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1 Fatty acid and stable isotope (δ13c, δ15n) signatures of particulate organic matter in the Lower Amazon River: Seasonal contrasts and connectivity between floodplain lakes and the mainstem Mortillaro J.M., Abril G., Moreira-Turcq P., Sobrinho R.L., Perez M., Meziane T. UMR-BOREA : MNHN-CNRS IRD-UPMC Organic geochemistry, In Press

2 Introduction The Amazon is the largest river system on Earth (6 x 10 6 Km², up to 20% of all river discharge to the oceans, Goulding et al. 2003) At a world level, remains a lack of understanding about organic carbon dynamics, due to high degree of spatial and temporal variabilities of organic matter (OM) sources in large-river ecosystem (Bianchi and Allison 2009, PNAS) Throughout the seasons, autochthonous OM production in the Amazon River is limited due to a shallow euphotic depth, a deep water column and an intense vertical mixing (Sioli, 1984)

3 Sources of Organic Matter in Várzea and Rivers? Transfer of OM between lakes and rivers in the Amazon ecosystem? Differences between lakes? Gradient upstreamdownstream? - Characterizing the SPOM by a multi markers approach: Fatty acids and stable isotopes (δ 13 C, δ 15 N) Seasonal and spatial comparisons Modeling and conceptualisation

4 Different primary producers, and sometimes animals, bear singular isotopic or biochemical (Fatty acids : FAs) composition This singularity, linked to the type of habitat is then traced in the environment : Sediment, SPOM, Organisms, Particulate or Dissolved -Long chain Fatty acids (LCFAs, 24:0) : trees, -20:5ω3 : diatoms, -Iso and anteiso-15:0 : bacteria, 16:1ω7 : cyanobacteria

5 Material and Methods 1. Study area Sampling during HW and LW periods (June and October 2009, respectively)

6 Material and Methods 2. Sampling Aquatic plants: Eichornia sp. (C 3 ) Pistia stratiotes (C 3 ) Salvinia auriculata (C 3 ) Paspalum repens (C 4 ) 63µm and 20µm mesh (i.e. zoo + phytoplankton) Sediment (Van Veen) Suspend particulate organic matter (SPOM): Neskin surface water sampling GF/F filtration 0.7µm Soils

GC Varian 3800 + GC Varian 450 with MS 220 Fatty acid and stable isotope (δ 13 C, δ 15

2 nd step: Saponification Carboxylic Acid RCOOR' + - OH ---> RCOO - + R'OH 3 rd step:

7 GC Varian GC Varian 450 with MS 220 Fatty acid and stable isotope (δ 13 C, δ 15 N) signatures of particulate organic matter in the Lower Amazon River Material and Methods 3. Samples preparation 1 st step: Extraction of total lipids Solvents: CHCl 3 H 2 O MeOH 2 nd step: Saponification Carboxylic Acid RCOOR' + - OH ---> RCOO - + R'OH 3 rd step: Methylation Fatty Acids Methyl Esters RCOOH + BF 3 CH 3 OH ---> RCOO-CH 3 + BF 3 + H 2 O Process of each sample by GC-FID and GC-MS analysis, for spectra interpretation

18:4ω3 0.00 0.00 0.00 0.18 0.19 0.46 20:1x 0.00 0.00 0.00 0.77 0.75 0.

FA Data analysis Analysis of FA proportions (%) with PRIMER software E sp leaves A E sp leaves B E sp leaves C E sp roots A E sp roots B E sp roots C E sp leaves A E sp leaves B 96.

48 0.89 0.82 0.56 E sp leaves C 93.92 96.85 E sp roots A 60.70 59.86 58.50 Bray-Curtis similarity matrix E sp roots B 60.21 59.73 58.42 96.35 E sp roots C 59.49 57.86 56.82 90.41 90.08 16:0 36.82 34.

8 18:4ω :1x Fatty acid and stable isotope (δ 13 C, δ 15 N) signatures of particulate organic matter in the Lower Amazon River Material and Methods 4. FA Data analysis Analysis of FA proportions (%) with PRIMER software E sp leaves A E sp leaves B E sp leaves C E sp roots A E sp roots B E sp roots C E sp leaves A E sp leaves B E spleaves leaves leaves roots roots roots C E sp E sp E sp E sp E sp Name 12: : : : E sp leaves C E sp roots A Bray-Curtis similarity matrix E sp roots B E sp roots C : : : : : : : : : : : : : : : : :0anteiso :0iso :0iso :1ω?? :1ω :1ω :0iso Plot the similarity distance between samples 18:1ω :1ω :1ω FAs matrix (%) 18:2ω :3ω non-metric Multidimensional Scaling (nmds) 18:3ω

