Sirenians: Manatee's Discerning Palette

Image by Chokniti Khongchu

Remember this: A manatee can be two things at once. It can hold an ecosystem together and reflect environmental health through its sensitivity to change. 

As we forge ahead with the intrepid manatee, we learn that it is a keystone species and an indicator species. Like everything else, it must live and it must eat. 

For your education going into this, a keystone species is an organism that has an essential impact on its ecosystem relative to its small population size, while the indicator species  is an organism whose health or presence reflects the overall condition and quality of an environment.

The manatee's aura is very interesting. For interest sake, because I was chewing the fat on the eelgrass, what other things does the manatee eat, or has its eating habits changed due to the changing world that some politicians are in denial of while calling scientists fake and liars. 

Let us look at some research. Our topic has been eelgrass or seagrass and manatee habitat-diet. I was reading an article titled, "Nutritional composition of forage resources consumed by Florida manatees (Trichechus manatus latirostris) vulnerable to seagrass decline in the Indian River Lagoon" printed in Aquatic botany, May 2026.

The dominate food source for a manatee is seagrasses but they are known to consume sixty species of aquatic macrophytes. Macrophytes are large aquatic plants visible to the naked eye that grow in or near water. There are three kinds:

Emergent: Cattails

Submerged: Eelgrass

Floating: water lilies and duckweed

Harmful algal blooms have caused seagrasses to decline. These are some of the algal blooms that threaten Florida Eelgrass:

1. Brown Tide (Aureoumbra Iagunensis)-Indian River Lagoon

2. Picocyanobacteria (Synechococcus spp)-Florida Bay

3. Blue-green algae (Cyanobacteria)-Creates low-oxygen dead zones

4. Nuisance Macroalgae and Phytoplankton aka Super Blooms-Starve vegetation of photons

In this one specific location of the Indian River Lagoon (IRL), studies suggested the manatees populating this area had a dietary shift from seagrass to macroalgae over the past fifty years. 

Would this cause an evolution to the manatee? Darwinism? Or was it there all along as the backup plan?

The concern at this intersection is the consequence of this shift in food selection. This will express itself in nutritional and energetic means that suggestibly will have a variation of data difference based on different time frames for food source availability. 

This study compared macronutrients of Carbon, Nitrogen and phosphorus and proximate composition (acid detergent fiber [ADF], ash, crude fat, crude protein, total digestible nutrients [TDN], and total nonstructural CHO [TNC] ) to ten known forage items consumed by manatees in the IRL. 

The aim was to quantify macronutrient and elemental stoichiometry (C:N:P) of items consumed by manatees, evaluate the proximate composition of forage resources, and investigate the seasonal (wet vs dry) variations in macronutrient and proximate compositions. 

The results from the abstract stated, "a macroalgae-rich diet provides readily digestible energy but contains significantly less fiber, and exhibits altered nutritional balances compared to seagrass. Such a dietary transition may compromise hindgut fermentation efficiency, disrupt symbiotic microbiota, and exacerbate malnutrition risks to manatees in Florida." (Allen et al., May 2026, 

Pretty much, manatees need the grasses in their diet. Its one thing to do a short-term run on the switching of food based on availability but ideally you want them on the grasses. 

When you consider the diet of a manatee, you get informed on the anatomy of this creature. The manatee's large intestine and cecum form a fermentation vat measuring 20-30 meters long, making up to 70% of their total gut mass. Just wow. 

Digestion takes up to 4 to 10 days to pass through their gut allowing microbes time to break down tough plant cellulose. Genetic sequencing has identified 2,000 operational taxonomic units of bacteria in manatee faeces that is responsible for cellulose breakdown from low-nutrient seagrasses and abrasive aquatic plants.

When devising a plan to improve the diet of a manatee, you have to keep in mind that it is like gardening. You have to have good soil and nutrients to gain a payout of a harvest that is high quality and boost availability. 

Scientific studies point out overwintering in Florida indicate seasonal temperature drops and dietary shifts, or fasting alter their gut flora and elevate stress indicators like fecal cortisol metabolites. This is in the arena of Cold Stress Syndrome.

