Aquatic Sciences Meeting, Albuquerque 2001

SS16 Iron Bioavailability and Limitation to Primary Production (Disciplinary Connections)

Date: Monday, February 12, 2001, Time: 10:45:00 AM

Location: Mesilla

Loscher, B, M, University of Delaware, Lewes, USA, bettina@udel.edu

Weaver, R, S, University of Delaware, Lewes, USA, weaverri@udel.edu

Scholey, C, , University of Western Ontario, Ontario, Canada, caschole@julian.uwo.ca

Hutchins, D, A, University of Delaware, Lewes, USA, dahutch@udel.edu

THE CIRCADIAN RHYTHM OF FE UPTAKE BY THE MICROBIAL COMMUNITY

Oligotrophic open ocean systems are characterized by a strong competition for nutrients between phyto- and bacterioplankton. We investigated here the competition of these two microbial compartments for iron over diel cycles. Two diatom (Thalassiosira pseudonana, Skeletonema costatum) and 2 Synechococcus strains (PCC7002, WH7803) showed pronounced diel fluctuations in the uptake of Fe. This diel pattern in Fe uptake can be considered as a circadian rhythm since it continued under constant radiation conditions (either light or dark) over 48 h. From uptake experiments in the Sargasso Sea on the >0.2 and >0.6 micrometer fraction, it could be concluded that heterotrophic bacteria do not contribute significantly to the overall Fe uptake. More than 99% of the total Fe uptake is estimated to be due to algae. Maximum Fe uptake per algae cell occurred shortly before dusk. The difference between maximum and minimum Fe uptake was about one order of magnitude. The detected circadian rhythm of Fe uptake shown here also point to the importance of short-term (1h) incubations over diel cycles when investigating the uptake of Fe by the microbial community.

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Aquatic Sciences Meeting, Albuquerque 2001

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