Releasing water from Lake Okeechobee apparently helped break up an algal bloom in the canal near the Port Mayaca lock, just as the Florida Department of Environmental Protection (FDEP) scientists predicted it would.
An algal bloom was first reported on April 23 in the area of the Port Mayaca lock on the east side of Lake Okeechobee, in Martin County.
The U.S. Army Corps of Engineers suspended releases of water from Lake Okeechobee while the water was tested.
Monitoring and observations by FDEP and the South Florida Water Management District (SFWMD) were initiated on April 24. Initial results from samples collected by both agencies on April 24 indicated an algal bloom with low levels of toxin detected (less than 10 micrograms/liter) on the canal side of Port Mayaca.
After consulting with FDEP and SFWMD biologists, the Corps decided to resume discharges at the St. Lucie Lock in an effort to break up the algal bloom.
Corps officials explained that algae thrives in stagnant water and it was hoped that the flow would break up and dissipate the algal bloom.
From May 1 to May 3, flows to the St. Lucie Estuary were limited to runoff from recent rains that drained into the St. Lucie Canal. On May 4, the target flow was increased to 900 cubic feet per second (cfs) of water as measured at the St. Lucie Lock, with lake water making up the difference between the runoff and the target flow.
Since that time there have been four additional sampling events performed by the SFWMD. Those samples were shipped to the FDEP laboratory in Tallahassee, which has both algal identification and toxin analysis capabilities.
Samples collected since May 4 have not indicated bloom conditions, and no dominant algal species have been identified. The water samples have consisted of a mixture of various species of algae. Results from toxin analyses have decreased throughout the monitoring period, with no toxin detected in the most recently analyzed samples from May 7.
In addition, FDEP staff visited the Port Mayaca Lock on May 12 and found no algal bloom conditions in the area.
All of these efforts have included coordination with the Corps, which has the responsibility of maintaining water levels in the lake and adjacent canals in order to minimize risks of flooding, and the Florida Department of Health (FDOH), which is responsible for protecting human health against exposure to potentially harmful algae.
On Friday, May 15, the Corps adjusted the discharges from the big lake again — decreasing the amount of lake water released to the St. Lucie Estuary. The new target flow for the St. Lucie Estuary is a seven-day average of 700 cubic feet per second (cfs) as measured at St. Lucie Lock & Dam (S-80) near Stuart.
The target flow for the Caloosahatchee Estuary is unchanged at a seven-day average of 2,000 cfs as measured W.P. Franklin Lock (S-79) near Fort Myers. Flows at one or both locations could occasionally be exceeded by runoff from rain that accumulates in the Caloosahatchee or St. Lucie basins. The basin runoff is allowed to pass through structures as necessary.
“The lake has dropped two-tenths of a foot over the past week,” said Jim Jeffords, Operations Division chief for the Corps’ Jacksonville District on May14. “Additional capacity to send water south has become available as drier conditions have returned. This makes it possible to reduce flows to the east to help keep salinities in a good range in the estuary.”
Lake Okeechobee is currently in the Operational Low Sub-Band as defined by the 2008 Lake Okeechobee Regulation Schedule (LORS). Under current conditions, LORS authorizes the Corps to discharge up to 3,000 cfs to the Caloosahatchee and up to 1,170 cfs to the St. Lucie.
Meanwhile, FDEP is monitoring a reported algal bloom in the canal in Palm City off Mooring Drive. If a bloom is observed, samples will be collected.
In addition, a separate bloom incident has been reported on the northwest shore of Lake Okeechobee. During a fly over exercise performed by the South Florida Water Management District (SFWMD) on Thursday, May 14, an algal bloom was observed from the area of the Lake Okeechobee pier and Pierce Canal along the outer edge of the marsh to the south of Cochran’s Pass. The SFWMD conducted a follow-up investigation on Monday, May 18, which confirmed the extent of the bloom to be from the Lake Okeechobee observation pier on the north end of the lake to Cochran’s Pass and in and around the area of the S77 Moore Haven Lock on the west side of the lake. Samples were collected and shipped to the DEP laboratory for algal identification and toxin analysis. Results should be available by the end of the week.
About algal blooms
There are many types of algae that occur naturally in Florida waterways. Cyanobacteria (blue-green algae) are a type of algae found naturally in aquatic environments. Under the right conditions, cyanobacteria can grow rapidly resulting in an algal bloom. Environmental factors such as light, temperature and nutrients contribute to bloom formation. Some species of cyanobacteria have the potential to produce toxins that can be harmful to humans, pets, wildlife and fish. Even non-toxic blooms can cause harm by creating low dissolved oxygen levels in the water column and reducing the amount of light that reaches submerged plants. With these factors, a rapidly forming, dense concentration of this algae is called a Harmful Algal Bloom (HAB).
According to FDEP, algal blooms vary in appearance and density and it is impossible to predict when or where a bloom will occur, how extensive it will be or whether it will be toxic.
A number of state agencies work together to address algal blooms as a response team, each with a specific role. FDEP, the five water management districts, the FDOH, the Florida Fish and Wildlife Conservation Commission (FWC) and the Florida Department of Agriculture and Consumer Services (FDACS) coordinate and respond to HAB events as soon as staff observe them or they are reported.
FDEP monitors waters throughout the state and maintains laboratory staff who can quickly identify bloom species and determine whether they have the potential to produce toxins.
FWC documents and determines the causes of fish and wildlife mortality events. FWC also monitors coastal waters for HABs, typically referred to as red tides.
DOH has the lead role when a HAB presents a risk to human health or there are reported health incidents associated with a bloom. DOH may post warning signs when blooms affect public bathing beaches or other areas where there is the risk of human exposure. These actions are typically directed out of local county health departments, most often in consultation with staff from DOH’s Aquatic Toxins Program.
DOH also follows up on reports of pets that may have been exposed to a bloom, since these events may predict potential human health threats.
The state’s bloom response team encourages everyone to be on the lookout for blooms and report them. Establishing a schedule for routine observations is one way local citizens, volunteer groups and others can help agencies identify potential HABs and make sure we can respond to them quickly and effectively.
A bloom’s toxicity cannot be determined by looking at or smelling the water; therefore, it is recommended that people avoid contact with algal blooms.
Children and pets are especially vulnerable, so keeping them away from the water during a bloom is especially important.
SOURCES: Information for this article was provided by the U.S. Army Corps of Engineers and the Florida Department of Environmental Protection.