HR: 17:00h
AN: OS44B-05    [Abstracts]
TI: A High Iron, Low Chlorophyll Coastal Ecosystem: the Gulf of Aqaba, Red Sea
AU: * Chase, Z
EM: zanna@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences Oregon State University, 104 Ocean Admin Building, Corvallis, OR 97331 United States
AU: Paytan, A
EM: apaytan@pangea.stanford.edu
AF: Department of Geological & Environmental Sciences Stanford University, Bldg. 320 , Stanford, CA 94305-2115 United States
AU: Johnson, K S
EM: kjohnson@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039-9644 United States
AU: Street, J
EM: jstreet@stanford.edu
AF: Department of Geological & Environmental Sciences Stanford University, Bldg. 320 , Stanford, CA 94305-2115 United States
AU: Post, A
EM: anton@vms.huji.ac.il
AF: Interuniversity Institute of Marine Sciences Hebrew University, P.O. Box 469 , Eilat, 88103 Israel
AU: Genin, A
EM: amatzia@vms.huji.ac.il
AF: Interuniversity Institute of Marine Sciences Hebrew University, P.O. Box 469 , Eilat, 88103 Israel
AB: The Gulf of Aqaba, Red Sea, is a deep, narrow, semi-enclosed oligotrophic basin surrounded by desert. Precipitation and runoff are close to zero and benthic sources of iron are minimized by the steep shelf and intense summertime stratification. Exchange of seawater between the Gulf and the Red Sea proper occurs only across a 250 m sill at the southern end. This system represents an end-member with respect to aeolian dry deposition of iron to the ocean. We have measured dissolved and total iron concentrations in the Gulf during the stratified summer (August 2003) and well mixed winter (March 2004) seasons. Profiles from the middle of the Gulf in summer show a strong surface maximum in dissolved ($<$0.2 $\mu$m) and total dissolvable (dissolved plus particulate) iron. Dissolved concentrations are 6-10 nM at the surface and decrease abruptly to ~0.7 nM below the surface mixed layer (50 m). Total dissolvable concentrations are 10-40 nM at the surface and decrease to ~ 4 nM below the mixed layer. In winter, profiles are uniform throughout the water column, with dissolved iron about 1 nM and total dissolvable iron about 3 nM. Coupled with a yearlong record of dust deposition from an on-site aerosol collector, these data provide insight into the residence time and solubility of iron in an oligotrophic coastal system. Preliminary analysis suggests residence times in the mixed layer with respect to dust deposition in both seasons are on the order of a day for total iron, and a week for dissolved iron. Although observed iron concentrations are high compared to the open ocean, given the extremely high dust deposition to the Gulf, and very low biological productivity, the fact that the concentrations are not much higher suggests a low solubility for dry-deposited aerosol iron.
DE: 4875 Trace elements
DE: 4243 Marginal and semienclosed seas
DE: 4801 Aerosols (0305)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting