Phil Busey Agronomy
Consulting Inc.


 

Ecosystems

Runoff

Photo Credit: Lynn Betts | USDA NRCS

Eutrophication and invasive species are major management challenges in natural ecosystems. Eutrophication is caused mostly by nutrient enrichment, nonpoint source pollution of excess phosphorus and reactive nitrogen, e.g., nitrate. Nonpoint sources include runoff from agricultural areas, failed septic systems, construction, and atmospheric deposition. Karst geology in some spring areas of Florida can be polluted by leaching. Freshwater ecosystems are generally more impacted by phosphorus, while saltwater ecosystems are more generally impacted by nitrate.

Wetlands and shallow water bodies are particularly prone to eutrophication. Excess enrichment of nutrients can stimulate cycles of rapid plant growth, often of algae and invasive higher plant species, seasonal decay and anoxia (low oxygen), buildup of organic matter and sediment, and rapid aging. During the process of degradation, wetlands and shallow water bodies lose habitat value for wildlife, recreation, watershed, and other economic activities such as hunting and fishing. In the Everglades, natural levels of phosphorus are less than rainfall, which makes the Everglades vulnerable to enrichment by exogenous (external) anthropogenic (human-generated) sources of phosphorus.

Fortunately, reduction of exogenous phosphate and nitrate can slowly reverse the process of eutrophication or, with professional management plans, reduce it in the first place. There are many ways this can be accomplished.

Buffer strips reduce nutrient laden runoff. Soil testing before fertilizer application reduces unnecessary nutrient application. Redirection of runoff can allow for reuse of nutrients in cropland or retention in areas for physical and biological purification.

Invasive plants, some particularly well adapted to eutrophic wetlands, contribute to habitat change and can reduce access and food reserves for local fauna. A management plan for new wetlands, e.g., mitigation areas, and restored wetlands, should include monitoring and testing of soil and water during site development, and thereafter periodic monitoring of nutrient levels and species distribution. Phosphorus can be tied up in sediment and be released over time, so testing of sediments is important in developing a long-term management plan.