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Distribution of species
As per census by COE (1983), 60 exclusive species of 16 families and 23 non-exclusive species were recorded. UNESCO (1986) confirmed 65 species of true mangroves all over the world while Tomlison (1986) agreed to only 48 mangrove species and Saenger et al (1983) reported 60 species, which are recognized as true mangroves in the list of IUCN. 44 species have been documented in Asia, out of which, 32 are found in India, 13 species on the west coast and 23 species on the east coast. Andaman & Nicobar is quite rich in number of species having about 27 number of species.
Species wise description of mangroves found in Goa
1. Rhizophora mucronata:
It is a moderate sized tree, much branched, very rough bark, leaves elliptic, broad, opposite, pale beneath with black dots, flowers yellowish white, four petals, radicle slender, elongated, 15 to 40 cms. long, flowering & fruiting takes place in between December to Mid June. Locally known as Kandal, it is available in plenty in the high salinity areas in all the estuaries.
2. Rhizophora apiculata:
It is a moderate sized much branched tree with rough bark, leaves elliptic, lanceolate, dark green above, base tapering, pink petioled, clustered towards end of branches, infloroscence 3-4 times forked, 4-8 flowered, flowers white, radicle thick, short and cylindrical, upto 30 cms. in length. Flowering and fruiting takes place in between December to May. It is seen mainly in between R. mucronata trees, which is dominant species. The species is found occasionally here and there and its total occurrence is quite less in Goa.
3. Bruguiera gymnorrhiza:
It is a straight stemmed, buttressed tall tree, upto 30m. in height, dark coloured, fissured bark, leaves elliptic, pointed, pale beneath, crowded at branchlet end, flowers solitary, petals bifid with hairs at the base, calyx red to bright red, radicle 15-20 cms. long, faintly ribbed, alike ladyfinger. Flowering and fruiting takes place in between November to April. It is found in low salinity areas and can be seen in the interior areas of the State. The tree has a conical shape and is seen mainly in Zuari & Chapora rivers.
4. Bruguiera cylindrica:
It is a medium to tall buttressed tree with smooth grey bark, leaves oblanceolate, thin, elliptic, flowers white to greenish, radicle 10-15 cms., short. Flowering and fruiting takes place in between the months of November to April. The species is observed in most of the river estuaries of the State and smaller size trees only are seen. It does not form a colony and is seen scattered here and there.
5. Ceriops tagal:
It is a small, 1to 2 m. tall straight stemmed tree or shrub forming buttress. Stem has lot of lenticels, leaves simple, opposite narrowed downwards, collected at branchlet end, flowers white, small and in cyma inflorescences. The species is localized to Terekhol river only and also planted in Chapora river. Flowering and fruiting takes place in between January to April.
6. Kandelia candel (K. rheedi):
It is a small, 5-6 tall tree with smooth reddish bark, leaves dark green, polished above, shortly petioled, elliptic, flowers white, radicle 30-40 cm. long and slender. Distributed in all estuaries of Goa. Flowering and fruiting takes place two times in a year, prominently from December to April and also from September to December.
7. Avicennia officinalis:
A tree with smooth yellowish grey bark, low branching, leaves very fine, silvery white, tomentose beneath. Flowers yellow, collected in small clusters, capsule velvety, compressed, obvate and pointed. It is found in all estuaries and make colonies. Profuse seedings & regeneration is observed. Flowering & fruiting takes place in between March to August.
8. Avicennia marina:
It is known as White mangrove due to its white bark, leaves opposite, shortly petioled, glossy green on upper side & dull grey or silvery white tomentose hair on lower side, flowers yellow or white, fruit a compressed capsule. Found in all estuaries and make colonies. Flowering & fruiting takes place in between March to August. Profuse seedings & regeneration is observed.
