Fungal Succession and Carbon Quality as Drivers of Nitrogen Removal Capacity in a Constructed Salt Marsh PDF Download
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Author: Sommer Faith Starr
Publisher:
ISBN:
Category :
Languages : en
Pages : 152
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Coastal wetlands mitigate excess nutrient inputs by acting as important sites of denitrification. Despite their role in removing excess nitrogen, coastal wetland area has declined by more than 50% in the 20th century, representing a potential loss of ecosystem service. To restore lost function, managers have devoted much effort to salt marsh restoration and construction. However, constructed marshes have lower function than natural marshes even with similar plant biomass. I conducted two experimental studies to 1) compare nitrogen (N) cycling rates between constructed and natural marshes, and 2) to assess microbial biomass/activity and carbon (C) quality differences as potential factors influencing the return of N cycling in constructed Gulf of Mexico salt marshes. In the first experiment, sediment was collected from a constructed and natural marsh and treated with inhibitors to isolate bacterial and fungal contributions to total denitrification. The constructed marsh had 3x lower total denitrification, 4x lower sediment fungal biomass and lower fungal denitrification than the natural marsh. Increased process rates following microbial inhibition in the natural marsh indicate the occurrence of microbial competition for nitrate. These results suggest that fungi and bacteria contribute differently to rates of incomplete denitrification between natural and constructed marshes and that constructed marshes have lower fungal biomass than natural marshes. In the second experiment, sediment was incubated for 19 days in ~149L aquaria and treated with labile or recalcitrant C under ambient or high nitrate conditions. Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates and microbial biomass were measured at three points during the incubation, and overlying water was sampled every two days for nutrient concentrations. Both denitrification and DNRA rates were similar between marshes, and labile C additions increased DNRA by more than 12x and reduced the ratio of denitrification to DNRA by as much as 22x. Nutrient concentrations were similar between marshes. Both fungal and bacterial biomass were lower in the constructed marsh. Collectively, the results of these experiments highlight that constructed marshes can reach functional recovery after 30 years and remove N as effectively as reference marshes, despite differences in microbial biomass and starting C and N stocks.
Author: Sommer Faith Starr
Publisher:
ISBN:
Category :
Languages : en
Pages : 152
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Book Description
Coastal wetlands mitigate excess nutrient inputs by acting as important sites of denitrification. Despite their role in removing excess nitrogen, coastal wetland area has declined by more than 50% in the 20th century, representing a potential loss of ecosystem service. To restore lost function, managers have devoted much effort to salt marsh restoration and construction. However, constructed marshes have lower function than natural marshes even with similar plant biomass. I conducted two experimental studies to 1) compare nitrogen (N) cycling rates between constructed and natural marshes, and 2) to assess microbial biomass/activity and carbon (C) quality differences as potential factors influencing the return of N cycling in constructed Gulf of Mexico salt marshes. In the first experiment, sediment was collected from a constructed and natural marsh and treated with inhibitors to isolate bacterial and fungal contributions to total denitrification. The constructed marsh had 3x lower total denitrification, 4x lower sediment fungal biomass and lower fungal denitrification than the natural marsh. Increased process rates following microbial inhibition in the natural marsh indicate the occurrence of microbial competition for nitrate. These results suggest that fungi and bacteria contribute differently to rates of incomplete denitrification between natural and constructed marshes and that constructed marshes have lower fungal biomass than natural marshes. In the second experiment, sediment was incubated for 19 days in ~149L aquaria and treated with labile or recalcitrant C under ambient or high nitrate conditions. Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates and microbial biomass were measured at three points during the incubation, and overlying water was sampled every two days for nutrient concentrations. Both denitrification and DNRA rates were similar between marshes, and labile C additions increased DNRA by more than 12x and reduced the ratio of denitrification to DNRA by as much as 22x. Nutrient concentrations were similar between marshes. Both fungal and bacterial biomass were lower in the constructed marsh. Collectively, the results of these experiments highlight that constructed marshes can reach functional recovery after 30 years and remove N as effectively as reference marshes, despite differences in microbial biomass and starting C and N stocks.
