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BackgroundAt the northern end of the Everglades lies the Arthur R. Marshall Loxahatchee National Wildlife Refuge (LNWR), about 20 miles southeast of Lake Okeechobee and 50 miles north of Everglades National Park (see Figure 1). LNWR is composed of 147,368 acres of Everglades habitat. LNWR is part of a large freshwater storage area connected by a series of canals and levees built by the U.S. Army Corps of Engineers (see House Document 643). In 1949, this area was placed under the jurisdiction of what is now the South Florida Water Management District (SFWMD). An agreement between SFWMD and the U.S. Fish and Wildlife Service (USFWS ) in 1951 enabled the establishment of LNWR under the Migratory Bird Conservation Act of 1929 for the purpose of protecting and managing the unique northern Everglades habitat and all of its associated flora and fauna. Loxahatchee Refuge consists partially of the 143,116-acre Water Conservation Area 1 (WCA 1) and the 1,595-acre Strazzulla Marsh, leased from the State of Florida through a cooperative agreement with SFWMD. In addition, USFWS owns approximately 2,550 acres in fee title, which is sub-divided into five compartments that can be managed separately: A, B, C, and the cypress swamp units are located on the east side of LNWR in the Headquarters area; D is on the western boundary, just north of the confluence of the L-7 and L-39 canals.
Loxahatchee Refuge is the largest and most pristine remaining part of the northern Everglades. In 1978, LNWR was designated as "Outstanding Florida Waters", which affords it greater water quality protection. To the southwest of LNWR lie the other large remaining portions of the Everglades: Water Conservation Areas 2 and 3 and Everglades National Park. However, to the west of LNWR is the 700,000-acre Everglades Agricultural Area (EAA), which includes large sugar cane farms, winter vegetable and sod farms, and cattle ranches. Immediately east of LNWR lies a conglomerate of urban communities. The surrounding land use makes it a challenge to protect the water quality of LNWR. The limestone bottom of this vast freshwater marsh is covered with a layer of peat varying from 7 to 12 feet thick. The underlying aquifer provides water to nearby coastal communities. A 57-mile levee and associated inside borrow canal defines the perimeter of WCA 1. A 400-acre cypress swamp, the largest remaining section of the strand that once stretched from Lake Okeechobee to Ft. Lauderdale, is located in the Headquarters area. Typical Everglades vegetation of wet prairies, sloughs, sawgrass marshes, and tree islands (ranging in size from less than one acre to more than 300 acres), comprises approximately 85 percent of LNWR. The tree islands are the features that best characterize LNWR, for nowhere else can such an abundance be found (see Figure 2). The primary trust resources dependent on LNWR are the snail kite, wood stork, peregrine falcon, alligator, eastern indigo snake, and tropical curly-grass fern to name a few. Numerous other wading birds and waterfowl utilize LNWR. Historically, such fish as tarpon and mullet used the area, but the presence of water control structures has long since restricted this access.
Credit: J. Kleen USFWS Figure 2: Tree Islands in A.R.M. Loxahatchee National Wildlife Refuge Approximately 100,000 people visit LNWR each year. Popular activities are birding, fishing, photography, and canoeing. In the winter, hunters participate in the annual waterfowl hunt allowed in the southern part of the refuge. The Visitor Center hosts educational programs for all ages as well as exhibits pertaining to the Everglades. LNWR was originally named Loxahatchee National Wildlife Refuge because it was physiographically connected to the Loxahatchee River via the Loxahatchee Slough. The connection has since been dredged, filled, and developed. In 1986, Congress renamed LNWR the Arthur R. Marshall Loxahatchee NWR to honor Arthur Raymond Marshall, Jr. (1919-1985), an influential conservationist in South Florida. Marshall was a marine fisheries biologist for the USFWS for 15 years, taught at two Florida universities, and served as a Governing Board member for the SFWMD. He was instrumental in securing protection for the Big Cypress National Preserve, Biscayne National Preserve, and Pelican Island NWR. The three major sources of water for WCA 1 are rainfall (58 percent), the S-5A pump station at Twenty-Mile Bend (32 percent), and the S-6 pump station near the confluence of the Hillsboro and L-7 canals (10 percent). Approximately 75 percent of the water pumped onto LNWR is drained from agricultural lands north and west of LNWR. Water levels in WCA 1 are managed according to a Regulation Schedule established cooperatively by the COE, SFWMD, and USFWS. The current Interim Regulation Schedule was designed to restore water levels within the marsh to approximate what are believed to be historic marsh water levels, while meeting the objectives of the COE and SFWMD with respect to water supply and flood control. By maintaining high water levels going into the dry season, the area serves as a water storage area, with water available during the dry season for urban and agricultural use. a gradually declining water level throughout the spring provides the capacity for storm water when the wet season begins. the schedule also has a great deal of flexibility, allowing the water levels to flucuate up and down in response to rainfall. The resulting flucuations in water levels provide the type of variablility which was present in the system prior to man's intervention, and allows for the maintenance of a spatially complex floral community. High nutrient runoff from agricultural lands is one of the most serious issues facing LNWR. This water allows undesirable imbalances in the ecosystem and will be discussed in detail below. Mercury is also a major water quality problem which is being addressed partially by the same methods used to clean up the nutrients; the U.S. Environmental Protection Agency has taken the lead on the mercury problem in the Everglades. Yet another major issue is the spread of exotic plants which displace native vegetation, such as melaleuca (Melaleuca quinquenervia), Brazilian pepper (Schinus terebinthefolius), and Old World climbing fern (Lygodium microphyllum). Other issues arise from new land use projects associated with the large urban area to the east that are incompatible with a national wildlife refuge, such as maintaining the water supply and a buffer zone.
