Single-cell Karenia brevis packs a mean punch.

Biologists and experienced anglers are quick to note that fish stocks do rebound in the wake of red tides. “In the past it’s bounced back quick,” said Sargeant, “but this one was so long lasting and widespread it may have more of an impact.”

While red tide was heavy in Sarasota Bay, Mote Marine performed some of the first-ever research on systems which could be used to control the blooms. One involved the spraying of clay slurry on the surface; a study showed that clay trapped suspended red tide particles and carried them into bottom sediments. Ozone was also being studied in a laboratory setting at Mote. A few miles south, at Venice High School, an enterprising, if somewhat secretive, science teacher demonstrated small-scale, lab success with a formula he claims kills the red tide organism. More interpretation of data was forthcoming, as was speculation on the economics of using such measures—and possible side effects.

Coastal residents asked about possible links between red tide blooms and nutrient runoff, such as that which contributes annually to the huge algae bloom off the Mississippi River delta—an oxygen-depleted (hypoxic) dead zone nearly the size of Connecticut. Researchers can predict, with surprising accuracy, the size of those blooms based on phosphorous and nitrogen loads in the Mississippi and Atchafalaya River basins. They have determined that the primary source of the two elements is runoff from agricultural lands in the upper areas of the Mississippi watershed—fertilizers used on farmlands in Iowa, Ohio and other areas.

A key difference between red tide and the algae blooms off Louisiana: Red tide is caused by a single dinoflagellate whose behavior scientists are still struggling to understand; the Louisiana blooms are composed of many kinds of phytoplankton, whose overall behavior has been clearly linked to certain human-related inputs.

Florida has taken some modest strides to track and study red tides. The FWC issues a regular update on red tide conditions. Pierce said that Mote and FWRI are currently engaged in a 3-year cooperative effort to assess the issue of nutrient loading from sources like the Caloosahatchee River and tributaries to Tampa Bay.

For an online global perspective on red tides and other harmful algae blooms, check out the Woods Hole Oceanographic Institute Harmful Algae Page, www.whoi.edu/redtide/.

(Next month: Plankton Power, all about these tiny life forms.)

FS