9. Avicennia alba:
It is a Small tree, about 2m. high brownish black bark, leaves lanceolate, whitish, tomentose beneath, wrap on both sides unlike other species of Avicennia. It is found in all estuaries and make colonies. Flowering & fruiting takes place in between March to August. Profuse seedlings & regeneration is observed.
10. Sonneratia alba:
It is much branched moderate size tree, bark orange brown / grey, branches silvery grey, swollen, leaves leathery, opposite, elliptic, thickened, flowers solitary or in threes, white, pale green, fruit about 3 cms. dome shaped. It is available in plenty in higher salinity areas. Profuse regeneration forming pure patches is observed. Flowering and fruiting takes place twice in a year, from January to April and September to December.
11. Sonneratia caseolaris:
It is a moderate sized tree, brown rough bark, leaves 5-10 cms. long, broadly obvate, flowers tinged with rose colour, fruit fleshy, cushion shaped. It is found in low salinity areas, on the higher reaches of the rivers. Flowering and fruiting takes place twice in a year, from January to April and September to December. Fine patches showing excellent growth are seen at many places, particularly along Zuari river, in Khazan land in Borim and Shiroda.
12. Aegiceras corniculatum:
It is a small shrubby tree, bark brown with reddish tinge, leaves alternate, elliptic, flowers white, in umbels, fruit cylindrical, curved, very small. Available in plenty in low salinity areas. Flowering and fruiting takes place in between February to April.
13. Excoecaria agallocha:
It is a much branched tree, upto 5 m high. Bark greyish, leaves pale green, alternate, elliptic, produce latex which is poisonous & dangerous to eyes. Flowers dioecious, arranged in sessile axillary catkins. Male and female plants found separately with distinct characters. Found in all the estuaries and is a common species in Goa.
14. Acanthus illici folius:
It is a shrub, upto 2 m high, aerial root formation is seen. Leaves glabrous, decussate with pair of spines. Flowers light blue to violet. Fruit 2-3 cms. long. It is found in abundance in all the estuaries. Flowering and fruiting takes place in between February to April.
15. Lumnitzera racemosa :
A small tree upto 10 m. high. Bark grey and fissured. Pneumatophores are thin, knee shaped. Leaves small, fleshy, oval, clustered towards end of branches Flowers white. Fruit hard, ovoid. Flowering and fruiting in between March to September. Localised to Siolim area, along the bunds.
COMPOSITION AND CONFIGURATION OF MANGROVES
Species in estuaries: -
The composition and configuration of mangrove species in estuaries varies as per the salinity gradient, which varies from the mouth of the river to the rise of river. This gradient decreases as we proceed from the mouth to the upstream of the river. The gradient also varies from day to day due to the high tide-low tide phenomena. The longitudinal and vertical strata is very distinct and it forms a compact mass of canopy from high tide level to the low tide level with varying colour of canopy from pale green, pale yellowish green to dark green and blackish green from high tide level to low tide level. From distance, the varying conglomerate colour gives the clear appearance of species. The size of the propugules of different species plays an important role in establishment of the species in different zones which are formed from high tide level to the low tide level in varying depth of the silt in the substratum.
The composition of species as per the salinity gradient in Goa is as follows :
Estuary wise composition and configuration of mangrove species
The estuary wise composition of mangrove species in various river estuaries in Goa are given below:
I) Mandovi: (i) Mapusa side
(a) Betim Fisheries Jetty & near Mandovi Bridge : Sonneratia alba - 90%; Rhizophora mucronata & Avicennia alba - 10%.
(b) Penha De Franca (Britona): Avecenia alba & Avicennia officinalis - 90%; and Acanthus illicifolius & Deris heterophylla - 10%.
(c) Salvador do Mundo & Pomburpha : Avicennia officinalis & Avicennia alba - 80%; and Rhizophora mucronata & Kandelia candel - 20%.
(d) Moira & Aldona : Avicennia alba - 60%; Kandelia candel - 10% and Acrosticum aurum & Acanthus illicifolius - 10%.
