by Gray Merriam

Wetlands trap nutrients from surface runoff and store those nutrients in organic matter and sediments. Much of this process is carried out by green plants taking up the nutrients as they grow. Later, dead plant matter, and dead animals that fed on the plants, all sink to the bottom of the wetlands and become part of the sediments trapped there.

The water gathering in wetlands carries nutrients from the bedrock, the soil and from decomposition of the leaves and other parts of land plants. The aquatic plants of the wetlands assemble those nutrients together with carbon taken in as carbon dioxide and organic matter produced pumps all those nutrients and that carbon back into the sediment in the wetlands.

One wetland filtering the outflow from the Mississippi watershed, downstream of the everglades, received water with 99 parts per billion (pbb) of phosphorus. Filtration by that wetland, lowered the phosphorus content of the water to only 17 pbb of phosphorus. Much of the removal of the phosphorus was done by aquatic plants such as water lily, sedges, spike rush and cattails.

The concentration of nutrients in the inflow to wetlands can be so significant that increasing the nutrient inflow can change the composition of the aquatic plant community. A major impact of the high nutrient load coming down the Mississippi watershed into the everglades was that the characteristic sedge-dominated plant community of the everglades was changed to a community dominated by cattails. Cattails are an indicator of increased nutrients such as phosphorus.

It is this role in removing excess nutrients that earned wetlands the appellation "kidneys of the landscape". Our landscapes in the Frontenacs are blessed with a generous wetland filter system. Just one of the ecosystem services supplied without cost to society.

More information: http://fgcu.edu/swamp Mitsch, W. and J.G Gosselink. 2015. Wetlands. 5th edition, Wiley.