Just because I want you to learn this term, in vitro, it is Latin for "in glass". It describes biological or medical experiments, tests, and procedures conducted outside a living organism in a controlled artificial environment such as a test tube or a petri dish. You are welcome. 

Image by Qbert Studio

Did you know manatees are called Sirenians?

Manatees can eat 4-9 % of their body weight of aquatic vegetation each day. Because of foraging and diet, manatees can influence plant biomass, productivity, and community composition, while indirectly influencing invertebrate community and nutrient dynamics, including carbon sequestration. 

Manatees possess extensive digestive systems that efficiently digest plant material such as cellulose via hindgut fermentation and absorb water from the plants they consume. Manatees consume foods high in fiber but low in protein and caloric value. They maximize extraction of nutrient through a slow gut passage time and demonstrate high digestive efficiency compared to other mammalian herbivores. 

This is where the science paper reiterates the increasing anthropogenic impact due to changing environmental conditions since 2013, manatees along the Atlantic coast of Florida have experienced two consecutive unusual mortality events. 

Between December 2020 and April 2022, a total of 1392 cases were documented that included 1255 manatee mortalities and 137 field interventions to assist live individuals exhibiting signs of starvation. The necropsies showed signs of malnutrition. The prevalence of emaciated manatees were high in the IRL where a regime shift from seagrass to phytoplankton based primary production has occurred since 2011 following a major decline in seagrass areal cover in the estuary. 

A study investigating the UME (unusual mortality events) that occurred between 2012-2019 linked mortalities to clostridiosis (toxic effects of bacteria clostridium spp) and hypothesized that a diet low in fiber may have cause GI lesions providing a route for clostridial infection. 

Image by K Fuadi

This reenforces the reasoning that federal and state agencies along with help from the public to set up manatee report and rescue routes, restoration of aquatic habitat for long and short-term habitat, and ensuring these endeavors have a clear plan on monitoring the efforts to rehabilitate the manatee in its environments.

What we have left after humanity has decided to re-imagine a location that is on an ecosystem or habits is our responsibility to protect. We must do everything humanly possible to make sure that it does not go asunder. It depends on the good human and what exactly that re-imagining is for, and in what way it can benefit the stewardship of the creatures of the Earth.

~Courtesy of the AOFH~

Interesting things to read:

"The In vitro Effects of Simulated Cold Stress Syndrome on the Gut Microflora of the Florida Manatee, Trichechus manatus latirostris".

https://www.vin.com/apputil/content/defaultadv1.aspx?pId=11257&catId=32327&id=3865006&ind=487&objTypeID=17

Sources citated:

Allen, A.C., Sattleberger, D.C., Campbell, J.E., Kiszka, J.J. (2026, May) "Nutritional composition of forage resources consumed by Florida manatees (Trichechus manatus latirostris)". Aquatic Botany, Article 103972, Vol 204. https://www.sciencedirect.com/science/article/abs/pii/S030437702500107X#section-snippets

 

Snorkeling with Manatees: Chomp, Chomp, Chomp

Image by Qbert Studio

Remember this: Imagine going on a hunt without a weapon. Just a snorkel and mask.

In August, I had a bucket list item. It was more a strong pull towards something. It happened to be a giant sea potato. I am a Celt, Magyar, and Irish among other things. Potatoes, potatoes, potatoes.

Let me go ahead and get the information that the Manatee is a threatened species under the  U. S. Fish and Wildlife Service. The manatee is not considered endangered but are protected under the federal Endangered Species Act and the Marine Mammal Protection Act. You are not suppose to touch them. No touchy-touchy!

I do feel like our current Potus is trying to destroy all things good in life with whoever these poison Wormwood advisors are. Lets move on.

Conservation groups are trying to return them to endangered status. When you watch videos of boaters not paying attention, that run the manatees over, and how the water substrate manatees live in is being polluted up, it makes one wonder what is going on in people's heads. 

The rate at which hunters and outdoor sport people are radicalizing me is epic.  I am going to make this one about the manatee habitat. 

So we begin this new tale of the underwater meadow in the bay. 

