Modelling DOC assimilation and bacterial growth efficiency in biodegradation experiments: a case study in the Northeast Atlantic Ocean
Eichinger, M., Poggiale, J.-C. and Wambeke, F. Van and Lefèvre, D. and Sempéré, R. 2006.
Modelling DOC assimilation and bacterial growth efficiency in biodegradation experiments: a case study in the Northeast Atlantic Ocean.
Aquatic Microbial Ecology 43: 139 - 151
Abstract
A Monod (1942) model was used to describe the interaction and dynamics
between marine bacteria and labile-dissolved organic carbon (l-DOC)
using data obtained from 36 biodegradation experiments. This model is
governed by 2 state variables, DOC and bacterial biomass (BB), and 3
parameters, specific maximum assimilation rate (Vmax),
half-saturation constant (KS) and bacterial growth
efficiency (BGE). The calibrations were obtained from biodegradation
experiments carried out in the Northeast Atlantic Ocean over different
seasons and at different depths. We also conducted a sensitivity
analysis to determine (1) which parameter had the greatest influence
on the model, and (2) whether the model was robust with regard to
experimental errors. Our results indicate that BGE is greater in
surface layers than in deeper waters, with minimum values observed
during winter. In contrast, the Vmax/KS ratio is
inversely dependent on depth and does not show any seasonal
trend. This reflects an increase in bacterial affinity for substrate
with increasing depth (decrease of KS) and/or better
specific maximum assimilation rates (increase of Vmax). The
sensitivity and robustness analyses demonstrate that the model is more
sensitive to the Vmax/KS ratio than to BGE, and
that the parameters estimated are reliable. However, although the BGE
values are close to those estimated experimentally, the use of a
constant Vmax/KS ratio and BGE in a
1-dimensional model is not appropriate as these parameters should be
described as variables that take depth and season into account.