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Marine Ecology Progress Series

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MEPS 233:303-306 (2002)  -  doi:10.3354/meps233303

Calculating microbial growth rates from data on production and standing stocks

David L. Kirchman*

College of Marine Studies, University of Delaware, 700 Pilottown Road, Lewes, Delaware 19958, USA

ABSTRACT: Growth rates of microbial assemblages are commonly estimated from data on biomass or cell abundance and rates of biomass or cell production. There are 2 algorithms for calculating growth rates from these data. One is to extrapolate from the measured standing stock (B0) to another standing stock level using the measured production rate. The growth rate is then calculated as ln[(PT + B0)/B0]/T where P is the production rate and T is a specific time interval which is 1 d when the growth rate is expressed with units of d-1 . I argue here that this algorithm is conceptually incorrect and can underestimate the actual growth rate. The most appropriate approach is the simplest, that is, to divide the production rate by the estimate of biomass or cell abundance (P/B). Additionally, propagation of errors analysis indicates that the uncertainty associated with growth rates estimates calculated from P/B is lower than that calculated from ln[(PT + B0)/B0]/T.

KEY WORDS: Exponential growth · Growth equations · Thymidine incorporation · Leucine incorporation

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