November 9, 2014
Scientist say red tide fueled by 12 sources
By Chad Gillis
Scientists studying red tide have identified a dozen nutrients sources that feed blooms, but they say no single source is responsible for the toxic outbreaks.
Scientists hope this latest research will help them better track future blooms, which can harm the marine ecosystem and Florida's tourism industry.
have likely occurred for thousands of years and are a natural phenomena, but
scientists haven't pinpointed exactly what causes Karenia brevis to go from
normal to deadly levels. Upward of 236 manatees were killed in Lee County by a
red tide outbreak in 2013. Causes of death for some animals were undetermined
but thought to be related to the red tide bloom. It occurs throughout the
of the most interesting things that hadn't previously been taken into account
is the organism's ability to not just use sunlight, like plants, but also
consume other single-celled organisms as a nutrient source," researcher
Judith O'Neil, a
nutrient sources listed in the report include: bacteria transforming nitrogen
in the water into more useful forms, decay of
things I hadn't heard about red tide consuming before were small phytoplankton
other than Trichodesmium and
known sources include stormwater run-off, septic tanks, and excess nutrients
from the upstream water management system, which starts south of Orlando and
current bloom is mostly offshore of Lee and
"It started offshore and came into the passes, like Redfish and Boca Grande," he said. "Concentrations are still higher in the north part of Pine Island Sound."
Bartleson said he wasn't surprised that red tide can subsist on a variety of nutrients, most of which are too small to be seen by the naked eye.
"I can see how they would discriminate based on particle size," Bartleson said. "It's not like they have brains and eyes to see what they're eating.
Connect with this reporter: ChadGillisNP on twitter.
Karenia brevis in cells per liter
• Background: 1,000 or less
• Very low: 1,000 to 10,000
• Low: 10,000 to 100,000
• Medium: 100,000 to 1 million
• High: 1 million and above
— Source: Florida Fish and Wildlife Conservation Commission