Carbon isotopes and iodine concentrations in a Mississippi River delta core recording land use, sediment transport, and dam building in the river’s drainage basin

Santschi, Peter H.; Oktay, Sarah; Cifuentes, Luis A.

doi:10.1016/j.marenvres.2006.11.002

Cited by 12 publications

(5 citation statements)

References 21 publications

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“…The Distal core shows a similarly large peak around the same time period with very large lignin concentration of minimally degraded woody angiosperm material ( Figure 5). The lack of a large increase in sedimentary organic carbon content in the Dist Core is consistent with Santschi et al [2007] description of an older d 13 C enriched low organic matter layer attributed to a time of maximum wetland loss.…”

Section: Spatial Effects On the Louisiana Continental Marginsupporting

confidence: 88%

“…Recent work also showed a significant gradient of higher concentrations of dissolved lignin and dissolved organic carbon from the Terrebonne Bay, Louisiana, United States, to the inner shelf of the northern Gulf of Mexico, indicative of export of terrestrially derived (marsh) dissolved organic carbon to the coast [ Bianchi et al , 2009b]. Episodic deposition from C 4 wetland plant residues were suggested at a 60 m water depth between the years 1950 and 1960 by using iodine concentrations in one core immediately northwest of the southwest pass outlet [ Santschi et al , 2007]. The Distal core shows a similarly large peak around the same time period with very large lignin concentration of minimally degraded woody angiosperm material (Figure 5).…”

Section: Discussionmentioning

confidence: 99%

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Historical changes in terrestrially derived organic carbon inputs to Louisiana continental margin sediments over the past 150 years

Sampere

Bianchi

2011

J. Geophys. Res.

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[1] Major rivers (and associated deltaic environments) provide the dominant pathway for the input of terrestrial-derived organic carbon in sediments (TOC T ) to the ocean. Natural watershed processes and land-use changes are important in dictating the amount and character of carbon being buried on continental margins. Seven core sites were occupied on the Louisiana continental margin aboard the R/V Pelican in July 2003 along two major sediment transport pathways south and west of the Mississippi River mouth. Lignin profiles in these age-dated cores ( 210 Pb geochronology) indicate artificial reservoir retention as a primary control on organic carbon quantity and quality reaching the margin post-1950, whereas pre-1950 sediments may reflect soil erosion due to land clearing and farming practices. Lignin (L 8 ) concentrations (range 0.2 to 1.7) also indicate that TOC T delivery rates/decay processes have probably remained relatively consistent from proximal to distal stations along transects. The down-core profile at the Canyon station seems to be temporally linked and connected to inner shelf deposition, suggestive of rapid cross-shelf transport. Sources of terrestrially derived organic carbon were reflective of mixed angiosperms over the last 150 years in cores west and south of the Mississippi River delta. The lignin-phenol vegetation index (LPVI) (range 130.0 to 510) proved to be a sensitive indicator of source changes in these sediments and eliminated some of the variability compared to C/V (range 0.01 to 0.4) and S/V (range 0.9 to 2.1) ratios. Stochastic events such as hurricanes and large river floods have a measurable, albeit ephemeral, effect on the shelf TOC T record. Burial of TOC T on the river-dominated Louisiana continental margin is largely driven by anthropogenic land-use alterations in the last 150 years. Land-use changes in the Mississippi River basin and river damming have likely affected carbon cycling and TOC T burial on the Louisiana continental margin over a large spatial extent as observed by similar trends in cores from across and along the margin.Citation: Sampere, T. P., T. S. Bianchi, and M. A. Allison (2011), Historical changes in terrestrially derived organic carbon inputs to Louisiana continental margin sediments over the past 150 years,

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Section: Spatial Effects On the Louisiana Continental Marginsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Historical changes in terrestrially derived organic carbon inputs to Louisiana continental margin sediments over the past 150 years

Sampere

Bianchi

2011

J. Geophys. Res.

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“…These observations clearly highlight that the δ 13 C of riverine organic C pools may not be an accurate proxy for extrapolating C 3 and C 4 vegetation cover of a drainage basin, but appear to be strongly biased towards the dominant photosynthetic pathway of riparian fringe vegetation. Our δ 13 C values of riverine sediments in a basin dominated by tropical grassland indicate that upon deposition these sediments are not representative of the overall vegetation distribution in the contributing drainage basin, and that the analysis of sedimentary δ 13 C signatures for the purpose of paleo-reconstruction of vegetation distribution (Cerling and others 1988; Mora and others 2002; Santschi and others 2007; dos Santos and others 2013) may lead to significant over-estimation of the areal C 3 cover within drainage basins characterised by considerable expanses of C 4 grassland.…”

Section: Discussionmentioning

confidence: 85%

“…Indeed, others have employed stable isotope techniques to reconstruct paleo-vegetation distribution and paleo-climate regime from OM buried within various environments, including lacustrine and fluvial deposits (Cerling and others 1988; Mora and others 2002) as well as nearshore (Santschi and others 2007) and offshore (dos Santos and others 2013) marine deposits. Yet, such studies often assume no inherent differences in sediment entrainment or transport between C 3 - and C 4 -derived carbon from source to sink (Wynn and Bird 2007).…”

