Model of interactions between dissolved organic carbon and bacteria in marine systems

Abstract

We propose a theoretical model describing the interactions between dissolved organic carbon (DOC) and bacteria and the mechanisms leading to DOC accumulation. The model assumes that DOC cycling time-scales may vary depending on the chemical characteristics of the dissolved organic matter (DOM) and describes the temporal variability of the bacterial growth efficiency (BGE) in response to changing availability of nutrients, semi-labile and semi-refractory DOC. The conceptual framework is tested in a zero-dimensional numerical model in 2 different contexts: a diatom-bacteria system, and a microbial loop system (with bacteria, pico-phytoplankton and heterotrophic nano-flagellates). Sensitivity analyses were performed on both systems by varying the initial conditions of nutrients. Model simulations highlight the link between DOC accumulation and nutrient availability and reproduce some of the observed bacterial and microbial loop features such as the competition between bacteria and phytoplankton for nutrients and the BGE decrease in the transition from eutrophic to oligotrophic conditions. In the microbial loop simulations the model reaches a steady state and the system sustains itself without invoking external sources of N and P. KEY WORDS: Bacterial growth efficiency · DOC cycling · Microbial loop · Ecological modellingResale or republication not permitted without written consent of the publisher

Impacts of light shading and nutrient enrichment geo-engineering approaches on the productivity of a stratified, oligotrophic ocean ecosystem

“…DOM is subdivided into labile and semilabile components, in order to provide a representation of the range of organic compounds present in marine DOM and their different degrees of degradability. We have used the bacterial submodel proposed by Polimene et al [48], as previously applied for the Sargasso Sea [44]. This submodel implies a semilabile carbon release by bacteria in order to re-equilibrate the internal stoichiometry in case of nutrient limitation.…”

“…Functional types belonging to the same group share common process descriptions but different parametrizations. General parametrizations used in ERSEM are listed in [37] with the bacterial submodel described in [48].…”

Modeling the seasonal autochthonous sources of dissolved organic carbon and nitrogen in the upper Chesapeake Bay

“…They are also valuable for determining the magnitude and importance of processes that are difficult to measure and observe in the field. Many recent coastal and open ocean biogeochemical ecosystem models have included DOM (Anderson and Pondaven, 2003;Anderson et al, 2007;Anderson andWilliams, 1998, 1999;Aumont et al, 2003;Baklouti et al, 2006a,b;Druon et al, 2010;Faure et al, 2006;Grégoire and Soetaert, 2010;Llebot et al, 2010;Luo et al, 2010;Nakata and Doi, 2006;Pahlow and Vézina, 2003;Pahlow et al, 2008;Polimene et al, 2006Polimene et al, , 2007Ruardij et al, 2005;Salihoglu et al, 2008;Schmittner et al, 2005;Vichi et al, 2007) in order to better simulate and understand biogeochemical cycles. Carbon and nitrogen are typically accounted for in these models, although a few include phosphorus as well.…”

Accumulation of DOC in Low Phosphate Low Chlorophyll (LPLC) area: is it related to higher production under high N:P ratio?

“…This is a significant aspect that is not always taken into account when one wants to explain the particularly high DOC concentration in the surface layer of the Mediterranean Sea. While some authors have suggested that P-limitation of heterotrophic bacteria could cause and accumulation of DOC during summer , other have used refractorization of DOC to explain the observed accumulation (Polimene et al, 2006) but differences may also arise from the producing end (Cauwet et al, 2002). We propose in this model a possible mechanism to explain the high DOC production under high N:P ratio.…”