Human activities have greatly altered the nitrogen (N) cycle, accelerating the rate of N fixation... more Human activities have greatly altered the nitrogen (N) cycle, accelerating the rate of N fixation in landscapes and delivery of N to water bodies. To examine relationships between anthropogenic N inputs and riverine N export, we constructed budgets describing N inputs and losses for 16 catchments, which encompass a range of climatic variability and are major drainages to the coast
A regression model (RivR-N) was developed that predicts the proportion of N removed from streams ... more A regression model (RivR-N) was developed that predicts the proportion of N removed from streams and reservoirs as an inverse function of the water displacement time of the water body (ratio of water body depth to water time of travel). When applied to 16 drainage networks in the eastern U.S., the RivR-N model predicted that 37% to 76% of N input to these rivers is removed during transport through the river networks. Approximately half of that is removed in 1st through 4th order streams which account for 90% of the total stream length. The other half is removed in 5th order and higher rivers which account for only about 10% of the total stream length. Most N removed in these higher orders is predicted to originate from watershed loading to small and intermediate sized streams. The proportion of N removed from all streams in the watersheds (37-76%) is considerably higher than the proportion of N input to an individual reach that is removed in that reach (generally <20%) because of the cumulative effect of continued nitrogen removal along the entire flow path in downstream reaches. This generally has not been recognized in previous studies, but is critical to an evaluation of the total amount of N removed within a river network. At the river network scale, reservoirs were predicted to have a minimal effect on N removal. A fairly modest decrease (<10 percentage points) in the N removed at the river network scale was predicted when a third of the direct watershed loading was to the two highest orders compared to a uniform loading. d Under summer, baseflow conditions.
Eutrophication is arguably the biggest pollution problem facing estuaries globally, with extensiv... more Eutrophication is arguably the biggest pollution problem facing estuaries globally, with extensive consequences including anoxic and hypoxic waters, reduced fishery harvests, toxic algal blooms, and loss of biotic diversity. However, estuaries vary greatly in their susceptibility to eutrophication. The Hudson River estuary receives very high levels of nutrient inputs yet in the past has shown relatively low rates of phytoplankton productivity and is generally considered to be only moderately susceptible to eutrophication. Here, we show that eutrophication and primary production in the Hudson estuary can increase dramatically in response to climatic variation and lowered freshwater discharge from the watershed. During dry summer periods in 1995 and 1997, rates of primary production were substantially higher than those measured during the 1970s, when freshwater discharge tended to be high. In the Hudson, low freshwater discharge increases water
Some 60% of coastal rivers and bays in the U.S. have been moderately to severely degraded by nutr... more Some 60% of coastal rivers and bays in the U.S. have been moderately to severely degraded by nutrient pollution. Both nitrogen (N) and phosphorus (P) contribute to the problem, although for most coastal systems N additions cause more damage. Globally, human activity has increased the flux of N and P from land to the oceans by 2-fold and 3-fold, respectively.
Sulfate inhibits molybdate assimilation by phytoplankton, making molybdate less available in seaw... more Sulfate inhibits molybdate assimilation by phytoplankton, making molybdate less available in seawater than it is in freshwater. As a result, nitrogen fixation and nitrate assimilation, both processes that require molybdenum, may require a greater expenditure of energy in seawater than in freshwater. This may explain in part why coastal marine ecosystems are usually nitrogen limited whereas lakes usually are not.
The Nitrogen Cycle at Regional to Global Scales, 2002
SYBIL P. SEITZINGER1∗, RENÉE V. STYLES1, ELIZABETH W. BOYER2, RICHARD B. ALEXANDER3, GILLES BILLE... more SYBIL P. SEITZINGER1∗, RENÉE V. STYLES1, ELIZABETH W. BOYER2, RICHARD B. ALEXANDER3, GILLES BILLEN4, ROBERT W. HOWARTH5, BERNHARD MAYER6 & NICO VAN BREEMEN7 1Rutgers University, Rutgers/NOAA CMER Program, Institute of Marine ...
