Preferential depletion of zinc within Costa Rica upwelling dome creates conditions for zinc co-limitation of primary production.
The Costa Rica Dome (CRD) is a wind-driven feature characterized by high primary production and an unusual cyanobacterial bloom in surface waters. It is not clear whether this bloom arises from top-down or bottom-up processes. Several studies have argued that trace metal geochemistry within the CRD contributes to the composition of the phytoplankton assemblages, since cyanobacteria and eukaryotic phytoplankton have different transition metal requirements. Here, we report that total dissolved zinc (Zn) is significantly depleted relative to phosphate (P) and silicate (Si) within the upper water column of the CRD compared with other oceanic systems, and this may create conditions favorable for cyanobacteria, which have lower Zn requirements than their eukaryotic competitors. Shipboard grow-out experiments revealed that while Si was a limiting factor under our experimental conditions, additions of Si and either iron (Fe) or Zn led to higher biomass than Si additions alone. The addition of Fe and Zn alone did not lead to significant enhancements. Our results suggest that the depletion of Zn relative to P in upwelled waters may create conditions in the near-surface waters that favor phytoplankton with low Zn requirements, including cyanobacteria.
Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA; Department of Ocean, Earth, and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529, USA.
P
P
Dreux Chappell
Department of Biological Sciences , University of Southern California , Los Angeles, CA 90089 , USA.
Jagruti
J
Vedmati
Department of Oceanography , University of Hawaii at Manoa , Honolulu, HI 96822 , USA.
Karen E
KE
Selph
Department of Cell and Molecular Biology , University of Rhode Island , Kingston, RI 02881 , USA.
Heather A
HA
Cyr
Department of Cell and Molecular Biology , University of Rhode Island , Kingston, RI 02881 , USA.
Bethany D
BD
Jenkins
Scripps Institution of Oceanography , University of California at San Diego , 9500 Gilman Dr., La Jolla, CA 92093-0227 , USA.
Michael R
MR
Landry
Department of Biological Sciences , University of Southern California , Los Angeles, CA 90089 , USA.
James W
JW
Moffett
phytoplankton; upwelling; zinc