The cooperative effort that helped bay managers “hold the line” on nitrogen loading in Tampa Bay over the last decade is moving into its next stage, morphing from a volunteer initiative to become one of the nation’s largest nitrogen management groups.
While the new rules are complicated, the results of previous efforts are clear: working together, the Tampa Bay Nitrogen Management Consortium has reduced nitrogen flowing into the bay by a total of 410 tons since 1995 even as the region’s population grew by nearly a million people. Over the past two years, both water quality and water clarity goals were met in all four major bay segments for the first time since record-keeping began in 1974. The tangible result of that success is more seagrasses growing in the bay than seen since 1950 – an increase of 3480 acres since 1999.
“Tampa Bay is recognized across the country as one of the few estuaries where water quality is improving in the face of population growth,” notes Holly Greening, executive director of the Tampa Bay Estuary Program. “It’s the partnership and the willingness of members to work together that have made the difference.”
The future, however, will be more challenging on a series of fronts. First, the low-hanging fruit has been picked and ongoing reductions in nitrogen are likely to require more money and increased commitments from government, industry, developers and residents.
And the program that began on a voluntary basis has now opted to meet water quality regulatory requirements from both the state and federal governments.
Recognizing the success of the voluntary initiative, both the Florida Department of Environmental Protection and the US Environmental Protection Agency are comfortable that the consortium’s plans will address areas of Tampa Bay where water quality does not meet current standards.
The local targets were developed specifically so that water would be clear enough for seagrasses to grow to depths where they had been found in 1950. Enhancing those living resources has been a top priority of the TBEP since its inception, and ongoing efforts have proven to be successful. FDEP and EPA have both adopted nutrient limits based on those site-specific targets.
“TBEP sets specific targets for each bay segment because water quality naturally varies throughout the bay,” Greening notes. “We expect the water in the upper part of the bay to be less clear than water nearest the Gulf of Mexico so water quality targets are less stringent in Hillsborough Bay than in Lower Tampa Bay.”
One issue remaining for the consortium will be allocating nitrogen loads for major point and non-point sources. TBEP and the consortium have traditionally focused on overall loadings and worked as a partnership to ensure that nitrogen loadings in each bay segment do not exceed levels measured in 1992-1994. Under federal regulations, however, cumulative permitted point source loads cannot exceed maximum allowed levels.
“Currently the actual loads are very close to allowable loads, but the maximum permitted loads are higher,” Greening said. The consortium is working now to reallocate those permitted loads so that they meet the state and federal standards. Basinwide allocations are scheduled to be complete by May 2008. The final allocation, including new permitted levels for individual sources that comply with EPA limits, must be completed by July 2009.
Nitrogen
| Around the world, eutrophication – resulting from an excess of nutrients in water – has become a leading cause of water quality degradation. A recent study by the World Resources Institute indicates high levels of nutrients affect nearly 80% of coastal water bodies in the continental US. While necessary for life, high levels of nutrients fuel the growth of microscopic algae that limit sunlight reaching seagrass beds. When the algae die, they sink to the bottom where bacteria use available oxygen to break them down. Over time, these low levels of oxygen create hypoxic “dead zones,” like that found at the mouth of the Mississippi River. Of the total 415 ecosystems worldwide identified as having some form of eutrophication, 169 are considered to be hypoxic. In the US, only two estuaries are classified as “systems in recovery” – Tampa Bay and Boston Harbor, where a $3.4 billion tunnel carries treated wastewater nearly 10 miles out to sea. Tampa Bay’s recovery began in 1979 when the city of Tampa upgraded its wastewater treatment plant and sharply reduced the amount of nitrogen it discharged. Across the bay, the city of St. Petersburg pioneered the country’s first large-scale reclaimed water program, dispersing wastewater on lawns and golf courses where plants absorb remaining nutrients. State stormwater regulations initiated in the 1980s also contributed to the bay’s recovery. |
More than 250 projects, from sweeping streets to rebuilding stormwater ponds, have helped bay managers “hold the line” on nitrogen loadings across Tampa Bay since 1998. Here’s a closer look at some of the projects that are making a difference.