9 Results and discussion HW SPOM LW Várzea 16:1ω7 : FA marker of cyanobacteria In aquatic plants: high concentrations of 18:3ω3 + 18:2ω6 = In soils: high concentrations of LCFAs, (Terrestrial plants) White Rivers Clear/Black Rivers Várzea SPOM composition from Várzea suggest a major contribution of autochthonous OM derived from cyanobacteria (LW) and aquatic plants

10 Results and discussion Larger contribution of C 3 plants Low contribution (particulate) of C 4 aquatic plants (δ 13 C ± 0.5 ), Várzea HW Larger contribution of plankton (cyanobacteria) LW Significant depletion of δ 15 N from HW to LW in plankton (> 63µm) and SPOM (Várzea) : Atmospheric N 2 fixation by cyanobacteria (LW)?

Results and discussion High water (HW) In the Várzea Large areas of Varzea lakes covered by aquatic macrophytes diluted plankton biomass wind Low water (LW) Plankton maximum standing-stock

11 Results and discussion High water (HW) In the Várzea Large areas of Varzea lakes covered by aquatic macrophytes diluted plankton biomass wind Low water (LW) Plankton maximum standing-stock Resuspension of bottom sediment (wind action) Intensive degradation processes on macrophytes HW: Enrichment of 18:3ω3 in SPOM from Várzea / δ 13 C of C 3 plants Accumulation of plant detritus in the ecosystem LW: Increase of phytoplanktonic markers in Várzea (14:0, 16:1ω7, 18:4ω3, 18:1ω7) + depletion in δ 15 N Phytoplankton and zooplankton reach their maximum standing-stock during LW LW 11

(%) 2 4 6 8 10 12 HW FW LW RW 18:3ω3 Aquatic plants (%) 5 10 15 20 25 30 HW FW LW RW Cyanobacteria 16:1ω7 % SPOM (%) Cabaliana

12 (%) HW FW LW RW 18:3ω3 Aquatic plants (%) HW FW LW RW Cyanobacteria 16:1ω7 % SPOM (%) Cabaliana (µg l HW FW LW RW (µg l HW FW LW RW 1 ) 1 ) Janauaca Miratuba 18:3ω3 16:1ω7 Canacari Curuaï μg. l -1

13 SPOM Cabaliana Janauaca Miratuba Canacari Curuaï (%) (µg l 1 ) Terrestrial 24:0 24:0 % μg. l -1

14 C3 aquatic plants Litter R. Solimoes R. Manacapuru R. Negro R. Amazonas R. Madeira R. Urubu Soils C4 aquatic plants Plankton (63µm) HW FW SPOM LW RW δ 13 C ( ) Cabaliana Janauaca Miratuba Canacari Curuaï

15 Results and discussion Rivers HW SPOM LW = From HW to LW, increasing concentrations of phytoplanktonic and aquatic plants markers in the Amazon River suggest a transfer of OM from the Várzea White Rivers Clear/Black Rivers Várzea

16 Ftty acid and stable isotope (δ 13 C, δ 15 N) signatures of particulate organic matter in the Lower Amazon River Conclusions Autochthonous production in Várzea (phytoplankton and aquatic plants FA markers) Allochthonous OM in the rivers (detrital and terrestrial FA markers) Increasing primary production in the Várzea during LW + accumulation of plant detritus Transfer of OM between Várzea and the Amazon River (flood pulse concept)

17 Results and discussion : a conceptual approach on connectivity Particulate organic matter distribution along the Lower Amazon River: addressing aquatic ecology concepts using fatty acids (paper submitted) GPS Coordinates Latitude Longitude + L L L L L L Eigenvector Matrix Connectivity between stations Forward selection on the FAs data set, to select significant Eigenvectors

1) PCNM: principal coordinates of neighbor matrices (with connectivity) And : -2.0-2.5-3.0-3.5-2.0-2.5 Latitude -3.0 a) HW (PCNM) b) HW (AEM) FAs as spatial and temporal predictors of OM quality -3.

18 1) PCNM: principal coordinates of neighbor matrices (with connectivity) And : Latitude -3.0 a) HW (PCNM) b) HW (AEM) FAs as spatial and temporal predictors of OM quality c) LW (AEM) Várzea/Amazon River segregation Longitude HW Gradient of OM retention in Várzea associated to floodplain occupation by forest (River continuum concept, as suggested by Hess et al., 2003)

19 THANK YOU!

Dinamic of the dissolved organic matter in the Amazone basin: sorption onto mineral surfaces

4 th Scientific Meeting of the ORE-HYBAM Lima Perou 6 to 11 september 2011 Dinamic of the dissolved organic matter in the Amazone basin: sorption onto mineral surfaces Marcela Andrea Pérez Pérez (GEO/UFAM