Environmental Engineering Reference
In-Depth Information
4.2
Seagrass and Salt Marsh Grass
just below the surface of the bottom sediments
(Fig.
4.16
). The rhizomes and roots of seagrasses
help to stabilize the bottom and along with the
leaves help trap large amounts of sediment. The
leaves are
4.2.1 Seagrass
fl
at and oval,
ribbon-shaped, or
Seagrasses are marine plants that generally
inhabit the protected shallow waters of temper-
ature and tropical coastal areas. These plants are
not true grasses, and the represent several genera
appear to be more closely related to members of
the lily family. The most extensive areas of
seagrasses are found in the tropics. They are
concentrated in two major reasons of the indo-
Paci
cylindrical and
exible to better withstand water
movement while remaining erect. Leaves either
develop directly from the rhizomes or develop
from small vertical side stems called short
shoots. Roots develop from both the rhizomes
and the base of short shoots. Unlike the
fl
brous
roots of terrestrial grasses, roots of seagrasses are
usually thicker and
owers, nor-
mally inconspicuous, small and pale white, are
usually located at the bases of the leaves. The
stamens (male
fl
eshlier. The
fl
c, as well as both coast of the Americas.
Seagrasses do not thrive in areas in low light
intensity. If the water becomes too turbid (clou-
ded with sediments), it can destroy the seagrasses
and other dependent organisms. A massive die-
off of seagrasses in Maryland
fl
ower parts) and pistils (female
fl
ower parts) generally extend above the petals of
the
ower. As a rule, the pollen is released from
the stamens in long, gelatinous strands that are
carried by water currents to the pistils.
The internal structure of seagrasses is typical
of a hydrophyte. One of the most characteristic
features is the regular arrangement of air spaces
in the soft tissues of the plant. This tissue plays
an important role in
fl
s Chesapeake Bay
estuary during the 1960s is largely due to
diminished light associate with excessive sedi-
ments run-off from the land surrounding the land.
Seagrasses are hydrophytes, which means
they generally live submerged beneath the water
(Fig.
4.16
). To survive in their subtidal habitat,
these plants must be adapted to a saline envi-
ronment with wave action and tidal currents.
They must also be able to carry out pollination
and seed dispersal under water.
The major stems of seagrasses, called rhi-
zomes or long shoots, grow horizontally, usually
'
otation of the leaves and in
gas exchange throughout the plant. The outer cell
layer of the plant is called epidermis. Unlike
most land plants, the epidermal cells of seag-
rasses contain maintaining the proper amount of
salts in the cell
fl
'
s environment. Since water helps
Fig. 4.16
Seagrass
community under the water
