IRLNews:2021-03-07/Indian River Lagoon Manatee Mortality
A record 254 (63%) of Florida's total reported manatee deaths were within the Indian River Lagoon National Estuary watershed.[2]
- Volusia = 16
- Brevard = 168
- Indian River = 13
- St. Lucie = 4
- Martin = 24
- Palm Beach = 29
Why does Brevard County have more manatee deaths than any other county in Florida?
There are several factors affecting Brevard's manatee population. All from human impact:
- Natural Migration Interruption - There are an abnormal amount of manatees in the Port St. John's area of the North Indian River Lagoon due to the warm water discharge from the electric power plant. Manatees would normally migrate south as the temperature drops but the power plant's warm water outflow distracts them from their natural migration. During the winter Port St. John's manatee population easily exceeds 500 individuals.
- Loss of seagrass - It is estimated that the Indian River Lagoon has lost over 60% of the record high seagrass coverage recorded in 2005. Nutrient pollution from vehicle emissions, aging septic/sewer systems, and fertilizer in stormwater has increased the levels of Nitrogen and Phosphorus in the estuary. These excessive nutrients feed the spring algae blooms, which cloud the water and block the sun, which causes the seagrass to die. Manatees eat up to 10% of their body weight daily and there just isn't enough seagrass in the North IRL to feed the unnaturally large population.
- Loss of habitat - Most of Brevard's shoreline's are lined with seawalls or impoundment dike roads, there isn't much living shoreline remaining. Manatees have been known to eat shoreline vegetation in Brevard's residential canals, but they can't climb the lagoon's embankments to reach it.
- Compartmentalization - There are eight earthen berm causeways across the Northern Indian River and 5 across the Banana River. These berms are dams that block 80% or more of the lagoon's width. Only a small percentage is open water spanned by Intracoastal Waterway bridges. Having a causeway every few miles is compartmentalizing the Banana and Indian Rivers. Each compartment has it's own feeders, tributaries, drainage canals and saltwater inflows. Some compartments have no inflows at all. The water in some of these IRL compartments has a very low water exchange rate, so what happens in these compartments may remain for over 200 days. The Titusville to Port St. John compartment of the IRL recently received a 7 million gallon sewage spill that may take months to fully dissipate.
Brevard boaters and anglers have been reporting the unusual manatee deaths since December, 2020.
"We should have worked to restore the migration when the lagoon was still healthy, instead of allowing a historic population of 200-300 migratory manatees, that occupied the upper IRL for only part of the year, to grow into a population of over 2000 animals, 1/3 of the states entire population, that now live in and help cause damage to the upper IRL year round.
NASA has been studying overgrazing of the upper lagoons sea grass by this unnatural manatee herd for decades. Manatee organizations and FWC have started to realize the mistake in allowing over reliance on thermal pollution from power plants, but now it’s too late because the manatees are trapped and starving.
This tragic die off that has happened to every other species in the lagoon and now to the manatees is not preventable at this point and we need to focus our efforts on doing what’s right for the manatees and the lagoon, restoring their natural migration before the FPL Frontenac plant is taken offline completely and thousands of manatees die of cold stress much less starvation."commented Billy Rotne, North IRL and Mosquito Lagoon Guide.
Web Links
Documents
- FWC 2021 Preliminary Manatee Mortality Table (PDF 14pp 562KB)
- FWC 2021 YTD Manatee Mortality Table (PDF 1p 113KB)
References
- ↑ FWC 2021 Preliminary Manatee Mortality Table (PDF 14pp 562KB), retrieved on 2021-03-07.
- ↑ FWC 2021 YTD Manatee Mortality Table (PDF 1p 113KB), retrieved 2021-03-07
