Doctors Lake was Florida’s most toxic body of water

My fondest memories of growing up were along Doctors Lake, but never actually in the water.

After hearing “brain-eating amoeba” stories my entire life, I was reluctant to kick off my paddleboard or cast a fishing line. However, the dock jutting from Doctors Lake Park was the centerpiece of my adolescence — my friends and I slumped out on the plywood boards watching meteor showers, contemplating life and death and what comes after.

One evening years ago, we were passing a vape pen back and forth when we decided someone needed to jump in off the dock and swim around for a bit. As a joke, I raised my hand to volunteer.

My friends Ibram and Bishoy put up real money if I went through with it. I held up my Venmo account—again, as a joke — and I was shocked that their payments went through.

In a video they recorded, I shakily climbed up onto the railing and made a sign of the cross. My feet lifted off the railing, and I felt the embrace of the black, brackish water, which was warm like a bath.

When I swam back to shore, my body was covered in a film. Still, it was the easiest $50 I had ever made. As I dried off, I told them I’d do a backflip if they offered the deal again.

I would turn down the $50 deal if it were offered today.

I've been following the Florida Department of Health's weekly blue-green algae reports this past summer. Doctors Lake has quietly and consistently topped the leaderboard. 

Whenever the FDEP or St. Johns River Water Management District identified positive samples of toxic chemicals, the vast majority came from Doctors Lake — 79% of all positive sites at the beginning of July and 58% at the beginning of August.

Toxins known as "microcystins" have been found all along the inlet's shoreline —Mill Cove, Pace Island, Wyndegate Drive, Camp Echockotee, Magnolia Road and the end of Lawrence Road — and also at the inlet's center. 

Short-term exposure to microcystins can trigger flu-like symptoms, while long-term exposure has been linked to neurodegenerative and liver diseases. Even worse, the toxins are durable and can linger along the water’s surface for weeks. They cannot be removed or neutralized even by boiling water.

FDEP found a particularly potent and damaging strand of microcystin, “MC-LR,” at its highest concentration of 12 mg/L on July 9. This is 12,000 times higher than the World Health Organization deems safe for potable water. 

Based on the FDEP blue-algae dashboard, the only sites with a higher toxin concentration than Doctors Lake this summer have been a few canals in South Florida and Lake Okeechobee. Unlike the canals and Lake Okeechobee, where concentrations would spike and then plummet back to “trace levels,” Doctors Lake has consistently sported concerning concentrations all summer.

Why has Doctors Lake been so particularly hazardous? The answer could be the 15th element on the periodic table — phosphorus.

Just like plants, blue-green algae need phosphorous to grow naturally. When the water is warm, slow-moving and rich in nutrients—phosphorous most especially — the algae “blooms” and appears as a green slimy muck on the water's surface, like a viridescent oil spill. Algae grows out of control when the water is overloaded with phosphorous, and that's typically when its toxins are able to harm animals and people. 

One common source of phosphorous is in fertilizer. Similar to how it increases crops in farm fields, phosphate-based fertilizer runoff increases algae growth in water. Another source is found in sewage (yuck), which can also leach into bodies of water.

While phosphorous is in demand worldwide, Florida ironically suffers from having too much of it. Central Florida’s “Bone Valley” contains the nation's largest phosphate deposits, which are mined and exported internationally. However, the phosphorous leaching into Doctors Lake may be from sources closer to home.

Years ago, the Clay County Water Authority led a campaign along Doctors Lake that connected 68 homes to a central sewer line to prevent runoff from faulty septic systems. Despite CCUA’s best efforts, Doctors Lake continues to be plagued by toxic algae blooms. This is the third summer in a row that the FDEP has issued health advisories for the inlet. Phosphorus still somehow manages to find its way in. 

Doctors Lake is surrounded by suburban developments: Pace Island, Eagle Harbor, Heritage Farm, Lakeside and Orange Park. A defining feature of suburban living is a hearty, manicured green lawn. Stroll around Doctors Lake in the summer, and you’ll smell the aroma of freshly cut grass.

Phosphate-based fertilizers are commonly applied to lawns, and overfertilizing leads to severe environmental consequences. Excess fertilizer is washed away with the rain into storm water drains that carry the phosphorous and other excess nutrients into natural water ways, such as Doctors Lake.  

Green yards. Green shorelines.

The algae blooms are a literal and symbolic reflection not just of Florida's green yards but also of the chemicals that keep them that way.