Page 132 - (DK) Ocean - The Definitive Visual Guide

130 COASTS AND THE SEASHORE

Mangrove Swamps

A MANGROVE SWAMP IS A COLLECTION of salt-tolerant evergreen trees, thriving in
an intertidal environment in the tropics or subtropics. Mangrove swamps line about
eight percent of the world’s coastlines, where they filter pollutants
AERIAL ROOTS
from river runoff and help prevent the silting up of adjacent Many mangrove species
marine habitats. They also protect coastlines against erosion and have aerial roots. These
prop the tree up and
provide a home for fish, invertebrates, and many other animals. take in oxygen, which is
usually not available in
the mud that most
Formation mangroves grow in.
Mangrove swamps develop in coastal areas protected from direct wave action.
These areas often fringe estuaries and coastal lagoons (see p. 114). Most
mangroves develop in fine muds or sandy sediments that form in these
environments. As the lower parts of the mangrove roots develop in
the sediment, aerial roots form a tangled
network above it. This traps silt and other DISTRIBUTION
Mangrove swamps occur only
material carried there by rivers and tides.
between latitudes 32˚N and 38˚S.
Land is built up, and then colonized by Salt marshes and tidal flats (see PA CIFIC ATLANTIC OCEAN
other types of vegetation. p.124) replace them elsewhere. OCEAN
INDIAN
OCEAN
S O U T H E R N O C E A N

OCEAN ENVIRONMENTS Plants PNEUMATOPHORES RED MANGROVE

Some 54 species of trees and shrubs are classified as “true” mangroves,
occurring only in mangrove habitats. Each has evolved special adaptations
to the conditions they grow in, such as salty water. For example, some
mangroves can excrete salt in their leaves. On most mangrove shorelines,
there are two or three zones, each dominated by different mangrove
species. In the Americas, just four main species are found. The area
closest to the sea is dominated by red mangroves. Landward of this are
black mangroves—the roots of this and some
other species develop pencil-like breathing
This mangrove species can
grow in deep water by means
These vertical tubes grow
tubes, called pneumatophores. White and
of its numerous prop roots,
up out of the sand or mud
button mangroves grow farther landward. The
which often have a reddish
as extensions of horizontal
mangrove swamps on the coasts of the rest of
tint. It also has a particularly
roots. When exposed to
the tropics contain greater species richness.
high salt tolerance.
the air, they take in oxygen.