Species
Diversity:
Coral
Reefs
Mangroves
Seaweeds
Seagrass
Terrestrial flora
Marine fauna
Environmental Status
Coral
reefs
The
coral reefs of Gulf of Kachchh are located in the northern most region of Arabian
sea. Most of the islands support fringing reefs and coral patches are found in
between the islands. Due to extreme conditions of temperature and salinity and
high turbidity coral growth is limited, perhaps can be termed as patchy than fringing.
Coral growth is primarily confined to intertidal sandstone's or wave-cut eroded,
shallow banks. Reefs are generally restricted to areas exposed to the strongest
tidal currents. The most northerly reefs are coral patches found at Mundra reef
and Pirotan island, but solitary corals are found as far as Jakhau in the east
and Dwarka on the Saurashtra coast.
Diversity
of living corals is poor with only 37 species under 24 genera of hermatypes, and
4 species under 4 genera of hermatypes. The low diversity is due to a combination
of circumstances including geographical isolation and extreme environmental conditions
prevalent in this region. Presence of semifossilized forms of Acropora is indicative
of their presence in the past, and is an evidence of the degradation of coral
diversity in recent years. Cause for the poor state and low diversity of the corals
are both natural and man-made, that is...
- Geographic
isolation which does not permit migration of other species form nearby reefs.
-
Extreme variations of environmental conditions.
Though
corals are stenotypic, they may be found under wide ranges in the environmental
conditions but the tolerance is again with some limitations. Similar coral species
may live at two different localities, each having a different environmental regime,
yet adapt easily to the prevailing conditions but with only a narrow tolerance
limit. For example Pocillapora
damicornis from Hawii grows at an optimum temperature of 27ºC whereas
the same species at Enewatak atoll grows at an optimum temperature of 31ºC. But
only the hardy forms such as faviids and poritids withstand a much larger amplitude
in environmental conditions. Similarly good water circulation is conducive for
coral growth as it renews oxygen and food supply, whereas extreme current velocities
are not ideal. This is perhaps the cause for absence of corals on the northern
shores of the Gulf, where current velocities are 4 knots. Along the southern shores,
current velocities are relatively low.
Very
few forms can survive to a certain extent of desiccation, as is common with the
forms growing on reef flats and inter-tidal regions, prolonged exposure is detrimental
to their survival.Siltation is another cause for mortality of corals of small-polyp
forms, for example. Acropora
and Pocillopora
are absent in the Katchchh waters. Tectonic changes could also because
of decline in coral reefs. Presence of raised reefs along the southern shores
of the gulf is a clear indication of this cause.
Coral:
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Mangroves:
All
the islands of Gulf of Katchchh are intersected by creeks fringed with mangroves.
The coast between Okhamandal and Dhani has continuous mangrove vegetation. The
mangrove species seen along this coast and in the above islands comprise of Avicennia
officinalis, Ceriops tagal, Rhizophora mucronata and, R.conjugata.
Further from Dhani onwards, pirotan island, Pirotan swamp, Cheja and Ambla creek
also have the good mangrove vegations. The dominant species found along the Pirotan
island and pirotan swamp are A.marina,
A officinalis, Aegiceros corniculatum, Bruguiera perviflora, gymorhiza, eriops
condollena, R. Mucronata, R.apiculata,
and Sonneratia
apetala. The coast from Jamnagar onwards upto jodiya is muddy
with coral reefs and marshy swamps covered with patchy fringing mangroves.
Mangrove:
Avicennia
officinalis and Rhizopora mucronata
Local
people of Gulf of Katchchh utilize the mangroves in different ways:
- Tall mangrove trees
are retained and are used as "signal trees" while navigating in the creek
- Tannin
is extracted from the barks of Rhizophora
mucronata, Ceriops candolena
-
Stakes required for fishermen are made from mangrove wood
-
Wood is also used for manufacture of toys and also in the match box industries
-
Mangrove provide major source of fodder for cattle, goats and camels
- It also provides
a cheaper fire wood to the local people.
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Seaweeds
About
108 species of algae have been recorded. The common species found in the Gulf
includes Caulerpa
peltata, C. racemosa, Corallina sp., Padina tetrastomatica Porphyra sp., Sargassum
ilicifolium, S.tennerium, Ulva fasciata and U.reticulata.
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Seagrass
The
following seagrasses commonly occur in Gulf of Katchchh.
They are Halophila
ovalis,
H.beccerii, Urochondra seeulosa
and
Sostera
marina.
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Terrestrial
flora
Natural
vegetation in and around the islands consists of xerophytic and halophytic species
such as
Aloe
vera, Calotropis procera, Eragrostis unioloides, Euphorbia neriifolia, E.candicifolia,
Ipomea prescaprae, Sporobolan madraspatneus, fimbristylis sp. etc.
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Marine
Fauna
The
marine fauna includes corals,
edible oysters and pearl oysters, sponges, polychaetes, sea
anemones,
octopus, crabs, turtles, bonnnelids, dolphin fishes
and
sharks.
Sea turtles migrate to this area for nesting
in October/November.
A
total of 25 hard (Scleractinia)
and 12 soft (Alcyonaria)
corals have been recorded along with 150 species of fishes and 27 species of prawns
and a variety of invertebrates and shore birds. The dugong (Dugong
dugon) is present in small number, being the only population
recorded on the west coast of India. Several species of snakes occur particularly
in the mangrove scrubs. One species of banded sea snake is also recorded for this
area.
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Environmental
Status
The
Gulf of Kachchh, is an arid zone with scanty rainfall, is devoid of other extensive
vegetation to be used as firewood or fodder for camels and cattle. As a result,
cutting of mangroves become a practice for the local people. Over 1,10,000 tones
of mangrove trees were cut down between the years 1948-78. This rate of exploitation
has resulted in patchy, bushy and stunted mangrove vegetation all along the Gulf
of Kachchh. The reclamation of mangrove forests for agriculture in Gulf of Kachchh
is not practiced as the leaching of salt from soil is impossible due to scanty
rainfall. Construction
of salt pan itself needs complete clearing of mangrove vegetation form the particular
area. Presently 30 salt pans between Okha and Navlakhi are existing and a proposal
for more than 50 salt pans between Sachana and Hanshtal are planned.Creation of
harbors, new ports, ship breaking yard at Sachana have created more severe impact
on the mangroves. The tanks of the steamers carrying chemicals to Kandala port
area are usually cleaned in the Gulf of Kachchh waters, which inturn contaminate
the waters and have adverse effect on the mangrove forest.
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