Like many springs in Florida, Gemini Springs was developed as a swimming hole decades ago.  A cement wall dams the flow a short way down the run, creating a shallow reservoir that was previously used for swimming.  However, in 2000, concerns about fecal coliform bacteria led to closure of the springs to swimming.  Since that time, Gemini Springs Park has been used for its aesthetics, for fishing below the dam, and for terrestrial recreation (playground, dog park, etc.).

Gemini Springs is a pair of springs that together release 6.5 million gallons per day (10 cfs) to a spring run that eventually flows into a “lagoon” and into Lake Monroe.  Originally, there was a third “spring” that was actually a well, according to the St. Johns River Water Management District (http://www.sjrwmd.com/springs/gemini.html), but the well was abandoned and I think that it no longer flows.

The other two springs are small in diameter and the force of the water leaving these springs makes them appear as true boils.  Only one of these springs really has a run, which is quite shallow and sandy; the other spring is adjacent to the first one’s run.  Because the runs are so shallow, the flow rate is quite high and it was pretty challenging to seine where the flow was highest.

The boil of spring 1–the area that looks smoother and slightly milky to the right is where the water boils up.

The run of spring 1 with Missy Gibbs on the bridge doing our “interpretation” for passersby.  Spring 2 is adjacent to the run, just past the bridge.

A portion of the sandy run of spring 1 with the adjacent spring 2 in the background of the photo.  The milky area is the boil of spring 2.  The banks are highly eroded, although this condition appears to be natural.

The sandy area run of spring 1 is firm and, other than the high flow rate and the snags, relatively easy to seine.  It was more challenging in the reservoir due to silt on the bottom and tilapia nests dotting the substrate.  Nitrate and phosphate concentrations in this spring, like many in Florida, are relatively high (nitrate = 1.04 mg L-1, phosphate = 0.06 mg L-1, http://www.sjrwmd.com/springs/gemini.html).  The relatively high nutrient concentrations, which were comparable to those of Volusia Blue Spring, likely contribute to the silt production on the bottom of the run.  Interestingly, the conductivity of Gemini Springs also was somewhat high (2300 microS cm-1); perhaps ancient sea water contributes to its flow, as is the case of its neighbor Volusia Blue (Toth and Katz 2006).

Seining in the reservoir with Adam Freeman.

Not surprisingly, we got only mosquitofish (Gambusia holbrooki) in the boil of spring 1; we measured the lowest oxygen there (0.47 mg L-1).  Oddly, the fish actually were swimming right over the boil rather than along the edges.  The dissolved oxygen was a little higher in the run of spring 1 (0.64 mg L-1) and we caught a greater diversity of fish: sailfin mollies (Poecilia latipinna), bluefin killifish (Lucania goodei), rainwater killifish (Lucania parva), least killifish (Heterandria formosa), a bluegill sunfish (Lepomis macrochirus), and lots of freshwater shrimp!.  The dissolved oxygen was quite a bit higher as the spring entered the reservoir (1.6 mg L-1) and in the reservoir itself (3.1 mg L-1), although still quite low.  Here, we caught a Seminole killifish in addition to the other fish mentioned above.  Although we did not catch them, we observed larger bluegill sunfish and the exotic tilapia (Oreochromis aureus).  We also saw evidence (feces) of Pterygoplichthys disjunctivus, the exotic sailfin suckermouth catfish from the Amazon that Missy Gibbs has studied extensively in Volusia Blue Spring.