Water: a decorahnews.com special report

The Gulf of Mexico has the second largest "Dead Zone" in the entire world, with an area the size of Connecticut unable to support the marine life that would normally thrive there.

Classified as hypoxic, with less than 2 ppm of dissolved oxygen, the Gulf of Mexico's Dead Zone is inextricably linked to nutrient enrichment from agricultural field runoff along the Mississippi River Valley. The Mississippi River's delta is also subject to nutrient-laden waters fed from the watersheds from the Missouri, Tennessee and Ohio rivers.

Runoff is one major factor in the amount of nutrients that are carried to the Gulf from agricultural fields upstream. The largest dead zone recorded was at the end 2002, at 8,497 square miles. There was a record amount of rainfall in the year preceding this.

Watersheds from states neighboring these rivers carry nutrients, most notably nitrogen and phosphorous, from the surrounding grow fields. The waters of the Mississippi carry these nutrients to the waters of the Gulf, where they can disrupt the local marine ecosystem.

As Luther College biology professor Jodi Enos-Berlage points out, this extreme algae growth leads to a depletion of oxygen levels in the water and has had a fatal impact on the biodiversity of the Gulf's once teeming ecosystem.

Certain types of phytoplankton, which use nitrogen and phosphorous as the building blocks of life, can rapidly increase their populations, which would normally be limited. This algal bloom leads to a depletion of oxygen available to native marine life, effectively suffocating life out of the area.

However, agricultural runoff is not the only factor in the creation of this Dead Zone. Nearly 12 million people live in the urban zones surrounding the Mississippi River.  According the the National Oceanic and Atmospheric Administration, runoff enrichment is complemented by the release of treated sewage from urban areas. Together, the Mississippi delivers an estimated 1.7 million tons of nutrients to the Gulf each year.

As research has determined that Iowa, Illinois and Indiana contribute the most amount of nitrogen and phosphorous to the Gulf each year, state and local efforts are being put forth in Iowa to reduce contributions of these nutrients to the water.

The Iowa Nutrient Reduction Strategy is an combined effort from the Iowa Department of Agriculture and Land Stewardship, the Iowa Department of Natural Resources and the Iowa State University College of Agriculture and Life Sciences to identify the most cost effective practices for nutrient reduction.

Not only will this strategy aim to reduce nutrients from non-point sources like agricultural runoff, but also from point sources, such as municipal and industrial waste from urban centers.

Researchers involved in this project are ultimately hoping to reduce Iowa's total nitrogen and phosphorous contribution by 45 percent. While reduction for non-point source pollution is currently operating on a volunteer basis, the point source reduction plan will require 102 Iowa municipalities (including the Decorah Wastewater Treatment plant) to implement new removal processes for nutrients in the water, funded primarily through municipal water fees and local initiatives, such as Decorah's new storm water utility.

According to local farmers like John Lubke, while non-point source pollution is a major facet in the issue of Iowa's water quality, many involved in the agricultural industry have taken steps toward conservation with strategies such as using cover crops, crop rotation and buffer strips. This series' next article will explore some of the urban issues which adversely affect Iowa's water.