Taming an Urban Jungle
The restoration of Lake Seminole is a classic case of the “leg bone connected to the hip bone.”
Residents living in urban areas surrounding the lake fertilize their lawns, and stormwater carries excess nutrients to Lake Seminole. In fresh water, high levels of phosphorus fuel the growth of algae which is then carried out to Tampa Bay. As the algae die, they increase nitrogen levels that, in turn, encourage yet another algal bloom in salt water.
Created in the 1940s when Pinellas County dammed off part of Long Bayou to form a freshwater lake for recreation, Lake Seminole has become a 684-acre stormwater pond for the surrounding 8,000-acre highly urbanized watershed. Over the last 60 years, it went from a favorite fishing and swimming hole to a sickly green lake where dead algae decomposed into thick layers of muck that covered the sandy floor and choked out native vegetation.
While discussions about how to clean up the lake began more than 10 years ago, restoration efforts seriously began in 2006 when the lake’s water level was dropped by two feet so that accumulated muck – up to three feet deep in some places – could be mechanically removed from 17 acres. Thousands of invasive plants were removed from shorelines, and more than 100,000 plants have been placed in the cleared areas to filter nutrients before they enter the lake.
The next phase of restoration gets underway in May 2008 with the construction of a state-of-the-art alum treatment system that can remove up to 95% of phosphorus and 70% of nitrogen in the stormwater flowing into the lake. Aluminum has been used to clean water for thousands of years. It attracts contaminants, including nutrients, suspended solids and bacteria, and creates a heavy particle that falls to the bottom in a process called flocculation.
The process is both safe and effective, but its annual operating cost of $550,000 make it an expensive way to clean up fertilizer that should never have been used in the first place, says Kelli Hammer Levy, program coordinator for Pinellas County’s Environmental Management Department.
“The lake is in the middle of an urban jungle – there’s no industry and very few septic tanks so we’re clearly cleaning up fertilizer.”
Education is important but Levy believes that restricting availability of high-nitrogen fertilizer will be even more necessary at some point. “Source control is better than restricting use,” she said.
Capturing Nutrients at the Source
Phosphate has been an important export in Tampa Bay since 1892 when sailing schooners laden with the life-giving nutrient began sailing from docks built by Henry Plant. Even with changing market conditions, fertilizer is still one of the top commodities shipped through the Port of Tampa.
But prior to 1990, fertilizer facilities bordering East Bay had been releasing elevated levels of nutrients into bay waters, typically when small spills onsite were washed away in stormwater. FDEP and the Environmental Protection Commission of Hillsborough County documented the discharges and, operating under consent orders, the five companies undertook very specific plans to clean up their acts.
“There was a lot of opportunity to improve the way we handled fertilizer to reduce spillage and nitrogen loadings to Tampa Bay,” notes Jeff Stewart, Mosaic’s environmental superintendent.
Depending upon the individual facility, actions ranged from onsite ponds to treat stormwater before it was discharged to enclosing conveyor belts or setting up deflectors to captured fertilizer products. “As an industry, we’ve been very happy with the successes we’ve achieved,” Stewart said. “It’s really amazing how the health of the bay has improved over the last decade. Water clarity has improved and seagrasses are recovering.”
The focus on limiting nitrogen inputs has gone upstream as well, to the beneficiation plants where sand and clay are separated from the phosphate. Mosaic once used ammonia to adjust pH during the process; it now uses soda ash. “We still use ammonia to manufacture fertilizer but not in the beneficiation process where some of it ends up in the water in our circulation system and could escape.”
Although their names have changed over the past 18 years, the major players in the phosphate industry have been part of the Nitrogen Management Consortium since its inception in 1996. “We feel like working with the Nitrogen Management Consortium and the estuary program is the most effective way to handle nitrogen loadings in Tampa Bay,” he said. “We need to keep moving forward, including recruiting new members like non-point sources further up the basin by providing them information on the consortium and what it’s accomplished.”
