCE 9024373, in collaboration with ONR, such an experiments will be undertaken. The type of iron to be used will be determined as well as the best way to administer it to a 75 km2 "patch". Initial experiments will be performed in the high nutrient, low chlorophyll region south of the Galapagos Islands. The patch will be tracked using the inert tracer sulphur hexaflouride. Chlorophyll and nutrients as well as other variables will be monitored to determine the effects of the added iron. In conjunction with this research a study will be made of the high chlorophyll, low nutr ient water west of the Galapagos Islands. This area is of interest since it appears to represent a natural enrichment experiment. This interagency transfer provides NSF's share of the costs for NASA P 3B overflights to provide real time remotely sensed measurements, necessary for the success for this experiments.
