Streamflow and nutrient fluxes of the Mississippi-Atchafalaya River Basin and subbasins for the period of record through 2005

Aulenbach, Brent T.; Buxton, Herbert T.; Battaglin, William A.; Coupe, Richard H.

doi:10.3133/ofr20071080

Cited by 116 publications

(132 citation statements)

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“…Climatologies from Mexican river discharges were derived from He et al (2011), Munoz-Salinas andCastillo (2015), and Martinez-Lopez and Zavala-Hidalgo (2009). Monthly observations of dissolved inorganic nutrients (nitrate, ammonia, silicate) and organic nitrogen in the MS-A rivers were retrieved from the USGS (http://toxics.usgs.gov, last access: 21 August 2017; Aulenbach et al, 2007). Following Yu et al (2015), the MS-A particulate organic nitrogen (PON) was determined as the difference between unfiltered and filtered total Kjendahl nitrogen (TKN), while the dissolved organic nitrogen (DON) was estimated as the difference between filtered TKN and ammonia.…”

Section: Model Descriptionmentioning

confidence: 99%

“…Productivity in this last region is strongly influenced by river runoff. The Mississippi-Atchafalaya (MS-A) river system is the largest river input with a mean river discharge of 21 524 m 3 s −1 (Aulenbach et al, 2007), contributing more than 80 % of the entire dissolved inorganic nitrogen (DIN) load into the northern GoM (Xue et al, 2013). The large plankton production and vertical stratification driven by the MS-A river system discharge promote the development of a hypoxic bottom layer a few meters thick off Louisiana and Texas during summer (Obenour et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Seasonal patterns in phytoplankton biomass across the northern and deep Gulf of Mexico: a numerical model study

et al. 2018

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Abstract. Biogeochemical models that simulate realistic lower-trophic-level dynamics, including the representation of main phytoplankton and zooplankton functional groups, are valuable tools for improving our understanding of natural and anthropogenic disturbances in marine ecosystems. Previous three-dimensional biogeochemical modeling studies in the northern and deep Gulf of Mexico (GoM) have used only one phytoplankton and one zooplankton type. To advance our modeling capability of the GoM ecosystem and to investigate the dominant spatial and seasonal patterns of phytoplankton biomass, we configured a 13-component biogeochemical model that explicitly represents nanophytoplankton, diatoms, micro-, and mesozooplankton. Our model outputs compare reasonably well with observed patterns in chlorophyll, primary production, and nutrients over the Louisiana-Texas shelf and deep GoM region. Our model suggests silica limitation of diatom growth in the deep GoM during winter and near the Mississippi delta during spring. Model nanophytoplankton growth is weakly nutrient limited in the Mississippi delta year-round and strongly nutrient limited in the deep GoM during summer. Our examination of primary production and net phytoplankton growth from the model indicates that the biomass losses, mainly due to zooplankton grazing, play an important role in modulating the simulated seasonal biomass patterns of nanophytoplankton and diatoms. Our analysis further shows that the dominant physical process influencing the local rate of change of model phytoplankton is horizontal advection in the northern shelf and vertical mixing in the deep GoM. This study highlights the need for an integrated analysis of biologically and physically driven biomass fluxes to better understand phytoplankton biomass phenologies in the GoM.

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Section: Model Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seasonal patterns in phytoplankton biomass across the northern and deep Gulf of Mexico: a numerical model study

et al. 2018

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“…Monitoring data on discharge and nutrient loads, derived from long-term flux estimations of periodic water quality samples, for the main stem of the Mississippi and Atchafalaya Rivers (Table 1) as well as upstream subbasins (Table 2) were obtained through long-term records from two U.S. Geological Survey (USGS) data sets [Aulenbach et al, 2007;Upper Midwest Environmental Sciences Center, 2006]. These data sets were chosen because they been used in the past to assess the influence of landscape and hydrologic factors on the flux of individual nutrients in the Mississippi-Atchafalaya River Basin [Donner, 2003;Houser and Richardson, 2010], and they contain the long, uninterrupted time series of the flux of different species of the three key nutrients (N, P, and Si) in large river basins necessary for this analysis.…”

