Manatee Springs felt like the first of several monster boils that I visited on the Suwannee River.  The blue of its vent was truly awe-inspiring.

An underwater view of the Manatee Springs vent; the swimmer gives a scale perspective on the size of the vent.

Being from the eastern part of central Florida, I had not truly appreciated the number of sizable springs on the Suwannee and Santa Fe rivers before starting this project.  Not only are there many more springs in parks on these two rivers than on the St. Johns, but there are many, many, many tiny springs, some even in the rivers themselves.

Map of major (and some smaller) springs of the lower Suwannee River.  http://fcit.usf.edu/florida/maps/pages/9000/f9072/f9072.htm

The area to the west of Manatee Springs appears to be largely preserved, but to the east, most of the land appears to be in agriculture and, perhaps as a result, the springs support a remarkable density of algae.  The nitrate concentration for Manatee Springs appears to be quite high (2.1 mg/L), although the phosphate concentration is low (0.03 mg/L).  Often phosphate is a limiting nutrient, so that the ratio of nitrate to phosphate is as important as the absolute concentrations of the nutrients.  With a phosphate concentration that low, I’m a little surprised that the algae was as thick as it was.

Aerial view of the landscape around Manatee Springs.

Algae in the vicinity of the headspring of Manatee Springs.

The run of Manatee Springs is quite short (this photo shows about the half of the run) and the Suwannee feels quite large at the point where Manatee enters the river.

The run of Manatee Springs.

The Suwannee River where Manatee Springs enters; the trees on the right of the photo are on the bank of the Manatee run.

Although the Suwannee River is quite large at Manatee Springs, the spring produces quite a large plume of clear, freshwater that penetrates into the river due to its high discharge (~150 cfs).  There were a bunch of exotic grass carp (Ctenopharyngodon idella) hanging around in this plume; it was an impressive biomass of fish.  There also were loads of mullet (Mugil cephalus), but they were everywhere.

The grass carp in the freshwater plume from Manatee Springs; apparently, I scared them off into the brown water of the river.

Manatee Springs had a larger proportion of small fish, like bluefin killifish (Lucania goodei) and shiners (Notropis sp.), and a lower proportion of sunfish than the springs that I had visited previously.  I also saw a number of bowfin (Amia calva), which I have only seen rarely at Volusia Blue Spring and I had not seen in any of the other videos so far.

A bowfin coming out of the gloom to menace unsuspecting small fish.  Alas, it didn’t eat one; that would have been exciting.

Bowfin often hide in algae; can you find the one in this photo?  (My kids and I used to love to do those kinds of books when they were small.)