Aquatic Sciences Meeting, Albuquerque 2001
| SS16 Iron Bioavailability and Limitation to Primary Production (Disciplinary Connections) |
| Date: Monday, February 12, 2001, Time: 11:30:00 AM |
| Location: Mesilla |
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| Hare, C, E, College of Marine Studies, University of Delaware, Lewes, USA, schroff@udel.edu |
| Hutchins, D, A, College of Marine Studies, University of Delaware, Lewes, USA, dahutch@udel.edu |
| Bruland, K, W, Institute of Marine Sciences, University of California, Santa Cruz, USA, bruland@cats.ucsc.edu |
| Rue, E, L, Institute of Marine Sciences, University of California, Santa Cruz, USA, elrue@cats.ucsc.edu |
| DiTullio, J, R, Grice Marine Laboratory, University of Charleston, Charleston, USA, ditullioj@cofc.edu |
| Alm, M, B, Grice Marine Laboratory, Univeristy of Charleston, Charleston, USA, melalm@yahoo.com |
| Trick, C, G, Department of Plant Science, University of Western Ontario, London, Canada, cyano@julian.uwo.ca |
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| PHYTOPLANKTON IRON LIMITATION AND NUTRIENT DRAWDOWN RATIOS IN THE PERU UPWELLING AND HUMBOLDT CURRENT |
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| A series of shipboard iron addition experiments were carried out in the Peru coastal upwelling and offshore Humboldt Current in September 2000. As in previous studies in the California upwelling system, dissolved Fe concentrations were generally low (< 0.1 nM) and nitrate and silicic acid levels were high (5-20 micromolar) in surface waters off the narrow Peruvian shelf, leading to community Fe limitation. Total chlorophyll a levels, photosynthetic efficiency, and nitrate drawdown all increased in proportion to the amount of Fe added (0.2- 2.8 nM). Unlike the California system, however, community Si:N molar drawdown ratios were very low (0.2-0.4), and only weakly dependent on Fe availability. The main phytoplankton groups responding to Fe additions were not large chain-forming centric diatoms as in California, but instead were either very small (< 5 micron), lightly-silicified unicellular pennate diatoms (Peru region) or macroscopic colonies of Phaeocystis sp. (Humboldt Current). These results conclusively show that Fe limitation occurs in the Peru upwelling and Humboldt Current systems, but the consequences for biological community structure and nutrient biogeochemistry are very different than in California waters.
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