Nitrogen – State/Effects

Nitrogen – State/Effects

Click on elements of the flow chart or select from the tabs below

• Pressures
• Management response
• State/Effects
• Vulnerability

Physical-chemical state Changes to the nitrogen load entering a wetland can affect nutrient concentrations in the water/soil.

Nitrogen is transported in the water column and are stored in sediments and plants/algae. Algal (both macroalgae and microalgae) blooms and increased plant growth occur in areas with increased nitrogen and high light availability. Plants and algae can act as nitrogen sinks as they remove nutrients from the water. In wetlands that experience stratification and resultant low dissolved oxygen levels in deeper water, nitrogen can be released from the sediments in significant quantities.

Biological impacts Changes to the nutrient concentrations in the water/soil of a wetland can result in: altered primary production altered food webs a loss of sensitive species altered community structure eutrophication.

Nitrogen rich water entering a freshwater wetland may result in increased primary production which, in turn, may alter the light conditions for submerged aquatic plants, sometimes to the point where they cannot survive. This may lead to a complete change in the ecology of the wetland from one dominated by submerged macrophytes to one dominated by phytoplankton. This has numerous flow-on effects on the biota of the wetland. The death of submerged plants leaves a large pool of organic matter to be decomposed, greatly reducing dissolved oxygen levels.

Nitrogen rich water entering a wetland may result in a change in the food web structure from allochthonous to autochthonous and a change in autotroph and heterotroph biomass. Changes in phytoplankton species composition, size structure and growth rates may occur and plants or animals sensitive to nitrogen may be lost. Higher nitrogen levels may also increase the growth and successful invasion of weed species.

See the nitrogen conceptual model pages for additional information on nitrogen and how it interacts with, and moves through, different systems.

Last updated: 16 October 2020