Nitrogen Cycling in Coastal Marine Environments
Nitrogen Cycling in Coastal Marine Environments

Author: T. Henry Blackburn

Publisher:

Published: 1988-03-21

Total Pages: 488

ISBN-13:

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Nitrogen discharge to the coastal environment has been increasing, posing the threat of accelerated eutrofication. Considerable research has been conducted in recent years to examine the impact of the nitrogen loading in coastal ecosystems. Based on proceedings from a SCOPE symposium held at the University of Aarhus in July of 1985, this volume covers a variety of up-to-date developments in research on nitrogen cycling in coastal marine environments. Topics include the role of nitrogen in algal productivity, regeneration of nutrients in the water column and the sediments, and the flow of nitrogen in coastal ecosystems.

Nitrogen in the Marine Environment
Nitrogen in the Marine Environment

Author: Edward J. Carpenter

Publisher: Elsevier

Published: 2013-10-22

Total Pages: 919

ISBN-13: 1483288293

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Nitrogen in the Marine Environment provides information pertinent to the many aspects of the nitrogen cycle. This book presents the advances in ocean productivity research, with emphasis on the role of microbes in nitrogen transformations with excursions to higher trophic levels. Organized into 24 chapters, this book begins with an overview of the abundance and distribution of the various forms of nitrogen in a number of estuaries. This text then provides a comparison of the nitrogen cycling of various ecosystems within the marine environment. Other chapters consider chemical distributions and methodology as an aid to those entering the field. This book discusses as well the enzymology of the initial steps of inorganic nitrogen assimilation. The final chapter deals with the philosophy and application of modeling as an investigative method in basic research on nitrogen dynamics in coastal and open-ocean marine environments. This book is a valuable resource for plant biochemists, microbiologists, aquatic ecologists, and bacteriologists.

Concepts and Controversies in Tidal Marsh Ecology
Concepts and Controversies in Tidal Marsh Ecology

Author: M.P. Weinstein

Publisher: Springer Science & Business Media

Published: 2000-10-31

Total Pages: 862

ISBN-13: 0792360192

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Tidal salt marshes are viewed as critical habitats for the production of fish and shellfish. As a result, considerable legislation has been promulgated to conserve and protect these habitats, and much of it is in effect today. The relatively young science of ecological engineering has also emerged, and there are now attempts to reverse centuries-old losses by encouraging sound wetland restoration practices. Today, tens of thousands of hectares of degraded or isolated coastal wetlands are being restored worldwide. Whether restored wetlands reach functional equivalency to `natural' systems is a subject of heated debate. Equally debatable is the paradigm that depicts tidal salt marshes as the `great engine' that drives much of the secondary production in coastal waters. This view was questioned in the early 1980s by investigators who noted that total carbon export, on the order of 100 to 200 g m-2 y-1 was of much lower magnitude than originally thought. These authors also recognized that some marshes were either net importers of carbon, or showed no net exchange. Thus, the notion of `outwelling' has become but a single element in an evolving view of marsh function and the link between primary and secondary production. The `revisionist' movement was launched in 1979 when stable isotopic ratios of macrophytes and animal tissues were found to be `mismatched'. Some eighteen years later, the view of marsh function is still undergoing additional modification, and we are slowly unraveling the complexities of biogeochemical cycles, nutrient exchange, and the links between primary producers and the marsh/estuary fauna. Yet, since Teal's seminal paper nearly forty years ago, we are not much closer to understanding how marshes work. If anything, we have learned that the story is far more complicated than originally thought. Despite more than four decades of intense research, we do not yet know how salt marshes function as essential habitat, nor do we know the relative contributions to secondary production, both in situ or in the open waters of the estuary. The theme of this Symposium was to review the status of salt marsh research and revisit the existing paradigm(s) for salt marsh function. Challenge questions were designed to meet the controversy head on: Do marshes support the production of marine transient species? If so, how? Are any of these species marsh obligates? How much of the production takes place in situ versus in open waters of the estuary/coastal zone? Sessions were devoted to reviews of landmark studies, or current findings that advance our knowledge of salt marsh function. A day was also devoted to ecological engineering and wetland restoration papers addressing state-of-the-art methodology and specific case histories. Several challenge papers arguing for and against our ability to restore functional salt marshes led off each session. This volume is intended to serve as a synthesis of our current understanding of the ecological role of salt marshes, and will, it is hoped, pave the way for a new generation of research.

The Role of Denitrification in the Nitrogen Cycle of New England Salt Marshes
The Role of Denitrification in the Nitrogen Cycle of New England Salt Marshes

Author: Michael Robert Hamersley

Publisher:

Published: 2002

Total Pages: 188

ISBN-13:

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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.

