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.


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.


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.

If you have any questions about this article or suggestions for future topics, please visit my author forum on Reef Central.

Reefkeeping Magazine™ Reef Central, LLC-Copyright © 2008

Science Notes & News by Habib Sekha -