A seasonal cycle in the carbon‐isotope composition of organic carbon in the Sanaga River, Cameroon

Bird, Michael I.; Giresse, Pierre; Ngos, Simon

doi:10.4319/lo.1998.43.1.0143

Cited by 47 publications

(45 citation statements)

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“…Seston is a mixture of organic and inorganic particulate material with both terrestrial and aquatic origins (Lamberti et al ., 1987; Ward et al ., 1994Bird, Giresse & Ngos, 1998). Once in suspension, seston particles travel in the water column for variable periods of time, depending on factors such as depth, current velocity, and turbulence (Reynolds et al ., 1990).…”

Section: Discussionmentioning

confidence: 99%

Temporal shift in contribution of terrestrial organic matter to consumer production in a grassland river

et al. 2001

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1. We used stable isotopes to study the temporal (early summer versus autumn) pattern of use of terrestrial and aquatic sources of organic carbon by consumers in two bedrock‐confined reaches of a grassland river in New Zealand.  2. The major sources of organic carbon available to primary consumers were expected to be terrestrial leaf‐litter and biofilm from the stream channel. These putative carbon sources showed no significant change in mean δ13C between summer and autumn. Leaf litter (mean δ13C<−26.25) was depleted in 13C compared to biofilm (mean δ13C>−19.92).  3. In contrast to leaf litter and biofilm, the δ13C of consumers changed over time, being enriched in 13C in the autumn compared with early summer. Both the magnitude (>5‰ in some cases) and rapidity of this shift (<3 months) was surprising.  4. A two‐source mixing model indicated that, during early summer, terrestrial carbon comprised> 50% of tissue carbon for 15 of the 17 taxa of aquatic consumers analysed. During autumn, terrestrial carbon comprised> 50% of the tissue carbon of only five of 25 taxa. Because the mean δ13C of putative food sources was consistent over time, the shift in δ13C values for consumers is attributed to a change in relative amounts of terrestrial and aquatic carbon available for consumption.  5. Because seston consists of a mixture of many particles of diverse origin, it may provide an integrated measure of catchment‐wide sources of organic matter entering a stream channel. Like the tissues of most consumers, mean δ13C values for seston showed a significant shift toward 13C enrichment. This indicated that the relative availability of terrestrial carbon decreased from summer to autumn.  6. The actual quantity of carbon contributed to the stream food‐web by this potential terrestrial–aquatic link is unknown. Although terrestrial carbon may comprise a high proportion of the tissue carbon of consumers prior to summer, the majority of secondary production (and carbon sequestration) probably occurs during early summer as a consequence of rising temperature and high quality food in the form of biofilm.

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Section: Discussionmentioning

confidence: 99%

Temporal shift in contribution of terrestrial organic matter to consumer production in a grassland river

et al. 2001

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“…In contrast, POM in the St Lawrence River (Canada) was dominated by phytoplanktonic material during warm seasons, and terrestrial detritus during colder periods and storm surges (Barth et al, 1998). In the Sanaga River (Cameroon) and Congo River (Central Africa), POM also varied with discharge, with high proportions derived from C 4 plants in savannas during high discharge periods, and high proportions derived from C 3 plants from the riverbanks during low discharge periods (Mariotti et al, 1991;Bird et al, 1998).…”

Section: Introductionmentioning

confidence: 90%

Tracing soil organic carbon in the lower Amazon River and its tributaries using GDGT distributions and bulk organic matter properties

Kim

Zell

Moreira-Turcq

et al. 2012

Geochimica et Cosmochimica Acta

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“…However, it is difficult to delineate the pathways of particulate organic matter (POM) in the estuaries because of the intensive physical mixing and biological processes. A stable carbon isotope (d 13 C) has been used frequently to characterize riverine POM for the temporal and spatial variations in its biological origin and biogeochemical processes (Owens 1985;Hamilton and Lewis 1992;Bird et al 1998;Hellings et al 1999;Dehairs et al 2000;Kendall et al 2001;Bouillon et al 2002;Bellanger et al 2004;Middelburg and Herman 2007;Chen and Jia 2009). Besides, stable nitrogen isotopes (d 15 N) have also been found to be a potentially useful tracer for aquatic biogeochemical studies (Kendall et al 2001;Delong and Thorp 2006).…”

Section: Introductionmentioning

confidence: 98%

Stable isotopes of carbon and nitrogen in suspended matter and sediments from the Godavari estuary

et al. 2012

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Spatial distribution of the carbon and nitrogen content and their isotopic enrichment in suspended matter and sediments were measured in the Godavari estuary to identify the sources and transformation mechanism of organic matter. Significant variability in isotopic distribution was found over the entire length of the Godavari estuary, suggesting multiple sources of organic matter. The mean isotopic ratios (d 13 C sed -25.1 ± 0.9, d 13 C sus -24.9 ± 1, d 15 N sed 8.0 ± 2 and d 15 N sus 6.5 ± 0.9%) and elemental concentrations (C sed 0.45 ± 0.2%, C sus 0.9 ± 0.7%, N sed 0.07 ± 0.05% and N sus 0.16 ± 0.1%) support a predominantly terrigenous source. Significant enrichment in the isotopic ratios of d 13 C from the upper to lower estuary in both suspended (-27.5 and -24.3%, respectively) and sedimentary (-26.2 and -24.9%, respectively) phases indicates a decrease in the influence of terrigeneous material toward the mouth of the estuary. A significant positive relationship exists between the d 13 C of suspended and sediment, which indicates that these two organic carbon pools are likely coupled in the form of a significant exchange between the two phases. A positive relationship exists between chlorophyll a and suspended organic matter, which may mean that a significant source of organic carbon is the in situ produced phytoplankton. But, applying a simple mixing model to our isotopes, data yielded about 46% as the contribution of the terrestrial source to suspended matter, which may support the excessive heterotrophic activity in the Godavari estuary reported earlier.

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A seasonal cycle in the carbon‐isotope composition of organic carbon in the Sanaga River, Cameroon

Cited by 47 publications

References 0 publications

Temporal shift in contribution of terrestrial organic matter to consumer production in a grassland river

Temporal shift in contribution of terrestrial organic matter to consumer production in a grassland river

Tracing soil organic carbon in the lower Amazon River and its tributaries using GDGT distributions and bulk organic matter properties

Stable isotopes of carbon and nitrogen in suspended matter and sediments from the Godavari estuary

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