Author: Taylor Ledford
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 49
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Book Description
Increased anthropogenic nutrient loading of nitrogen (N) and phosphorus (P) to estuaries and bays can lead to eutrophication, anoxia or hypoxia, and/or loss of native or other important species. Coastal salt marshes help to counteract eutrophication by removing excess N through microbially-mediated denitrification. One important factor that regulates salt marsh N removal is vegetation type, which affects sediment N-removal capacity by modifying redox potential and altering the microbial community structure within sediments. Additionally, plant community structure can alter carbon (C) uptake via photosynthesis and C release via sediment oxidation and organic matter degradation. A 1-year field study was conducted in a salt marsh located on Dauphin Island, AL, where we increased N and P inputs by 20 g N m-2 yr-1/ 1.25 g P m-2 yr-1 (low fertilization) and 40 g N m-2 yr-1/2.5 g P m-2 yr-1 (high fertilization) in plots dominated by either Juncus roemerianus (black needlerush) or Spartina alterniflora (smooth cordgrass). Denitrification was 5X higher in unamended J. roemerianus plots versus S. alterniflora, but denitrification in S. alterniflora was more responsive to fertilization, increasing ten-fold while denitrification in J. roemerianus plots did not respond to fertilization. Gross primary productivity (GPP) was marginally higher (~5%) in control plots of J. roemerianus than in control S. alterniflora plots. High fertilization increased GPP by 27% in S. alterniflora plots, however, GPP did not respond to fertilization in J. roemerianus plots. Additionally, ERCO2 was similar across vegetation types in control plots, and did not respond to fertilization in either vegetation type. Net ecosystem exchange was similar in J. roemerianus and S. alterniflora control plots and did not change in response to N and P additions for either vegetation type. Our results illustrate that while both J. roemerianus and S. alterniflora marshes have the capacity to withstand nutrient loading in the Gulf of Mexico via N removal, S. alterniflora dominated marshes may have a greater capacity to mitigate N inputs. Additionally, in a world with higher nutrient inputs and despite higher GPP in S. alterniflora, both vegetation types will continue to sequester C at similar rates.
Author: Theodore Paul Winfield
Publisher:
ISBN:
Category : Halophytes
Languages : en
Pages : 102
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Author: L. R. Pomeroy
Publisher: Springer Science & Business Media
ISBN: 1461258936
Category : Science
Languages : en
Pages : 277
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Book Description
Ecologists have two long-standing ways to study large ecosystems such as lakes, forests, and salt-marsh estuaries. In the first, which G. E. Hutchinson has called the holological approach, the whole ecosystem is first studied as a "black box," and its components are investigated as needed. In the second, which Hutchinson has called the merological approach, the parts of the system are studied first, and an attempt is then made to build up the whole from them. For long-term studies, the holological approach has special advantages, since the general patterns and tentative hypotheses that are first worked out help direct attention to the components of the system which need to be studied in greater detail. In this approach, teams of investigators focus on major func tions and hypotheses and thereby coordinate their independent study efforts. Thus, although there have been waves, as it were, of investigators and graduate students working on different aspects of the Georgia salt-marsh estuaries (personnel at the Marine Institute on Sapelo Island changes every few years), the emphasis on the holo logical approach has resulted in a highly differentiated and well-coordinated long-term study. Very briefly, the history of the salt-marsh studies can be outlined as follows. First, the general patterns of food chains and other energy flows in the marshes and creeks were worked out, and the nature of imports and exports to and from the system and its subsystems were delimited.
Author: Kenneth Michael Czapla
Publisher:
ISBN:
Category : Nitrogen
Languages : en
Pages :
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Book Description
Salt marshes provide valuable ecosystem services to human society, but are currently under threat from accelerating sea level rise and nutrient enrichment. Carbon (C) and mineral accumulation allow salt marshes to maintain elevation above sea level and survive. Anthropogenic nitrogen (N) loading is increasing in many salt marshes, causing negative impacts on marsh resilience such as increased decomposition and decreased below-ground production. However, increasing N may also have simultaneous positive effects such as increased primary production and above-ground biomass, surface sediment accretion, and denitrification rates, which remove excess N from coastal waters. Many studies have been conducted to determine the effect of fertilization on salt marsh resilience; however, inconsistent conclusions across studies may result from varying physical and chemical characteristics across salt marsh locations that impact responses to fertilization. In this dissertation we performed experiments to determine how C cycling, C accumulation, N cycling, and microbial communities vary in both natural and fertilized salt marsh locations at Marine Corps Base Camp Lejeune, North Carolina, USA. Here we show that edge marsh with a high elevation berm had lower pore water sulfide, ammonium, dissolved organic C (DOC), and dissolved organic C (DIC) concentrations than interior marsh, which displayed longer pore water residence time and flooding duration with high pore water sulfide, ammonium, DOC, and DIC concentrations. Respiration and primary production were higher in the edge marsh compared to the interior marsh but net ecosystem CO2 exchange (NEE) was nearly balanced at all sites. Fertilization had a much greater impact on edge than interior NEE, shifting edge NEE toward net CO2 emission. Net ecosystem carbon balance (NECB), based on the mass balance of NEE, lateral C export, and sediment C deposition for edge and interior sites was calculated to examine the effect of fertilization on net C accumulation. NECB displayed a net C gain in the interior marsh but a large net C loss on the edge; fertilization stimulated more C loss on the edge than in the interior. When extrapolating NECB to the entire marsh, C loss on the edge greatly impacted the whole marsh C budget, causing the marsh to have a net loss of 53 kg C yr-1 under natural conditions and a five-fold increase in C loss with fertilization. N removal through denitrification was greater on the edge and increased with fertilization, but was not affected by fertilization at the site with highest sulfide concentrations. DNRA, which retains N in the marsh, dominated over denitrification only during summer, and varied widely across locations. Fertilization generally decreased DNRA rates. Microbial community composition was distinct on the edge vs. interior, with differences driven by the differences in pore water sulfide, ammonium, DOC, and DIC. The edge was a hotspot for nitrifying microbial communities. The processes of respiration and denitrification were positively correlated to the relative abundance of sulfate reducers and ammonia oxidizers, respectively. Thus, we conclude that fertilization had an overall negative effect on marsh resilience with especially large impacts on edge marsh.
