Effects of tributary inputs on nutrient export from the Mississippi and Atchafalaya Rivers to the Gulf of Mexico

2010 ◽  
Vol 61 (9) ◽  
pp. 1029 ◽  
Author(s):  
Shuiwang Duan ◽  
Thomas S. Bianchi ◽  
Peter H. Santschi ◽  
Rainer M. W. Amon
Keyword(s):  
Gulf Of Mexico ◽  
Mississippi River ◽  
Soluble Reactive Phosphorus ◽  
Suspended Sediments ◽  
River System ◽  
Nitrogen And Phosphorus ◽  
Channel Processes ◽  
Particulate Nitrogen ◽  
Nutrient Mass Balance ◽  
Reactive Phosphorus

In order to better understand the seasonal patterns of nutrient loadings from the Mississippi River to the Gulf of Mexico, nutrient mass balance analyses were performed for the Mississippi River system to separate the effects of primary tributary inputs from in-channel processes. Our results showed that seasonal changes in dissolved inorganic nutrients resulted from conservative mixing of primary tributaries. Maximal values of nitrate plus nitrite (NO3+2) and soluble reactive phosphorus (SRP) fluxes during May through July were largely attributed to inputs from the upper Mississippi River (UMR), which was highest in NO3+2 and SRP levels and contributed more water during this period. Mass balances also showed net losses of particulate nitrogen and phosphorus (29% and 18%, respectively), with the highest values occurring during the falling stage. We speculate that one possible reason was retention of coarse suspended sediments that were mainly derived from the Missouri River. The loss of dissolved organic nitrogen and phosphorus was also apparent (∼12% and 20%, respectively), and the largest loss occurred during summer. This study highlights the importance of divergent processes in controlling different forms of nutrients in large rivers.

Temperature Control on Soluble Reactive Phosphorus in the Lower Mississippi River?

2010 ◽  
Vol 34 (1) ◽  
pp. 78-89 ◽  
Author(s):  
Shuiwang Duan ◽  
Rainer Amon ◽  
Thomas S. Bianchi ◽  
Peter H. Santschi
Keyword(s):  
Temperature Control ◽  
Mississippi River ◽  
Soluble Reactive Phosphorus ◽  
Lower Mississippi River ◽  
Reactive Phosphorus

scholarly journals Controls on Nutrient Cycling in Estuarine Mangrove Lake Sediments

2021 ◽  
Vol 9 (6) ◽  
pp. 626
Author(s):  
Michael S. Owens ◽  
Stephen P. Kelly ◽  
Thomas A. Frankovich ◽  
David T. Rudnick ◽  
James W. Fourqurean ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Algal Blooms ◽  
Aquatic Macrophyte ◽  
Soluble Reactive Phosphorus ◽  
Florida Bay ◽  
Nitrogen And Phosphorus ◽  
Phosphorus Species ◽  
Gross Photosynthesis ◽  
Sediment Respiration ◽  
Reactive Phosphorus

We estimated the net exchange of nitrogen and phosphorus species using core incubations under light and dark conditions in estuarine lakes that are the aquatic interface between the freshwater Everglades and marine Florida Bay. These lakes and adjacent shallow water Florida Bay environments are sites where the restoration of hydrological flows will likely have the largest impact on salinity. Sediment respiration, measured by oxygen uptake, averaged (±S.D.) −2400 ± 1300, −300 ± 1000, and 1900 ± 1400 μmol m−2 h−1 for dark incubations, light incubations, and gross photosynthesis estimates, respectively, with dark incubations consistent with oxygen uptake measured by microelectrode profiles. Although most fluxes of soluble reactive phosphorus, nitrate, and N2–N were low under both light and dark incubation conditions, we observed a number of very high efflux events of NH4+ during dark incubations. A significant decrease in NH4+flux was observed in the light. The largest differences between light and dark effluxes of NH4+ occurred in lakes during periods of low coverage of the aquatic macrophyte Chara hornemannii Wallman, with NH4+ effluxes > 200 μmol m−2 h−1. Increasing freshwater flow from the Everglades is expected to expand lower salinity environments suitable for Chara, and therefore, diminish the sediment NH4+ effluxes that may fuel algal blooms.

