WASHINGTON — Last spring's floods that inundated several Midwestern states washed near-record amounts of nitrogen and phosphorus into the Mississippi River and its tributaries.
As a result, this year's oxygen-deprived "dead zone" that forms annually in the Gulf of Mexico may have exceeded the 8,500-square-mile area that formed in 2002, according to the U.S. Geological Survey (USGS).
In an effort to protect fish populations and other aquatic life, a coalition of national and regional environmental organizations has petitioned the U.S. Environmental Protection Agency (EPA) to set tighter limits on nitrogen and phosphorus levels in the Mississippi River watershed.
Massive amounts of these nutrients contribute to the formation of large algae blooms in lakes and rivers, particularly during the warmer months. As the alga dies, it impairs fishing for bass and other sportfish by reducing the levels of dissolved oxygen in the water. In addition, the alga may form enormous mats that block sunlight needed by native aquatic plant species.
According to the USGS, post-flood nitrogen levels in the lower Mississippi River were the highest recorded since 1991. An estimated 817,000 tons of nitrogen flowed into the Mississippi River drainage. In addition, the river absorbed 83,000 tons of phosphorus, which produced the highest phosphorus concentrations recorded in almost 30 years. Flood waters from swollen rivers and streams cascaded into the Mississippi/Atchafalaya river basin at the rate of 45,000 cubic meters per second, washing away a water flow record that had stood for 25 years.
In 1998, the EPA informed the nine states bordering the Mississippi River that they had no more than five years to develop and implement their own fertilizer limits. Otherwise, the EPA would step in and enforce federal regulations.
But the EPA has never made good on its threat. "The EPA has allowed this situation to worsen," said Susan Heathcote of the Iowa Environmental Council, "by not enforcing its own deadlines."
The National Academy of Sciences (NAS) issued a report earlier this year that stated: "The EPA has failed to use its mandatory and discretionary authorities under the Clean Water Act to provide adequate interstate coordination and oversight of state water quality activities along the Mississippi River."
The EPA has offered no comment or response to the petition for Clean Water Act rulemaking.
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