Phytoplankton production and taxon-specific growth rates in the Costa Rica Dome.
During summer 2010, we investigated phytoplankton production and growth rates at 19 stations in the eastern tropical Pacific, where winds and strong opposing currents generate the Costa Rica Dome (CRD), an open-ocean upwelling feature. Primary production (14C-incorporation) and group-specific growth and net growth rates (two-treatment seawater dilution method) were estimated from samples incubatedin situat eight depths. Our cruise coincided with a mild El Niño event, and only weak upwelling was observed in the CRD. Nevertheless, the highest phytoplankton abundances were found near the dome center. However, mixed-layer growth rates were lowest in the dome center (∼0.5-0.9 day-1), but higher on the edge of the dome (∼0.9-1.0 day-1) and in adjacent coastal waters (0.9-1.3 day-1). We found good agreement between independent methods to estimate growth rates. Mixed-layer growth rates ofProchlorococcusandSynechococcuswere largely balanced by mortality, whereas eukaryotic phytoplankton showed positive net growth (∼0.5-0.6 day-1), that is, growth available to support larger (mesozooplankton) consumer biomass. These are the first group-specific phytoplankton rate estimates in this region, and they demonstrate that integrated primary production is high, exceeding 1 g C m-2day-1on average, even during a period of reduced upwelling.
Department of Oceanography , University of Hawaii at Manoa , Honolulu, HI 96822 , USA.
Karen E
KE
Selph
Scripps Institution of Oceanography , 9500 Gilman Dr., La Jolla, CA 92093-0227 , USA.
Michael R
MR
Landry
Scripps Institution of Oceanography , 9500 Gilman Dr., La Jolla, CA 92093-0227 , USA.
Andrew G
AG
Taylor
Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0227, USA; Centre National de la Recherche Scientifique and Universite Pierre et Marie Curie, Station Biologique, 29680 Roscoff, France.
Andrés
A
Gutiérrez-Rodríguez
Earth, Ocean and Atmospheric Science , Florida State University , Tallahassee, FL 32306 , USA.
Michael R
MR
Stukel
Scripps Institution of Oceanography , 9500 Gilman Dr., La Jolla, CA 92093-0227 , USA.
John
J
Wokuluk
Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0227, USA; Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
Alexis
A
Pasulka
Costa Rica Dome; growth; microzooplankton; mortality; phytoplankton