reports > 2010 5th annual report
(Note: entire PDF is available for download below)Congress appropriated funds to the U.S. Fish and Wildlife Service in 2004 which funded an enhanced water quality monitoring network and hydrodynamic and water quality models to improve the scientific understanding of water quality in the Arthur R. Marshall Loxahatchee National Wildlife Refuge1 (Refuge). The network and models provide information that is used in management decisions to better protect Refuge resources. The enhanced water quality monitoring network complements the compliance network monitored as a part of the 1992 Federal Consent Decree (Case No. 88-1886-CIVMORENO) by characterizing the water quality of a larger Refuge area, particularly the fringe area potentially impacted by canal water intrusions. Monthly grab samples have been collected at 37 to 39 sites located in the marsh and canal since June 2004. The number of grab sample sites has reduced to 37 in recent years because two sites located near the canal were overrun with cattail making them inaccessible. Continuous measurements of conductivity additionally have been collected along seven transects, four of which extend from surface water discharge points in the canal into the interior. This report is the fifth annual report, with analyses focused on January through December 2008, and with comparisons made to the preceding years (2004 through 2007).
Water quality data and analyses of canal water intrusion into the Refuge marsh presented in this report document continued intrusion of rim canal water into the Refuge interior, adding to a growing information base about canal water impacts to the Refuge. Intrusion of nutrient-rich and high conductivity water from the canal network surrounding the Refuge has been shown to negatively impact Refuge flora and fauna. Important insights gained from 2008 canal water intrusion analyses include:
Based on the surface water conductivity data, we classified the Refuge into four geographic zones: (1) Canal Zone; (2) Perimeter Zone, located from the canal to 2.5 km (1.6 miles) into the marsh; (3) Transition Zone, located from 2.5 km (1.6 miles) to 4.5 km (2.8 miles) into the marsh; and (4) Interior Zone, greater than 4.5 km (2.8 miles) into the marsh. Overall, water quality conditions in the Perimeter and Transition Zones continue to be different from, and more impacted than, the Interior Zone. Cattail expansion in the Refuge marsh, negative impacts to Xyris spp. (yellow-eyed-grass) from nutrient and mineral enrichment, and displacement of sawgrass in the canal water-exposed areas of the marsh are examples of deleterious marsh ecosystem changes associated with canal water intrusion.
This report continues to document that water movement between the canals and the marsh is influenced by rainfall, structure-controlled water inflow and outflow into perimeter canals, the difference between canal and marsh stages, and marsh elevation. When combined with our understanding of canal water intrusion's influence on the marsh, the data presented in this report continue to suggest that high-nutrient water is having a negative impact on the Refuge marsh (e.g., enriched soil TP, displacement of sawgrass by cattails, loss of Xyris spp., etc.).
An excursion of the long-term TP level, as defined by the Consent Decree, occurred in November 2008. Rainfall, inflows, and canal water intrusion suggest that conditions were prime for an excursion event in October, but the geometric mean TP concentration in October was equal to the long-term compliance level. In November 2008, rainfall and canal inflows diminished, but intrusion remained extensive. The extended period of canal water intrusion likely was associated with the November 2008 excursion.
In 2008, we designed and initiated a study to investigate the growth and survival of native Florida apple snails (Pomacea paludosa) as a response to periphyton compositions from the Perimeter, Transition, and Interior Zones. We also began a study investigating how P. paludosa life histories are affected by water chemistry in the Northern Everglades. Analysis of the data from these studies will be available in a future annual report.
Model development for the suite of Refuge models continued during 2008. Water quality constituents were incorporated into the simple and complex models to enhance our understanding of water movement in the marsh and phosphorus dynamics in the water column. The independent model advisory review panel provided valuable insights that have been incorporated into the modeling program, and results of calibration runs for each model were presented at several conferences this year. Public workshops enhanced modeling effectiveness through interagency/interdisciplinary dialog.
Based on our water quality and hydrodynamic analyses, we submitted two manuscripts for peer-review journal publication. One paper was submitted to Wetlands and focused on canal water intrusion into the marsh, and a second paper was submitted to Environmental Monitoring and Assessment and focused on impacts of canal water intrusion on the water quality in the marsh.
1 Public Law 108-108; see House Report No. 108-195, p. 39-41 (2004)
The authors thank the following contributors, without whom this report would not have been possible: Angela De'Bree, Marcie Dixson, Rebekah Gibble, April Ostrom, Serena Rinker, and Tiffany Trent for water quality sample collection and sonde deployments and collections; SFWMD and Columbia Analytical Services for water chemistry analyses; April Ostrom for extensive data quality assurance and control; Paul McCormick (formerly with USGS) for assistance with the ecological effects research; and SFWMD for the use of DBHYDRO for data availability. Laura Brandt and Mark Musaus provided valuable contributions to the initial phase of this overall program. Finally, we thank Refuge Manager Sylvia Pelizza and Deputy Manager Rolf Olson for their continued support and leadership throughout this project. Funds to conduct the expanded monitoring network at A.R.M. Loxahatchee NWR were provided by the U.S. Congress in P.L. 108-108, the Department of the Interior and Environment Appropriations Act of 2004. Funding for 2008 was obtained, in part, from the Everglades National Park through the DOI Critical Ecosystem Studies Initiative program. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the U.S. Fish and Wildlife Service or the National Park Service.
This report should be cited as:
USFWS, 2010. A.R.M. Loxahatchee National Wildlife Refuge - Enhanced Water Quality Program - 5th Annual Report for calendar year 2008 - September 2010. LOXA08-007, U.S. Fish and Wildlife Service, Boynton Beach, FL. 43 pp.