Sources, Ages, and Alteration of Organic Matter in Estuaries

Canuel, Elizabeth A.; Hardison, Amber K.

doi:10.1146/annurev-marine-122414-034058

Cited by 175 publications

(113 citation statements)

References 155 publications

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“…Observations over 3 years in the tidal fresh Hudson found that particulate organic carbon concentration depended more on processes in the tidal river than the external loading from tributaries, consistent with a long residence time and extensive internal processing (Findlay et al, ). Note that the sediment age calculated here represents time in the tidal river and estuary, rather than the much longer time scales for the age of organic carbon that also depend on characteristics of the aquatic, terrigenous, and anthropogenic carbon sources (Canuel & Hardison, ).…”

Section: Discussionmentioning

confidence: 99%

Sediment Transport Time Scales and Trapping Efficiency in a Tidal River

Ralston

Geyer

2017

JGR Earth Surface

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Observations and a numerical model are used to characterize sediment transport in the tidal Hudson River. A sediment budget over 11 years including major discharge events indicates the tidal fresh region traps about 40% of the sediment input from the watershed. Sediment input scales with the river discharge cubed, while seaward transport in the tidal river scales linearly, so the tidal river accumulates sediment during the highest discharge events. Sediment pulses associated with discharge events dissipate moving seaward and lag the advection speed of the river by a factor of 1.5 to 3. Idealized model simulations with a range of discharge and settling velocity were used to evaluate the trapping efficiency, transport rate, and mean age of sediment input from the watershed. The seaward transport of suspended sediment scales linearly with discharge but lags the river velocity by a factor that is linear with settling velocity. The lag factor is 30–40 times the settling velocity (mm s−1), so transport speeds vary by orders of magnitude from clay (0.01 mm s−1) to coarse silt (1 mm s−1). Deposition along the tidal river depends strongly on settling velocity, and a simple advection‐reaction equation represents the loss due to settling on depositional shoals. The long‐term discharge record is used to represent statistically the distribution of transport times, and time scales for settling velocities of 0.1 mm s−1 and 1 mm s−1 range from several months to several years for transport through the tidal river and several years to several decades through the estuary.

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Section: Discussionmentioning

confidence: 99%

Sediment Transport Time Scales and Trapping Efficiency in a Tidal River

Ralston

Geyer

2017

JGR Earth Surface

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“…Estuaries are important zones for the production, transformation and removal of organic matter, both in dissolved and particulate form [e.g., Hedges et al ., ; Canuel and Hardison , ]. Organic matter (OM) in estuaries is derived from autochthonous (in situ production) and allochthonous (e.g., terrestrial soils and urban sewage) sources.…”

Section: Introductionmentioning

confidence: 99%

Seasonal dynamics of particulate organic matter and its response to flooding in the Pearl River Estuary, China, revealed by stable isotope (δ¹³C and δ¹⁵N) analyses

Guo

et al. 2017

JGR Oceans

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Nine cruises were conducted on a seasonal basis from 2013 to 2015 to investigate the spatial distribution and seasonal variability of δ13C and δ15N in particulate organic matter (POM), and its response to flooding in the Pearl River Estuary (PRE), south China. Our study reveals highly variable isotope ratios between seasons in this subtropical estuary, following seasonal climatic and hydrological cycles. Wet seasons had more isotopically depleted δ13C values, indicating the dominance of terrestrial and freshwater algae POM, whereas the contribution from marine phytoplankton (16%–59%) was higher during the dry seasons. In contrast, δ15N exhibited a sharp increase (up to 17.6‰) at low salinities (0–5) during high flow seasons. This was consistent with high NO3− concentrations, reflecting phytoplankton and bacteria assimilation of δ15N enriched‐ NO3− as well as notable isotope fractionation during microbial mineralization. There was little annual variability in δ13C over the 2 year period; however, particulate nitrogen (PN) exhibited lower concentrations but more enriched isotope values in 2015 than in 2014. This can be best explained by temperature‐modulated biological processing of particulate organic nitrogen, partially due to different biogeochemical responses during normal (2014) and strong El Niño (2015) years. After flooding in June 2015, terrestrial organic matter and freshwater phytoplankton were the major components of POM within the estuary and shelf areas, whereas marine phytoplankton was the dominant component in the adjacent coastal waters with mid‐salinities (10 < S < 20), as revealed by a phytoplankton bloom (>10 μg L−1) and δ13C‐enriched but δ15N‐depleted POM.

