Volusia Blue Spring is like home.  I have dodged happy, tube-wielding swimmers in summer and overly-friendly manatees in winter.  I have seen the sunlight stealing into the boil over the trees along its edge in the early morning and the long rays of the setting sun streaming up the run from the direction of the river at dusk.  I have seen the spring steaming in winter; winter is actually my favorite time in the spring.  I have watched rain hitting the water from under the surface; rain drops look like diamonds hitting the water.  I have looked up through the iced tea-colored St Johns River water as it slips over the spring water in the fall when the river is full from the fall rains and the river water is warmer than the spring water.  Probably anyone who has worked on Florida springs has had similar experiences. I have seen impossibly small newborn least killifish (Heterandria formosa) and surprisingly large longnose gar (Lepisosteus osseus).  I have seen more blue tilapia (Oreochromis aureus) and exotic catfish (Pterygoplicthys disjunctivus) than I ever wanted to see.  After visiting all of these other springs, I realized how much I value Volusia Blue.

My happy selfie at the boil of Volusia Blue Spring.

Volusia Blue Spring run, looking up from the St. Johns River early in the morning.

The Volusia Blue Spring headspring with a large tree that fell into the run a few years ago.  The vent itself is just past the tree.

Another shot of the headspring with a little blue heron (that I probably started) flying over to the bank on the left side of the photo.

Volusia Blue Spring is the largest spring on the St. Johns River with a historical average discharge of 157 cfs (its discharge is a little below that now).  Like many of the springs of Florida, it supports a lot of tourism, but the only permanent human elements that intrude on the spring are a set of stairs near the headspring and a big metal swim dock a little more than halfway down the run.  It is managed for swimmers and picnickers in the summer, for manatees in the winter, and for divers year round.

The vent.  I took this photo years ago, but it shows the long, thin vent.  The big springs on the Suwannee, Manatee, Fanning, and Troy, have more circular vents.  In the summer, there are many more swimmers than shown in this photo.

Bubbles from divers in the cave streaming around the tree in the vent at Volusia Blue Spring.  As the divers move through the cave, the bubbles will sometimes seem to come from nowhere, from the sand on the side of the headspring, because the cave travels horizontally so divers can be under foot even when you’re not over the vent.  In this photo, the divers were coming up so there were a lot of bubbles coming out of the vent itself.

Video of the vent with divers’ bubbles.  I thought that that they were prettier in motion than in the still.

Like most of the St. Johns River springs (and probably springs all over Florida), municipal and agricultural water use threatens the maintenance of the discharge for the spring.  It seems like the balance of those two uses differ in the St. Johns River and the Suwannee River springs; I think that the St. Johns springs are more threatened by municipal water use and the Suwannee springs are more threatened by agricultural water use, given the landscapes around the springs.  To protect the discharge in the St. Johns River springs, the SJRWMD (St. Johns River Water Management District) has set a minimum flow level for Volusia Blue Spring that matches its historical mean (the other St. Johns springs minimum flows have been proposed for up to 15% reduction of their historic means) to maintain critical habitat for the Florida manatee (Trichechus manatus).  And manatees flock to the spring in ever greater numbers; this past year the short and wide spring run (~30 m x 650 m) hosted 533 manatees with 50 calves (http://www.savethemanatee.org/cam_manatee_reports.html).  Unfortunately, the other springs on St. Johns River do not have the protection of a large, noticeable, popular threatened species.

These juvenile manatees nursing on their mother made it to the “cutest twin animals” page for the Daily Rattle (http://www.dailyrattle.com/cutest-twin-animals-15-images/).  Too bad that they’re not twins!  The one on the right is clearly older; manatees stay with mothers for one to two years, so the one on the right was probably last year’s calf.  It does not appear that that individual has been in the run for very long; the exotic armored catfish (Pterygoplichthys disjunctivus) usually clean them off by grazing on their backs pretty quickly and that one clearly has algae on its back.

Although the discharge target for the minimum flow was set for its historic mean, the spring is not there yet; the last year for which I had a complete data set (Sept 2014 – Sept 2015), the discharge was ~142 cfs.  According to the MFL (minimum flow and level) program, the target was not supposed to be achieved until 2024.  Hopefully, we will get there.  The nutrient concentrations of Volusia Blue Spring also differ from the Suwannee River springs, which tend to be extraordinarily high for nitrate, but moderate for phosphate.  Volusia Blue, on the other hand, has moderate (although increasing) nitrate concentrations (~0.8 mg/L) and slightly high phosphate concentrations (~0.075 mg/L) than the Suwannee springs, according to SJRWMD (http://www.sjrwmd.com/springs/blue-volusia.html).  The difference may be due to the landuse around Volusia Blue, which tends to be municipal rather than agricultural.

