For the bacterial production protocol, see the Land-Water protocol accessible from the Landscape Interaactionr mainpage on the Arctic LTER web page or at http://www-personal.umich.edu/~gwk and clicking on the protocol link at the bottom of the page. Bacterial production is determined by the incorporation of 13C labeled Leucine (Simon and Azam 1989). Water samples are vacuum filtered through 0.22 um Millapore GS cellulose nitrate filters. Samples are extracted with 5mL of 5% TCA for 5 minutes, rinsed with additional TCA, and air dried in mini-scintillation vials. Following the addition of 1 mL cellusolve, filters are left to dissolve overnight. Scinti-safe scintillation cocktail (4 mL) is then added to each vial and samples are counted at Toolik Field Station on a liquid scintillation counter (Packard Tri-Carb 2100TR) . Calculations of bacterial productivity assume that the Internal Dilution (ID) of leucine is 1, but studies show it may range from 1-2 (Kirchman 1993). Some published data from these LTER files have used an ID value different than 1; in those studies, the ID value used is stated in the article. 1. Simon, M., and F. Azam. 1989. Protein content and protein synthesis rates of planktonic marine bacteria. Marine Ecology Progress Series 51:201-213. 2. Kirchmann, D.L. 1993. Leucine incorporation as a measure of biomass production by heterotrophic bacteria. Pages 509-512 in P.F. Kemp, B.F. Sherr, E.B. Sherr, and J.J. Cole, editors. Handbook of methods in aquatic microbial ecology. Lewis Publishers, Boca Raton, Florida, USA. http://arc.lternet.edu/landwater/lw_protocols