Low marsh is a tidal marsh zone. It is characterized as being flooded daily.
The water of the low marsh is shallow, silt laden, salty, and warm. These factors decrease the water's capacity to hold dissolved oxygen. Spartina alterniflora and some types of algae are the only plants that can survive in this zone. Some areas of the low marsh are covered by the tides for most of the day. The mud that makes up the soil in the low marsh has high levels of salinity. A plant that lives in soil that is highly saline is known as a halophyte.