Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin
Other literature type, Article
Sobrinho, R. L.
Bernardes, M. C.
Kim, J. H.
Zell, C. I.
Mortillaro, J. M.
Moreira Turcq, Patricia
Damste, J. S. S.
- Publisher: Copernicus Publications
(issn: 1726-4170, eissn: 1726-4189)
Ecology | http://aims.fao.org/aos/agrovoc/c_32372 | M40 - Ecologie aquatique | QH540-549.5 | QE1-996.5 | P33 - Chimie et physique du sol | QH501-531 | Geology | Life
In this study, we investigated the seasonal and spatial pattern of
sedimentary organic matter (SOM) in five floodplain lakes of the central
Amazon basin (Cabaliana, Janauaca, Canaçari, Mirituba and Curuai) which
have different morphologies, hydrodynamics and vegetation coverages. Surface
sediments were collected in four hydrological seasons: low water (LW),
rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010.
We investigated commonly used bulk geochemical tracers such as the C : N ratio
and the stable isotopic composition of organic carbon (<i>δ</i><sup>13</sup>C<sub>org</sub>). These results were compared with lignin phenol
parameters as an indicator of vascular plant detritus and branched glycerol
dialkyl glycerol tetraethers (brGDGTs) to trace the input of soil organic
matter (OM) from land to the aquatic settings. We also applied the
crenarchaeol as an indicator of aquatic (rivers and lakes) OM. Our data
showed that during the RW and FW seasons, the surface sediments were
enriched in lignin and brGDGTs in comparison to other seasons. Our study
also indicated that floodplain lake sediments primarily consisted of
allochthonous, C<sub>3</sub> plant-derived OM. However, a downstream increase in
C<sub>4</sub> macrophyte-derived OM contribution was observed along the gradient
of increasing open waters – i.e., from upstream to downstream. Accordingly, we
attribute the temporal and spatial difference in SOM composition to the
hydrological dynamics between the floodplain lakes and the surrounding