Eos, Transactions American Geophysical Union, 2009
During most summers over the past 30 years, bottom dissolved oxygen across a large area of the Lo... more During most summers over the past 30 years, bottom dissolved oxygen across a large area of the Louisiana and upper Texas continental shelf declined to concentrations too low (hypoxia) for most fish and large invertebrate animals to survive. This area is one of the best known ``dead zones&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; proliferating around the world [Diaz and Rosenberg, 2008]. During July 2008, hypoxic
To assess the fate of the large amounts of nitrogen (N) brought into the environment by human act... more To assess the fate of the large amounts of nitrogen (N) brought into the environment by human activities, we constructed N budgets for sixteen large watersheds (475 to 70,189 km2) in the northeastern U.S.A. These watersheds are mainly forested (48-87%), but vary widely with respect to land use and population density. We combined published data and empirical and process models
The Nitrogen Cycle at Regional to Global Scales, 2002
BERNHARD MAYER1,∗ , ELIZABETH W. BOYER2, CHRISTINE GOODALE3, NORBERT A. JAWORSKI4, NICO VAN BREEM... more BERNHARD MAYER1,∗ , ELIZABETH W. BOYER2, CHRISTINE GOODALE3, NORBERT A. JAWORSKI4, NICO VAN BREEMEN5, ROBERT W. HOWARTH6, SYBIL SEITZINGER7, GILLES BILLEN8, KATE LAJTHA9, KNUTE NADELHOFFER10, DOUWE VAN DAM5, LEO J. ...
The Study Group was asked to review the available literature and information, especially that dev... more The Study Group was asked to review the available literature and information, especially that developed since 2000, that would allow them to assess any changes and improvements in the understanding of nutrient sources and flux estimates within the Mississippi and Atchafalaya River basins (MARB) (see Fig. Fig 1.2) and the current ability to use watershed models to route and predict
Adaptive management offers a way to address the pressing need to take steps to manage for factors... more Adaptive management offers a way to address the pressing need to take steps to manage for factors affecting hypoxia in the NGOM in the face of uncertainties. The authors of a recent study undertaken by the National Research Council of the National Academy of Sciences identified six elements of adaptive management that are directly relevant to goal setting and research
This book responds to questions in three general areas: characterization of hypoxia; characteriza... more This book responds to questions in three general areas: characterization of hypoxia; characterization of nutrient fate, transport and sources; and the scientific basis for goals and management options. In the sections below, these questions (shown in italics below) are addressed very briefly with references to those sections of this book where more detailed science on that particular question may be
The hypoxic region along the northern Gulf of Mexico (NGOM) extends up to 125 km offshore and to ... more The hypoxic region along the northern Gulf of Mexico (NGOM) extends up to 125 km offshore and to 60 m water depth, has substantial variability with an average midsummer areal extent of 16,500 km2 (2001–2007), and extends in some years from the Mississippi River mouth westward to Texas coastal waters (Rabalais et al., 2007). This hypoxic region (Fig. 1.1) occurs along a relatively
The first special volume of Limnology and Oceanography,published in 1972, focused on whether phos... more The first special volume of Limnology and Oceanography,published in 1972, focused on whether phosphorus (P) or carbon (C) is the major agent causing eutrophication in aquatic ecosystems. Only slight mention was made that estuaries may behave differently from lakes and that nitrogen (N) may cause eutrophication in estuaries. In the following decade, an understanding of eutrophication in estuaries proceeded in
Nature of the problem Anthropogenic increase of nitrogen in water poses direct threats to human a... more Nature of the problem Anthropogenic increase of nitrogen in water poses direct threats to human and aquatic ecosystems. High nitrate concentrations in drink-• ing water are dangerous for human health. In aquatic ecosystems the nitrogen enrichment produces eutrophication, which is responsible for toxic algal blooms, water anoxia, fi sh kills and habitat and biodiversity loss. Th e continuous nitrogen export to waters reduces the capacity of aquatic ecosystems to absorb, reorganise and adapt to external stress, • increasing their vulnerability to future unexpected natural or climate events.
Due to a rapid increase in human population and development of neighborhood economy over the last... more Due to a rapid increase in human population and development of neighborhood economy over the last few decades, nitrogen (N) and other nutrient inputs in Lake Dianchi drainage basin have increased dramatically, changing the lake's trophic classification from oligotrophic to eutrophic. Although human activities are considered as main causes for the degradation of water quality in the lake, a numerical analysis of the share of the effect of different anthropogenic factors is still largely unexplored. We use the net anthropogenic N input (NANI) method to estimate human-induced N inputs to the drainage basin from 1980 to 2010, which covers the period of dramatic socioeconomic and environmental changes. For the last three decades, NANI increased linearly by a factor of three, from 4700kgkm(-2)year(-1) in 1980 to 12,600kgkm(-2)year(-1) in 2010. The main reason for the rise of NANI was due to fertilizer N application as well as human food and animal feed imports. From the perspective of...
