Red tide increased in waters off Anna Maria Island during the week ending Sept. 14, according to the latest report from the Florida Fish and Wildlife Conservation Commission (FWC), and forecasters predict high concentrations through at least Sept. 18.
While the Sept. 14 report shows that overall Manatee County red tide levels were from 5 percent to 25 percent lower than the previous week, high concentrations of red tide were found in water samples taken at the Rod & Reel Pier in Anna Maria and at Longboat Pass and Cortez Beach, both in Bradenton Beach. Low concentrations were found at the Palma Sola Bay bridge. Samples in all those locations showed higher red tide concentrations than the previous week.
At least 140 manatees have died during the red tide bloom that has plagued Southwest Florida since October 2017, and which reached Anna Maria Island on Aug. 3.
To date, 47 dead manatees tested positive for red tide, and red tide is suspected in 93 manatee deaths, according to the FWC.
Six manatee deaths have been recorded in Manatee County so far this year, two in Anna Maria Sound; none are confirmed from red tide.
So far this year, 599 manatees have died in state waters, compared to 538 in all of 2017.
Background concentrations of red tide cause no anticipated effects. Low levels can cause respiratory irritation, shellfish harvesting closures and possible fish kills. Medium levels can cause respiratory irritation, shellfish harvesting closures and probable fish kills. High levels can cause all of the above, plus water discoloration, which was reported on Friday, Sept. 14.
Respiratory irritation was reported from Sept. 9-12 at Coquina Beach (Bradenton Beach) and Sept. 7 and Sept. 9-14 at Manatee Beach (Holmes Beach).
The last reported fish kill in Manatee County was on Sept. 8.
Red tide is a type of algae that emits a neurotoxin when it blooms. Deadly to fish, sea turtles, marine mammals and shorebirds that feed on affected fish, red tide makes shellfish unfit to eat, and can cause respiratory irritation in people, especially those with asthma, COPD or other respiratory diseases.