Day 4: Manatees and Sea Turtles

 30/10/22

 28.88 °C

Manatee Lagoon

11.00 am

We, guided by a student at Florida Atlantic University called Sam, entered the eco discovery center at Manatee Lagoon in West Palm Beach Florida. Manatee Lagoon was built by Florida Power & Light Company, who own the Energy Center next door. The center aims to educate the general public on manatees and wildlife, primarily in Lake Worth Lagoon. 

Why manatees come to the center

Manatees are of the family Trichechidae, closely related to dugongs (who don`t have the single tail pad) and elephants

There are three species of manatees:

Amazonian 

West African

West Indian

In Florida they have a population of 6-10,000 Trichechus manatus (West Indian manatees), specifically the subspecies Florida manatee.

Manatees are marine mammals.

They have vibrissae that help them feel their environment, a lower jaw and marching molars that continually move forward to replace teeth worn down by grazing. Their pregnancy lasts a year and they suckle young using nipples behind their flippers.

Their main diet is seagrass which grows three to five feet down in brackish or salty waters. Adapted to this lifestyle, the manatees have flexible lips to grasp at the plants and solid bones so that they can sink with their three foot long lungs.

The downside of having a highly specialised diet is that seagrass limits their population. In the last two years 1000 have died from starvation in Florida. This is because nutrients from agriculture trigger algae blooms that cut off the light seagrass needs to grow. The term 'Red tide' refers to blooms of algae that are toxic both to us and manatees which can be triggered by the pollution.

To aid with limited food short term manatees are fed cabbage by the centre from a boat. Long term replanting of grasses and education is carried out as well. Part of the project is that locals are told not to mow lawns or put fertilizers on before heavy rain. 

Threats

Entanglement is another danger manatees face, cutting off circulation around the body. 

Motor Boats

Conservation

Manatees are curious animals, often approaching people and boats. But to ensure the safety of these endangered animals it is illegal to advance towards them and disturb them. 

In summer, boats are banned completely down Lake Worth Lagoon to prevent collisions. All year round there is supposed to be an enforced speed limit, Sam exclaims, but this is often ignored.

If a manatee is wounded or has been re-released from rehab (One of the main rescue centers is Seaworld) tracking tags are placed round the tail in front of their paddle. Attached to the tag is a coloured floaty device that identifies the animal and visually locates the manatee.

Other species that are found in Lake Worth Lagoon are loggerhead turtles, green, kemps and ridley turtles.

Us students went out at mid-day outside round the centre to attempt to spot manatees. None were seen but two students saw a green sea turtle.

I saw sergeant major fish, ribbon fish and trevally jacks swimming in groups of three to five.

You would not think it, but Lake Worth Lagoon actually used to be a lake, but was carved out into intercoastal manatee habitat in the early eighteenth century.

Loggerhead Marine Life Center

After Manatee Lagoon we swam in the sea and drove down to Loggerhead Marine Life Centre in Juno Beach.

Tina, an employee at the center, was there ready to give us a talk on turtles. 

The centre has no resident turtle, it is purely a place for turtles to recover and get back into the wild. Monitoring during the March to October breeding cycles is undertaken as well by the organisation on the 17,000 nesting sites along Juno, Jupiter-Carlin and Tequester Beaches.

As there is a shortage of space along the beaches primarily loggerhead turtles, who do not mind crowding, ride the gulf stream to reach the beach and nest.

Overall, there are seven different species of sea turtles ranging from the giant eight foot leatherback to the critically endangered kemp`s ridley.

Patients

Flippers can be lost and shells punctured by sharks, as long as a turtle keeps its rear flippers for digging nests it can manage without one front flipper. Infections in the shell can lead to floatation problems, one of the green turtles we noticed while going around the center suffered from this. A weight had been attached to its shell whilst the infecting gas releasing bacteria causing the turtle to float is killed off.

Boat strikes can cause floatation problems and paralysis as well. 

If a turtle is seen floating for long periods it is a serious sign that the reptile is injurd. Green turtles can hold their breath for 6.5 hours and will lower their heart rate and metabolism to sleep underwater. To tell If a turtle has been floating for a long time how the thickness of the epibiota growing on its shell can be studied. 

 

The center feeding a green turtle

Threats

Poaching, hawksbills are poached for their shells. 

Pollution such as plastic. Balloons are mistaken for jellyfish and so have been banned in Florida.

Turtles are caught as bycatch

Climate change, which alters the sex of hatchlings skewing the ratios of females to males

Nesting

Green sea turtle,  Chelonia mydas

Turtles will haul themselves out of the water to dig a nest. Sometimes they will do false crawls, where they determine that the spot is not right and double back into the sea. When they do find the right area the turtles can lay as many as 120 eggs in a nest. The reptiles can do this up to six times with different clutches from March to October.

Once eggs have been laid, turtles bury them, pat the site down and scatter loose sand. Scattering sand like this gets rid of the scent of the nest so that predators such as racoons, invasive armadillos, coyotes and bobcats cannot trace them. 

When the eggs hatch they release a chemical that stimulates other turtles to emerge in the nest. Through this turtles can swamp predators, coming out of the nest all at once.

Along the beach hatchlings face additional predators such as fire ants, birds and ghost crabs. Man-made                                                        dangers also threaten the hatchlings for instance Light pollution. Turtles will follow the direction of artificial lights, believing it to be the ocean, often onto roads.

Once out in the ocean, hatchlings, with a 50% chance of reaching it, will head for floating carpets of sargassum seaweed in the Sargasso sea where they will live rafting on top of the carpets for around a year.

Approximately only one out of a thousand hatchlings make it to adulthood.

Useful Links: https://marinelife.org/

https://www.visitmanateelagoon.com/