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“…For the preparation of silica gel impregnated with AgNO 3 (10 wt.%), 1 g of AgNO 3 was diluted in ethanol and water and mixed with 9 g of silica gel. The solvents were rotary evaporated and the silica activated at 100 °C for 2 h. A Pasteur pipette (5 mm i.d.)…”

Section: Silica Impregnated With Agnomentioning

confidence: 99%

“…2 Algae are characterized by shorter chain lengths with no expressive odd-over-even preference. 3 In contrast, n-alkanes in fossil fuels have a wide composition range, without predominance of odd or even-numbered chains. 4 However, despite these typical fingerprints, there are cases in which n-alkane profile of different classes of organisms overlap, resulting in ambiguous interpretations of the organic material sources.…”

Section: Introductionmentioning

confidence: 99%

Compound-Specific δ13C of n-Alkanes: Clean-Up Methods Appraisal and Application to Recent Sediments of a Highly Contaminated Bay

Ceccopieri

Scofield

Almeida

et al. 2018

J. Braz. Chem. Soc.

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Different clean-up methods to determine isotopic composition of n-alkanes were tested. Sources of organic matter in Guanabara Bay were re-examined through the δ 13 C of individual n-alkanes in surface sediment samples. The n-alkanes were efficiently isolated without significant losses of the compounds of interest. The δ 13 C of n-alkanes (n-C 17 to n-C 35 ) ranged between -34.0 and -26.4‰. More depleted δ 13 C values associated to higher carbon preference index (CPI > 4) suggest prevalence of biogenic n-alkanes from terrestrial origin in the inner stations influenced by inputs from mangrove areas. Small isotopic differences between odd and even-numbered chains and 13 C-enrichment in long-chain homologues indicate a petrogenic hydrocarbons contribution. Higher concentrations of short-chain compounds associated to a more 13 C-enriched total organic carbon (TOC) were found near the most intense sewage discharges. Results show that δ 13 C of n-alkanes can be applied to a highly degraded system as the Guanabara Bay and help improve the characterization of the organic matter. Keywords: GC-C-IRMS, UCM, urea adduction, organic matter, Guanabara Bay IntroductionThe composition and distribution of hydrocarbons in sediment samples provide information about the organic matter sources and transformation processes occurring in the environment. 1 Studies on n-alkanes have often been conducted to assess the origin of hydrocarbons, such as biogenic (marine or terrestrial) or petrogenic, found in the marine environment. The assessment makes use of the difference in the n-alkane chain length to draw conclusions on the sources of organic matter. In higher plants, for example, n-alkanes from epicuticular waxes show long chains and an odd over even-numbered carbon chain predominance. 2 Algae are characterized by shorter chain lengths with no expressive odd-over-even preference. 3 In contrast, n-alkanes in fossil fuels have a wide composition range, without predominance of odd or even-numbered chains. 4 However, despite these typical fingerprints, there are cases in which n-alkane profile of different classes of organisms overlap, resulting in ambiguous interpretations of the organic material sources. 5 Given this multiplicity of origins, an interpretation of the different sources exclusively by the concentrations of n-alkanes is very limited in more complex environments. 6 During the last decades, the carbon isotopic analysis of some biomarkers have been widely used as a valuable tool to better distinguish the sources of organic matter in marine environments. 5,[7][8][9][10][11][12][13][14] The carbon isotope composition in the biosynthesized organic material depends on both the isotopic composition of the carbon source used by organisms and the isotope discrimination that occurs during carbon fixation, which includes the steps of absorption and intracellular diffusion, and also the biosynthesis of the cell components. 15 Thus, when two classes of organisms present an overlap in the n-alkane distribution, additional information can b...

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Sources, Ages, and Alteration of Organic Matter in Estuaries

Cited by 175 publications

References 155 publications

Sediment Transport Time Scales and Trapping Efficiency in a Tidal River

Sediment Transport Time Scales and Trapping Efficiency in a Tidal River

Seasonal dynamics of particulate organic matter and its response to flooding in the Pearl River Estuary, China, revealed by stable isotope (δ¹³C and δ¹⁵N) analyses

Compound-Specific δ13C of n-Alkanes: Clean-Up Methods Appraisal and Application to Recent Sediments of a Highly Contaminated Bay

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Sources, Ages, and Alteration of Organic Matter in Estuaries

Cited by 175 publications

References 155 publications

Sediment Transport Time Scales and Trapping Efficiency in a Tidal River

Sediment Transport Time Scales and Trapping Efficiency in a Tidal River

Seasonal dynamics of particulate organic matter and its response to flooding in the Pearl River Estuary, China, revealed by stable isotope (δ13C and δ15N) analyses

Compound-Specific δ13C of n-Alkanes: Clean-Up Methods Appraisal and Application to Recent Sediments of a Highly Contaminated Bay

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Seasonal dynamics of particulate organic matter and its response to flooding in the Pearl River Estuary, China, revealed by stable isotope (δ¹³C and δ¹⁵N) analyses