(e) Mapusa & Peddem : Avicennia alba - 60%; Kandelia rheedii - 10%; Acrosticum aurum & Acanthus illicifolius - 30%.
(ii) Mandovi (Diwar Naroa side):
(a) Vanshi : Avicennia officinalis - 40%; Bruguiera cylindrica - 30%; Porterasia coaretata - 20%; & Acanthus illicifolius - 10%.
(b) Naroa & around : Avicennia officinalius - 80%; Porterasia coaretata - 10%; and Acanthus illicifolius - 10%.
(iii) Mandovi (Old Goa Side):
(a) Piedade & Old Goa : Avicennia officinalis - 30%; Sonneratia alba - 30%; and Porterasia coaretata -
(b) Panaji, Patto & Ribandar : Avicennia officinalis, Avicennia alba & Avicennia marina - 70%.
(c) Old Goa & Dhauji : Avicennia officinalis and Avicennia a alba - 80%; Sonneratia alba - 15%; and Acanthus illicifolius - 5%.
(d) Khandola, Amona, Tonca : Sonneratia caseolaris - 80%; and Acanthus illicifolius & Aegiceras corniculatum - 20%.
(iv) Chorao area (Sanctuary):
(a) Avicennia officinalis & Avicennia alba - 40%; Sonneratia alba - 10%; Rhizophora mucronata & Rhizophora apiculata - 15%; Acanthus illicifolius - 3%; Aegiceras corniculatum - 2%; Kandelia candel - 5%; Bruguiera cylindrica - 1%; Excoecaria agallocha - 20%; and Derris heterophylla - 4%.
Note: - In the west coast, Kandelia candel is rare, but it is very prominent and abundant in Mapusa river in Goa in between Pomburpa to Mapusa, Peddem - Goa.
(II) Zuari (1) Cortalim side:
(a) Cortalim: Avicennia officinalis & Avicennia alba - 40%; Acanthus illicifolius & Aegiceras corniculatum - 40%; and Excoecaria agallocha - 20%.
(b) Lotolim & Rai: Avicennia officinalis & Avicennia alba - 50%; Sonneratia alba - 20%; and Excoecaria agallocha & Acanthus illicifolius - 30%.
(c) Borim, Sanvordem: Avicennia officinalis & Avicennia alba - 40%; Sonneratia caseolaris - 40%; and Acanthus illicifolius & Acrosticum aurum - 20%.
(2) Agaciam side:
(a) Agacaim & Madkai: Avicennia officinalis & Avicennia alba - 60%; Rhizophora mucronata & Rhizophora apiculata - 20%; and Bruguiera gymnorrhiza - 20%.
(b) Durbhat & Borim: Avicennia officinalis & Avicennia alba - 60%; Rhizophora mucronata & Bruguiera gymnorrhiza - 20%; and Acanthus illicifolius - 40%.
(c) Panchwadi, Shrioda: Avicennia alba - 40%; Sonneratia caseolaris - 20%; Kandelia candel, Acanthus illicifolius & Acrosticum aurum - 40%.
Note: - Sonneratia caseolaris is very prominent and dense in Panchawadi, Shrioda areas which is due to the low salinity.
(III) Chapora (Colvale)
(1) Agarwada, Shivolim: Avicennia officinalis & Sonneratia alba - 40%; Acanthus illicifolius - 20%; Rhizophora mucronata - 10%; Derris heterophylla, Porterasia coaretata - 30%.
(2) Colvale Mecazone: Avicennia officinalis & Sonneratia alba - 40%; Ceriops togal - 10%; Kandelia candel, Acanthus illicifolius & Porteresia coaretata - 50%.
(3) Virnoda, Caturlim: Rhizophora mucronata, Rhizophora apiculata & Avicennia alba - 50%; Bruguiera gymnorrhiza & Aegiceras corniculatum - 20%; and Acanthus illicifolius, Sonneratia alba & Sonneratia caseolaris
Note: - This estuary is rich in Bruguiera gymnorrhiza and Aegiceras corniculatum at Virnoda & Caturlim.
