Refer to Collins et al., Global Biogeochem. Cycles (2015), in review. Excerpted from methods section:
Water column bacterial production (BP) rates were measured using the 3H-leucine incorporation microcentrifuge method of Simon and Azam (1989), as modified by Kirchman (2001). Incubations were conducted following each CTD cast using water samples from six depths; the first and sixth samples were always from the immediate surface layer (3-5 m) and 150 m. Triplicate 1 mL samples from each chosen depth or net trap were incubated with 3H-leucine (PerkinElmer, Inc., Waltham, MA; 146.5 Ci mmol-1, diluted to achieve 20 nM final concentration) for 4-12 hours at the temperature of the mixed layer. At the conclusion of the cruise, samples were processed and analyzed in a laboratory ashore according to Kirchman (2001) using Ultima Gold Low-Level Tritium cocktail (PerkinElmer, Inc.). Decay per minute counts in killed control samples were subtracted from the mean of each set of triplicates and divided by the incubation time to obtain a blank-corrected leucine incorporation rate in units of pmol leucine L-1 h-1.
References:
Collins, J. R., B. R. Edwards, K. Thamatrakoln, J. E. Ossolinksi, G. R. DiTullio, K. D. Bidle, S. C. Doney, and B. A. S. Van Mooy (2015), The multiple fates of sinking particles in the North Atlantic Ocean, Global Biogeochem. Cycles, in review.
Simon, M., and F. Azam (1989), Protein-content and protein-synthesis rates of planktonic marine bacteria, Mar. Ecol. Prog. Ser., 51(3), 201-213, doi:10.3354/Meps051201.
Kirchman, D. (2001), Measuring bacterial biomass production and growth rates from leucine incorporation in natural aquatic environments, in Methods in Microbiology, edited by J. H. Paul, pp. 227-237, Academic Press, doi:10.1016/S0580-9517(01)30047-8.