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

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.

[1]  F. Rassoulzadegan,et al.  Food-web mediated export of biogenic carbon in oceans: hydrodynamic control , 1996 .

[2]  W. Whitman,et al.  Prokaryotes: the unseen majority. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[3]  H. Ducklow,et al.  Annual flux of dissolved organic carbon from the euphotic zone in the northwestern Sargasso Sea , 1994, Nature.

[4]  H. Ducklow,et al.  Dissolved organic carbon in the upper ocean of the central equatorial Pacific Ocean, 1992: Daily and finescale vertical variations , 1995 .

[5]  F. Rassoulzadegan,et al.  Conceptual models for the biogeochemical role of the photic zone microbial food web, with particular reference to the Mediterranean Sea , 1999 .

[6]  Dennis A. Hansell,et al.  Effect of nutrient amendments on bacterioplankton production, community structure, and DOC utilization in the northwestern Sargasso Sea , 2002, Aquatic Microbial Ecology.

[7]  H. Ducklow,et al.  Effects of sunlight on decomposition of estuarine dissolved organic C, N and P and bacterial metabolism , 2005 .

[8]  H. Ogawa,et al.  Dissolved Organic Matter in Oceanic Waters , 2003 .

[9]  P. Conan,et al.  Relationship between primary producers and bacteria in an oligotrophic sea--the Mediterranean and biogeochemical implications , 2000 .

[10]  R. Benner,et al.  Major bacterial contribution to marine dissolved organic nitrogen , 1998, Science.

[11]  Dennis A. Hansell,et al.  Stocks and dynamics of dissolved and particulate organic matter in the southern Ross Sea, Antarctica , 2000 .

[12]  Jonathan J. Cole,et al.  Respiration rates in bacteria exceed phytoplankton production in unproductive aquatic systems , 1997, Nature.

[13]  H. Ducklow,et al.  A nitrogen-based model of plankton dynamics in the oceanic mixed layer , 1990 .

[14]  J. Cole,et al.  BACTERIAL GROWTH EFFICIENCY IN NATURAL AQUATIC SYSTEMS , 1998 .

[15]  J. Gasol,et al.  Bacteria–flagellate coupling in microcosm experiments in the Central Atlantic Ocean , 2000 .

[16]  Jerry Blackford,et al.  Ecosystem dynamics at six contrasting sites: a generic modelling study , 2004 .

[17]  I. Koike,et al.  Production of Refractory Dissolved Organic Matter by Bacteria , 2001, Science.

[18]  S. F. Umani,et al.  Calibration and validation of a one-dimensional complex marine biogeochemical flux model in different areas of the northern Adriatic shelf , 2003 .

[19]  H. Ducklow,et al.  Oceanic Bacterial Production , 1992 .

[20]  J. G. Field,et al.  The Ecological Role of Water-Column Microbes in the Sea* , 1983 .

[21]  Paul J. Somerfield,et al.  Primary and bacterial production in the Mediterranean Sea: a modelling study , 2002 .

[22]  P. Williams.  Evidence for the seasonal accumulation of carbon-rich dissolved organic material, its scale in comparison with changes in particulate material and the consequential effect on net CN assimilation ratios , 1995 .

[23]  Thomas R. Anderson,et al.  Modelling the Seasonal Cycle of Dissolved Organic Carbon at Station E1in the English Channel , 1998 .

[24]  V. Turk,et al.  The Accumulation and Release of Polysaccharides by Planktonic Cells and the Subsequent Bacterial Response during a Controlled Experiment , 1979 .

[25]  G. E. Hutchinson,et al.  The Balance of Nature and Human Impact: The paradox of the plankton , 2013 .

[26]  G. G. Leppard,et al.  Relationship between the Intracellular Integrity and the Morphology of the Capsular Envelope in Attached and Free-Living Marine Bacteria , 1996, Applied and environmental microbiology.

[27]  Valentina Zangrando,et al.  Temporal dynamics of dissolved and particulate organic carbon in the northern Adriatic Sea in relation to the mucilage events. , 2005, The Science of the total environment.

[28]  R. Benner,et al.  MARINE ORGANIC PHOSPHORUS CYCLING: NOVEL INSIGHTS FROM NUCLEAR MAGNETIC RESONANCE , 1999 .

[29]  M. Fasham,et al.  Dissolved organic matter in biogeochemical models of the Ocean , 1993 .

[30]  P. Ruardij,et al.  The European regional seas ecosystem model, a complex marine ecosystem model , 1995 .

[31]  J. C. Goldman,et al.  Regulation of gross growth efficiency and ammonium regeneration in bacteria by substrate C: N ratio1 , 1987 .

[32]  J. Bauer,et al.  Utilization and turnover of labile dissolved organic matter by bacterial heterotrophs in eastern North Pacific surface waters , 1996 .

[33]  F. Azam,et al.  Biogeochemical significance of bacterial biomass in the ocean's euphotic zone , 1990 .

[34]  E. Marañón,et al.  Significance and mechanisms of photosynthetic production of dissolved organic carbon in a coastal eutrophic ecosystem , 2004 .

[35]  G. Herndl,et al.  Production and release of bacterial capsular material and its subsequent utilization by marine bacterioplankton , 1998 .

[36]  I. Koike,et al.  Vertical distributions of dissolved organic carbon and nitrogen in the Southern Ocean , 1999 .

[37]  H. Ducklow,et al.  Limitation of Bacterial Growth by Dissolved Organic Matter and Iron in the Southern Ocean , 2000, Applied and Environmental Microbiology.

[38]  Stefan Bertilsson,et al.  Heterotrophic Bacterial Growth Efficiency and Community Structure at Different Natural Organic Carbon Concentrations , 2003, Applied and Environmental Microbiology.

[39]  F. Azam,et al.  Significance of bacteria in the mucilage phenomenon in the northern Adriatic Sea. , 1999, Annali dell'Istituto superiore di sanita.