Generators Provide Multiple Benefits
Tampa Bay began its nearly miraculous recovery 30 years ago when City of Tampa upgraded the Howard F. Curren Plant at Hooker’s Point, sharply reducing the amount of nitrogen being discharged into Hillsborough Bay.
The city’s most recent upgrade is a fleet of generators mounted on trucks to power wastewater lift stations when electrical power goes down.
“We have 222 pumping stations and about 200 of them have now been fitted for plugs so they can quickly tie into a trailer-mounted generator,” said Ralph Metcalf, the city’s wastewater director. “Each truck can pump down four stations a day running a circular round, so we’ll be in pretty good shape in a general electrical outage.”
The pump stations themselves have a remote telemetry connection to the city’s central system so they can be monitored from a control room for available power and capacity, he adds.
While the city is prepared for a worst-case hurricane, the most likely problem will be a summer thunderstorm that knocks out power, he said. And while the system will clearly benefit Tampa Bay, the initiative is first and foremost a public safety issue. “It’s a very big deal when sewage overflows into a house, street or the bay – in that order.”
High Levels of Nutrients Threaten Frog Populations Nationally
Scientists at the University of Colorado have demonstrated that high levels of nutrients – not pesticides as initially suspected – fuel parasite infections that have caused highly publicized frog deformities in ponds and lakes across the country.
The study, funded through the National Science Foundation, showed that increased levels of nitrogen and phosphorus cause sharp hikes in the abundance and reproduction of a snail species that hosts microscopic parasites known as trematodes. The nutrients stimulate algae growth, increasing snail populations and the number of infectious parasites released by snails into ponds and lakes. The parasites subsequently form cysts in the developing limbs of tadpoles causing missing limbs, extra limbs and other severe malformations, said Pieter Johnson of the University of Colorado, Boulder.
“This is the first study to show that nutrient enrichment drives the abundance of these parasites, increasing levels of amphibian infection and subsequent malformations,” said Johnson. “The research has implications for both worldwide amphibian declines and for a wide array of diseases potentially linked to nutrient pollution, including cholera, malaria, West Nile virus and diseases affecting coral reefs.”
Deformed frogs first gained international attention in the mid-1990s when a group of Minnesota schoolchildren discovered a pond where more than half of the leopard frogs had missing or extra limbs, he said. Since then, reports of deformed amphibians have become widespread in the United States, leading to speculation they were being caused by factors like pesticides, increased ultraviolet radiation or parasitic infection.
While parasite infection is now recognized as a major cause of such deformities, the environmental factors responsible for increases in parasite abundance had largely remained a mystery until the study was undertaken, Johnson said.
“One of our main goals was to understand how parasites respond to land-use changes and ecosystem alterations,” he said. “What we found is that nitrogen and phosphorus pollution from agriculture, cattle grazing and domestic runoff have the potential to significantly promote parasitic infection and deformities in frogs.”
Florida Frogs Faring Well
Florida frogs so far have not shown the deformities seen in other parts of the country, notes Paul Moler, a biologist with the Florida Fish and Wildlife Conservation Commission. “If you count a thousand frogs, you’ll see an occasional five legs, but we haven’t seen anything major in Florida,” he said. While agriculture is important across the state, it’s not as widespread as it is in states like Minnesota or Iowa where frogs have been severely impacted.
In Florida, only two frog populations are threatened: gopher frogs, because the gopher tortoises are declining and habitat is limited, and North Florida’s ornate chorus frog that lives in grassy fields and roadsides after rains. That decline, Moler adds, may be linked to the region’s ongoing drought rather than a manmade threat.
Native frogs, however are threatened by invasive species, like the Cuban tree frog that is becoming dominant in many Tampa Bay neighborhoods. “Luckily they tend to do better in an urban setting than a native ecosystem so they’re not quite so prevalent out of town,” Moler said.
They are voracious eaters – although they consume other frogs, toads and lizards as well as insects and spiders. Some biologists recommend euthanizing them, but controlling them will require a long-term commitment, Moler said.