ALOHA Seagliders

During 2012, the Nicholson Lab participate in a large, collaborative field program at the Hawaii Ocean Time-series Station ALOHA in 2012.  The goal of the study was to study how variability in the availability of light and nutrients impact the upper ocean ecosystem in the oligotrophic ocean at Station ALOHA.  As part of the project we utilized a low powered autonomous underwater vehicle called a Seaglider which can continuously profile the upper ocean for months at a time equipped with sensors to measure temperature, salinity, dissolved oxygen and chlorophyll.

When analyzing data collected over 110 days, spanning two glider deployments we noticed a curious pattern.  Over each day/night cycle there was a barely detectible, but clear cycle in dissolved oxygen in the surface ocean.  We attributed this pattern to the ‘breathing’ of upper ocean ecosystems.  During daytime photosynthesis by phytoplankton exceeds the rate of respiration (which tend to be somewhat constant through each 24-hour period).  At nighttime, photosynthesis is not active.  Since photosynthesis produces oxygen and respiration consumes it, the result is that dissolved oxygen increases during sunlit hours and decreases at night.  Using this information we developed a method of calculating rates of gross primary production (photosynthesis) and community respiration from Seaglider observations.

dielfig

Collaborators:

University of Hawaii: D.M. Karl, S.T. Wilson,  B. Barone, S. Martínez-García
WHOI: S.C. Doney, C. Stites-Clayton
University of Washington: S. Emerson, C.C. Eriksen

Funding:

NSF: Center for Microbial Oceanography: Research and Education (CMORE)
WHOI : Andrew W. Mellon Foundation Endowed Fund for Innovative Research
NASA: Earth System Science Graduate Fellowship

Related Publications:

Nicholson, D. P., S. T. Wilson, S. C. Doney, D.M. Karl, (2015) Quantifying subtropical North Pacific gyre primary productivity from Seaglider observations of diel oxygen cycles, Geophysical Research Letters, doi:10.1002/2015GL063065.

Wilson, S. T., B. Barone, F. Ascani, R. R. Bidigare, M. J. Church, D. A. del Valle, S. T. Dyhrman, S. Ferrón, J. N. Fitzsimmons, L. W. Juranek, Z. S. Kolber, R. M. Letelier, S. Martínez-García, D. P. Nicholson, K. J. Richards, Y. M. Rii, M. Rouco, D. A. Viviani, A. E. White, J. P. Zehr, and D. M. Karl (2015), Short-term variability in euphotic zone biogeochemistry and primary productivity at Station ALOHA: A case study of summer 2012, Global Biogeochem. Cycles, 2015GB005141, doi:10.1002/2015GB005141.

Nicholson, D., S. Emerson, C.C. Eriksen. (2008) Net community production in the deep euphotic zone of the subtropical North Pacific gyre from glider surveys. Limnology and Oceanography. 53: 2226-2236. doi:10.4319/lo.2008.53.5_part_2.2226.

Emerson, S., C. Stump, D. Nicholson (2008) Net biological oxygen production in the ocean: remote and in-situ measurements of O2 and N2 in surface waters. Global Biogeochemical Cycles. 22, GB3023, doi:10.1029/2007GB003095.

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