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Introduction
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Ecologically
Important Areas
Information
in Detail
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Gulf
of Mannar:
Gulf
of Mannar Biosphere Reserve
Natural Resources
Biodiversity
Threats
Gulf of Mannar
Biosphere Reserve:
Gulf
of Mannar biosphere reserve, extends from Rameswaram Island to Tuticorin in a
NE-SW direction and lies between 78° 5' E - 79° 30' E longitudes and 8° 45' N
- 9° 25' N latitudes, and extends to a distance of 140 km. There are 21 islands
running almost parallel to the coastline of Gulf of Mannar. These islands lie
between 8° 47' N - 9° 15' N latitudes and 78° 12' E - 79° 14' E longitudes. The
detailed account of each island is provided in Table 2. The islands are situated
at an average distance of about 8 km from the coastline of Gulf of Mannar. It
is bound by Palk Bay and Rameswaram Island in the north side; by Ramanathapuram
district in the northwest and west; and by Tuticorin district in the south and
by Bay of Bengal in the east. It is endowed with three distinct Marine ecosystems
namely corals, seagrass and mangroves.
Gulf
of Mannar experiences a tropical climate. The area comes under the spell of both
southwest and northeast monsoons. The southwest monsoon contributes only very
little towards the annual rainfall. Rainfall is moderate to heavy during October
to mid-December under the spell of northeast monsoon, with occasional gales. The
mean annual rainfall varies from 762 mm to 1270 mm (Neelakantan 1998). The period
from January to May is marked by unusually hot climate. The coldest month is December
with temperature dropping to a minimum of 25 C (Angusamy 1995).
The
velocity of the wind is generally high in the coastal plains of Gulf of Mannar
region. The wind direction is north-northeasterly from June to December and changes
to westerly during the rest of the period. The wind speed is lowest (6.9Km/hr)
in November (northeasterly) and highest (17.6 Km/hr) in August (southwesterly)
(Angusamy 1995).
The
ocean currents in Gulf of Mannar area are swift. The sea is rough between April
and August and calm during September, during June to August it is very stormy.
Tidal amplitude in the area is about half a meter. At Pamban the tides are irregular,
owing to the wind force.
The
drainage system in the coastal part of Gulf of Mannar consists of Vaigai, Kappalar,
Kottangui River, Gundar, Vembar, Vaippar and Kallar and its tributaries. The trend
of the rivers is from NW to SE. Vaigai and Vaippar are the biggest rivers in the
study area. All rivers in study area are non-perennial and get water only during
rainy.
Fig: Ecologically
Important Areas in Tamil Nadu: Gulf of Mannar
Table 2: Geographical
location and areas of Gulf of Mannar Islands
| Island
groups | Island |
Geographical
location | Approximate
area in ha | | Tuticorin
group | Van
Tivu | 8°
50' N to 78 13' E | 16.00 |
| Koswari
| 8°
52' N to 78 13' E | 19.50 |
| Karaiya
shulli | 8
°57' N to 78 14' E |
16 .46 | | Vilangu
Chulli | 8°
56' N to 78 15' E | 0.95 |
| Vembar
group | Uppu
tanni tivu | 9
°05' N to 78 30' E | 22.94 |
| Shalli
tivu | 9°
06' N to 78 35' E | 6.12 |
| Nalla
tanni tivu | 9
°06' N to 78 35' E | 101.00 |
| Kilakarai
group | Anaipar
tivu | 9
°09' N to 78 45' E | 11.00 |
| Palliyarmunai
tivu | 9°
09' N to 78 35' E | 6.72 |
| Puvarasanpatti
tivu | 9
°09' N to 78 49' E | 0.50 |
| Appa
tivu | 9
°09' N to 78 54' E | 28.63 |
| Talairi
tivu | 9°
11' N to 78 56' E | 75.15 |
| Valai
tivu | 9°
11' N to 78 56' E | 10.10 |
| Muli
tivu | 9
°11' N to 78 56' E | 10.20 |
| Mandapam
group | Musal
tivu | 9°
12' N to 79 05' E | 124.00 |
| Manalli
tivu | 9°
13' N to 79 07' E | 25.90 |
| Manalli
Putti tivu | 9°
13' N to 79 07' E | 2.34 |
| Pumurichan
tivu | 9°
14' N to 79 11' E | 16.58 |
| Kovi
tivu | 9°14'
N to 79 11' E | 29.95 |
| Kursadi | 9°15'
N to 79 12' E | 65.80 |
| Shingle | 9°
15' N to 79 14' E | 12.69 |
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Natural
Resources of Gulf of Mannar Area:
About
3,600 species of fauna and flora have been identified in Gulf of Mannar area by
Central Marine Fisheries Research Institute and other organizations (Neelakantan
1998). The fauna is said to be one of the richest in the whole of Indo-west Pacific
region.