Image by Adam Zubek-Nizol

Would not be an adventure if there wasn't some foreshadowing and a dire warning. Lewis and Clark are up in heaven saying, "Everyone has to die sometime."

My progeny tells me, "Don't go in the Florida water."

I say, "I am going in the Florida water."

My progeny says, "but there are brain eating amoebas."

I took what he said into consideration and decided that adventurers of old probably went into the Florida waters and ate the bear meat, which got them killed. Upward and onward. 

I booked a room right on the Florida water and went about securing a boat out to the center of the location where the year round population of manatees made their home. 

I am going to tell you now that I took a person that is afraid of dogs, horses, and a boulder shaped potato. He couldn't swim either.  The guide was told this because I was gonna need help with him. Difficulty level now went up to a 8.5 on the scale. I wasn't sure if this was going to end well, or with me being embarrassed.  

Weather is important in planning your excursion. You need to know when the tide is, if there is going to be lightning or rain, and what the temperature of the water is. The area we were in is King's Bay in Florida. It is 600-acres at the headwaters of Crystal River. Of course, in the 1950-80s there was a re-imagining of the shoreline around the area that had an impact on its natural attributes at the time. As humans go, there always has to be a re-imagining. UGH! I read there was a substantial agricultural and urban land use conversion that contributed to nitrate entering the springshed and there was mystery invasive aquatic vegetation introduced in the 1960s. That is the lore in short.

The King's Bay, a fresh spring waterway, is a first-magnitude spring system that feeds seventy individual limestone springs and pumps out hundreds of millions of gallons of water daily from a Florida Aquifer. It stays at a constant temperature of 72 degrees year-round. The King's Bay connects to Crystal River. Crystal River flows into the Gulf of Mexico, or is it the Gulf of America. I am not going to learn new land mass names or water routes so for me its the Gulf of Mexico. Adios mio!

This makes the area tidally influenced and slightly brackish in the outer sections. These springs act as the largest natural warm-water refuge for wintering West Indian manatees. 

The first guide we booked rained us out and wasn't trying to work around the weather. The next day, we secured another guide that worked around the weather for a three hour private guided tour. We went down to the meet site and drove over to where the captain is docked. We got aboard and cruised around the waterway. We cruised into the area of Hunter's Spring Park. There is a lot of people in the water and the amount of congestion from the water vehicles and toys looked like chaos. The water was clear and you could see the fish. 

The guide pointed out that the manatees were not in this area due to the amount of people but in one area there is a metal grate that has eelgrass growing in it. She said the manatees loved this grass and eventually used the weight of their bodies to bend and get under it to get to the grass. The submerged grass she mentioned is eelgrass (Vallisneria americana) but it is called tapegrass or wild celery.

We cruise over to the middle of the bay where the captain docked and we started to offload. My friend, who is 5'8" in a scuba suit, gets off and stands in the water. Reality sets in and he realizes that he is up to his chest in water standing with with a pool noodle. He can't see into the water because it has been disturbed so it is not clear. I am coming down the ladder and he decides he wants to go up the ladder. Much like Gandalf, my behind is letting him know he can not pass. I knew he was going to do that. The captain seen him making his move and distracted him to walk off toward the guide by letting him know he is standing in the water and not dying. It was long enough for me to get in. I begin to drive him toward the guide. 

For someone who had never snorkeled before, once he got away from the boat, started using the snorkel and tube then put his face in the water, he was okay. He is one of these people that never got the chance to let his brain grow from worldly interaction. He has come a long way. It is about experiencing life. 

We got out there snorkeling around and my mask wasn't fitting. It is leaking water into my nose area. I had to go back to the boat and get another one before I swallowed the Florida water. I didn't want to accepted the alien amoeba inside of me. I wondered if I was going to get a flesh-eating disease in my lungs. 

I get my mask changed out. The group has moved along following the manatees. I am swimming around. I decided to do as the giant potatoes do; sit still on top of the water.  I am pretty sure I looked like a bloated dead body out there waiting for the next CSI episode to happen. It wasn't long before my ears could hear the chomp, chomp, chomp of the boulder that had now come to rest underneath me. At this point, I was channeling alligator energy. 

