What Makes Wetlands Stink?


wetlandsOne of the most recognizable features of wetlands across the country is their smell. But what is it that makes these areas so pungent? To find out, you’d have to stick your nose all the way down to the mud, and even then, you wouldn’t be able to see the microscopic organisms that are responsible.

Wetlands serve an important function as “recycling stations” of sorts, collecting organic litter in the form of dead plant matter and animal waste and reducing it to usable nutrients again. Through this process, bacteria and fungi break down the structural elements of leaves and other materials, creating byproducts that either enrich the soil with nutrients or escape in the form of gasses.  This escaped gas is what we smell.  Different types of wetlands house different bacteria and fungi, resulting in different gaseous byproducts. Two common – and stinky – wetland gasses are sulfur and methane. In coastal salt marshes and estuaries, smooth cordgrass is a common wetland plant that stores large amounts of sulfuric compounds from the ground and water.  When the plant dies and begins to decompose, these sulfuric compounds are broken down through a series of steps resulting in the release of hydrogen sulfide gas, among other byproducts.  You may recognize this chemical better as the rotten egg smell you pick up around salt marshes and other wetlands.

Viewer Tip: Even though we can’t see the bacteria carrying out the decomposition processes, we can still have a major impact on their ability to help cycle nutrients through a wetland. Pollutants like fertilizer runoff or boat engine oil leakage can throw off the chemical balance that the bacteria rely on.  Learn more about small ways you can help protect wetland health in your region here.

(Sources: Sundareshwar, P.V. “Decomposers.” National Estuarine Research Reserve System, 2001.

Photo courtesy of maine.gov