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Aquatic Microbial Ecology

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AME 88:187-199 (2022)  -  DOI:

Carbon-nitrogen association influences response of the microplankton food web to enrichment

Junwen Guo1,3,*, Sonia Brugel1,2, Agneta Andersson1,2, Mehdi Cherif1,4

1Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden
2Umeå Marine Sciences Centre, Umeå University, 905 71 Hörnefors, Sweden
3Present address: Department of Public Health and Clinical Medicine, Umeå University, 901 87 Umeå, Sweden
4Present address: Aquatic Ecosystems and Global Change Research Unit, French National Institute for Agriculture, Food, and Environment (INRAE), 50 Avenue de Verdun, 33612 Cestas CEDEX, France
*Corresponding author:

ABSTRACT: In aquatic ecosystems, there are 2 major forms of N available at the base of the planktonic food web: dissolved organic N (DON) and dissolved inorganic N (DIN). In DON, N is associated with organic C, which may promote both heterotrophs and autotrophs. In environments where DIN nitrate is the prevailing N form and dissociated dissolved organic C (DOC) is available, heterotrophs may also be promoted, but they may compete with the autotrophs for DIN. The influence of associated or dissociated CN nutrient sources on the interaction between organisms and the food web function is poorly known and has not been studied before. To approach this question, we performed a microcosm experiment with a coastal microbial food web, where N and C nutrient sources were provided either associated in 1 molecular compound (DON), or dissociated in 2 separate molecular compounds (DIN and DOC). The results showed that association or dissociation of C and N input had marked effects on all trophic levels, most probably through its effect on bacteria-phytoplankton interaction, which switched between increased coupling and increased competition. The biomass of all components of the food web benefitted from the association of C and N in a single DON molecule. Our study indicated that the degree of association between C and N is an important factor affecting the productivity and efficiency of the microbial food web. Therefore, the C and N association should be considered when studying aquatic systems.

KEY WORDS: Organic nitrogen · Inorganic nitrogen · Organic carbon · Microbial food web · Ecological stoichiometry · Bacteria-phytoplankton interaction

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Cite this article as: Guo J, Brugel S, Andersson A, Cherif M (2022) Carbon-nitrogen association influences response of the microplankton food web to enrichment. Aquat Microb Ecol 88:187-199.

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