Google Earth image of the landscape around Volusia Blue Spring.  Although there are large green spaces along the St. Johns River to the west and in the lower lying areas to the east, the springshed is comprised of the lower half of DeLand, Orange City, and most of Deltona rather than these green spaces.  The springshed sits on the “DeLand Ridge”, which is high ground and great for building, hence the location of our towns.

Algae can grow pretty thick in Volusia Blue at times, but I have now seen many springs on the Suwannee that support much larger algal populations–even in winter.  Last winter, I tried to get some algae for a student project in Volusia Blue and I was unable to find much of anything.  No doubt the 500+ manatees affected the algal population size, if only by sitting on it, but still.  The exotic armored catfish (P. disjunctivus) and blue tilapia (O. aureus), both of which can be much more abundant than manatees, also likely reduce algal population sizes, as do people. In the spring, I can always tell when they open the swimming area after manatee season because there is a strip of sand down the middle of the run from people’s feet dislodging the blanket of algae where they walk most often.

The edge of the stripe that forms as people walk on the bottom of the spring.  It forms each year after the park opens the spring to swimmers.

I always thought that it was funny when I heard people say that there weren’t any fish in Blue Spring (you overhear all kinds of things while sampling) because there are millions of fish if you look.  There are gradients in fish abundances along the length of the run, from the headspring to the St. Johns river, following the oxygen gradient.  At the headspring, the oxygen is incredibly low; the dissolved oxygen in the water coming out of the vent is 0.1 mg/L, which is essentially nothing.  As a result, most of the fish at the headspring are the small mosquitofish (Gambusia holbrooki) and sailfin mollies (Poecilia latipinna) that can breathe at the air-water interface where the water is more oxygenated.  During our surveys, we often observed some scattered sunfish (Lepomis sp.) in some bushes on the bank of the headspring where some algae accumulates, but not really anywhere else.  However, in the videos I discovered fish that were in more open areas, but working really hard to breathe.

Video of sunfish breathing at the headspring.  When they were not breathing at the surface, it appeared that they were working really hard, holding their opercula (the flaps over their gills) out farther than normal and moving them faster.  I’m not sure when I’ve seen fish work so hard to breathe.  Mosquitofish and sailfin mollies are breathing at the surface in the background.

A little further down the run near the diver entry, the oxygen concentration is typically a bit higher (it was 1.15-1.32 mg/L when I visited in the morning) and the small fish diversity typically increases to include more killifish (Lucania spp., Fundulus spp.), shiners (Notropis spp., Notemigonus crysoleucas), and sunfish (Lepomis spp.).  Occasional largemouth bass (Micropterus salmoides) pass through.  However, I discovered a large number of juvenile sunfish breathing at the surface.  Up until then, I did not even realize that that was a sunfish behavior.

Sunfish (bluegills, Lepomis macrochirus, and redear, Lepomis microlophus) downstream of the headspring of Volusia Blue Spring.  These sunfish appeared to be interested in the camera, but those in the background are breathing at the surface.

The same location with a largemouth bass cruising through an aggregation of sunfish and seminole killifish (Fundulis seminolis– not apparent in this still, but in the footage right before the bass comes in).

Further still down the run in the refuge, the sunfish get larger and longnose gar become abundant.  The gar can be so large that they can be almost as long as Missy Gibbs is tall (she’s not short), which is how I evaluate how big they are while snorkeling with her.  Mullet (Mugil cephalus) and blue tilapia cruise up and down the run.  In the winter, small tarpon (Megalops atlanticus) invade the run.  Whereas the gar literally just hang there while we swim past, the tarpon are very skittish and freak out when we approach (and then sometime follow us, which is a little creepy).  Alas, there were no tarpon on the day that I visited the spring with cameras.

Video of gar and armored catfish in the refuge below the swimming area.  The armored catfish usually stick close to the bottom, but this one appeared to be following the gar.  The spring is much deeper in the refuge, so the footage appears blue.

The most dramatic event of the trip, after I had downloaded the footage, was the discovery of a cichlid that was not reputed to be in the St. Johns River drainage basin.  Given that I found this black acara (Cichlasoma bimaculatum) in 14 minutes of footage, there are likely to be many others.

A black acara near the small spring that enters the run about 1/3 of the distance from the headspring to the St. Johns River.

The distribution of the black acara in March 2017 (it goes farther north now, alas).

In addition to potential reductions in discharge, increases in nutrient concentrations, and invasions of exotic species, Volusia Blue Spring has an erosion problem.  This problem, at least at the headspring, is largely human-made.

This bank was not nearly as steep when Missy Gibbs and I started working here in 2000.  The park had to move the overlook in the background further back in the early 2000s because the previous one was going to fall into the spring.  Kids climb the bank and jump off.  Enough said.

That palm tree was not that far out into the headspring years ago (if I remember correctly, it was on the bank!).  The tree that protrudes across headspring in the background fell in due to erosion.  Kids like to sit on it now.  The eroded bank is visible behind the tree.  That bank, like the bank under the overlook, has been falling in for years.  Sigh.