We know not to touch them. It was amazing floating over it, watching and listening. One of them had a baby with her.

That chomping sound is like a loud earworm. I am thinking that is me at a Hotpot buffet eating octopus. Chomp, chomp, chomp. 

Image by Ovidiu Timplaru

Let us insert the science. 

I am over a bed of eelgrass, which is long and ribbon like with green leaves and can grow up to six foot long. This area looked like an underwater meadow due to the denseness of the plants. The sediment it grows on is soft and mushy but not completely without solidity. This grass is considered a foundational species. The manatee is considered an indicator and keystone species in the aquatic ecosystem. 

What is a foundational species?

A foundation species is a dominant organism that shapes, defines, and structures the bay by creating habitats and modulating the availability of resources. The role eelgrass plays is in stabilizing the sediment, improving the water clarity, producing oxygen, and sequestering carbon. If you have ever had a fish tank, it provides for food and nursery habitats for waterway creatures.

This eelgrass is actively modifying the environment by acting as an ecosystem engineer by constructing shelter, food, and safety from bad weather and predators. 

If you think about water, there is movement and flow brought on by underwater currents and airflow above that shuttles energy and nutrients around a given area. 

Given this knowledge, one can understand what would happen in the reverse of this situation. One of the problems with a reverse is it can cause the eelgrass to die. This die-off causes the manatee to starve if there is not another food source available. Manatees do migrate but not all. 

Water quality can be poor due to these factors:

• Nutrient pollution
• Eutrophication
• Increased turbidity
• Chemical toxins

These scenarios cause a murky, toxic condition where sunlight is not able to get to the plant and the plant suffocates then dies. 

Poor water quality can bring excess nitrogen and phosphorus from fertilizers or sewage. High nutrient levels that trigger microalgae blooms, phytoplankton, and epiphytic algae contribute to poor water quality. This can cause light starvation. The murky water and thick layers of algae on top can block out the sunlight obstructing photosynthesis for plants to grow.  Increased turbidity suspends the sediment and dense algae makes the water cloudy and dark. Heavy metals, pesticides, and oil build up in the local sediment and water can contribute to poor water quality from chemical toxins. These toxins can be absorbed by the eelgrass and make it fragile and prone to disease. 

As the eelgrass dies, it stops trapping sediment. This release of dirt goes back into the water and makes the area even worse for future growth.

What has been going on with the restoration of eelgrass (Vallisneria americana) in the great state of Florida 2026?

There have been several previous locations that have planted large amounts of eelgrass over a substantial acreage of shoreline. These are East Lake Tohopekaliga, Crystal River, Weeki Wachee River, and Indian River Lagoon. Specialized teams clear nuisance algae, plant new eelgrass, and install protective steel mesh cages over plants to revive springs and feed the manatees. The amount ranges around 150 cages per acre. The cages are cleaned monthly to allow sunlight to reach the plant. These cages stay in place for twelve months then they are removed. The process is simple: remove, replant, and maintain.

For 2026 restoration projects, spearheaded by the Florida Fish and Wildlife Conservation Commission (FWC) with conservation partners Conservation Florida and Sea & Shoreline, are restoring these areas:

East Lake Toho

Installation of 250,000 native eelgrass plants across 50 acres of the Northshore, funded by a $2.6 million state legislative appropriation administered through the FWC.

Lake George

41 fenced enclosures overing over 155 acres with an additional 1 million eelgrass plants installed. There is a subsequent St. Johns River eelgrass revegetation solicitation closing in Oct 2026.

Lake Poinsett

This site is used by researchers to test 864 experimental plots to determine the most effective plant sizing and densities for long term statewide propagation. 

In closing, when you consider all the ways in which weather, human habitation, and the shifting landscape cause damage to core habitats, it is great to know that there are plans being executed to rebuild and help the natural world flourish. 

What about the manatee's role in this as an indicator and a keystone species?  What about that lazy spud?

Image by Hamim Fadillah 

~Courtesy of the AOFH~