Just Cerfing Vol. 7, Issue 8, August 2016 Volume 5, Issue 3, March, 2014 | Page 16

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Water-Quality Parameters in the Mississippi River

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livery to deltaic wetlands due to levee and dam construction in the Mississippi
River basin (Blum and Roberts, 2009; Day et al., 2000), resulting in an 85%
decrease in sediment supply during the 20th century (Syvitski et al., 2009).
Subsidence, a process of soil and sediment compaction, currently exceeds 10
mm yr-1 in many regions of coastal Louisiana (Tornqvist et al., 2008), outpacing delta-building processes. Additionally, canal construction has resulted
in altered hydrology and has contributed to coastal wetland loss (Day et al.,
2000).
River diversions have been implemented in the Mississippi River deltaic
plain to slow wetland loss and promote wetland regeneration (LDNR, 1998).
Diversions have been shown to increase vertical accretion and marsh development (DeLaune et al., 2003; Lane, Day, and Day, 2006), though diversions
may make wetlands more susceptible to erosion during hurricanes (Howes et
al., 2010). Diversions also have been shown to promote riverine nutrient uptake and removal (Lane, Day, and Thibodeaux, 1999; 2007), and have therefore been proposed as a partial solution to coastal hypoxia (Day et al., 2003b;
Mitsch et al., 2001).
The purpose of this study is to use a multiyear dataset to investigate the
long-term temporal and spatial nutrient patterns in the Breton Sound estuary,
a coastal Louisiana estuarine wetland complex that receives Mississippi River
water input via the Caernarvon river diversion. Null hypotheses tested include: (1) no correlations exist among water quality parameters, (2) no seasonal or temporal variation in nutrient concentration exists, (3) nutrient removal
efficiency is unrelated to loading rate, and (4) there is no seasonal variation in
nutrient removal efficiency.
Additionally, we wanted to determine whether the diversion effectively improves the quality of water exported to the Gulf through nitrate removal.
Figure 1. Water-quality sampling sites in the Breton Sound estuary, Louisiana.
The star indicates the location of the Caernarvon river diversion control structure.

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