HR: 0800h
AN: OS31A-1434    [Abstracts]
TI: N and P Co-Limit Growth and Control Community Composition and Taxon Specific Nutrient Status in the Gulf of Aqaba, Red Sea
AU: * Mackey, K R
EM: kmackey@stanford.edu
AF: Department of Civil and Environmental Engineering, Stanford University, Terman Engineering Center M42, Stanford, CA 94305 United States
AU: Labiosa, R G
EM: jahajey@pangea.stanford.edu
AF: Department of Geophysics, Stanford University, Mitchell Bldg. Room 355, Stanford, CA 94305 United States
AU: Street, J
EM: jstreet@stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, 450 Serra Mall Braun Hall, Building 320 , Stanford, CA 94305 United States
AU: Paytan, A
EM: apaytan@pangea.stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, 450 Serra Mall Braun Hall, Building 320 , Stanford, CA 94305 United States
AB: The availability of growth limiting nutrients is a determining factor for phytoplankton productivity, community structure, and biological diversity in marine environments. The effects of varying nutrient availability on phytoplankton productivity and relative species abundance in the Gulf of Aqaba, Red Sea were assayed throughout a five day incubation experiment following fertilization with inorganic N, P, and Fe, locally collected aerosol dust, and/or the Fe chelator ethylene diamine tetra-acetic acid (EDTA). Changes in chlorophyll a (chl a) concentration, community composition, and alkaline phosphatase activity measured through enzyme labeled fluorescence (ELF) were recorded. Results suggest that the bioavailability of nutrient resources directly controls growth, species dominance, and nutrient status of phytoplankton in this oligotrophic region. Productivity levels strongly depended on nutrient addition treatment; samples amended with N and P grew the most followed by samples amended with dust (a natural source of N and P). Samples receiving a singular inorganic nutrient amendment or EDTA clustered with the control (no additions) treatment. Flow cytometry and microscopic examination of samples for ELF labeling indicated that for all treatments picoplankton represented the vast majority of cells counted and that the nutrient status of this group remained relatively constant for the duration of the incubation. Other phytoplankton groups exhibited marked changes in abundance and alkaline phosphatase activity in response to experimental treatment within the period of incubation, indicating that these groups are able to adapt quickly to exploit sudden nutrient perturbations. Rapid responses to changes in nutrient availability occur in the Gulf following seasonal stratification and mixing events, and result in shifts in species composition and nutrient status. Such responses may represent a key process that influences nutrient cycling dynamics and productivity in this and other oligotrophic marine systems.
DE: 4815 Ecosystems, structure, dynamics, and modeling (0439)
DE: 4845 Nutrients and nutrient cycling (0470, 1050)
DE: 4855 Phytoplankton
DE: 4858 Population dynamics and ecology
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005