Killing Turtles

July 31, 2018

We know the problems algae blooms can cause for humans—from unpleasantly slimy beaches to interruptions in the water supply to occasional respiratory problems in people who are exposed—and Florida seems to get more than its share each summer. Two years ago, thick algae on the state’s Atlantic coast led four counties to declare a state of emergency. The situation was blamed on nutrient-rich water from Lake Okeechobee; the Army Corps of Engineers had to release the water to relieve the pressure on an aging dam. Last summer, locals were afraid a repeat of the algae blooms would harm the state’s tourist industry, which brings in more than a billion dollars a year.

This year, in addition to the other problems they cause, the algae blooms are killing sea turtles, manatees, and fish. So far, 287 turtles are reported to have died because their food sources have been contaminated by toxic blue-green algae. Most are either loggerhead turtles, which are a threatened species, or Kemp’s ridley sea turtles, which are endangered. Researchers who have been encouraging their recovery are afraid this year’s deaths will be a tremendous setback. In this article, Kelly Sloan of the Sanibel-Captiva Conservation Foundation says most of the turtles her organization has rescued or has found dead have been mature adults. “Only one in 1,000 make it to adulthood,” she says. “It takes a loggerhead 25 to 30 years to mature, so that really does have a significant impact on their recovery.”

The turtles are dying at about double the rate normally expected for the time of year. Some are washed up on local beaches, while others are found floating in the water. “They float at the surface, and the waves bring them in, but we only get a certain percentage of what’s dead out there,” says a Collier County official. “We get what floats to the beach or if someone just happens to see one. Everything else decomposes or sinks after a while, so we get a small percentage, and we know the numbers are actually higher.”

Although the algae blooms occur naturally and are expected to some extent each year, this one is larger and has lasted longer than most—about nine months with few signs of abating. Typically, as this article explains, wind, water currents, and even competition from different types of algae cause the blooms to dissipate. The problem is again blamed on nutrient-laden runoff as well as on higher-than-normal water temperatures.

About the Author

Janice Kaspersen

Janice Kaspersen is the former editor of Erosion Control and Stormwater magazines.