Mangrove Trees: How And What They Actually Eat

Mangroves grow along intertidal and coastal waterways as you may have seen them sticking out of the water along the coast. They look like thick-leaved trees on stilts as the tide rushes in around them. Living in the salty water as they do, you’ve probably wondered, do mangrove trees eat anything to stay nourished?

Mangrove trees don’t truly eat anything, but they do extract nutrients from the ground through their roots with the help of other organisms in the habitat mangrove trees help to create. Waterlogged soil provides nutrients from waste from organisms such as bacteria, fish, and mollusks.

Keep reading on to find out more about these fascinating trees, how they create such a diverse ecosystem among themselves, and find out how and what exactly mangrove trees eat!

What Are Mangroves?

Mangrove trees are specific trees that grow in tropical areas around or near the equator that have adapted to life in areas with low oxygen content soil. In total, there are 80 species of mangrove trees that can potentially make up mangrove forests.

These trees are often found along coastal sea waters or areas of brackish water. Mangrove forests are recognized by their intertwined roots that reach into the water and keep the trunks and leaves above the waterline.

These dense tangles of roots get flooded with the rising of the tide and help protect against erosion, slow the movement of the tides which helps sediments settle to the bottom, and can help buffer the coast from tsunamis, rising waters, and hurricanes!

Most typically, mangrove trees are known to grow in salt water in the most general gist!

Mangroves Are A Diverse Ecosystem

A mangrove forest creates a densely populated ecosystem on its own from the roots in the water to the branches above.

Fish, mollusks, manatees, algae, and more all rely on the roots of the mangrove trees for survival while several bird species, amphibians, and reptiles call the branches and canopy home.

Mangroves Offer Homes For Animals, Fish, And Insects

Mangrove roots are specialized to let tidal water submerge them without letting the tree drown. All trees need oxygen to live, and they need that oxygen in all parts of the tree; from the leaves to the trunk, and down to the roots. Most plants will eventually die if their roots are constantly submerged in water.

To get enough oxygen to survive in the water, mangrove trees grow what are called aerial roots. These roots stick out of the water and have specialized pores in them called lenticels that allow oxygen to enter but not water or salt.

The tangle of roots from a mangrove forest that reaches into the tidal basin creates shelter and attracts food for a host of marine animals.

Some of the creatures you would find living among mangrove roots include mudskippers, shellfish, sharks, fish, reptiles such as turtles, snakes, crocodilians, and even mammals such as dolphins, and manatees.

The roots of mangrove forests offer hiding places for small fish, snails, and other creatures at the bottom of the food chain, which in turn brings in those larger predators.

In fact, many fish species lay their eggs among the mangrove roots because the tangle of roots provides shelter from larger predators.

For instance, lemon sharks are known to birth live young among the mangrove roots!

These dense areas of mangrove trees offer shelter for their young and provide them with plenty of food. When these sharks are grown, they return to the place they were born to birth their own pups, so mangroves are very important for these sharks.

Mangrove Canopies House Birds, Insects And Animals

Amongst the branches and leaves of mangrove trees, you’ll find many different species as well.

Ferns, orchids, spiders, insects, tree-climbing crabs, birds, and monkeys call the mangrove trees home. When the mangrove trees flower, hummingbirds and bats come to feed off the nectar, which pollinates the flowers to drop seeds for new mangrove trees.

Mangrove trees are extremely important for many animal species for food and shelter. Without them, many species of animals would have a hard time surviving.

How Mangrove Trees Eat And Get Nutrients

Mangrove trees, like all trees, create their own food by photosynthesis in their leaves. But like most other plants and trees they need to draw some of their nutrients through their roots in the soil.

The muddy, sandy, coastal waters where mangrove trees grow are usually very nutrient-lacking areas. Mangrove trees live in oxygen-poor, and nutrient-poor conditions, so how do they make up for the lack of nutrients.

