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A.R.M. Loxahatchee National Wildlife Refuge Enhanced Water Quality Program - 7th Annual Report - Calendar Year 2010

February 2012

Executive Summary

(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-CIV-MORENO) 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 stations located in the marsh and canal since June 2004. The number of grab sample stations has reduced to 37 in recent years because two stations 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 sixth annual report, with analyses focused on January through December 2010, and with comparisons made to the preceding years (2004 through 2009).

Water quality data and analyses of canal water intrusion into the Refuge marsh presented in this report documents 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 2010 canal water intrusion analyses include:

Analyses of these data continue to support previously suggested management practices that have the potential to minimize intrusion. A few of these recommendations are summarized as balancing inflow and outflow volumes, reducing the duration of inflows, and reducing inflow rates when the canal stage is lower than the marsh stage.

Based on the surface water conductivity data, the Refuge was classified 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 continue to be different from, and more impacted than, the Interior Zone. Cattail expansion in the Refuge marsh, negative impacts to periphyton and Xyris spp. in response to nutrient and mineral enrichment, and displacement of sawgrass in the canal waterexposed areas of the marsh are a few examples of marsh impacts.

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 influence on the marsh, these data 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.).

In 2009, we performed a second round of vegetation characterization and this year we provide a preliminary analysis of those data. Results of these analyses suggest that the similarity of plant communities (presence/absence using Sorensen's Similarity Index) among the water quality zones shifts in response to duration of drought and inundation. Further, assessment of select indicator plant species suggest that Typha spp. continues to expand into the interior marsh, while Eriocaulon spp., Eleocharis spp., and Xyris spp., which are generally indicative of unimpacted marsh conditions, did not show expansion at most of the water quality stations. Several more years of collection and analysis of these data is necessary to moderate variability resulting from sample collection conditions and samplers.

In 2010, the Simple Refuge Screening Model (SRSM) was successfully applied to assess a water management recommendation proposed by the South Florida Water Management District (SFWMD). In November 2010, the SRSM was applied to evaluate the potential for delivering make-up water  to the Refuge. Because of the unique rainfall pattern in 2010 (rainy dry season/dry wet season) and exceptionally low stages in the wet season, SFWMD offered to deliver nutrient enriched water from Lake Okeechobee to the Refuge in an attempt to offset the lower than normal stages observed during the wet season of 2010. Results from the SRSM suggested that the Refuge water levels achieved the high stage performance measure (PM) (water stage greater than 17 ft three to four weeks in a row of three to four consecutive years) three water years (May through April) in a row (2008, 2009, 2010) and as such it would be acceptable to not achieve the high stage PM in water year 2011 (May 2010 through April 2011), thus the make-up water  was rejected by Refuge management.

 

1 Public Law 108-108; see House Report No. 108-195, p. 39-41 (2004)


 

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Acknowledgments

The authors thank the following contributors, without whom this report would not have been possible: Marcie Kapsch, Rebekah Gibble, Elizabeth Lesley, April Ostrom, Darren Pecora, Tiffany Trent, and Meredith Wilson 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; 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 2010 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, 2012. A.R.M. Loxahatchee National Wildlife Refuge - Enhanced Water Quality Program - 7th Annual Report for calendar year 2010 - February 2012. LOXA12-001, U.S. Fish and Wildlife Service, Boynton Beach, FL. 45 pp.

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