(1) Keri, Palyem, Kiran Pani: Avicennia officinalis & Sonneratia alba - 40%; Ceriops tagal - 10%; Acanthus illicifolius, Derris heterophylla & Rhizophora mucronata - 50%.
(2) Deusum: Avicennia officinalis - 40%; Sonneratia alba - 20%; and Ceriops tagal & Acanthus illicifolius - 40%.
Note: -This is the only estuary where we find Ceriops tagal and now propagated and is also spread in other adjacent estuaries.
(1) Cavelosim: Avicennia officinalis - 60%; Sonneratia alba - 20% and Rhizophora mucronata - 20%.
(2) Margao: Avicennia officinalis - 60%; Sonneratia alba - 10%; Acrosticum aurum & Acanthus illicifolius - 30%
Note: - This is the smallest estuary with beautifully well protected banks by mangroves, which are now subjected to degradation due to urbanization.
(1) Talpona, Khalwada: Avicennia officinalis & Avicennia alba - 60%; Rhizophora mucronata - 20%; Bruguiera gymnorrhiza, Acanthus illicifolius, Derris heterophylla & Aegiceras corniculatum - 20%.
Note: - Mangroves are in few patches but dense.
(1) Mashem, Lolyem : Avicennia officinalis & A. alba - 30%; Rhizophora mucronata & Rhizophora apiculata - 60%; and Aegiceras corniculatum - 10%
(2) Binguinim & Galgibag : Avicennia officinalis & Avicennia alba - 50%; Rhizophora mucronata & Rhizophora apiculata - 40%; and Bruguiera gymnorrhiza & Bruguiera cylindrica - 10%.
Note: - Mangroves ae dense at the mouth of the river and forms a ground for fish.
(VIII) Kumbharjua Canal:
The prominent species are: Avicennia officinalis & Avicennia alba - 60%; Rhizophora mucronata & Rhizophora apiculata - 30%; and Acanthus illicifolius & Derris heterophylla - 10%.
Note: -The canal joins two major estuaries i.e., Mandovi and Zuari and bears good mangrove areas, which hosts number of estuarine crocodiles and encourages Eco - Tourism. These mangroves there protects the bunds, which prevents the entry of blackish water into the khazan lands.
This is a man made mangrove patch opposite Chorao jetty, which was blank till 1986. The then Research Officer established grass and then planted mangrove species like Rhizophora mucronata, Rhizophora apiculata, Avicennia officinalis, Avicennia alba and Sonneratia alba. Now it has become a dense mangrove forest and is gradually increasing in area. It also harbours different birds, particularly pin tailed ducks in thousands. It has become a very good example of edaphic climax.
Associates of Mangroves
The associates, which are the plants
found along with the mangroves, are:
Special Characteristics of Mangroves
Mangroves are typical coastal plants, which are subjected to periodic tidal inundation. They exhibit a number of morphological and anatomical adaptations and physiological characteristics which enable them to flourish under these conditions. Some of the important characteristics which are clearly visible in the mangroves of Goa are as follows:
1. Root system: Root system of mangroves is not deep and is extensively branched due to poor aeration of substratum. The surrounding soil is very deficient in oxygen. Therefore, mangroves has root adaptations to help them grow well in adverse conditions, main of which are:
Fauna Associated with the mangroves of Goa
Mangroves forests are a unique eco-system in themselves. The mangrove vegetation and associated animal communities form a food chain. Many of the fauna present thrives on leaves, branches, flowers and fruits of mangroves, which thereafter become food for bigger animals. Mangroves in Goa are also heaven for resident as well as the migratory birds, which can be seen in plenty at any point of time. Variety of fishes, crabs, prawns, oysters, etc. are there in these mangrove forests.
