Environmental ▼ News Everglades restoration may not repair water quality
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Meanwhile, the Corps published on August 2 draft programmatic regulations (Fed. Regist. 2002, 67, 50,539–50,575) that describe processes for developing interim hydrologic and ecological goals for its Comprehensive Everglades Restoration Plan (CERP), which was approved by Congress in 2000. The proposed regulations focus on
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The U.S. Army Corps of Engineers’ $7.8 billion plan to restore southern Florida’s Everglades may cause further problems or not meet its goals. Replenishing freshwater flows to the Everglades could further destabilize the receiving waters of Florida Bay with elevated levels of nitrogen, according to a National Research Council (NRC) study. And U.S. Army Corps of Engineers (Corps) officials admit that proposed regulations for implementing the plan will not solve all the area’s water quality problems. The Corps’ plan assumes that renewed freshwater flows in the Everglades will restore Florida Bay, off the southern tip of Florida but that may not be correct, according to the NRC report Consequences of Everglades Restoration for Florida Bay Are Uncertain, which was released August 8. Crystal clear for several decades until the late 1980s, the bay is now murky with algal blooms, and seagrass beds and fish are declining for unknown reasons. The report recommends that the Corps develop a circulation model for Florida Bay and fund more research to quantify the bay’s water and nutrient budgets. These two steps could help resolve one contentious issue in the report: whether the bay is limited by phosphorus or nitrogen or by both nutrients, says Scott Nixon, an author of the report and coastal marine ecologist at the University of Rhode Island. Although increased water flows will carry more dissolved organic nitrogen out of the western side of the Everglades, no one knows just how much will be washed back from the edge of the Gulf of Mexico and into the bay. New research suggesting that dissolved organic nitrogen is more bioavailable than originally thought raises questions about how the nitrogen-limited western part of the bay will react, he says. Confounding the dilemma is new evidence that suggests that Florida Bay was turbid under pristine conditions, Nixon adds.
Efforts to restore Florida’s Everglades may fall short or create problems elsewhere.
replumbing the heavily diked and drained Everglades so that water is delivered when and where it is needed (Environ. Sci. Technol. 2000, 34, 86A). However, says Stu Appelbaum, civil engineer with the Corps, “CERP does not deal with all the water quality issues in southern Florida and was not designed to.” For example, urban and agricultural runoff is polluting the Everglades with nutrients, sediment, pesticides, and metals. Phosphorus from fertilizers has had the biggest impact on the ecosystem. Historically, water containing 40 parts-per-billion (ppb) phosphorus spilled south over the lip of Lake Okeechobee and into wetlands that sucked the nutrient out of the water, dropping concentrations to 10 ppb, explains Alan Steinman, aquatic ecologist at Grand Valley State University in Michigan. Now, canals drain the wetlands south of the lake and deliver water containing 100–200 ppb phosphorus to remaining parts of the Everglades. When phosphorus concentrations climb above 10
ENVIRONMENTAL SCIENCE & TECHNOLOGY / OCTOBER 1, 2002
ppb, the microorganisms at the bottom of the food chain begin to change, and the conversion of sawgrass prairies to cattail marshes eliminates habitat for birds and fish, he says. “The Corps feels that if it gets the hydrology right, everything else will follow,” Steinman says. The Corps plans to construct 50,000 acres of wetland treatment areas on drained land that will retain water and sequester excess phosphorus. “It is easy to reduce phosphorus concentrations from 110 ppb down to 50 ppb, but it is going to be expensive to get the levels down to 10–20 ppb,” he says. The answer he says is to reduce phosphorus concentrations in Lake Okeechobee so that the water reaching the wetland treatment areas is initially cleaner. However, Lake Okeechobee receives 600 tons of phosphorus annually, adds Paul Gray, ecologist with the conservation group Audubon of Florida. Florida’s voluntary best management practices (BMPs) for farms will cut annual phosphorus loads by less than 125 tons, and the stormwater treatment areas called for under CERP will only remove about 100 tons each year from Lake Okeechobee inflows, Gray says. Over the past 50 years, 500,000 tons of phosphorus in fertilizer has been used by farmers, some of which has accumulated in the hard soil and now leaches out. In addition, a 300-square-mile “blob of mud” containing an estimated 50,000 tons of phosphorus sits at the bottom of Lake Okeechobee. Even EPA officials in Region IV’s West Palm Beach office agree that the Corps’ plan cannot fix all the water quality problems. “It is still up to the state to make agricultural operations come into compliance [with state phosphorus limits] for the Lake Okeechobee watershed,” says Richard Harvey, environmental engineer with EPA Region IV. Meanwhile, Jerry Brooks, deputy director of water resource management with the Florida Department of Environmental Protection, says that the federal government must share half the costs of treating the phosphorus runoff. —JANET PELLEY
