Most people come here to Yap in the middle of the Pacific Ocean, to dive on beautiful
coral reefs and meet the manta rays, I noticed that 90% of the island is covered in these
beautiful lush mangrove forests, so I got special permission from the chief of Baychel
Village to explore the mangroves.
Hi, I'm Jonathan Bird and welcome to my world!
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Mangroves are a type of plant living in the tidal coastal areas between sea and land.
All share the trait of being able to tolerate partial submersion in salt water, and poor
oxygen content in the ground where their roots penetrate. Mangroves only grow in the tropics
like these rich mangrove forests in Yap.
Mangroves are extremely important for several reasons. First, they serve as a buffer zone
between the ocean and the shore. Their roots hold the shoreline together, limiting erosion
and attenuating the waves. In effect, they form a protective barrier between the ocean
and the land.
Second, and perhaps more importantly, mangroves serve as a refuge for marine life. The tangled
maze of roots in the mangrove forest creates a confusing shallow water labyrinth. Taking
refuge in this protective maze, many animals survive here when they couldn't survive
anywhere else. The mangrove is a nursery for juvenile fish and invertebrates. In the protection
of the calm sheltered waters of the mangroves away from predators, the juvenile fish find
food and safety. Without the mangrove nursery, life on the reefs would be in trouble.
Mangroves live in salt water, which is a tough environment for a plant. The roots are designed
to soak up the water and exclude as much salt as possible in the process. They have little
filters built into their cells. But the plants still take in a fair amount of salt and they
have to get rid of it or it will kill the tree. They get rid of it by concentrating
it in their leaves. Some mangrove trees excrete the salt out through the leaf as a crystal,
which is then washed away by rain.
You can taste the salt on the leaves. Mmm!
Other trees concentrate the salt in older leaves, which then turn yellow and fall off,
taking the salt with them.
All those leaves land in the water, sink to the bottom and decompose. The mud has a high
concentration of bacteria to break down all the organic material.
These bubbles on the bottom are mostly methane—the by-product of decomposition.
The bacteria consume the leaves, releasing nutrients that wash out to sea every day on
the receding tide.
So the mangroves are an important food and nutrient source for animals and plants on
the reefs and in the open ocean.
Most trees have their roots completely underground. Mangrove trees have their roots coming up
out of the water into the air like this. That's because the soil down below the water here
is a black muck that's high in bacteria and has very little oxygen in it so the roots
can't absorb any oxygen. So when they come up into the air, they absorb the oxygen directly
through their skin.
Partially submerged conditions in mangrove forests make it hard for traditional seeds
to take root, so reproduction requires special seeds.
This is a mangrove seed. The seed part is up here but it has a long root already on
it. When it falls off the tree, it floats like a cork with this part up and this part
down. When it floats into shallow water, this part will go right into the soft bottom and
the leaves will come out the top and you have an instant mangrove tree, ready to start growing.
This adaptation allows a seed to take root in shallow water with the root in the bottom
and the leaves at the surface.
Exploring the mangroves, I realize not only how fascinating this habitat is, but important
as well. It is imperative that as coastal development continues, care is taken not to
overlook the importance and beauty of the mangrove forests, the nurseries of the reefs.
They're not just part of the land, or part of the ocean but a critically important link
between these two worlds.
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