Dynamics of Carbon and Nitrogen in a Southern California Salt Marsh
Dynamics of Carbon and Nitrogen in a Southern California Salt Marsh

Author: Theodore Paul Winfield

Publisher:

Published: 1980

Total Pages: 182

ISBN-13:

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This study explores three functional aspects of the salt marsh-estuarine ecosystem in the Tijuana Estuary (southern California): primary productivity of the salt marsh vascular plants, organic carbon cycle, and inorganic nitrogen cycle. The productivity study was designed to test the hypothesis that the salt marsh vascular plants in the Tijuana Estuary are not as productive as those in eastern coastal marshes. Spartina foliosa was found to be the most productive individual species in terms of dry weight and carbon, but succulent plant species as a group contributed more to the overall vascular plant productivity. On a dry weight basis net above-ground primary productivity (NAPP) averaged 0.8kg/m('2)/yr which was approximately 240g C/m('2)/yr. Carbon productivity of vascular plants was low in comparison to Atlantic and Gulf of Mexico marshes, and differences were attributed to the more saline soils of southern California. Standing dead biomass and litter averaged over the total marsh surface were constant throughout the study period. The decomposition rate of selected grass species was slower than that for succulent species and the decomposition rate for all plant material varied with elevation, being faster in the tidal creeks and slowest in the upper marsh. The organic carbon study was designed to provide data on the quality and quantity of the various forms of organic carbon being transported to and from the marsh surface in the tidal waters. The data were used in conjunction with those generated from the productivity study to evaluate the hypothesis that the Tijuana Estuary salt marsh exports a substantial amount (45-50%) of the organic carbon produced and that a major portion of the export is as particulate organic carbon (POC). The concentration of POC, dissolved organic carbon (DOC), ATP and chlorophyll a was measured in water samples collected periodically during a tidal cycle each month. Organic carbon was exported as DOC (40-110g C/m('2)/yr) and showed a slight import of POC (5-6g C/m('2)/yr). POC was mainly detrital carbon as opposed to biomass carbon. The Tijuana Estuary salt marsh exports substantially less than 50% of its NAPP, and export is in the dissolved form as opposed to particulate. Results of this and other recent studies suggest that a re-evaluation of salt marsh carbon flow models is needed. The purpose of the inorganic nitrogen study was to document the distribution of ammonium, nitrate and nitrite in the tidal waters draining the Tijuana Estuary salt marsh and to evaluate the tidal waters as a source of nitrogen for salt marsh vegetation. The inorganic nitrogen cycle was characterized by the annual import of ammonium and slight annual export of nitrate. Ammonium was found to be the dominant form of inorganic nitrogen except in the late spring when nitrate was dominant. Inorganic nitrogen import totalled 1.1 - 2.16g N/m('2)/yr. The import of inorganic nitrogen accounted for 28% of the nitrogen required by salt marsh vascular plants, but only 6% of the combined productivity of vascular plants and benthic algae. Nitrogen regeneration processes within the salt marsh are important in meeting the nitrogen needs of salt marsh vegetation.

Fungal Succession and Carbon Quality as Drivers of Nitrogen Removal Capacity in a Constructed Salt Marsh
Fungal Succession and Carbon Quality as Drivers of Nitrogen Removal Capacity in a Constructed Salt Marsh

Author: Sommer Faith Starr

Publisher:

Published: 2020

Total Pages: 152

ISBN-13:

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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.

Biogeochemistry of Wetlands
Biogeochemistry of Wetlands

Author: K. Ramesh Reddy

Publisher: CRC Press

Published: 2022-09-10

Total Pages: 926

ISBN-13: 0429531931

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The globally important nature of wetland ecosystems has led to their increased protection and restoration as well as their use in engineered systems. Underpinning the beneficial functions of wetlands are a unique suite of physical, chemical, and biological processes that regulate elemental cycling in soils and the water column. This book provides an in-depth coverage of these wetland biogeochemical processes related to the cycling of macroelements including carbon, nitrogen, phosphorus, and sulfur, secondary and trace elements, and toxic organic compounds. In this synthesis, the authors combine more than 100 years of experience studying wetlands and biogeochemistry to look inside the black box of elemental transformations in wetland ecosystems. This new edition is updated throughout to include more topics and provide an integrated view of the coupled nature of biogeochemical cycles in wetland systems. The influence of the elemental cycles is discussed at a range of scales in the context of environmental change including climate, sea level rise, and water quality. Frequent examples of key methods and major case studies are also included to help the reader extend the basic theories for application in their own system. Some of the major topics discussed are: Flooded soil and sediment characteristics Aerobic-anaerobic interfaces Redox chemistry in flooded soil and sediment systems Anaerobic microbial metabolism Plant adaptations to reducing conditions Regulators of organic matter decomposition and accretion Major nutrient sources and sinks Greenhouse gas production and emission Elemental flux processes Remediation of contaminated soils and sediments Coupled C-N-P-S processes Consequences of environmental change in wetlands# The book provides the foundation for a basic understanding of key biogeochemical processes and its applications to solve real world problems. It is detailed, but also assists the reader with box inserts, artfully designed diagrams, and summary tables all supported by numerous current references. This book is an excellent resource for senior undergraduates and graduate students studying ecosystem biogeochemistry with a focus in wetlands and aquatic systems.