Environmental Engineering Reference
In-Depth Information
Manatees mate and give birth under water and
the male remains with his mate even after the
breeding season. The females give birth to a
single calf after 11-month gestation period.
Manatees are strict vegetarians and consume
large amounts of shallow water plants. A single
manatee may consume at least 27 kg (60 pounds)
of aquatic plants per day. When manatees eat,
they guide the water plants to their mouths with
their
Africa and Australia. Presently the growth of
human populations has posed an increasing
hunting pressure on the dugong in the southern
Paci
c. Another close relative, Stellar
'
s cow,
which was present along the Paci
c coast from
Mexico to Japan, was commercially hunted to
extinction by 1768. Dugongs are also being
given the same kind of barbarous treatment even
after more than two hundred years of develop-
ment in human civilization.
It is interesting to note that sea mammals such
as sea lion, whale and sea otter thrive and depend
on the blue carbon domain such as kelp com-
munity. Thus, carbon
ippers. This observation may account for
the association with mermaids.
Dugongs
are interesting marine mammals.
They live up to 70 years and grow up to a length
of 3 m. They are commonly called as
fl
'
since they graze only on seagrass meadows.
Modi
'
sea cows
ows from seaweeds to
members of higher trophic level in the marine
ecosystem (Fig.
2.27
).
fl
ed according to the medium, in which they
live, dugongs have got a streamlined body with a
massive head and a small mouth with nostrils
situated on top of the head for surface breathing.
They have got a whale-like
2.3
Decomposer Community
uked tail for
swimming. A pair of clawed limbs in the front is
used for balancing and turning. Body is grey or
bronze grey in colour dorsally and white or flesh
coloured ventrally. Adult males possess tusk-like
incisors useful for tilling the grass meadows
while feeding. Dugongs mostly prefer to dwell at
depths below 1 fathom where seagrasses grow in
plenty. They feed predominantly on seagrass
species of the genera
fl
The marine and estuarine environments are the
nursery and survival place for a large variety of
bacterial strains. The abundance of microbes in
the neritic zone of this ecosystem may be related
to the discharge of huge amount of untreated
sewage into this system, run-off from the adjacent
forest or mangrove ecosystem containing litter
and detritus, discharge from the aquacultural
farms, etc. In the Indian subcontinent, a very
important picture has been obtained regarding the
trend of bacterial load while approaching from the
inshore to the offshore region. The bacterial
population is very high and variable all along the
nearshore coastal waters, which, however,
decreases towards the offshore region. This is
primarily because of grossly inadequate sanita-
tion in coastal areas and discharge of untreated
sewage and other ef
Halophila
and
Halodule
,
which are pioneer species that are low in
bre,
low in available nitrogen and very easily
digestible. An average adult consumes an esti-
mated biomass of 25 kg a day. When seagrass is
scarce, marine algae are also consumed. Decline
in dugong numbers due to habitat loss was doc-
umented in India during 1964 cyclone. At Palk
Bay, large quantities of sand brought by
oods
were deported over seagrass and algal beds and
completely destroyed them. This led to the near
total absence of turtles and dugongs in the late
1960s and early 1970s. In this area,
fl
uents through land drainage
(Table
2.19
). In Indian Sundarbans region, a case
study conducted by the present authors during
1990
fl
Cymodacea
2012 in three stations, viz. Harinbari
(inshore region; marked as 1 in Fig.
2.28
), Che-
maguri (midshore region; marked as 2 in
Fig.
2.28
) and Jambu Island (offshore region;
marked as 3 in Fig.
2.28
), exhibited unique spatial
variation of nitrate and phosphate level. The
gradual decrease of nitrate and phosphate level
(which are primarily liberated from sewage)
-
serrulata
form the major food
items of dugong. The same phenomenon occur-
red in 1992 at Hewey Bay, Australia, where the
seagrass bed was lost due to flood leading to the
death of dugongs. Dugongs are related more to
elephants than to other marine mammals. Dug-
ongs are found in waters around South-East Asia,
and
C. isoetifolida
