Comparison of an inactive submarine spring with an active nearshore anchialine spring in Florida

Jewfish Sink is a former anchialine karst feature located in the Gulf of Mexico off the coast of West Central Florida. Freshwater flowed from the feature until 1962 and it is now an anoxic marine basin. The current biodiversity within Jewfish Sink was examined in terms of Bacteria, Archaea, and Eukaryota using a combination of 16S and 18S ribosomal RNA analysis from environmental samples. Analysis of 16S rRNA sequences from microbial mats in the anoxic zones revealed a broad diversity of bacteria (265 clones) and archaea (392 clones), many of which had previously been identified in anoxic environmental samples and are likely to be involved with sulfur, nitrogen, and methane metabolism. Sequence analysis of 785 18S clones revealed that fungi and dinoflagellate sequences dominate the eukaryote sequences. Because Jewfish Sink water is anoxic and high in sulfide, we investigated the effect of Jewfish Sink on the nearby shallow benthic environment. We compared the shallow benthic macrofauna near Jewfish Sink with that near Crystal Beach Spring, an active submarine spring. We found significantly greater species richness, abundance, and diversity of benthic fauna near the Jewfish Sink site than near Crystal Beach Spring. This comparison suggests that greater submarine groundwater discharge in an area with active submarine springs is a significant factor reducing the richness and diversity of the benthic community structure in the nearshore, shallow marine environment.