Erratum: Nitrate flux in the Mississippi River

We evaluated patterns of denitrification and factors effecting denitrification in the upper Mississippi River. Measurements were taken over 2 years, during which river discharge ranged from record flooding to base flow conditions. Over the period of study, average denitrification enzyme activity was highest in backwater lakes and lowest in the main channel. Throughout the study reach, highest denitrification enzyme activity occurred during fall and lowest occurred in winter. Rates during spring floods (2001) were only slightly higher than during the preceding winter. Mean unamended denitrification rates ranged from 0.02 (fall 2001 in backwaters) to 0.40 µg N·cm2·h1 (spring 2001 in backwaters). Laboratory experiments showed that denitrification rates increased significantly with addition of NO3 regardless of sediment C content, while rates increased little with addition of labile C (glucose). Denitrification in this reach of the upper Mississippi River appears to be NO3 limited throughout the growing season and the delivery of NO3 is strongly controlled by river discharge and hydrologic connectivity across the floodplain. We estimate that denitrification removes 6939 t N·year1 or 6.9% of the total annual NO3 input to the reach. Hydrologic connectivity and resultant NO3 delivery to high-C sediments is a critical determinant of reach-scale processing of N in this floodplain system.

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Nitrate Flux into the Sediments of a Shallow Oligohaline Estuary during Large Flood Pulses of Mississippi River Water

Journal of Environmental Quality ◽

10.2134/jeq2011.0420 ◽

2012 ◽

Vol 41 (5) ◽

pp. 1549-1556 ◽

Cited By ~ 17

Author(s):

Eric D. Roy ◽

John R. White

Keyword(s):

River Water ◽

Mississippi River ◽

Flood Pulses ◽

Nitrate Flux ◽

Mississippi River Water

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Water discharge, nitrate concentration and nitrate flux in the lower Mississippi river

Journal of Marine Systems ◽

10.1016/0924-7963(93)90027-j ◽

1993 ◽

Vol 4 (4) ◽

pp. 315-326 ◽

Cited By ~ 2

Author(s):

S.P. Dinnel ◽

A. Bratkovich

Keyword(s):

Mississippi River ◽

Nitrate Concentration ◽

Water Discharge ◽

Lower Mississippi River ◽

Nitrate Flux

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The Effect of Exogenous Fluoride on the Calcium PUMP, Ciliary Activity, and Shell Formation of the Fingernail Clam, Musculium Transversum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100053097 ◽

1982 ◽

Vol 40 ◽

pp. 58-59

Author(s):

Anthony Paparo ◽

Judy A. Murphy ◽

Robert Dean

Keyword(s):

Mississippi River ◽

Calcium Pump ◽

Bottom Fauna ◽

Ciliary Activity ◽

Shell Formation ◽

Middle Reach ◽

Shell Matrix ◽

Fingernail Clams ◽

Ca Carbonate

In the mid-1950's, fingernail clams virtually disappeared from a 100-mile section of the IL River, a tributary of the Mississippi River, due to unknown causes. A survey of the bottom fauna of the IL River in 1979, revealed that the clams were still absent from the middle reach of the River, where they had been abundant prior to the die-off in the 1950's. Some factor(s) in the River currently prevent the clams from recolonizing areas where they were formerly abundant. Recently, clams exposed to fluoride developed abnormal grooves in the shell matrix. Fluorides are known to be protoplasmic poisons removing essential body calcium by precipitation. Since the shell consists primarily of Ca carbonate, this investigation examines the possible role of fluoride on shell formation and the poisoning of the Ca pump which can directly inhibit lateral ciliary activity on the gill.

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