Section: Data Sourcesmentioning

confidence: 99%

Sensitivity of stoichiometric ratios in the Mississippi River to hydrologic variability

et al. 2014

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(2014), Sensitivity of stoichiometric ratios in the Mississippi River to hydrologic variability, J. Geophys. Res. Biogeosci., 119, 1049-1062, doi:10.1002 AbstractThe ratio of key elements such as nitrogen, phosphorus, and silica determines nutrient limitations that are important to regulating primary productivity and species composition in aquatic ecosystems. The flux of these nutrients in streams, as dissolved constituents or as particulate matter, is sensitive to variability in flow conditions. Most previous research on nutrient flux and hydrologic variability has focused on the response of individual elements, especially nitrogen, to changes in flow over time. This study examines how the ratios of total nitrogen to total phosphorus (N:P) and total nitrogen to dissolved silica (N:Si) respond to hydrologic variability in the Mississippi-Atchafalaya River Basin. A doubling of the discharge by the Mississippi and Atchafalaya Rivers to the Gulf of Mexico is found to increase the N:P by 10% and the N:Si by 4%. Analysis of data from upstream stations indicates that the N:P increases with discharge in subbasins with intensive row crop agriculture and high fertilizer application rates but is less predictable in other subbasins. Conversely, the response of N:Si to discharge does not vary predictably with the land use characteristics of the subbasin. The response of the nutrient ratios to variability in flow may be linked to the different sources and sinks of each nutrient, as well as the difference between the dominant transport pathways of each nutrient. High-resolution data and models that describe the dissolved and particulate nutrient cycling are needed to assess the relative contribution of different drivers to these observed patterns and to identify the response of nutrient ratios to hydrologic variability under future land use and climate change.

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“…Using USGS-estimated (28) monthly nutrient values at St. Francisville, LA, we obtain the baseline structural component of model-predicted hypoxia h base = hðN obs Þ. To compare the baseline hypoxia estimates with the outcomes from model simulations, which assign CEAP scenarios to 8-digit subwatersheds, we use the "delta change" method (e.g., ref.…”

Section: Methodsmentioning

confidence: 99%

Cost-effective targeting of conservation investments to reduce the northern Gulf of Mexico hypoxic zone

Rabotyagov

Campbell

White

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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A seasonally occurring summer hypoxic (low oxygen) zone in the northern Gulf of Mexico is the second largest in the world. Reductions in nutrients from agricultural cropland in its watershed are needed to reduce the hypoxic zone size to the national policy goal of 5,000 km 2 (as a 5-y running average) set by the national Gulf of Mexico Task Force's Action Plan. We develop an integrated assessment model linking the water quality effects of cropland conservation investment decisions on the more than 550 agricultural subwatersheds that deliver nutrients into the Gulf with a hypoxic zone model. We use this integrated assessment model to identify the most cost-effective subwatersheds to target for cropland conservation investments. We consider targeting of the location (which subwatersheds to treat) and the extent of conservation investment to undertake (how much cropland within a subwatershed to treat). We use process models to simulate the dynamics of the effects of cropland conservation investments on nutrient delivery to the Gulf and use an evolutionary algorithm to solve the optimization problem. Model results suggest that by targeting cropland conservation investments to the most cost-effective location and extent of coverage, the Action Plan goal of 5,000 km 2 can be achieved at a cost of $2.7 billion annually. A large set of costhypoxia tradeoffs is developed, ranging from the baseline to the nontargeted adoption of the most aggressive cropland conservation investments in all subwatersheds (estimated to reduce the hypoxic zone to less than 3,000 km 2 at a cost of $5.6 billion annually).waters are proliferating worldwide, impacting more than 400 coastal marine systems (1, 2). A major cause of their formation and persistence is nutrient pollution (from agricultural, urban, and other sources) delivered from their watersheds. Excess nutrients threaten not only coastal waters (3), but also pose problems within the watersheds (4), diminishing the quantity and quality of the ecosystem services they provide (5-7). For example, 55 percent of US streams are in "poor" condition (4), drinking water supplies are compromised by high nitrate concentrations, harmful algal blooms risk human health, and commercial fisheries are threatened. The second-largest hypoxic zone in the global ocean is in the northern Gulf of Mexico and covers an area averaging more than 14,500 km 2 in the summers of 2004 through 2013 (8). The documentation of this pervasive phenomenon led to the 2008 Action Plan for Reducing, Mitigating, and Controlling Hypoxia in the northern Gulf of Mexico (9). The Action Plan, a joint federal-state effort, set the goal of reducing the size of Gulf hypoxia to less than 5,000 km 2 over a 5-y period.Current analysis of the sources of nutrient loads from the Mississippi-Atchafalaya River Basin (hereafter referred to as the Mississippi Basin) into the Gulf indicate that agricultural sources in the watershed contribute 80% of the delivered nitrogen (N) and more than 60% of the delivered phosphorus (P) (10).A number of cr...

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Streamflow and nutrient fluxes of the Mississippi-Atchafalaya River Basin and subbasins for the period of record through 2005

Cited by 116 publications

References 0 publications

Seasonal patterns in phytoplankton biomass across the northern and deep Gulf of Mexico: a numerical model study

Seasonal patterns in phytoplankton biomass across the northern and deep Gulf of Mexico: a numerical model study

Sensitivity of stoichiometric ratios in the Mississippi River to hydrologic variability

Cost-effective targeting of conservation investments to reduce the northern Gulf of Mexico hypoxic zone

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