%0 Journal Article
%9 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES
%A Mortillaro, J. M.
%A Passarelli, C.
%A Abril, Gwenaël
%A Hubas, C.
%A Alberic, P.
%A Artigas, L. F.
%A Benedetti, M. F.
%A Thiney, N.
%A Moreira Turcq, Patricia
%A Perez, M. A. P.
%A Vidal, L. O.
%A Meziane, T.
%T The fate of C-4 and C-3 macrophyte carbon in central Amazon floodplain waters : insights from a batch experiment
%D 2016
%L fdi:010067718
%G ENG
%J Limnologica
%@ 0075-9511
%K Central amazon ; Floodplains ; Fatty acids ; Stables isotopes ; Macrophytes ; Degradation
%K BRESIL
%K AMAZONE BASSIN ; CAMALEAO LAC
%M ISI:000380418300008
%P 90-98
%R 10.1016/j.limno.2016.03.008
%U https://www.documentation.ird.fr/hor/fdi:010067718
%> https://www.documentation.ird.fr/intranet/publi/2016/09/010067718.pdf
%V 59
%W Horizon (IRD)
%X The central Amazon floodplains are particularly productive ecosystems, where a large diversity of organic carbon sources are available for aquatic organisms. Despite the fact that C-4 macrophytes generally produce larger biomasses than C-3 macrophytes, food webs in the central Amazon floodplains appear dominantly based on a C-3 carbon source. In order to investigate the respective fate and degradation patterns of C-4 and C-3 aquatic plant-derived material in central Amazon floodplains, we developed a 23-days batch experiment. Fatty acid and carbon concentrations as well as stable isotope compositions were monitored over time in 60 L tanks. These tanks contained Amazon water, with different biomasses of C-3 and C-4 macrophyte, representative of in situ densities occurring in central Amazon floodplains. In the C-4 Paspalum repens treatments, organic (POC, DOC) and inorganic carbon (DIC) got rapidly enriched in C-13, whereas in the C-3 Salvinia auriculata treatments, POC and DOC showed little change in concentration and isotopic composition, and DIC got depleted in C-13. The contribution of P. repens to POC and DOC was estimated to reach up to 94.2 and 70.7%, respectively. In contrast, no differences were reported between the C-3 S. auriculata and control treatments, an observation attributed to the lower C-3 biomass encountered in the field, to a slower degradation rate of C-3 compared to C-4 compounds, and to similar isotopic compositions for river POC and DOC, and C-3 compounds. The C-13 enrichments of POC, DOC, and DIC from P. repens treatments were attributed to an enhanced bacterially-mediated hydrolysis and mineralization of C-4 material. Evolutions of bacterial abundance and branched fatty acid concentrations confirmed the role of heterotrophic microbial communities in the high P. repens decomposition rate. Our experiment highlights the predominant role of C-4 aquatic plants, as a large source of almost entirely biodegradable organic matter available for heterotrophic activity and CO2 outgassing to the atmosphere.
%$ 036