Fortunately for mangrove trees, there is usually a bacteria in the top layer of the soil that can convert fish waste, often in the form of ammonium deposits, into nitrates, which plants need.

The trees then help to feed the bacteria and other small invertebrates when the mangrove trees drop dead leaves. These leaves slowly decompose and provide more food for the bacteria, snails, and other small animals.

Fish come along to feed on the snails, plankton, and bacteria and drop their waste, which continues the cycle. Mangrove trees don’t actually eat anything in the sense that humans do, but they do absorb nutrients from the salty, muddy soil, thanks to bacteria.

How Mangrove Trees Grow In Saltwater

There aren’t many plants or trees that can live in harsh, salty regions. The rich salinity of seawater will kill most plants. In fact, mangroves are the only trees that can live submerged in saltwater. Some trees have adapted to live along coastal regions where salt spray is common, but if the roots get submerged by salt water, they won’t last for too long.

Mangrove trees still need plenty of fresh water to survive, so how do they get enough life-sustaining non-saline water? Mangrove trees have several unique adaptations that allow them to get enough water to not only survive but flourish.

You can learn more about where the most common places to find mangrove trees is here!

Dealing With Evaporation

The leaves of a mangrove tree are very similar to succulent plants. The leaves are thick and broad to be able to store a lot of water in them. Some also have a waxy coating that helps to keep the precious water inside and reduces evaporation when the sun is beating down.

Some species of mangrove trees have tiny hairs on them that deflect sunlight and wind, which would evaporate a lot of water when the leaves pass gasses during photosynthesis. Others have pores on the bottom of the leaves instead of the sides and the upper face of the leaves.

Mangrove tree leaves also utilize a type of sap or milky latex type substance that keeps insects and other leaf-eating animals away. This way the tree can keep more moisture inside it since freshwater is hard to come by when the roots are completely submerged in saltwater.

The Leaves Remove Salt

Another adaptation to harsh, salty environments is the ability of mangrove trees to extract salt from seawater. With their roots constantly submerged in saltwater, it would be difficult for mangrove trees to get freshwater, even when it rains, but these trees can filter out the salt.

According to the American Museum of Natural History, mangrove trees can filter up to 90% of salt out of seawater that is absorbed by its roots. Some mangrove trees use glands in their leaves to expel the salt, which can form crystals on the leaves.

Other trees store excess salt in leaves and bark that have outlived their usefulness. The old leaves and bark then fall off the tree, which gets rid of the excess salt and minerals. The tree not only renews itself but gets rid of salty waste at the same time.

Even Mangrove Seeds Are Adapted To Life In The Sea

Mangrove seeds will germinate while still hanging on the tree. If they fall during low tide and hit the ground, the roots will spread very quickly and anchor themselves in the mud before the high tide returns. If the seeds fall when the tide is in, the seeds will float until they reach solid ground where they can start growing.

It has been thought that some mangrove seeds have floated on the currents for years before coming to rest on a distant shore, and growing into a tree. On the ground, the seeds need to grow fast or they could be washed away. In fact, some mangrove trees will grow more than two feet in their first year so they can get above the waterline.

Some species of mangrove seeds will form roots while still attached to the parent tree. After one to three years, the roots will detach from the parent tree and either start growing nearby or be carried to another shore.

The way mangrove trees propagate, in a matter of a decade, one solitary seed can become a new, small forest of mangrove trees.

While mangrove trees can grow in freshwater, they do prefer saltwater!

Benefits Of Mangroves

Mangrove forests are extremely important to the global environment. They provide a home for a vast, biodiverse array of animals from microscopic, single-celled organisms to top of the food chain predators, some of which are only found among the mangroves.

Coastal Stabilization

Groups of these trees help to stabilize coastlines from erosion caused by storms, waves, and incoming tides.

The roots hold together the soil while the dropped leaves help to provide nutrients to areas that are nearly empty in nutrients. The trunks and canopies help to reduce floods, and rising waters and slow down winds from big storms.

