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Böttjer, D. ., University of Hawaii, Honolulu, USA, dbottjer@hawaii.edu
Church, M. J., University of Hawaii, Honolulu, USA, mjchurch@hawaii.edu
Letelier, R. M., Oregon State University, Corvallis, USA, letelier@coas.oregonstate.edu
Sadler, D. ., University of Hawaii, Honolulu, USA, sadler@hawaii.edu
Viviani, D. ., University of Hawaii, Honolulu, USA, viviani@hawaii.edu
Watkins-Brandt, K. S., Oregon State University, Corvallis, USA, kwatkins@coas.oregonstate.edu

DIAZOTROPH ACTIVITY AND POPULATION STRUCTURE IN AN INCREASED CO2 WORLD

Human reliance on fossil fuel combustion continues to alter atmospheric and oceanic CO2 inventories. Because CO2 readily dissolves in the surface ocean, its impact on ocean chemistry can be significant, as seen by the long-term increase of surface ocean pCO2 (1.92 µatm year-1) and concomitant decrease in upper ocean pH (0.0019 year-1) recorded at Station ALOHA (A Long-term Oligotrophic Habitat Assessment; 22° 45’N, 158° 00’W). How these changes affect ocean ecosystem processes and the planktonic food web structure still remains uncertain. We explored the response of natural assemblages of marine dinitrogen (N2) fixing bacteria (termed diazotrophs), an important biological source of new nitrogen in the North Pacific Subtropical Gyre (NPSG), to changes in seawater pCO2. Our combined CO2 and nutrient perturbation experiments, carried out between May and October 2010, suggest a complex response in rates of N2-fixation and diazotroph community structure in response to short term (24-72 hours) variations in CO2 (387 vs. 1100ppm) and nutrient availability (phosphorus, iron and/or silica). These preliminary findings, as well as ongoing analysis, will be placed into the context of the monthly Hawaii Ocean Time-series (HOT) measurements of diazotroph dynamics in the NPSG.

Poster presentation

Session #:S58
Date: 02-15-2011
Time: 16:00 - 18:00

Presentation is given by student: Yes

PosterID: 88