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PROP ROOTS
For sea kayakers especially, the most notable
things about mangroves are the prop roots
of the red mangrove (Rhizophora mangle).
On low, scrubby mangroves they form a tangle
of wood that can withstand huge storms—
on taller mangroves they become “drop
roots” that come down from branches high
above water. Under the surface, they are excellent
habitat and fascinating to snorkel.
RED MANGROVE SEEDLINGS
On the tree, they look like exotic tropical fruit.
When they fall off they float, horizontally at
first, so they drift away from the parent plant.
After a day or three the root-end gets waterlogged
and sinks, waiting to bump into bottom
to attach to and grow. Remarkably, these
little trees can drift for up to a year and still
successfully “plant” themselves.
SNORKEL ROOTS
Black mangrove (Avicennia
germinans) roots avoid smothering
in dense mud by putting up distinctive,
knobby looking
pneumatophores. Looking like fingers
reaching up from the mud,
they surround the main trunk, radiating
outward in patterns that follow the roots below. Squeeze
one—they have a spongy feel because much of their tissue is
airy, all the better to allow oxygen to diffuse downward.
TANNIC ACID
Like our own red cedars, red mangroves contain tannin, which
makes them unpalatable to most herbivores. Venture deep into
mangrove swamps and the water will likely become a murky
reddish brown, much like a slow moving stream or pond in the
Northwest. It’s best to do your snorkeling on the clearer fringes
of the swamp, not the murky center.
SULFUR
That nasty rotten egg smell you might experience in a mangrove
swamp means that the flooded soil has lost all its oxygen. This
would normally kill just about everything except bacteria which
can use the sulfate in seawater instead, producing stinky hydrogen
sulfide, which is also toxic to plants. Mangroves manage to
survive (and be productive) using their prop roots or snorkel
roots to bring oxygen down to the roots below ground, preventing
them from smothering in the toxic muck.
FRIGATES & EGRETS
Mangrove islands make great habitat for nesting
and resting seabirds. The smaller the island,
the less likely there’ll be any predators,
and certain islands and even specific trees can
be completely covered in birds. Near shore,
egrets will converge on specific trees, while
farther offshore frigates, pelicans, boobies and
other seabirds can easily be spotted drifting above or resting in
the branches of mangroves. Kayaks are a great way to see these
birds as many nesting islands are “no walking” zones.
Checklist 27—Mangrove Mania
CROCODILES
Yes, there just might be crocodiles
lurking in Caribbean mangroves.
Though the alligator is
restricted to Florida and fresh
water (strays don’t last long in
the salt), the American crocodile (Crocodylus acutus) is fond of
brackish and salty mangrove swamps. Though it gets big (rarely
to seven meters!), this species is remarkably shy and nocturnal,
making sightings rare. A night paddle with a flashlight might
reveal those reflective eyes, and juveniles like the one in the
picture can occasionally be found in shallow pools near camp.
SPONGE (FIRE AND CHICKEN LIVER)
Pop into the water and take a look at those red
mangrove roots—they’ll likely be covered in all
sorts of things, including colorful sponges in
blues, purples, reds and yes, even liver colors.
Colonies of these simple, filter feeding animals
use the roots as a base to feed in the passing
currents. Don’t touch the red ones—they’re not
called fire sponges because they’re flammable.
TUNICATES
Though they form colorful encrustations like
sponges, a close look at colonies of bluebell
and lightbulb tunicates will reveal they are tiny
little animals with two siphons. An even closer
(microscopic) look would reveal they are related
to us—in Phylum Chordata.
ANEMONES
Zoanthids and several species of anemone are
common on and among mangrove roots, their
tentacles stretching into the current to catch and
consume passing animals. Though they’re far
to small to catch you or your boat, one or two
species can give you a mild sting if you get too
intimate.
FISH
Fish, especially juvenile fish, love
mangrove roots. Sport fishers cast
along the roots hoping for
bonefish, snook and even tarpon.
As a paddler or snorkeler you’ll likely see schools of silversides
and snapper ducking for cover as you drift by. If you’re lucky, you
might even see rays and the occasional big barracuda.
MANATEES
Everybody loves marine
mammals, even when
they’re big and blubbery
and likely less than brilliant.
These large, elusive vegetarians are a Florida favorite, and
in the wild they (and their Pacific relatives the dugongs) tend to
roam the swampy coastlines created by mangroves. Shy and mild
mannered, they can be difficult to spot—from your kayak look
for a large, dark mass followed by a paddle shaped tail, or perhaps
a whiskery snout rising for a breath out of murky shallows.
All photos ©Bryan Nichols except black mangrove snorkel roots
© Jeannine Lessmann (a marine botany geek)
October/November 2002 www.WaveLengthMagazine.com
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