Monterey Bay Aquarium Research Institute

Iron and macronutrients in coastal upwelling regimes: Central California and Peru

Ken Bruland, Ph.D.
University of California, Santa Cruz

Wednesday, April 28, 2004
Pacific Forum 3:00 p.m.

The supply of the micronutrient iron has been shown to play a critical role in allowing extensive blooms of large diatoms to develop along the central California coast. Coastal diatoms have relatively high iron requirements that cannot be met by the small amount of iron present with the macronutrients in subsurface oceanic waters. It has been shown that the California upwelling system has a mosaic of conditions ranging from iron-replete to iron-limited. The presence of absence of a broad continental shelf with river-derived mud deposits can greatly influence the external supply of iron to the upwelled surface waters in coastal upwelling regimes.

Similar physical characteristics are present in the Peru upwelling regime and led us to predict a mosaic of similar conditions would be found off Peru. Such a range of conditions was observed with some areas of iron-replete upwelled waters with extensive diatom blooms and also large nutrient-rich areas with relatively low chlorophyll as a result of iron-limitation.

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