Response of Coastal Plants to Salt Water Intrusion

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Southern Florida's relatively shallow freshwater table in a porous substrate, (oolitic limestone), is particularly susceptible to ocean water intrusion. Other than gross effects, little is known about more subtle effects and processes responsible for this intrusion. It is well known that pumping of ground water to supply expanding urban areas and canal building have contributed to intrusion problems. Several questions about salt water intrusion remain to be answered, however. For example, Is there a seasonality of intrusion; dry season versus wet season? If ocean levels are rising because of global climatic changes, is this effect already detectable in coastal plant communities of southern Florida? What about the effect of salt water intrusion in plant communities; will this mean an increase in exotic pest plants? The proposed research addresses such questions. The results of this research will answer many basic scientific questions about how plants react to periodic and chronic salt water stress. The research will rely heavily on stable isotope analysis of plant biomass. Recently much has been learned about biological systems with this technique. Stable isotope analysis will shed light on the history of salt water intrusion in plant communities. In addition, stable isotope techniques can be used to integrate hydrological and ecophysiological concepts in the study of salt water intrusion. The potential applications of this research are quite clear. Much of the salt water intrusion in southern Florida is caused by water management projects. This research can aid in predicting more precisely the effects of water management strategies. As an example; if ocean water intrusion is seasonal, then an appropriate strategy would be limitation of freshwater pumping during the dry season. Further, the experimental techniques to be used here will permit the detection of salt water intrusion in plant communities before irreversible changes occur.