CDC to study and monitor cyanobacterial blooms
The Centers for Disease Control plan to study the health of Lake Okeechobee fishing guides has local anglers questioning the premise of the study and the reasons behind it: Why study the effect of algal blooms on anglers on the lake when the highest toxin levels are in coastal waterways?
In a May 30 email, the CDC clarified the plan, adding that the study may include the Caloosahatchee and St. Lucie rivers.
In an email to the Lake Okeechobee News, the Environmental Health Media office of the CDC stated:
“CDC and the Florida Department of Health are in the early stages of planning a study looking at exposure to and health effects of aerosolized cyanotoxins from blue-green algal blooms and the gases released as the blooms die off. We will use monitoring data to identify geographic areas likely to have toxin-producing blooms and plan to recruit study participants who are likely to be highly exposed to the blooms. We would like to start the study early in 2020 and do study activities throughout the bloom season. The study timing will depend on when CDC obtains approval for the study, as well as the occurrence of any blooms.
“Regarding Lake Okeechobee, we plan to monitor cyanobacterial blooms associated with Lake Okeechobee, which may include connected rivers. Previous sampling by the Florida Department of Environmental Protection on Lake Okeechobee and both the Caloosahatchee and St. Lucie Rivers has shown toxin-producing blooms over the last few seasons. The final sample size and geographical scope of the study will depend on available resources. Exact areas will depend both on location of the bloom and availability of a large enough sample of potentially affected people.
“We will recruit study participants and collect baseline information from them before blooms fully develop. We will also collect data during the bloom season and compare data from the two periods. In this type of study, participants serve as their own controls.”
Closed door meeting
On May 7, Congressman Francis Rooney hosted a meeting of federal, state and local leaders to discuss harmful algae blooms. Members of the press were not allowed at the meeting, which was closed to the public. Following the meeting, Senior Scientist and Environmental Epidemiologist at the National Center for Environmental Health (NCEH) at the Centers for Disease Control and Prevention (CDC) Dr. Lorraine Backer told reporters the CDC would conduct a study on Lake Okeechobee fishing guides to determine if there were any health issues connected with the algae in the lake.
The CDC intends to recruit 50 volunteers for the research, people “likely to be highly exposed to the blooms on Lake Okeechobee … fishing guides (and) people who do charter fishing expeditions,” said Dr. Backer, according to a story in The News-Press.
On May 20, Jenny Birch at the CDC confirmed such a study is in the planning phase.
Lake Okeechobee fishing guides question the need to spend tax dollars on a such a study. They have not noticed any health issues connected to their work on the lake.
What did make their blood pressure rise are concerns that publicity about the study could lead readers to incorrectly assume that toxins are a problem in the Big O. Over the past three summers, when coastal waterways were choked with thick mats of blue green algae that grew as dense as 6 inches thick and produced high levels of toxins, tests on samples of Lake Okeechobee algae showed no toxins or very low levels of toxins, well below the level the World Health Organization has indicated is safe for human recreational contact, according to the FDEP tests. While in coastal waterways, the algae was described as looking like guacamole, the microscopic algae in the water column in the lake was often not even visible to the unaided human eye.
The NOAA satellite images, which some media and politicians touted as showing the lake was “covered with algae” are not photographs, but instead are computer-generated images that use an algorithm to estimate how much algae is present based on levels of chlorophyll. The NOAA images do not indicate what kind of blue-green algae is present. The NOAA images do not indicate whether any toxins are present.
The fishing guides are confident that the lake poses no health risks and a CDC study would prove that, but they worry that the publicity about the study will hurt Lake Okeechobee tourism. Even if the study determines there are no adverse impacts from exposure to the algae in the lake, the fact that the CDC is conducting the study could be used to infer there is a problem.
Algal blooms are common in Lake Okeechobee in the summer, and some cyanobacteria (aka blue-green algae) in the lake can produce toxins, not all blue-green algae has the potential to produce toxins and even blue-green algae that can produce toxins does not always do so. Florida Department of Environmental Protection scientists are still trying to determine what causes blue-green algae to produce toxins.
In the lake, the blue-green algae is usually in the water column rather than at the surface. In the lake, the blue-green algae is feathery and ephemeral. It is moved about with the wind or carried on the currents. Over the past three years, most lake samples found no toxins or very low levels of toxins, well below the World Health Organization’s recommended level as safe for human recreational contact. In coastal waterways, the blue-green algae forms thick mats, described as “guacamole” algae. In coastal waterways, the toxin levels are much higher than found in the lake.
While the prevailing scientific theory is that blue green-algae in water released in the freshwater from Lake Okeechobee “seeds” the algal blooms in coastal waterways, researchers point out that this theory is based on anecdotal evidence and has not been scientifically proven. If the lake algae has seeded the coastal algal blooms, something in the coastal waterways makes it behave differently there. The high levels of nitrogen and phosphorus in basin runoff into the coastal waterways have been described as feeding the blue-green algae “Big Macs,” or an “all you can eat nitrogen and phosphorus buffet” or, as one fisherman described it, “This is your algae on crack.”