Section: Introductionmentioning

confidence: 99%

Disproportionate Contribution of Riparian Inputs to Organic Carbon Pools in Freshwater Systems

et al. 2014

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A lack of appropriate proxies has traditionally hampered our ability to distinguish riverine organic carbon (OC) sources at the landscape scale. However, the dissection of C4 grasslands by C3-enriched riparian vegetation, and the distinct carbon stable isotope signature (δ13C) of these two photosynthetic pathways, provides a unique setting to assess the relative contribution of riparian and more distant sources to riverine C pools. Here, we compared δ13C signatures of bulk sub-basin vegetation (δ13CVEG) with those of riverine OC pools for a wide range of sites within two contrasting river basins in Madagascar. Although C3-derived carbon dominated in the eastern Rianala catchment, consistent with the dominant vegetation, we found that in the C4-dominated Betsiboka basin, riverine OC is disproportionately sourced from the C3-enriched riparian fringe, irrespective of climatic season, even though δ13CVEG estimates suggest as much as 96% of vegetation cover in some Betsiboka sub-basins may be accounted for by C4 biomass. For example, δ13C values for river bed OC were on average 6.9 ± 2.7‰ depleted in 13C compared to paired estimates of δ13CVEG. The disconnection of the wider C4-dominated basin is considered the primary driver of the under-representation of C4-derived C within riverine OC pools in the Betsiboka basin, although combustion of grassland biomass by fire is likely a subsidiary constraint on the quantity of terrestrial organic matter available for export to these streams and rivers. Our findings carry implications for the use of sedimentary δ13C signatures as proxies for past forest-grassland distribution and climate, as the C4 component may be considerably underestimated due to its disconnection from riverine OC pools.Electronic supplementary materialThe online version of this article (doi:10.1007/s10021-014-9772-6) contains supplementary material, which is available to authorized users.

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“…Our rates are likely faster than erosion rates along other portions of the United States because Texas salt marshes are generally located along the estuary edge and major tributaries, whereas previous work commonly includes marshes located along small tidal creeks with limited fetches and therefore edge erosion. Observations along the western part of Galveston Bay suggest that the large sediment deficit (i.e., the low sediment accretion rate (~0.20 cm year −1 ) relative to the local rate of relative sea level rise (~0.65 cm year −1 )) is likely to be the main reason for marsh erosion in this region, where recent dam constructions along the Trinity and Mississippi Rivers significantly decreased sediment supply to Galveston Bay by 50-75% [60].…”

Section: Texas Marsh Migration and Erosionmentioning

confidence: 99%

Massive Sea-Level-Driven Marsh Migration and Implications for Coastal Resilience along the Texas Coast

Jung,

Doe,

Jung

et al. 2024

Remote Sensing

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Tidal salt marshes offer crucial ecosystem services in the form of carbon sequestration, fisheries, property and recreational values, and protection from storm surges, and are therefore considered one of the most valuable and fragile ecosystems worldwide, where sea-level rise and direct human modifications resulted in the loss of vast regions of today’s marshland. The extent of salt marshes therefore relies heavily on the interplay between upland migration and edge erosion. We measured changes in marsh size based on historical topographic sheets from the 1850s and 2019 satellite imagery along the Texas coast, which is home to three of the largest estuaries in North America (e.g., Galveston, Corpus Christi, and Matagorda Bays). We further distinguished between changes in high and low marsh based on local elevation data in an effort to estimate changes in local ecosystem services. Our results showed that approximately 410 km2 (58%) of salt marshes were lost due to coastal erosion and marsh ponding and nearly 510 km2 (72%) of salt marshes were created, likely due to upland submergence. Statistical analyses showed a significant relationship between marsh migration and upland slope, suggesting that today’s marshland formed as a result of submergence of barren uplands along gently sloping coastal plains. Although the overall areal extent of Texas marshes increased throughout the last century (~100 km2 or 14%), economic gains through upland migration of high marshes (mostly in the form of property value (USD 0.7–1.0 trillion)) were too small to offset sea-level-driven losses of crucial ecosystem services of Texan low marshes (in the form of storm protection and fisheries (USD 2.1–2.7 trillion)). Together, our results suggest that despite significant increases in marsh area, the loss of crucial ecosystem services underscores the complexity and importance of considering not only quantity but also quality in marshland conservation efforts.

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Carbon isotopes and iodine concentrations in a Mississippi River delta core recording land use, sediment transport, and dam building in the river’s drainage basin

Cited by 12 publications

References 21 publications

Historical changes in terrestrially derived organic carbon inputs to Louisiana continental margin sediments over the past 150 years

Historical changes in terrestrially derived organic carbon inputs to Louisiana continental margin sediments over the past 150 years

Disproportionate Contribution of Riparian Inputs to Organic Carbon Pools in Freshwater Systems

Massive Sea-Level-Driven Marsh Migration and Implications for Coastal Resilience along the Texas Coast

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