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Evidence for manganese-catalyzed nitrogen cycling in salt marsh sedimentsNewton, Jennifer Denise 12 April 2006 (has links)
Fixed nitrogen is important as a nutrient for organic matter formation and as an electron donor (nitrification) and acceptor (denitrification) for energy generation, but it is scarcely available in aquatic systems. Nitrification oxidizes ammonium to nitrite and nitrate. Denitrification uses these fixed species to form dinitrogen gas. The classic understanding of the nitrogen cycle requires dissolved oxygen for nitrification and assumes denitrification reduces nitrate to dinitrogen through various intermediates in anaerobic conditions. The global nitrogen budget is imbalanced with more marine denitrification measrued than previously estimated in the classic nitrogen cycle, suggesting alternative anaerobic nitrification and denitrification pathways exist. One alternative denitrification pathway is anammox, which directly oxidizes ammonium to dinitrogen with nitrite as the electron acceptor. Other alternative pathways for both nitrification and denitrification involve redox metals as catalysts. Manganese-catalyzed anaerobic nitrification and denitrification are thermodynamically favorable at neutral pH. However, experimental evidence for these processes is still lacking. This investigation seeks to uncover evidence of manganese-catalyzed nitrification and denitrification in saltmarsh sediments.
Batch reactors with anaerobic sediment slurries from a saltmarsh in coastal Georgia were incubated in the presence and absence of colloidal manganese oxides and isotope-labeled ammonium and nitrate to trace dinitrogen formation. Results show that denitrification is more prominent in the manganese-treated reactors and that the classic denitrification pathway may not be substantial in shallow saltmarsh sediments. These data indicate that anammox and/or manganese-coupled denitrification are major contributors to the removal of fixed nitrogen. Ammonium removal in the manganese-treated reactors is accompanied by a high nitrite production compared to the nitrogen-only treatment, indicating manganese-coupled denitrification exists and/or anammox is promoted in the presence of manganese.
Primary productivity is generally high in saltmarshes, but oxygen penetrates less than a few millimeters in the sediment. These observations suggest that oxygenic nitrification does not fuel denitrification below the sediment-water interface. The data show that manganese may play a role in the formation of nitrite and nitrate in oxygen-limited sediments.
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Application of intertidal salt-marsh foraminifera to reconstruct late Holocene sea-level change at Kariega Estuary, South Africa.Strachan, Kate Leigh. January 2013 (has links)
Unclear predictions surrounding climate change, associated sea-level rise and potential impacts upon coastal
environments have placed an emphasis on the importance of sea-level change. Past sea-level fluctuations
have been measured using biological and geomorphological forms of evidence. One such biological proxy is
salt-marsh foraminifera, which have been used as a high-resolution indicator of past sea-level change, based
on the assumption that surface foraminiferal assemblages are similar in composition to buried fossil
foraminifera. In South Africa, there is ongoing research seeking to produce high-resolution records of sealevel
change, however foraminifera remain an underutilized source of proxy evidence. This research applies
salt-marsh foraminifera as precise indicators of relative sea-level change at Kariega Estuary on the Eastern
Cape coastline of South Africa. Distributions of modern foraminiferal assemblages were investigated,
revealing vertical zonation across the intertidal zone. The foraminiferal and marsh vegetation zones were in
part similar and overlapped to a certain extent, identifying three zones; high, low and tidal flats. This
suggested foraminiferal distribution is a direct function of elevation relative to tidal fluctuation. A 94 cm
core consisting of peat, sand and clay sediments was extracted from the salt marsh. A chronological
framework for the core was based on five AMS radiocarbon age determinations of both bulk sediment and
shell fragment samples placing the record within the last 1500 years Before Present (BP). The basal shell age
was a clear outlier to all bulk sediment ages, possibly as a result of shell recrystallisation. The bulk sediment
age determinations suggested two possible age reversals, potentially linked to sedimentary hiatus or
contamination. These inconsistencies in the chronology were best viewed as separate age models. The core
was analysed at a high resolution, whereby fossil foraminifera were extracted every 2 cm’s down the core. A
transfer function was applied to calculate the former elevation at which each core sample once existed, to
produce a relative sea-level reconstruction. The reconstruction was related to the age models to produce two
possible sea-level curve scenarios. Reconstructed curves from both scenarios depict a 0.5 m (±0.16 m) sealevel
highstand at 1500 cal years BP followed by a lowstand of -0.6 m (±0.03 m). Scenario One reached its
lowest recorded sea-level between 600 cal years BP and 500 cal years BP and then fluctuated below present
day levels. Scenario Two reached its lowest recorded sea-level around 1200 cal years BP, followed by low
amplitude fluctuations and a relatively stable period from 100 cal years BP till the present day. The 1500 cal
years BP highstand recorded for both scenarios correlates well with existing palaeoenvironmental literature
from the southern African coastline. Chronological limitations associated with the remainder of the record
hinder inter-comparison with previous studies. The outcomes of this research suggest that intertidal saltmarsh
foraminifera demonstrate enormous potential for the high-resolution reconstruction of relative sealevel
change in the South African context. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.
