Each of the springs of Florida seems to have its own character and Lafayette Blue Spring seems even more exceptional than most.  It is one of a host of short-run springs on the Suwannee River, but it is further north than the springs that I had visited previously (Manatee, Fanning, Troy, Otter, Hart).  Two characteristics make it different than the other springs: it has a natural limestone bridge that divides the spring on the surface into two pools and discharge that is so variable that the average for 2015 was negative (-13 cfs, the range was -179 to 138 cfs, http://www.mysuwanneeriver.org/portal/springs.htm).  Not knowing the discharge at the time of my visit, what struck me first was the limestone bridge, which looked as if it had been smoothed out to accommodate visitors.

Lafayette Blue Spring from the boardwalk overlook.  The natural limestone bridge is about halfway down the short run.

The limestone bridge of Lafayette Blue.  I was surprised by how wide and flat it was.  Water travels under the bridge from the pool on the right to the pool on the left.

A close-up of the limestone that makes up the bridge.  Limestone is a very soft rock that erodes relatively easily in even very slightly acidic water.

The website “Florida’s Springs” describes Lafayette Blue in this way: “Lafayette Blue Springs is one of the 33 first-magnitude springs in Florida and discharges at a very variable rate, ranging from approximately 13 million to 168 million gallons per day. When the Suwannee River floods the spring vent, which happens fairly frequently, it can become a siphon”  (http://www.floridasprings.org/visit/map/lafayette%20blue%20springs/).  This siphon phenomenon occurs because the aquifer is shallow and unconfined in this portion of Florida (http://www.dep.state.fl.us/parks/planning/parkplans/LaFayetteBlueSpringsStatePark.pdf).  An aquifer is considered confined if it has a layer of relatively impenetrable clay above it.  This clay layer keeps this water separate from the surface water, so without the clay layer, the aquifer water in the vicinity of Lafayette Blue Spring may be more vulnerable to intrusion from the river.  An unconfined aquifer also would be more vulnerable to pollution from surface water.  It appears that the reversal of the Lafayette Blue Spring is a dry season phenomenon, but there were more negative values in 2015 than in any previous year.  I am not sure of the discharge on the day that I was there, but it definitely appeared discharging (rather than siphoning) due to the flow downstream.  At the mouth of the spring where it gets quite shallow, the water velocity was actually somewhat strong, and I had to paddle hard to keep myself from floating out into the river.  Usually, I like to go out into the river, but on that particular day, it was very windy and there were whitecaps out in the Suwannee, so I decided to keep my little boat in the protected valley of the spring.

Video of water rushing out of Lafayette Blue Spring.

Like the other springs that I visited on the Suwannee River, Lafayette Blue had high nitrate concentrations (2.88 mg/L) and moderate phosphate concentrations (0.05 mg/L).  Perhaps as a result of both the nutrient concentrations and the recent rain, the water clarity was not super high and my fish videos were not great.  Lafayette Blue is in a similar type of area, in terms of landuse, as the other Suwannee Springs and its nitrate and phosphate concentrations were comparable to these other springs, but its oxygen concentrations were the lowest of any spring that I have visited to date.  The highest dissolved oxygen concentration that I measured in the spring was 1.12 mg/L on the bank of the first pool in the algae.  Oddly, the oxygen was even lower in the second pool (0.66-0.83 mg/L).  By comparison, the dissolved oxygen  in Rainbow Springs ranged from 6.25 mg/L to 8.11 mg/L in January (during the slow growing season for plants and algae) and the measurements in Salt Springs ranged 3.16 mg/L to 9.98 mg/L in April.  Lafayette Blue Spring oxygen concentrations were an order of magnitude lower than these springs and the oxygen stress showed in the fish behavior.

Google Earth image of the landscape around Lafayette Blue Spring.  Like the other Suwannee Springs, Lafayette Blue sits in a landscape matrix of green corridor along the river surrounded by agricultural fields.  A large green space sits to the west of the spring, but I don’t know the size or shape of the springshed, nor do I know the pattern of flow in that springshed, other than its more superficial connection to surface water than in areas with a confined aquifer.

Juvenile sunfish (Lepomis sp.) breathing at the air-water interface of the first pool of Lafayette Blue Spring.  Small fish like mosquitofish (Gambusia holbrooki) often perform this behavior in low oxygen conditions, but I had not seen sunfish breathing at the surface this way.  Mosquitofish are better suited anatomically for this behavior because the top of their heads are flat.

Female mosquitofish–photo by Missy Gibbs.

Not all of the fish appeared so stressed.  This juvenile sunfish was clearly not gulping air at the surface.  The bubbles on the algae are supersaturated oxygen.  The water cannot absorb the oxygen as fast as the algae are producing it.  The string and float help me find my camera; I usually try to keep them out of the videos…

Overall, the density of fish at Lafayette Blue Spring was comparable to other springs that I visited, even with my probable low estimate due to the poor water clarity.  However, the diversity of fish was lower than any other spring that I have visited.  My diversity estimate is probably artificially low because of the water clarity issue, but I think that the diversity honestly was really low in this spring.  Low diversity would not be surprising given the low oxygen concentrations; many fish would not be able to persist at concentrations that low.

Despite the low oxygen and poor water clarity, my visit to Lafayette Blue Spring was lovely.  I stayed in one of the cabins on the property (which are very nice!) and I was able to experience the spring at dawn and dusk.  I had not realized the full extent of how peaceful a spring can be until I went down there at dawn and dusk.  I was told that the spring can get quite crowded in the summer and the reinforced wall on the side of the second pool was like an echo of summer crowds.  In a way, it made my time there all the more peaceful.

A retaining wall on the bank of the second pool keeps the many summer visitors from causing the bank to cave in.

The Suwannee River at dusk and dawn was amazing, too.

The Suwannee River upstream of Lafayette Blue Spring just before dusk.  I was playing with the color filters on the camera.

The Suwannee River downstream of the spring at dawn.  The float line represents the edge of the swimming area for the spring.