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Characterizing Carbon Cycling Dynamics in Salt Marshes: The Sources and Fates of Natural and Plastic-Derived Organic Carbon /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Characterizing Carbon Cycling Dynamics in Salt Marshes: The Sources and Fates of Natural and Plastic-Derived Organic Carbon // Mackenzie M Fiss-Nealley.
Author:	Fiss-Nealley, Mackenzie M.,
Description:	1 electronic resource (168 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-06, Section: B.
Contained By:	Dissertations Abstracts International86-06B.
Subject:	Biogeochemistry. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31764360
ISBN:	9798346813484

Characterizing Carbon Cycling Dynamics in Salt Marshes: The Sources and Fates of Natural and Plastic-Derived Organic Carbon /
Fiss-Nealley, Mackenzie M.,

Characterizing Carbon Cycling Dynamics in Salt Marshes: The Sources and Fates of Natural and Plastic-Derived Organic Carbon /Mackenzie M Fiss-Nealley. - 1 electronic resource (168 pages)

Source: Dissertations Abstracts International, Volume: 86-06, Section: B.

Salt marshes are coastal links between the terrestrial and marine ecosystems. Through this connection, salt marshes receive organic carbon (OC) from different sources (e.g., terrigenous, anthropogenic, marigenous), in different forms and size fractions (e.g., natural, plastic-derived; dissolved, particulate), with different reactivities (e.g., labile, semi-labile, refractory), and ultimately experience different transformations and fates within salt marshes (e.g., burial, biodegradation, photochemical transformations, export to adjacent waters). I sought to understand OC dynamics within salt marshes by examining dissolved and particulate OC, as well as natural and anthropogenic OC.My first research chapter investigated the sources of dissolved organic matter (DOM) to a Georgia salt marsh creek (Groves Creek) and the subsequent fates within the tidal creek by ultrahigh-resolution mass spectrometry (Fourier-transform ion cyclotron resonance mass spectrometry; FT-ICR MS) to measure DOM composition in samples over a 17-month timespan. DOM molecular composition from over 400 samples was paired with five different environmental drivers to determine which processes were most important in shaping DOM chemistry. The majority of the variance in the DOM dataset was explained by a gradient in oxidation (i.e., O/C, NOSC), sulfur-containing molecular formulas, and indices indicative of a reactivity continuum (e.g., biolability (%MLBL), degradation (IDEG)). As the trend followed by samples in this study was very similar to a study of a transect from porewater in a nearby tidal creek to the open ocean, the dominant driver of DOM composition in Groves Creek is interpreted as marsh-derived outwelling of porewater DOM into the oxic water column. Marsh outwelling allows for the export of previously sequestered C, which is a flux that needs to be quantified in C budgets, especially in the context of climate change.My second research chapter examined the degradation of Spartina alterniflora in a New England salt marsh (Belle Isle Marsh). Spartina alterniflora is the dominant vascular plant in salt marshes along the Atlantic and Gulf of Mexico coasts, and therefore is an important contributor to above-and belowground organic matter throughout its lifecycle and decomposition. Fresh and senescent Spartina plant material was collected from Belle Isle Marsh and then buried for up to one year in litterbags, with collections at 5, 12, 28, 72, 163, and 356 days, and then analyzed for particulate organic carbon concentrations, stable carbon isotopes, total phenolic content, and optical properties (via base-extracted particulate organic matter; BEPOM). Three OC pools were observed in the decay of the fresh Spartina litter, and two pools were observed in the decay of the senescent litter. Although the quality of the Spartina litter types was initially different, qualitative optical and isotopic metrics converged between the fresh and senescent litter during the year-long burial. Fully characterizing the mechanisms surrounding the decomposition of Spartina alterniflora will shed light on the transformations and fate in Spartina-dominated salt marshes.My third research chapter explored the degradability of 'biodegradable' plastic single-use items in a New England salt marsh setting (Belle Isle) and compares the degradation of the modified plastic items to that of conventional plastic items. We assessed the degradability of commercially available drinking straws made of four materials (conventional plastic, biodegradable plastic, polylactic acid (PLA; a compostable bioplastic derived from cornstarch), and paper) and disposable forks made of three materials (conventional plastic, biodegradable plastic, and polylactic acid). They were initially characterized with Fourier transform infrared (FT-IR) spectroscopy. The PLA and paper products were confirmed as PLA and paper, respectively. FT-IR analysis identified the conventional and modified plastic straws as polypropylene (PP) and the conventional and modified plastic forks as polystyrene (PS). Although some additives were apparent in the FT-IR spectra of the modified plastics, the high spectral similarity between the conventional and modified plastics suggested that the PP and PS polymers were not significantly modified. Samples were buried in Belle Isle sediments in litterbags, collected at 5, 12, 28, 72, 163, and 356 days, and assessed for changes in mass. After one year, the largest mass loss was 5%, which was observed in the paper straws. The plastics, including those that had been modified to be "biodegradable," lost no mass throughout the experiment. Although these single-use items may be degradable in an industrial setting, this study indicates that they are not biodegradable in the salt marsh sediments, a coastal system where plastics can accumulate. Plastics are another source of OC in salt marshes, and their degradation (or preservation) is necessary to understand modern C cycling, as the geochemical cycle now unfortunately involves both natural and artificial sources of OC.This dissertation contributes to a growing body of work regarding the various sources, processes, and fates of biogenic and plastic C in salt marshes. It illustrates the merits of different chemical analyses and of studying different forms of organic C to better constrain the dynamics of biogenic and plastic C in complex coastal environments like salt marshes.