Prescribed fire, soils, and stream water chemistry in a watershed in the Lake Tahoe Basin, California

2004 ◽  
Vol 13 (1) ◽  
pp. 27 ◽  
Author(s):  
Scott L. Stephens ◽  
Thomas Meixner ◽  
Mark Poth ◽  
Bruce McGurk ◽  
Dale Payne
Keyword(s):  
Prescribed Fire ◽  
Stream Water ◽  
Soluble Reactive Phosphorus ◽  
Lake Tahoe ◽  
Prescribed Fires ◽  
Lake Tahoe Basin ◽  
Nitrogen And Phosphorus ◽  
Stream Water Chemistry ◽  
Tahoe Basin ◽  
Reactive Phosphorus

Before Euro-American settlement fire was a common process in the forests of the Lake Tahoe Basin. The combination of drought, fire suppression, and past harvesting has produced ecosystems that are susceptible to high-severity wildfires. Consequently, a program of prescribed fire has been recommended but there is incomplete understanding of the ecological effects of fuels treatments, especially with regard to how treatments will affect the flow of nutrients to Lake Tahoe. Nitrogen and phosphorus are the most important nutrients affecting algal growth, and thus lake clarity. Existing data demonstrate a long-term shift from a co-limitation by both nitrogen and phosphorus to phosphorus limitation. Two high-consumption, moderate-intensity prescribed fires were conducted to determine their effects on soil and stream water chemistry. Stream water calcium concentrations increased in burned watersheds whereas soluble reactive phosphorus concentrations were not significantly different. Prescribed fires released calcium and raised soil pH and this may have resulted in the incorporation of phosphorus into insoluble forms. Stream monitoring data indicates water quality effects last for ~3 months. Prescribed fires did not significantly increase the amount of soluble reactive phosphorus in stream waters. However, additional research is needed to determine if prescribed fire increases erosion or movement of particulate P, particularly in areas with steep slopes.

scholarly journals Nutrient concentrations and fluxes for podzolic and gley soils at Plynlimon, mid-Wales: implications for modelling inorganic nitrogen and phosphorus in upland UK environments

2002 ◽  
Vol 6 (3) ◽  
pp. 403-420
Author(s):  
C. Neal
Keyword(s):  
Inorganic Nitrogen ◽  
Soluble Reactive Phosphorus ◽  
Sitka Spruce ◽  
Nutrient Concentrations ◽  
Nitrogen And Phosphorus ◽  
Podzolic Soils ◽  
Forestry Management ◽  
Order Of Magnitude ◽  
Reactive Phosphorus ◽  
Stream Nitrate

Abstract. The effect of felling on stream nitrate, ammonium and soluble reactive phosphate (SRP) concentrations is examined for acidic and acid sensitive Sitka Spruce afforested catchments with podzolic and gley soils in mid-Wales. For the streams draining the felled podzolic areas, the concentrations of nitrate can be up to an order of magnitude higher than pre-fell values and post-fell concentrations can even be lower than the pre-fell values. Felling for the podzolic soils barely leads to any changes in ammonium or SRP concentration. For the gley soils, felling results in an order of magnitude increase in nitrate, ammonium and SRP for a small drainage ditch, but the pulse is much reduced before it reaches the main Nant Tanllwyth channel. Rather, within-catchment and within-stream processes not only imbibe nitrate, ammonium and SRP fluxes generated, but in the case of nitrate, concentrations with- and post-felling are lower than pre-felling concentrations. The flux changes involved are described in terms of (a) input-output relationships and (b) "felling disruption" and "felling recovery responses". The findings are linked to issues of hydrobiological controls and forestry management. Keywords: Plynlimon, Hafren, Hore, streams, nitrate, ammonium, SRP, phosphorus, soluble reactive phosphorus, phosphate, orthophosphate, Sitka spruce, forestry, felling, podzol, gley

scholarly journals A coupled physical-biological model of the Northern Gulf of Mexico shelf: model description, validation and analysis of phytoplankton variability

