INVESTIGATING THE RELATIONSHIP OF CRITICAL STURGEON HABITAT TO GROUNDWATER SPRINGS IN THE COASTAL PLAIN OF SOUTHEAST GEORGIA

Groundwater springs emanating from the Floridan aquifer system into rivers are well known on the Florida peninsula. The groundwater system there is generally unconfined and karst in nature. Moreover, isolated spring discharge has created zones of localized stream habitat that support certain species. In the southeast Coastal Plain of Georgia, the Floridan aquifer system becomes confined, with confining material reaching a thickness of over 500 ft. Based on a saltwater contamination plume in the upper Floridan aquifer at a major pumping center, high-angle fractures are thought to act as conduits, allowing the upward movement of hypersaline water from deeper parts of the system. In the present study it is hypothesized that such fractures exist elsewhere within the sedimentary section and may breach the surface, creating isolated springs within coastal rivers.

The spring hypothesis is being tested at several deep pools in coastal rivers in southeast Georgia. Aquatic biologists mapping the movement of endangered shortnosed sturgeon have found that the fish congregate in isolated deep pools during summer periods of high temperature and low flow. They believe that sturgeon migrate to the pools for conditions of lower temperature and or salinity created by artesian springs. By collecting discrete bottom samples within the pools and at upstream control sites, the current study is attempting to determine if springs actually exist in the deep pools. Field parameters of temperature, pH, conductivity and dissolved oxygen are measured for each sample along with a complete laboratory analysis of major cations and anions. Should physical and chemical data indicate spring vents, the aquifer source will be identified by installing a piezometer nest near a spring to compare its geochemistry to various aquifers. To date, preliminary results indicate a conductivity and temperature anomaly within the one deep pool sampled. More detailed data will be collected from this and other pools during the upcoming low-flow period. This research is significant since artesian springs have not been identified in southeast Georgia coastal rivers. Furthermore, should springs be found, their association with critical sturgeon habitat may have an important impact on the management of those aquifers contributing to the spring flow.