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Effects of introduced fish on aquatic insect abundance : a case study of Hamakua Marsh, Oahu HawaiʻiMcGuire, Christina January 2006 (has links)
Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 98-106). / vii, 106 leaves, bound 29 cm
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Sediment deposition and availability in the riparian wetlands of the Cape Fear RiverEulie, Devon Olivola. January 2008 (has links) (PDF)
Thesis (M.S.)--University of North Carolina Wilmington, 2008. / Title from PDF title page (viewed September 22, 2008) Includes bibliographical references (p. 60-62)
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The impacts of macrobenthos on the rates and pathways of organic matter mineralization in two coastal marine ecosystems of the Southeastern United StatesSmith, April Christine. Kostka, Joel E. January 2005 (has links)
Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Dr. Joel Kostka, Florida State University, College of Arts and Sciences, Dept. of Oceanography. Title and description from dissertation home page (viewed June 22, 2005). Document formatted into pages; contains xi, 108 pages. Includes bibliographical references.
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Environmental change in San Francisco Estuary tidal marshesWatson, Elizabeth Burke. January 2006 (has links)
Thesis (Ph. D.)--University of California, Berkeley, 2006. / Includes bibliographical references.
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Comparison of nekton utilization of smooth cordgrass (Spartina alterniflora) marsh based on marsh size and degree of isolation from like habitat : do size and site location matter? /Meyer, David L. January 2006 (has links) (PDF)
Thesis (Ph.D.)--University of North Carolina at Wilmington, 2006. / Includes bibliographical references (leaves: 198-208)
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Palynologic determination of historical sediment accumulation rates and paleoecological variation in marshes on the St. Jones River, Delaware, USAMoskalski, Susanne M. January 2005 (has links)
Thesis (M.S.)--University of Delaware, 2005. / Principal faculty advisor: Ronald E. Martin, Dept. of Geology. Includes bibliographical references.
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Ecogeomorphology of Salt Pools of the Webhannet Estuary, Wells, Maine, U.S.A.Wilson, Kristin R. January 2006 (has links) (PDF)
No description available.
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Tidal exchanges of carbon, nitrogen and phosphorus between a Sarcocornia salt-marsh and the Kariega estuary, and the role of salt-marsh brachyura in this transferTaylor, David Ian January 1988 (has links)
Tidal exchanges of organic carbon, nitrogen and phosphorus between a south temperate Sarcocornia marsh and its associated estuary are examined. Subterranean water flow was small, and the hydraulic exchange between the two systems largely surficial. The dominant tidal signal was semi-diurnal, and the extent of inundation of the marsh varied considerably as a consequence of interactions of semi-lunar tidal cycles with changes in daily mean sea level. Annual net fluxes of organic carbon were directed from the marsh to the estuary, but amounted to less than 2% of marsh aerial net primary productivity. This indicates the incompatibility of E.P. Odum's outwelling hypothesis to this marsh-estuarine system. The direction of net flux of organic carbon switched on a time-scale of days. These directions were largely correlated with mesoscale oceanic events, which materially altered the extent of marsh inundation, and which provided evidence of the mutual exclusivity of outwelling of DOC from the marsh and oceanic upwelling. Laboratory mesocosm experiments using intact marsh blocks of sediment from the marsh were conducted to identify the proximate processes and interactions at the marsh-water interface responsible for the variability of marsh-estuarine exchanges. Patterns of fluxes of organic carbon, total nitrogen and phosphorus were markedly different in the structurally contrasted tidal creek and Sarcocornia Zone regions of the marsh. Both regions exported these components, but the fluxes of organic carbon and total phosphorus were significantly larger from the tidal creek than from the Sarcocornia zone, and the opposite applied to nitrogen. The presence of brachyuran crabs . the most numerous macrofauna on the marsh enhanced the flux of carbon, nitrogen and phosphorus from the marsh biocoenosis, largely as a result of the effect of their bioturbation. Evidence is examined which suggests that differential mobilization of nutrients in the two zones by crabs is responsible for biogeochemical coupling of these two regions , which may account for the elevated productivity of salt- marsh systems
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