2011 ◽  
Vol 8 (1) ◽  
pp. 121-156 ◽  
Author(s):  
K. Fennel ◽  
R. Hetland ◽  
Y. Feng ◽  
S. DiMarco
Keyword(s):  
Organic Matter ◽  
Gulf Of Mexico ◽  
Primary Production ◽  
Mississippi River ◽  
River System ◽  
Biological Model ◽  
Model Description ◽  
Ecological Gradient ◽  
Northern Gulf Of Mexico ◽  
Plume Region

Abstract. The Texas-Louisiana shelf in the Northern Gulf of Mexico receives large inputs of nutrients and freshwater from the Mississippi/Atchafalaya River system. The nutrients stimulate high rates of primary production in the river plume, which contributes to the development of a large and recurring hypoxic area in summer. The mechanistic links between hypoxia and river discharge of freshwater and nutrients are complex as the accumulation and vertical export of organic matter, the establishment and maintenance of vertical stratification, and the microbial degradation of organic matter are controlled by a non-linear interplay of factors. We present results from a realistic, 3-dimensional, physical-biological model that includes the processes thought to be of first order importance to hypoxia formation and demonstrate that the model realistically reproduces many features of observed nitrate and phytoplankton dynamics including observed property distributions and rates. We then contrast the environmental factors and phytoplankton source and sink terms characteristic of three model subregions that represent an ecological gradient from eutrophic to oligotrophic conditions. We analyze specifically the reasons behind the counterintuitive observation that primary production in the light-limited plume region near the Mississippi River delta is positively correlated with river nutrient input. We find that, while primary production and phytoplankton biomass are positively correlated with nutrient load, phytoplankton growth rate is not. This suggests that accumulation of biomass in this region is not primarily controlled bottom up by nutrient-stimulation, but top down by systematic differences in the loss processes. We hypothesize that increased retention of river water in high discharge years explains this phenomenon.

A laboratory culture system for pathological and physiological studies of rooted aquatic plants

1984 ◽  
Vol 62 (11) ◽  
pp. 2290-2296 ◽  
Author(s):  
J. P. Hoffmann ◽  
J. A. Colman ◽  
K. M. Kutchera ◽  
E. V. Nordheim ◽  
J. H. Andrews
Keyword(s):  
Growth Rate ◽  
Myriophyllum Spicatum ◽  
Soluble Reactive Phosphorus ◽  
Growth Period ◽  
Dry Weight ◽  
Laboratory Culture ◽  
Ammonium Nitrogen ◽  
Nitrogen And Phosphorus ◽  
Mineral Salts ◽  
Reactive Phosphorus

A biphasic system was designed for growing rooted Eurasian water milfoil, Myriophyllum spicatum L., to avoid artificial characteristics of flask culture. Aquaria (21 L) containing undergravel filters, air-lift pumps, 50-W heaters, and Plexiglas lids were sterilized in 70% ethanol and assembled aseptically. Plant shoots were rooted separately in polypropylene cups containing 60 g of artificial sediment approximating natural marl. The sediment provided over 90% of the nitrogen and phosphorus in the plants after 22 days growth. Plants were immersed in a mineral-salts medium with levels of nitrogen and phosphorus comparable with lake concentrations. Aeration was at 0.15 L ∙ min−1 and ranges of temperature and light intensity were from 17 to 32 °C and 30 to 250 μE ∙ m−2 ∙ s−1, respectively. The peak photosynthetic rate was 14 mg O2 ∙ g dry weight−1 ∙ h−1. The maximum specific growth rate, 0.14 mg ∙ mg−1 ∙ day−1, occurred at 27 °C and 250 μE ∙ m−2 ∙ s−1 and lasted for about 3 weeks before light became limiting. Bacterial density, ammonium nitrogen, soluble reactive phosphorus, and total phosphorus exhibited rapid changes during the first 12 days of the growth period, after which fluctuations diminished. The between-aquaria variance in shoot growth rate was insignificant (P > 0.70). When inorganic carbon in the liquid medium and phosphorus in the sediment were lowered from 2.86 to 1.14 mmol C ∙ L−1 and from 0.7 to 0.2 mg P ∙ g dry weight−1, milfoil growth was reduced by 47 and 74%, respectively. Control of the physiochemical environment, small variability, and high reproducibility make this a sensitive system for discerning various treatment effects, including those of pathogens.