Human activities have greatly altered the nitrogen (N) cycle, accelerating the rate of N fixation... more Human activities have greatly altered the nitrogen (N) cycle, accelerating the rate of N fixation in landscapes and delivery of N to water bodies. To examine relationships between anthropogenic N inputs and riverine N export, we constructed budgets describing N inputs and losses for 16 catchments, which encompass a range of climatic variability and are major drainages to the coast
A regression model (RivR-N) was developed that predicts the proportion of N removed from streams ... more A regression model (RivR-N) was developed that predicts the proportion of N removed from streams and reservoirs as an inverse function of the water displacement time of the water body (ratio of water body depth to water time of travel). When applied to 16 drainage networks in the eastern U.S., the RivR-N model predicted that 37% to 76% of N input to these rivers is removed during transport through the river networks. Approximately half of that is removed in 1st through 4th order streams which account for 90% of the total stream length. The other half is removed in 5th order and higher rivers which account for only about 10% of the total stream length. Most N removed in these higher orders is predicted to originate from watershed loading to small and intermediate sized streams. The proportion of N removed from all streams in the watersheds (37-76%) is considerably higher than the proportion of N input to an individual reach that is removed in that reach (generally <20%) because of the cumulative effect of continued nitrogen removal along the entire flow path in downstream reaches. This generally has not been recognized in previous studies, but is critical to an evaluation of the total amount of N removed within a river network. At the river network scale, reservoirs were predicted to have a minimal effect on N removal. A fairly modest decrease (<10 percentage points) in the N removed at the river network scale was predicted when a third of the direct watershed loading was to the two highest orders compared to a uniform loading. d Under summer, baseflow conditions.
Eutrophication is arguably the biggest pollution problem facing estuaries globally, with extensiv... more Eutrophication is arguably the biggest pollution problem facing estuaries globally, with extensive consequences including anoxic and hypoxic waters, reduced fishery harvests, toxic algal blooms, and loss of biotic diversity. However, estuaries vary greatly in their susceptibility to eutrophication. The Hudson River estuary receives very high levels of nutrient inputs yet in the past has shown relatively low rates of phytoplankton productivity and is generally considered to be only moderately susceptible to eutrophication. Here, we show that eutrophication and primary production in the Hudson estuary can increase dramatically in response to climatic variation and lowered freshwater discharge from the watershed. During dry summer periods in 1995 and 1997, rates of primary production were substantially higher than those measured during the 1970s, when freshwater discharge tended to be high. In the Hudson, low freshwater discharge increases water
Some 60% of coastal rivers and bays in the U.S. have been moderately to severely degraded by nutr... more Some 60% of coastal rivers and bays in the U.S. have been moderately to severely degraded by nutrient pollution. Both nitrogen (N) and phosphorus (P) contribute to the problem, although for most coastal systems N additions cause more damage. Globally, human activity has increased the flux of N and P from land to the oceans by 2-fold and 3-fold, respectively.
Sulfate inhibits molybdate assimilation by phytoplankton, making molybdate less available in seaw... more Sulfate inhibits molybdate assimilation by phytoplankton, making molybdate less available in seawater than it is in freshwater. As a result, nitrogen fixation and nitrate assimilation, both processes that require molybdenum, may require a greater expenditure of energy in seawater than in freshwater. This may explain in part why coastal marine ecosystems are usually nitrogen limited whereas lakes usually are not.
The Nitrogen Cycle at Regional to Global Scales, 2002
SYBIL P. SEITZINGER1∗, RENÉE V. STYLES1, ELIZABETH W. BOYER2, RICHARD B. ALEXANDER3, GILLES BILLE... more SYBIL P. SEITZINGER1∗, RENÉE V. STYLES1, ELIZABETH W. BOYER2, RICHARD B. ALEXANDER3, GILLES BILLEN4, ROBERT W. HOWARTH5, BERNHARD MAYER6 & NICO VAN BREEMEN7 1Rutgers University, Rutgers/NOAA CMER Program, Institute of Marine ...
