Exponential and linear estimations of grazing on bacteria: effects of changes in the proportion of marked cells

We develop a method to calculate grazing on bacteria determined by the disappearance of marked cells or particles. The method uses an exponential model based on population dynamics. We also describe 2 linear approaches: one is a model currently in use that takes into account only the initial proportion of marked cells; the other also includes their final proportion. An expenmental data set 1s used to compare the 3 models. The first linear model tends to underestimate grazing due to lack of information concerning the final proportion of marked cells. The second linear model, whch does take into account the final abundances of marked and natural cells, results in a good approximation to the exponential. We conclude that consideration of the final proportion of marked to natural cells IS crucial to correctly estimate bacterial grazing.