scholarly journals Forces Driving the Morphological Evolution of a Mud-Capped Dredge Pit, Northern Gulf of Mexico

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1001 ◽  
Author(s):  
Jiaze Wang ◽  
Kehui Xu ◽  
Chunyan Li ◽  
Jeffrey Obelcz
Keyword(s):  
Gulf Of Mexico ◽  
Observational Data ◽  
Mississippi River ◽  
Numerical Models ◽  
Morphological Evolution ◽  
Suspended Sediments ◽  
Weather Conditions ◽  
Sediment Concentration ◽  
Northern Gulf Of Mexico ◽  
Island Restoration

Sandy sediments preserved as paleo-channel fill on the inner shelf, some of which are overlain by modern muds, have been mined for barrier island restoration along the northern Gulf of Mexico. These mined areas have been termed “mud-capped” dredge pits. The processes governing the morphological evolution of the pits are poorly constrained due to limited observational data. Physical oceanographic (e.g., currents and waves) and sedimentary data were collected at Sandy Point dredge pit offshore Plaquemines Parish, Louisiana in summer 2015. Currents outside the pit flowed southward and/or southeastward at speeds of 8–20 cm/s, while currents inside the pit had speeds less than 2 cm/s with no clear dominant direction. Wave heights detected inside the pit were less than 0.4 m. A high turbidity layer with suspended sediment concentration around 4 g/L was observed above the pit floor, and its thickness was ~0.5 m. With observational data as input, three 2–D numerical models were employed to predict pit morphological responses, including pit infilling, margin erosion and slope change. The model results suggest that resuspension events were rare on the seafloor adjacent to the pit under summer fair weather conditions. Modeled pit margin erosion was very limited. With little resuspension of seafloor sediment locally, weak margin erosion and stable pit walls, the dominant process governing pit evolution was infilling sourced by the deposition of suspended sediments from the Mississippi River plume.

scholarly journals Dissolved Carbon Transport and Processing in North America’s Largest Swamp River Entering the Northern Gulf of Mexico

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1395
Author(s):  
Emily M. DelDuco ◽  
Y. Jun Xu
Keyword(s):  
Gulf Of Mexico ◽  
Carbon Cycling ◽  
Mississippi River ◽  
Dissolved Inorganic Carbon ◽  
Isotope Composition ◽  
River System ◽  
Floodplain Wetland ◽  
Co2 Partial Pressure ◽  
River Waters ◽  
Dissolved Carbon

Transport and transformation of riverine dissolved carbon is an important component of global carbon cycling. The Atchafalaya River (AR) flows 189 kilometers through the largest bottomland swamp in North America and discharges ~25% of the flow of the Mississippi River into the Gulf of Mexico annually, providing a unique opportunity to study the floodplain/wetland impacts on dissolved carbon. The aim of this study is to determine how dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the AR change spatially and seasonally, and to elucidate which processes control the carbon cycling in this intricate swamp-river system. From May 2015 to May 2016, we conducted monthly river sampling from the river’s inflow to its outflow, analyzing samples for concentrations and δ13C stable isotope composition of DOC and DIC. We found that DIC concentrations in the AR were three times higher than the DOC concentrations on average, and showed more pronounced downstream changes than the DOC. During the study period, the river discharged a total of 5.35 Tg DIC and a total of 2.34 Tg DOC into the Gulf of Mexico. Based on the mass inflow–outflow balance, approximately 0.53 Tg (~10%) of the total DIC exported was produced within the floodplain/wetland system, while 0.24 Tg (~10%) of the DOC entering the basin was removed. The AR’s water was consistently oversaturated with CO2 partial pressure (pCO2) above the atmospheric pCO2 (with pCO2 varying from 551 µatm to 6922 µatm), indicating a large source of DIC from river waters to the atmosphere as well as to the coastal margins. Largest changes in carbon constituents occurred during periods of greatest inundation of the swamp-river basin and corresponded with shifts in isotopic composition. This effect was particularly pronounced during the initial flood stages, supporting the hypothesis that subtropical floodplains can act as effective enhancers of the biogeochemical cycling of dissolved carbon.

Sign in / Sign up

Export Citation Format

Share Document