English

ISBN: 9798346813484Subjects--Topical Terms:

545717
Biogeochemistry.
Subjects--Index Terms:

Carbon cycling

Characterizing Carbon Cycling Dynamics in Salt Marshes: The Sources and Fates of Natural and Plastic-Derived Organic Carbon /
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I sought to understand OC dynamics within salt marshes by examining dissolved and particulate OC, as well as natural and anthropogenic OC.My first research chapter investigated the sources of dissolved organic matter (DOM) to a Georgia salt marsh creek (Groves Creek) and the subsequent fates within the tidal creek by ultrahigh-resolution mass spectrometry (Fourier-transform ion cyclotron resonance mass spectrometry; FT-ICR MS) to measure DOM composition in samples over a 17-month timespan. DOM molecular composition from over 400 samples was paired with five different environmental drivers to determine which processes were most important in shaping DOM chemistry. The majority of the variance in the DOM dataset was explained by a gradient in oxidation (i.e., O/C, NOSC), sulfur-containing molecular formulas, and indices indicative of a reactivity continuum (e.g., biolability (%MLBL), degradation (IDEG)). As the trend followed by samples in this study was very similar to a study of a transect from porewater in a nearby tidal creek to the open ocean, the dominant driver of DOM composition in Groves Creek is interpreted as marsh-derived outwelling of porewater DOM into the oxic water column. Marsh outwelling allows for the export of previously sequestered C, which is a flux that needs to be quantified in C budgets, especially in the context of climate change.My second research chapter examined the degradation of Spartina alterniflora in a New England salt marsh (Belle Isle Marsh). Spartina alterniflora is the dominant vascular plant in salt marshes along the Atlantic and Gulf of Mexico coasts, and therefore is an important contributor to above-and belowground organic matter throughout its lifecycle and decomposition. Fresh and senescent Spartina plant material was collected from Belle Isle Marsh and then buried for up to one year in litterbags, with collections at 5, 12, 28, 72, 163, and 356 days, and then analyzed for particulate organic carbon concentrations, stable carbon isotopes, total phenolic content, and optical properties (via base-extracted particulate organic matter; BEPOM). Three OC pools were observed in the decay of the fresh Spartina litter, and two pools were observed in the decay of the senescent litter. Although the quality of the Spartina litter types was initially different, qualitative optical and isotopic metrics converged between the fresh and senescent litter during the year-long burial. Fully characterizing the mechanisms surrounding the decomposition of Spartina alterniflora will shed light on the transformations and fate in Spartina-dominated salt marshes.My third research chapter explored the degradability of 'biodegradable' plastic single-use items in a New England salt marsh setting (Belle Isle) and compares the degradation of the modified plastic items to that of conventional plastic items. We assessed the degradability of commercially available drinking straws made of four materials (conventional plastic, biodegradable plastic, polylactic acid (PLA; a compostable bioplastic derived from cornstarch), and paper) and disposable forks made of three materials (conventional plastic, biodegradable plastic, and polylactic acid). They were initially characterized with Fourier transform infrared (FT-IR) spectroscopy. The PLA and paper products were confirmed as PLA and paper, respectively. FT-IR analysis identified the conventional and modified plastic straws as polypropylene (PP) and the conventional and modified plastic forks as polystyrene (PS). Although some additives were apparent in the FT-IR spectra of the modified plastics, the high spectral similarity between the conventional and modified plastics suggested that the PP and PS polymers were not significantly modified. Samples were buried in Belle Isle sediments in litterbags, collected at 5, 12, 28, 72, 163, and 356 days, and assessed for changes in mass. After one year, the largest mass loss was 5%, which was observed in the paper straws. The plastics, including those that had been modified to be "biodegradable," lost no mass throughout the experiment. Although these single-use items may be degradable in an industrial setting, this study indicates that they are not biodegradable in the salt marsh sediments, a coastal system where plastics can accumulate. Plastics are another source of OC in salt marshes, and their degradation (or preservation) is necessary to understand modern C cycling, as the geochemical cycle now unfortunately involves both natural and artificial sources of OC.This dissertation contributes to a growing body of work regarding the various sources, processes, and fates of biogenic and plastic C in salt marshes. It illustrates the merits of different chemical analyses and of studying different forms of organic C to better constrain the dynamics of biogenic and plastic C in complex coastal environments like salt marshes.
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