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Coral
Reef Science: Development Highlights
Habib
Sekha
**The following article is not officially
published yet and only the abstract is currently available.**
Duhamel, Solange, F. Zeman, T. Moutin. A dual labeling
method for the simultaneous measurement of dissolved inorganic
carbon and phosphate uptake by marine planktonic species.
Limnol. Oceanogr.
Abstract:
The measurement of primary production is the foundation for
aquatic biogeochemistry research. The biogeochemical cycles
of phosphate (P) and other biolimiting elements are tightly
linked to marine primary production. We have optimized an
existing method of carbon (C) and P dual isotope labeling
to study the simultaneous C and P uptake by plankton species
in marine environments. The two main objectives of this study
were (1) to test the preservation properties of the labeled
samples and the calculation methods used in separating the
signals of the different radionuclides, and (2) to adapt the
method to marine environments. The procedure was successfully
implemented in contrasting locations within the Southeast
Pacific (between 146.36°W and 72.49°W). The uptake
rates determined using this method ranged from 14 to 900 nM
h-1 for dissolved inorganic
C and from 0.03 to 4.5 nM h-1
for dissolved inorganic P in surface water. The detection
limit found in ultraoligotrophic surface water was of 3.33
nM h-1 and 0.01 nM h-1
for C and P respectively. Carbon and P assimilation fluxes
in low and high productivity open-ocean systems may be studied
using this sensitive method. We outline a protocol for marine
environments that is appropriate for use under oceanographic
cruise conditions. Results from the application of this method
will lead to a better understanding of the interplay between
carbon and phosphate biogeochemical cycles in the upper ocean.
Comments:
The authors have developed a method to simultaneously measure
the uptake rates of organics and phosphate by marine planktonic
species e.g., phytoplankton, zooplankton, cyanobacteria and
true bacteria.
The values they cite from a few initial trials are interesting,
particularly the phosphate values. In what might be oligotrophic
waters, the uptake rate for phosphate were between 0.03 to
4.5 nM h-1 which corresponds
to 0.000003 - 0.00045 ppm phosphate per hour. Such values
are extremely small compared to the usual input and release
of phosphate in an aquarium. However, a priori, an
aquarium would have a much larger count of planktonic species.
Nevertheless, a relatively large planktonic species count
might be required to decrease the phosphate concentration
in the water by "planktonic" bacteria in an aquarium.
The authors found even lower uptake rates in ultraoligotrophic
water.
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