Subsurface hydrology is controlled by lithology, buried subaerial unconformities, and by Holocene carbonate mud overlying karstic Pleistocene grainstones and reef deposits. Tidal pumping, sufficient to raise water 20 cm above sea level, suggests leakage of nutrients and bacteria into surface marine waters, especially near shore where there is no overlying Holocene sediment. Higher sea level in Florida Bay causes ground water to flow through the Keys and likely incorporates nutrients and bacteria from the 30,000 septic-tank drain fields and approximately 700 shallow sewage water injection wells. Because flow is toward the reef tract, both natural and anthropogenic nutrients may cause observed blooms of benthic algae and coral diseases.
What is the volume of groundwater seepage from limestone surfaces in Florida Bay and the Florida Reef Tract?
What are the nutrient level and coliform bacteria content of water seeping from the limestone?
What is the origin of coastal green water?
What is the effect of nutrient-rich, oxygen-depleted groundwater seepage on benthic biota?
How does tidal pumping affect seepage rate and water quality?
Is seepage more prevalent on the Atlantic or the Florida Bay side of the Keys?
Are there tracers in the seeping groundwater that will identify the source of nutrients? and
Is seepage of groundwater the ultimate source of nutrients leading to algal blooms?
The sampling is done by attaching a plastic bag to the station and collecting over one tidal cycle. The sampling is coordinated with another USGS groundwater flow and direction study. Initial assumptions are that the groundwater flow is east to west and the seepage from groundwater, especially near shore, is related to algal bloom festations increasing in the Keys. Lab analyses follow the COMPQAP 910161G for quality assurance/quality control.