Environmental Engineering Reference
In-Depth Information
mangrove community. Scholander ( 1968 )
demonstrated experimentally that the salt
separation process in mangroves occurs at or
near the root surface. This is mediated by
physical processes alone, since it is not
inhibited by poisons or high temperature,
which may cause an inhibitory effect on
metabolic process.
may therefore be accepted as a part of their
adaptation in an environment that provides
ample water at the expense of some com-
pensation for high aquatic salinity.
Studies on salt tolerance in
Aegiceros corni-
culatum
and
Sesuvium partulacastrum
generated
few interesting
ndings as follows: (i) NaCl
salinity has considerable effect on the degree of
succulence. With the increase of NaCl salinity in
the ambient media, the mass and volume of the
leaves increases due to increment in the water
content. (ii) Effect of NaCl and Na 2 SO 4 is more
pronounced in
In the root area,
the
physical mechanism for
salt
separation
involves ultra-
ltration which occurs either
at the root surface (Epiblema) or at the root
endodermis. However, the latter region
might be the most preferable site (Tomlinson
1986 ) because the ultimate absorbing roots
in most of the mangroves lack root hairs (e.g.
capillary rootlets of
Sesuvium
sp. than
Aegiceros
sp.
(iii) In
sp., effect of chloride salinity is
more prominent than that of sulphate salinity.
(iv) NaCl is most effective salt in promoting
succulence (Van Eijk 1939 ). Succulence is due to
expansion of the cell wall leading to increase in
the size of cells. (v) Accumulation of NaCl is
more in
Sesuvium
sp.). This
indicates that the absorbing area of man-
groves is reduced in comparison to non-
mangrove plants.
(iii) Salt accumulation : In this type of man-
grove plants, the species possess neither salt
glands nor ultra-
Rhizophora
due to their
difference in the mode of salt regulation. (vi)
Chlorophyll content decreases sharply at high
concentration of NaCl in both the plant species.
(vii) High concentration of Na 2 SO 4 stimulates
the synthesis of chlorophyll in
Sesuvium
than
Aegiceros
ltration system, but they
have the capacity to accumulate a large
amount of salts in their leaves. This imparts
succulence
to their
leaves.
Sonneratia
Aegiceros corni-
apetala
,
Lumnitzera racemosa
,
Excoecaria
culatum
sp.
The mangroves not only stabilize the shore-
line and act as a bulwark against the encroach-
ment by the sea, but they also act as the abode of
several species of
, but inhibits the same in
Sesuvium
agallocha
,
Sesuvium portulacastrum
,
Sue-
ada maritima
are
included in this category. Leaf succulence in
mangroves has a simple explanation in
terms of salt balance. The osmotic potential
of the leaf cells of mangroves is high
(Scholander et al. 1964 ) which is essential if
mangroves are to draw water from the sea
with its high negative water potential.
However, Scholander ( 1968 ) noted that the
salt concentration of mangrove leaves
remain constant and independent of age.
Measurement of salt content in xylem sap
demonstrates incomplete salt exclusion at
the roots. But mangroves accumulate salt,
and so this accumulation is partly compen-
sated by salt glands, mainly in the less
ef
and
Sueada nudiflora
n
sh, nursery of a wide
range of
sh juveniles and bi-
opurifying matrix of wastes generated as a result
of industrialization and urbanization. In man-
grove ecosystem, different kinds of unrelated
fauna and
n
sh and shell
fl
ora get themselves adapted to thrive
under
uence of tidal inundation and
brackish water. This ecosystem is thus a zone of
adaptive convergence, which is a critical issue in
the sphere evolutionary biology.
the in
fl
2.2
Consumer Community
2.2.1 Zooplankton
cient salt excluders. Since salt concen-
tration is constant and independent of leaf
age, salt must accumulate by an increase in
the volume of the leaf cells inducing suc-
culence. The leaf succulence in mangroves
Zooplankton are found in almost all the layers of
the photic zone of the ocean. They are potentially
limited by two factors in the coastal and estuarine
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