A theoretical investigation of the organic carbon-microbial biomass relation in muddy sediments

Abstract

A population/diagenetic model is developed to describe the behavior/dynamics of the microbial biomass in aquatic sedirnents. This model is analyzed in order to establish the dominant terms, i.e. processes, in that balance. The result of this analysis shows that production-removal processes, i.e. growth, death, grazing, transformation to inactive or active, etc., are essentially in balance to the best (lowest order) approximation, while all varieties of transport processes, i.e. motility, chemotaxis, bioturbation, burial, etc.. contribute only higher order corrections to this balance. The balance between production-removal processes is shown to imply a linear relation between the size of the microbial biomass and the concentration of organic substrate, as advanced by Rublee (1982; Estuarine comparisons, Academic Press, p. 159-1821, based on empirical evidence.

The fate of bacterial carbon in an intertidal sediment: Modeling an in situ isotope tracer experiment

“…The regression models presented by Sander and Kalff (1993) Boudreau (1999) presented detailed mass balances of bacterial carbon in sediments and scaled the mass balance terms to derive a linear relation between bacteria and POC. The parameters of this linear relation are composed of parameters for irrigation, advection, bacterial production, mortality, grazing, and bacterial growth efficiency.…”

“…Carbon input to POC is constant (v2), but 13 C-glucose injection occurs in a period of 2 h (v4). POC dissolution (v5) and uptake of DOC by bacteria (v8) are first-order processes, which is conceptually equivalent to the common formulation in diagenetic models (Boudreau 1999). Adsorption of a part of the injected glucose (v3) occurs immediately after amendment (Henrichs and Sugai 1993).…”

“…The model structure was inspired by the bacterial mass balance description of Boudreau (1999), but was assumed to be zero dimensional as the incorporated processes did not require more complexity. POC, dissolved organic carbon (DOC), and bacterial carbon dynamics are implemented as C and excess 13 C balances, whereas meiobenthos and macrobenthos are modeled only as excess 13 C under the assumption that their total biomass is at steady state ( Fig.…”

“…Boudreau (1999) provided such an integration by developing spatial and temporal mass balance equations of bacterial carbon in sediments and used these in a theoretical investigation to explain the observed linear relationship between bacterial biomass and sediment particulate organic carbon (POC). The parameters of this linear relationship are nonlinear composites of parameters describing exchange processes, bacterial growth efficiency, and biological processes, including growth, mortality, and grazing.…”

“…13 C-glucose was injected into the surface 10 cm of an intertidal sediment and traced into bacterial specific polar-lipid-derived fatty acids (PLFA), total organic carbon, meiobenthos, macrobenthos, and respired carbon during a period of 4.5 months. The modeled processes were selected based on the comprehensive analysis by Boudreau (1999). The combined modeling-13 C isotope tracer study allowed us to quantify bacterial production, bacterial growth efficiency, mortality, exchange, and bacterial grazing.…”