Eos, Transactions American Geophysical Union, 2009
During most summers over the past 30 years, bottom dissolved oxygen across a large area of the Lo... more During most summers over the past 30 years, bottom dissolved oxygen across a large area of the Louisiana and upper Texas continental shelf declined to concentrations too low (hypoxia) for most fish and large invertebrate animals to survive. This area is one of the best known ``dead zones&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; proliferating around the world [Diaz and Rosenberg, 2008]. During July 2008, hypoxic
To assess the fate of the large amounts of nitrogen (N) brought into the environment by human act... more To assess the fate of the large amounts of nitrogen (N) brought into the environment by human activities, we constructed N budgets for sixteen large watersheds (475 to 70,189 km2) in the northeastern U.S.A. These watersheds are mainly forested (48-87%), but vary widely with respect to land use and population density. We combined published data and empirical and process models
The Nitrogen Cycle at Regional to Global Scales, 2002
BERNHARD MAYER1,∗ , ELIZABETH W. BOYER2, CHRISTINE GOODALE3, NORBERT A. JAWORSKI4, NICO VAN BREEM... more BERNHARD MAYER1,∗ , ELIZABETH W. BOYER2, CHRISTINE GOODALE3, NORBERT A. JAWORSKI4, NICO VAN BREEMEN5, ROBERT W. HOWARTH6, SYBIL SEITZINGER7, GILLES BILLEN8, KATE LAJTHA9, KNUTE NADELHOFFER10, DOUWE VAN DAM5, LEO J. ...
The Study Group was asked to review the available literature and information, especially that dev... more The Study Group was asked to review the available literature and information, especially that developed since 2000, that would allow them to assess any changes and improvements in the understanding of nutrient sources and flux estimates within the Mississippi and Atchafalaya River basins (MARB) (see Fig. Fig 1.2) and the current ability to use watershed models to route and predict
Adaptive management offers a way to address the pressing need to take steps to manage for factors... more Adaptive management offers a way to address the pressing need to take steps to manage for factors affecting hypoxia in the NGOM in the face of uncertainties. The authors of a recent study undertaken by the National Research Council of the National Academy of Sciences identified six elements of adaptive management that are directly relevant to goal setting and research
This book responds to questions in three general areas: characterization of hypoxia; characteriza... more This book responds to questions in three general areas: characterization of hypoxia; characterization of nutrient fate, transport and sources; and the scientific basis for goals and management options. In the sections below, these questions (shown in italics below) are addressed very briefly with references to those sections of this book where more detailed science on that particular question may be
The hypoxic region along the northern Gulf of Mexico (NGOM) extends up to 125 km offshore and to ... more The hypoxic region along the northern Gulf of Mexico (NGOM) extends up to 125 km offshore and to 60 m water depth, has substantial variability with an average midsummer areal extent of 16,500 km2 (2001–2007), and extends in some years from the Mississippi River mouth westward to Texas coastal waters (Rabalais et al., 2007). This hypoxic region (Fig. 1.1) occurs along a relatively
The first special volume of Limnology and Oceanography,published in 1972, focused on whether phos... more The first special volume of Limnology and Oceanography,published in 1972, focused on whether phosphorus (P) or carbon (C) is the major agent causing eutrophication in aquatic ecosystems. Only slight mention was made that estuaries may behave differently from lakes and that nitrogen (N) may cause eutrophication in estuaries. In the following decade, an understanding of eutrophication in estuaries proceeded in
Nature of the problem Anthropogenic increase of nitrogen in water poses direct threats to human a... more Nature of the problem Anthropogenic increase of nitrogen in water poses direct threats to human and aquatic ecosystems. High nitrate concentrations in drink-• ing water are dangerous for human health. In aquatic ecosystems the nitrogen enrichment produces eutrophication, which is responsible for toxic algal blooms, water anoxia, fi sh kills and habitat and biodiversity loss. Th e continuous nitrogen export to waters reduces the capacity of aquatic ecosystems to absorb, reorganise and adapt to external stress, • increasing their vulnerability to future unexpected natural or climate events.
Due to a rapid increase in human population and development of neighborhood economy over the last... more Due to a rapid increase in human population and development of neighborhood economy over the last few decades, nitrogen (N) and other nutrient inputs in Lake Dianchi drainage basin have increased dramatically, changing the lake's trophic classification from oligotrophic to eutrophic. Although human activities are considered as main causes for the degradation of water quality in the lake, a numerical analysis of the share of the effect of different anthropogenic factors is still largely unexplored. We use the net anthropogenic N input (NANI) method to estimate human-induced N inputs to the drainage basin from 1980 to 2010, which covers the period of dramatic socioeconomic and environmental changes. For the last three decades, NANI increased linearly by a factor of three, from 4700kgkm(-2)year(-1) in 1980 to 12,600kgkm(-2)year(-1) in 2010. The main reason for the rise of NANI was due to fertilizer N application as well as human food and animal feed imports. From the perspective of...
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