Effects of tributary inputs on nutrient export from the Mississippi and Atchafalaya Rivers to the Gulf of Mexico
Shuiwang Duan A C D , Thomas S. Bianchi B , Peter H. Santschi A B and Rainer M. W. Amon AA Department of Marine Sciences, Texas A&M University at Galveston, Galveston,TX 77551, USA.
B Department of Oceanography, Texas A&M University, College Station, TX 77843, USA.
C Present address: Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD 20688, USA.
D Corresponding author. Email: duan@cbl.umces.edu
Marine and Freshwater Research 61(9) 1029-1038 https://doi.org/10.1071/MF09235
Submitted: 21 September 2009 Accepted: 9 March 2010 Published: 23 September 2010
Abstract
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.
Additional keywords: in-channel processes, Mississippi River, nutrients, seasonal changes, tributaries.
Acknowledgements
This study was funded by a postdoctoral fellowship granted to Shuiwang Duan through Texas Institute of Oceanography (TIO) of Texas A&M University at Galveston. Additional support included grants from National Science Foundation to Rainer Amon (0425582) and Texas Commission of Environmental Quality to Robin Brinkmeyer, Rainer Amon and John Schwarz (582–5-72502–08). We also thank two anonymous reviewers for their suggestions to improve this manuscript.
Alexander, R. A. , Smith, R. B. , and Schwarz, G. E. (2000). Effect of stream channel size on the delivery of nitrogen to the Gulf of Mexico. Nature 403, 758–761.
| Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |
Battaglin, W. A. , Kendall, C. , Chang, C. C. Y. , Silva, S. R. , and Campbell, D. H. (2001). Chemical and isotopic evidence of nitrogen transformation in the Mississippi River, 1997–98. Hydrological Processes 15, 1285–1300.
| Crossref | GoogleScholarGoogle Scholar |
Duan, S. W. , and Bianchi, T. S. (2006). Seasonal changes in the abundance and composition of plant pigments in particulate organic carbon in the lower Mississippi and Pearl Rivers (USA). Estuaries and Coasts 29, 427–442.
| CAS |
Hernes, P. J. , and Benner, R. (2003). Photochemical and microbial degradation of dissolved lignin phenols: implications for the fate of terrigenous dissolved organic matter in marine environments. Journal of Geophysical Research – Oceans 108, 3291.
| Crossref | GoogleScholarGoogle Scholar |
Lohrenz, S. E. , Fahnenstiel, G. L. , Redalje, D. G. , Lang, G. A. , and Dagg, M. J. , et al. (1999). Nutrients, irradiance, and mixing as factors regulating primary production in coastal waters impacted by the Mississippi River plume. Continental Shelf Research 19, 1113–1141.
| Crossref | GoogleScholarGoogle Scholar |
Moody, J. A. , and Goolsby, D. A. (1993). Spatial variability of triazine herbicides in the lower Mississippi River. Environmental Science & Technology 27, 2120–2126.
| Crossref | GoogleScholarGoogle Scholar | CAS |
Scavia, D. , and Donnelly, K. A. (2007). Reassessing hypoxia forecasts for the Gulf of Mexico. Environmental Science & Technology 41, 8111–8117.
| Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |
Scavia, D. , Rabalais, N. N. , Turner, R. E. , Justić, D. , and Wiseman, W. J. (2003). Predicting the response of Gulf of Mexico hypoxia to variations in Mississippi River nitrogen load. Limnology and Oceanography 48, 951–956.
| Crossref | GoogleScholarGoogle Scholar | CAS |
Shields, F. D. , Testa, S. , and Cooper, C. M. (2009). Nitrogen and phosphorus levels in the Yazoo River Basin, Mississippi. Ecohydrology 2, 270–278.
| Crossref | GoogleScholarGoogle Scholar | CAS |
Sutula, M. , Bianchi, T. S. , and McKee, B. A. (2004). Effect of seasonal sediment storage in the lower Mississippi River on the flux of reactive particulate phosphorus to the Gulf of Mexico. Limnology and Oceanography 49, 2223–2235.
| Crossref | GoogleScholarGoogle Scholar |
Teissier, S. , Sauvage, S. , Vervier, P. , Garabetian, F. , and Sanchez-Perez, J.-M. (2008). A mass-balance approach to estimate in-stream processes in a large river. Hydrological Processes 22, 420–428.
| Crossref | GoogleScholarGoogle Scholar | CAS |
Turner, R. E. , Rabalais, N. N. , and Justic, D. (2006). Predicting summer hypoxia in the northern Gulf of Mexico: riverine N, P, and Si loading. Marine Pollution Bulletin 52, 139–148.
| Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |
White, P. A. , Kalff, J. , Rasmussen, J. B. , and Gasol, J. M. (1991). The effect of temperature and algal biomass on bacterial production and specific growth-rate in fresh-water and marine habitats. Microbial Ecology 21, 99–118.
| Crossref | GoogleScholarGoogle Scholar |