Author: Herbert L. Windom
Publisher:
ISBN:
Category : Heavy metals
Languages : en
Pages : 43
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Experimental raceways were constructed in a salt marsh adjacent to a dredged material confinement area to evaluate the use of this environment as an overland flow advanced treatment system for the effluent resulting from dredged material disposal. The research program was designed to determine the ability of the salt marsh systems to remove nitrogen, phosphorus, iron, manganese, cadmium, copper, nickel and zinc from the effluent. Application rates varied between 0.06 and 3.7 acre inches per day and the concentrations of the contaminants were determined in the effluent from the disposal area and the discharge from the experimental system. Although the results of this study clearly indicate that nutrients and heavy metal concentrations in effluents from dredged material disposal areas can be reduced during passage through a salt marsh, conclusions as to the efficiency of removal may be influenced by the size of the experimental system used. Large scale studies should be conducted to better judge the applicability of this approach to advanced treatment of dredged disposal area effluents.
Author: Michael Robert Hamersley
Publisher:
ISBN:
Category : Denitrification
Languages : en
Pages : 188
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(Cont.) Allochthonous denitrification accounted for 39% of total sediment denitrification (2.7 mol N m−2 yr−1). 46% of remineralized ammonium was denitrified, while the contribution of autochthonous denitrification to 02 and C02 fluxes was 18% and 10%, respectively. A 15N-ammonium tracer was used to study competition between plants and nitrifying bacteria for remineralized ammonium. In undisturbed sediments of Spartina alterniflora, plant uptake out-competed nitrification-denitrification, with plant uptake accounting for 66% of remineralized ammonium during the growing season. Under N fertilization (15.5 mol m−2 yr−1), both plant N uptake and denitrification increased, but denitrification dominated, accounting for 72% of the available N. When plant uptake was hydrologically suppressed, nitrification-denitrification was stimulated by the excess N, shifting the competitive balance toward denitrification.
Author: Sarah Goldsmith
Publisher:
ISBN:
Category : Hyperspectral imaging
Languages : en
Pages : 106
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Book Description
"Change in the coastal zone is accelerating with external forcing by sea-level rise, nutrient loading, drought and over-harvest is impacting salt marshes. Understanding marsh resilience, including recovery from coastal storms and detection of stress, is essential for conservation and prediction of ecosystem services. The ‘chronosequence approach’ of predicting future state change by examining ecosystem structure and function in existing ecosystems of different ages is a powerful tool, but assumes that the past mimics the future, and time is the dominant driver of change. This approach was evaluated by replicating a 1995 salt marsh chronosequence study in back-barrier marshes ranging from 4 to >170 yr old on Hog Island, Virginia. Physico-chemical properties, such as porewater redox potential and sediment organic matter and nutrients, followed predictable age-related patterns. However, invertebrate abundance, plant biomass, and sediment grain size instead seemed to respond to sea level rise and stochastic die-off and sand deposition. Thus, while time drives the intrinsic evolution of some physico-chemical components, extrinsic drivers exert a strong influence on key biotic-abiotic feedbacks. Exacerbation of external forcing may push the trajectory of marsh succession away from a predictable trajectory, limiting ecosystem services. This rapid evolution of marsh state makes the ability to detect stressors prior to marsh collapse important. Hyperspectral imagery of plants was collected in marshes of varying age/stressor characteristics, including salinity, sediment redox potential and nitrogen availability, and in the greenhouse, where environmental conditions were manipulated. Models developed to stressors based on plant spectral response were useful for salinity and nitrogen within the greenhouse or within the field, but were not transferable from lab to field. This study is an important step towards development of a remote sensing tool for tracking of ecosystem development, marsh health, and future ecosystem services."--Abstract.
Author: Jeff Cornell
Publisher:
ISBN:
Category :
Languages : en
Pages : 78
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Author: Harm van Wijnen
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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