In the late 1970s, managers at LNWR began to notice a change in the vegetation around the canals that they associated with water quality: cattails were growing densely in large areas that should have been sawgrass and other marsh vegetation (see Figure 3). In the natural Everglades, cattails (Typha spp.) are native, but they grow in small clumps around concentrations of natural nutrient inputs, such as alligator holes and bird roosts. After much investigation, scientists concluded that the cattail expansion was primarily caused by excess phosphorus entering the refuge via the pump stations along the perimeter canals (Nearhoof 1992; Davis 1994; Doren et al. 1997).
Credit: S.D. Jewell/ USFWS Figure 3: Dense cattails have infested over 6,000 acres of the refuge Because of the large volume of water pumped through the S-5A, this pump contributes the largest load of phosphorus to the Everglades of any of the pump stations. The S-5A pump, which drains a 230-miČ agricultural area, and the S-6 pump, which drains a 146-miČ basin, dumped an average of 76,178 and 29,426 kg (83.8 and 32.36 tons) respectively of phosphorus annually into the refuge (1979 - 1988; Burns and McDonnell 1994). A third source of surface phosphorus is the Acme Drainage Basin to the east of LNWR, which adds an estimated average of 5.39 tons to the refuge annually (Burns and McDonnell 1996). These inflow waters tend to flow easier along the canals, unless the water level across the refuge is very high, which is rare. Thus, the cattails spread deeper into the refuge from the canals and now cover over 6,000 acres. Cattails are the most visible effect of the nutrient imbalance. However, many detrimental changes in the abundance and diversity of algae, diatoms, desmids, and other microorganisms have already occurred by the time the cattail problem is evident. Changes such as these - starting at the bottom of the food chain - eventually work their way up to the more visible effects.
In 1988, U.S. Attorney Dexter Lehtinen filed the lawsuit against two state agencies (SFWMD and Florida Department of Environmental Protection; U.S. v. SFWMD, No. 88-1886) on behalf of LNWR and Everglades National Park (ENP). LNWR is a party to the Settlement Agreement, signed as a Consent Decree in Federal Court in 1992. This Settlement Agreement calls for two Stormwater Treatment Areas (STAs) that directly affect LNWR. STAs are constructed filtration marshes that allow plants and soil to absorb and adsorb excess nutrients and other pollutants. This type of water treatment enhances the filtering abilities of natural marshes without adding harmful chemicals or removing essential elements needed by microorganisms. LNWR staff have worked intensively since 1988 in cooperation with COE, SFWMD, Florida Department of Environmental Protection, ENP, the Miccosukee Tribe of Indians, and other agencies to plan and coordinate a cleanup. The Settlement Agreement mandates that LNWR should receive 85% fewer tons of phosphorus by February 1, 1999. This will be accomplished by the STAs, the Best Management Practices (BMPS, which farmers are using to reduce the nutrients being discharged from their farms), and the addition of smaller water treatment facilities. STA 1 will straddle the north end of the refuge, where pump station S-5A currently is. When that STA is complete, the water entering S-5A will pass through the filtering marsh before entering the refuge. The marsh will be constructed in two sections, STA 1W and STA 1E, and the Inflow and Distribution Works will connect the two sections. STA 1W includes the Everglades Nutrient Removal Project (ENR), which has been operating by SFWMD since August 1994. The ENR achieved an 80% load reduction of phosphorus in its second year of operation and brings optimism that the STAs will function as planned or better. To complete STA 1W, approximately 1,500 acres will be added to the ENR. STA 1W is being constructed by SFWMD and must be completed by January 1, 1999. STA 1E is being constructed by COE as a combined water quality and flood control project. It must be completed by July 1, 2002. Construction of STA 1 Inflow and Distribution Works began in May 1997 by SFWMD. STA 2 will be located downstream of LNWR and will receive the water from S-6 pump that will be diverted from the refuge. The water that the refuge will lose to STA 2 will be compensated for by more water being sent to S-5A. STA 2, a works of SFWMD, must be completed by February 1, 1999. Other methods of water treatment are currently being tested by various agencies to determine if they can produce good quality water, so that they can be used in conjunction with the STAs to further reduce the nutrient concentration. While there are numerous technologies in existence that can remove all the phosphorus and even make distilled water out of sewage, distilled water is not what the Everglades needs. Everglades water must contain a balance of small amounts of nutrients, elements such as silica and carbon, and naturally occurring microorganisms. Federal scientists refer to this as "marsh ready water"- that is, water that is ready to be reintroduced into the Everglades and is capable of sustaining aquatic organisms without further tampering. STAs produce marsh ready water, which is one reason that the Department of the Interior favors the system. The LNWR staff is committed to providing marsh ready water for the refuge. In spite of the efforts being made now to reduce water pollution to the refuge, it will take many years to manifest the improvements. In the mean time, tons of the insidious phosphorus will enter the refuge. Refuge staff will continue to make every effort to protect the water entering the refuge by supporting the Settlement Agreement and other laws.
Refuge Manager Telephone: (561)732-3684 written by Susan D. Jewell, September 1997
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06/29/08
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