Emersed (emergent) plants perform many functions in waterbodies:

• Provide habitat for fish.
  
• Provide food (seeds and leaves) and habitat for wildlife populations such as ducks.
  
• Reduce shoreline erosion.
  
• Increase evapotranspirational water losses from a waterbody, sometimes to the point where water levels are lowered.
  
• Shed leaves and other plant debris, adding to the sediments and making the water shallower. As emersed plant debris accumulates in shallow water areas, shorelines migrate lakeward.
  
• Uprooted plants can form floating islands called tussocks that can be significant navigational hazards and block access to parts of the waterbody. It should be noted tussocks also provide bird and wildlife habitat.

Sagittaria lancifolia leafstems are partly underwater and partly above.

Emersed plants react in various ways to changing water levels. When periods of low water are followed by a rapid rise in water level, large sections of emersed plants may be uprooted. Sustained high water can also reduce emersed plant abundance. In periods of low water, debris from emersed plants is a significant factor. Accumulated plant debris can eventually cause the lake to become more shallow, forming a swamp or marsh, and ultimately, peat deposits.

IN FLORIDA
Emersed plants occur naturally in all Florida waterbodies. The width of the emersed zone (from the shoreline out into the lake) may vary from a few feet to hundreds of feet. Its size changes most often in response to changing water levels.

If emersed plants have been allowed to grow without human intervention, the lakeward edge of the emersed plants can be used to show where a waterbody's low water level has been in the last few years or even decades.