Vegetation
in Gulf of Mannar coastal area is not uniformly spread and in general thorny scrubs
that can be said to correspond to group four littoral and swamp forests according
to the classification of Champion and Seth (1968). It is characterized by species
like Thespesia
Populnea, Acacia Planifrons, Tamarix, Vi-tex negundo etc.
Mangroves and their associated species are seen in Shingle, Kursadi, Kovi, Pumurichan,
Manalli and Manalliputti Islands. Avicennia,
Rhizopora, Brugeira, Pumphis, Pandanus, Skirting
occurs along the periphery of the islands in the study area. Palmyra, Casuarina,
Coconut, Mango and Tamarind trees, etc can be seen in the Kursadi, Musal and Nalla
Tanni Islands (Neelakantan 1998).
Algal
growth is very rich in Gulf of Mannar. The algal productive area along the coastline
from Mandapam to Kanyakumari is put at 17.125 hectares (MoEF 1987). Kursadi and
Shingle Islands have very rich algal beds of Litho
thamnion, Martensia, Clandia, Anadyomene, etc. There
are different types of algal species formed on coral reef in lagoons. It is rich
in sea grasses.
The
sacred chank Xancus
pyrum also
occurs in Gulf of Mannar area. The sacred chank is found on fine or soft sandy
substances under the water.
The
Gulf of Mannar is famous for its chank fisheries and pearl fisheries. There are
about ten pearl banks in the region. The maximum concentration of pearl bank is
found in the regions off Tuticorin and to some extent in between Nalla tanni tivu
and Valinokkam point. The region between Tuticorin and Kanyakumari has extensive
pearl banks (MoEF 1987; Neelakantan 1998).
The
Gulf of Mannar has some significant amounts of monozite,
illmenite, rutile and garnet, and a small amount of zircon
and sillimanite and also mined. These minerals are found as placer
deposits. It is expected that this activity will increase during the years to
come (Loveson and Rajamanicakam 1989; Mallik and Ray 1975). India was granted
the right to mine metal rich nodules over 53,000 kmē of the seabed south of Gulf
of Mannar (Govind 1989).
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Biodiversity
of Gulf of Mannar:
The
Gulf of Mannar with its islands comprises three different ecosystem viz..
- Seagrass
ecosystem
- Mangrove
ecosystem
- Coral
reef ecosystem
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Threats
The
degradation of coral reefs in the Gulf of Mannar has been well noticed and many
authors have reported that the degradation is quit severe due to the human stress
(anthropogenic) and also by natural agents (UNEP 1985; UNEP/IUCN 1988; Pillai
1973 and 1975; Salam 1975; Venkataramanujam et al 1981; Silas et al 1985a; Anon
1987; Venkataramanujam and Santhanam 1989; Wafar 1986; Mahadevan and Nagappan
Nayar 1972). Arjan Rajasuriya et al (1999) is of the opinion that the coral mining
for lime, sand mining, pollution, sedimentation, fisheries, mangrove cutting,
population pressure, commercial shell collection and industrial development has
led to the increase in coral reef degradation in India. DOD and SAC (1997) have
calculated the areal extent of coral reefs to be about 94.3 kmē including all
associated forms of coral reefs.
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