This natural barrier is more effective than artificially produced seawalls at protecting local, coastal communities. It’s also much less expensive to grow trees than it is to build walls.

Protect Water Quality

Mangrove forests filter pollutants from stormwater drainage before it reaches coral reefs.

These contaminants could damage and destroy coral reefs, but mangrove trees help to buffer these pollutants.

Important To Reducing Carbon

One of the most important factors of mangrove trees that directly affects us is the ability to store large amounts of carbon.

According to The Role of Mangroves Forests in Decarbonizing the Atmosphere, the forest of mangrove trees can store 3 to 4 times as much carbon dioxide as tropical rainforest can.

Mangrove trees also store that carbon in their leaves, trunks, and roots where they are simply an ultra-effective carbon filter!

So, mangroves are essential in the battle against climate change.

Mangroves Are Being Threatened

Whether it’s tourism, agriculture, coastal development, or shrimp farming, the mangrove forests are being threatened and wiped out. The most devastating of these are shrimp farming and coastal development.

Shrimp farmers come in, wipe out the trees, and place shallow ponds in their way for crowded shrimp hatcheries. Generally, many chemicals are used to keep the overcrowded shrimp healthy, which eventually affects everything around the area.

Pretty soon even the shrimp can’t live there, and the shrimp farmers move off to another area, leaving the destroyed landscape in their wake.

This isn’t to say ALL shrimp farmers, but thats the main idea.

With coastal development, the mangrove trees are cut down or damaged by all the pollutants that come along with building structures and roads. Eventually, these pollutants are too much for the mangrove forests to handle and they begin to fade away if they aren’t cut down and removed before development.

What You Can Do To Help The Mangroves

There are ways you can help the world’s mangrove forests. If you consume shrimp, look for sustainable alternatives to farmed shrimp that come from mangrove areas.

You can grow your own mangrove trees at home (near saltwater), and you can also donate to conservation sites, and help people who live in the coastal areas by purchasing directly from them.

Some people keep beehives along the mangroves and sell mangrove honey from these hives. These small farmers use sustainable means to provide a living for themselves and their families all while helping to protect the mangrove forests.

Grow Your Own Mangrove Tree

If you’d like to grow your own mangrove trees, you can start with these mangrove seedlings 8 Healthy Strong Red Mangrove Seedlings. You can grow these trees outdoors if you live in USDA Hardiness Zones 9-12. Mangroves will also grow in ponds, aquariums, or pots.

They will need a lot of heat and about 12 hours of full sun each day. If you want to grow them indoors in a pot, you will need a heating pad to keep the soil warm. Try out this highly rated heated grow mat, MET certified Seedling Heat Mat!

That’s A Wrap!

That’s all we’ve got for now!

Mangrove trees don’t really eat anything, they aren’t carnivorous plants like the Venus flytrap. But like all plants do require nutrients that they draw up through their roots and nutrients they make using photosynthesis.

Mangrove trees are fascinating, one-of-a-kind trees that provide a ton of benefits to the global environment, and positively affect each one of us. For these reasons and more, mangrove trees should be recognized for their usefulness and be protected.

Thank you so much for reading!

References

Feller, I.C., McKee, K.L., Whigham, D.F. et al. Nitrogen vs. phosphorus limitation across an ecotonal gradient in a mangrove forest. Biogeochemistry 62, 145–175 (2003).

Golley, Frank, Howard T. Odum, and Ronald F. Wilson. “The structure and metabolism of a Puerto Rican red mangrove forest in May.” Ecology (1962): 9-19.

Ruth Reef, Ilka C. Feller, Catherine E. Lovelock, Nutrition of mangroves, Tree Physiology, Volume 30, Issue 9, September 2010, Pages 1148–1160.

Thomas, Nathan, et al. “Distribution and drivers of global mangrove forest change, 1996–2010.” PloS one 12.6 (2017): e0179302.