02/21/1997

Alabama's Lakes May Be Fertilized to Death Without New Water Quality Regulations

AUBURN, Ala. - Alabama's lakes may be fertilized to death unless the state enacts regulations to monitor and control discharges of nitrogen and phosphorus into waterways. That's the bottom line of a position paper being circulated by the Alabama Fisheries Association (AFA).

Alabama's 39 public lakes cover 485,046 acres and support a recreational industry valued at more than $1 billion. While some nitrogen and phosphorus are beneficial to aquatic ecosystems, too much of these plant nutrients can cause algae and other water vegetation to become so productive that they cause fish kills and make water systems unusable for drinking or recreation. In extreme cases, lakes can be virtually lost, said David Bayne, an Auburn University professor of fisheries who drafted the AFA position paper.

"More than 10 years of research by Auburn, the Alabama Department of Environmental Management (ADEM), the Tennessee Valley Authority and the Environmental Protection Agency shows that about 77 percent of Alabama's public lake surface area is highly enriched with nitrogen and phosphorus, and that the nutrient load in most public lakes is steadily increasing," Bayne said. "Alabama currently has no water quality standards to stop this type of pollution.

"The economic value of clean, healthy water systems will increase in the future as greater demands are placed on our limited water resources," Bayne continued. "Conserving and protecting the quantity and quality of our water is in the best interest of all Alabama citizens. Placing limits on excessive nutrient enrichment in our lakes is a step in the right direction." In 1996, the AFA passed a resolution calling for the state to establish lake-specific water-quality criteria related to nutrient pollution and to require all those who discharge effluent to measure and report total nitrogen and phosphorus concentrations. AFA is comprised of aquatic resource scientists and managers concerned with protecting and improving Alabama surface waters.

Nutrient enrichment occurs naturally, Bayne said, but artificial sources have increased with population growth, industrialization, recreational activities, development of shoreline properties and intensive agriculture and forestry. Nutrients can come from direct sources, such as discharges into streams from wastewater treatment plants, paper mills or food processing plants. They can also come from indirect sources, such as rainwater runoff from farms, residential areas or timber plantations.

Bayne explained that excessive plant nutrients can damage lakes in a process called "eutrophication," in which increased levels of fertilization cause overabundant plant growth. In lakes with large areas of shallow water and relatively stable water levels, weeds can become a severe problem, as seen in lakes Guntersville and Seminole. However, in most Alabama lakes, increasing algae blooms have been the predominant problem. This not only makes the water green and murky, it can become so excessive that it removes all oxygen from lower water levels. Eutrophication has led to numerous fish kills in the Southeast, Bayne said.

"Sport fish depend on nutrient-driven growth of food organisms," Bayne said. "Therefore, limited nutrient enrichment can benefit the fishery. However, studies at AU have shown that high levels of nutrient loading do not improve the fishery of large reservoirs, but rather degrade fish habitat and threaten fish food organisms."

In healthy systems, plants remove oxygen from the water during respiration, but they produce more oxygen through photosynthesis than they consume. At high plant densities, however, plants may consume more oxygen than they produce. Making this problem even worse is the fact that algae blooms can block sunlight from lower water levels, decreasing the amount of photosynthesis and oxygen production. Further problems are caused when plants die and decompose. Bacteria that decompose the plants also use oxygen; the more organic matter, the greater the oxygen demand.

Under normal conditions, most fish can survive by avoiding the oxygen-depleted lake bottom, Bayne said. Unfortunately, even fish near the surface can be threatened when the water layers are disrupted and oxygen-depleted water is forced into the upper water column. This type of disruption can occur during intense summer storms or when water is drawn through a dam during hydroelectric power generation.

In addition to the oxygen depletion problems, high densities of aquatic plants can also cause wide shifts in the pH of a lake. In highly alkaline lakes, dense plant growth may not cause harmful shifts in pH. However, in low-alkalinity systems such as the Chattahoochee, Tallapoosa and Sipsey rivers, wide fluctuations in pH can be toxic to fish and other organisms. Excessive vegetation also increases organic material in lakes, which can cause problems in drinking water supplies, Bayne added. Organic matter reacts with chlorine in water processing to create chloroform and other compounds known or suspected to cause cancer and birth defects. Excess algae and organic matter can also cause expensive-to-remove taste and odor problems.

Based on more than 10 years of data reported by ADEM and others, Bayne said 25 of the state's 39 public lakes are now eutrophic, which means they have abundant nutrients and high plant productivity. The remaining 14 lakes have moderate nutrient levels and medium plant productivity.

"Trends of increasing eutrophication are evident in many Alabama lakes," Bayne said. "Of the 31 lakes sampled in 1994 or 1995, 17 had the highest eutrophication measurements ever recorded for that lake."

Lakes Aliceville, Neely-Henry, Weiss and Jordan were already eutrophic in 1985, when the first lake testing was done, and have become even more eutrophic, Bayne said. Weiss and Neely Henry, which are on the Coosa River, are nearing "hypereutrophic," which means excessive nutrients and plant production.

"Lakes on the Coosa River are of particular concern," Bayne said. "These are the most eutrophic lakes in the state, despite the fact that they have relatively short water retention times. In other words, water is flushed from these reservoirs at a fast rate, which lessens the impact of nutrient overloading. A reduction in Coosa River discharge, caused by a drought or upstream consumption of water, could dramatically increase algae production."

Some lakes, including Gainesville and Harris, had only moderate levels of nutrients and plant production in 1985 but are now eutrophic. The largest increases in trophic status since 1985 were seen in lakes Martin, Big Creek, Gantt and Tuscaloosa, which had low initial levels of nutrients. Big Creek, a water supply reservoir for the city of Mobile, is now almost as eutrophic as Weiss Lake. Martin, Gantt and Tuscaloosa are now approaching eutrophic.

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News from:

Office of Ag Communications & Marketing

Auburn University College of Agriculture
Alabama Agricultural Experiment Station
3 Comer Hall, Auburn University
Auburn, AL 36849
334-844-4877 (PHONE) 334-844-5892 (FAX)

Contact Jamie Creamer, 334-844-2783 or jcreamer@auburn.edu
by Robyn Hearn

Feb. 21, 1997