Soil water salinity variations and their effects on Spartina alterniflora

Soil water salinities at five intertidal elevations of two salt marshes, one on the bay side of Bolivar Peninsula and the other on the bay side of Galveston Island, Texas, were sampled during the summer of 1978. Samples were taken at high and low tides on Galveston Island and high, low, mid high, and mid low tides on Bolivar Peninsula during daylight hours. Salinity values of the soil water were higher near mean high water than at lower and higher elevations and sometimes reached 59 ppt on Bolivar Peninsula and 99 ppt on Galveston Island. The high salinity apparently physiologically damaged and killed the dominant vegetation, Spartina alterniflora, at approximate mean high water. The result was complete loss of plants or stunted growth of Spartina alterniflora at the zone of high salinity. High soil water salinities appeared to be caused by evaporation between tidal cycles and to be related to elevation, distance from bay waters, and range of tide.