Seasonal dynamics of organic matter and inorganic nitrogen in surface waters of Alaskan Arctic streams and rivers

dc.contributor.advisorMcClelland, James W.en
dc.contributor.committeeMemberDunton, Kenneth Hen
dc.contributor.committeeMemberLiu, Zhanfeien
dc.contributor.committeeMemberShank, Gerald Cen
dc.contributor.committeeMemberTownsend-Small, Amyen
dc.creatorKhosh, Matthew Solomonen
dc.creator.orcid0000-0002-5457-7724en
dc.date.accessioned2016-05-16T19:42:30Z
dc.date.available2016-05-16T19:42:30Z
dc.date.issued2015-12en
dc.date.submittedDecember 2015
dc.date.updated2016-05-16T19:42:30Z
dc.description.abstractClimate-linked changes in hydrology and biogeochemical processes within Arctic watersheds are likely already affecting fluvial export of waterborne materials, including organic matter (OM) and dissolved inorganic nitrogen (DIN). Our understanding of Arctic watershed OM and DIN export response to climate change is hampered by a lack of contemporary baselines, as well as a dearth of seasonally comprehensive studies. This work focuses on characterizing OM and DIN concentrations and sources in six streams/rivers on the North Slope of Alaska during the entirety of the hydrologic year (May through October) in 2009 and 2010. The highest OM concentrations occurred during spring snowmelt, with results indicating that terrestrial vegetation leachates are the major source of dissolved OM, while particulate OM originates from a degraded soil source. Over the hydrologic year, soils became a progressively increasing source of dissolved OM, while autochthonous production made up a sizeable proportion of particulate OM during base flow conditions. DIN concentrations were low throughout the spring and summer and increased markedly during the late summer and fall. Our findings suggest that penetration of water into thawed mineral soils, and a reduction in nitrogen assimilation relative to remineralization, may increase DIN export from Arctic watersheds during the late summer and fall. Although recent studies of Arctic rivers have emphasized the importance of the spring thaw period on OM export, our understanding of the mechanisms that control water chemistry observations during this time are still lacking. Experimental leaching results, from experiments conducted in 2014, suggest that aboveground plant biomass is a major source of dissolved OM in Arctic catchments during the spring, and that the timing of freezing and drying conditions during the fall may impact dissolved OM leaching dynamics on that same material the following snowmelt. Improved knowledge of OM and DIN temporal trends and the mechanisms that control seasonal concentrations is essential for understanding export dynamics of these water constituents in Arctic river systems. Perhaps more importantly, increased understanding of the seasonal controls on OM and DIN export in Arctic rivers is critical for predicting how these systems will respond under future climate change scenarios.en
dc.description.departmentMarine Scienceen
dc.format.mimetypeapplication/pdfen
dc.identifierdoi:10.15781/T2CK0Ben
dc.identifier.urihttp://hdl.handle.net/2152/35466en
dc.language.isoenen
dc.subjectArctic
dc.subjectAlaska
dc.subjectRivers
dc.subjectDissolved organic matter
dc.subjectDissolved organic carbon
dc.subjectDissolved organic nitrogen
dc.subjectParticulate organic matter
dc.subjectParticulate organic carbon
dc.subjectParticulate organic nitrogen
dc.subjectDissolved inorganic nitrogen
dc.subjectNitrate
dc.subjectDOC
dc.subjectDON
dc.subjectPOC
dc.subjectPON
dc.subjectDIN
dc.subjectBiogeochemistry
dc.titleSeasonal dynamics of organic matter and inorganic nitrogen in surface waters of Alaskan Arctic streams and riversen
dc.typeThesisen
dc.type.materialtexten
thesis.degree.departmentMarine Scienceen
thesis.degree.disciplineMarine scienceen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen
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