Wetlands and Water Quality: A Brief Primer
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A look into how and why wetlands are important.
By Jim Beets
Sierra Club member Jim Beets was a professor of marine biology at Jacksonville University until 2002, when he moved to Hawaii to continue in his profession.
Most of us recognize the importance of wetlands for preserving important habitats for plants and animals, but we usually don't consider the important functions (and free services) that wetlands do for us. In Florida, more than 50 percent of the state was once covered by wetlands; today we have approximately 10 percent wetlands cover (estimated at 60-80 percent loss), and we are still losing more annually. The remaining wetlands become increasingly important.
One of the most under appreciated services is maintaining water quality. Wetlands vary greatly in type (amount of water, soil type, location, etc.) and have varying important environmental functions. However, most help maintain water quality, especially the small streams that flow into rivers.
The greatest benefits of wetlands to maintaining and improving water quality are that they trap sediment, remove harmful amounts of nutrients (mostly nitrogen and phosphorus), and remove pesticides before they can enter streams. For all these reasons, there should be a strong effort to maintain or restore wetlands, especially adjacent to streams.
The appearance, character and function of wetlands vary depending on the depth of the water, length of flooding and characteristics of the surrounding land. The different types of wetlands provide a unique array of habitats for many species of wildlife. Wetlands that do not contain standing water all year still provide valuable wildlife habitat. The vegetation growing around the wetland edge serves as food and cover for many wildlife species, particularly during migration.
A big job: Nutrient and Sediment Filtering
Often found in areas of intense agricultural production, wetlands play an important role in maintaining local water quality. Wetlands preserve water quality by removing nitrogen, phosphorus and pesticides from agricultural runoff.
In most cases nutrients are recycled within the wetland. Emergent and submerged plants bring nutrients from the sediment into the water column, acting as "nutrients pumps." Algae and floating plants serve as "nutrient dumps" by taking nutrients from the water and depositing them back in the sediment when they die and settle on the bottom.
The cycle breaks when nutrients are removed from the wetland system, occurring when nutrient-rich water flows out of the wetland. The release of nitrogen gas to the atmosphere by denitrification, ammonia volatilization or possibly nitrification of ammonia also causes nutrients to be lost.
A wetland's natural filtering ability can become overloaded, disrupting the nutrient cycle. Steps can be taken to prevent overload by reducing nutrients and chemicals lost from agricultural fields.
A few other services are: Wildlife Protection, Fisheries Habitat (direct economic benefit!), Flood Water Retention, Storm and Flood Protection, and Erosion Control.
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