Effects of simulated saltwater intrusions on the growth and survival of Wild Celery, Vallisneria americana, from the Caloosahatchee Estuary (South Florida)

The effects of simulated saltwater intrusions on the growth and survival of the freshwater angiosperm, Vallisneria americana Michx., from the Caloosahatchee estuary (southwest Florida, USA) were examined experimentally using indoor mesocosms. Intrusions were simulated by raising salinity in the mesocosms to 18%o for varying durations and then returning the salinity to 3%o. In separate experiments, exposures of short duration (1, 5, 11, and 20 d) and long duration (20, 30, 50, and 70 d) were examined. Plants held at a constant 3%o served as controls. Mortality was proportional to the duration of exposure. Statistically significant (p < 0.05) losses of blades and shoots occurred at exposures of 20 d or longer, although during a 1-mo recovery period at 3%o viable plants survived the 70-d exposure to 18%o. Expressed as a percentage of initial levels, the extent of recovery after 1 mo was proportional to duration of exposure. V americana can survive the salinity stress associated with most intrusions of salt water in the upper Caloosahatchee estuary.