The fauna associated with mangroves in Goa can be enlisted broadly as:
1. Pin tailed duck 2. Coots 3. Purple moor hen 4. Cormorants 5. Shovellor 6. Terns 7. Pond Heron 8. Cattle Egret 9. Little Egret 10. Large Egret 11. Blackwinged Kite 12. Brahminy Kite 13. Small blue kingfisher 14. Blue eared kingfisher 15. White breasted kingfisher 16. Roller or Blue jay 17. Night Heron 18. Reef Heron 19. Common Sandpiper 20. Green bee eater 21. Black Drongo 22. Grey Drongo 23. Grey headed Myna 24. Tree pie 25. Lesser wood shrike 26. Large cuckoo shrike 27. Flying Foxes (bats) 28. Crocodiles 29. Turtles 30. Otters 31. Jackls 32. Snakes 33. Crabs 34. Oysters 35. Fish
Uses of Mangroves
Mangroves provide a vide range of services and benefits to the mankind. Ecological and economical values of mangroves are recognized world over. They are instrumental in providing ecological and livelihood security to coastal regions and people. People in Goa are making use of mangroves by protecting them as a nursery ground for various fish and crab species, which forms a part of their daily food. Good use of mangrove areas is also being made for eco-tourism and tourists from India and abroad are taken to these areas for a pleasant trip and crocodile watching. Felled dried branches of mangroves are also collected at a very limited scale for firewood purpose. However, no beehives have been reported and these areas are not being used for that purpose. Besides, all the river banks are protected by thick mangrove cover available everywhere. The general services provided by the mangroves to the mankind however are as follows -
1. Prevention from soil erosion and
stabilization of coasts and beaches
Activities of the Forest Department
1. Nursery: Forest Department of Goa is pioneer in the establishment of nursery and plantations in the country. The first nursery was established in the year 1985 at Chorao and since then, regular progress is being made in nursery activities. Study and research in mangrove nurseries is also in progress. Presently, temporary nurseries are being established every year near to the plating sites and seedlings raised are used for planting. A permanent demonstration cum production nursery has been established at Chorao, which consists of seedlings of different mangrove species. Raising of seedlings in root trainers away from planting site is under study and experimental work is already taken up, which again will be a pioneer work in the entire country in mangrove nursery.
2. Afforestation: Plantation of different mangrove species is being taken up every year by the Forest Department in most of the river estuaries. Species used for plantation are mainly R. mucronata, all species of Avicennia, Bruguira cylindrical, Ceriops tagal, Kandelia candel and other species to a limited extent. Enrichment of the old plantation is also being taken up.
3. Awareness / Education: Awareness programmes for students, people are organized by the Departemtn. They are made aware of the uses and need for conservation of mangroves. Brochures, stickers are distributed to them. Visiting Forest Officers, trainees (IFS / SFS / RFO / other staff), students from Universities outside Goa are being taken regularly to mangrove areas fro education & awareness. Forest Staff of the state is also made aware of mangroves in details during all the Refresher Courses conducted by the Department.
(a) All the twelve major species of mangroves found in Goa along with three important associates have been banned for felling by a notification issued by the Department under Goa, Daman & Diu Preservation of Trees Act, 1984.
(b) Forest Department has been declared as Nodal Agency for any activity related to mangroves. All proposals related to mangroves are to be routed through the department for better control.
(c) Excellent mangrove area of Chorao has been declared as Dr. Salim Ali Bird Sanctuary, which has not only helped in protection of area but has also become a potential eco-tourism spot.
(d) Extensive protection works are being taken up.
(e) A Mangrove Interpretation Centre has been created at Chorao, where people can see different species all around. Details of various mangrove species are depicted by way of drawing & text, which are placed at the Mangrove Interpretation Centre.
(f) Eco-tourism to mangrove areas is being promoted.
Threats to mangroves of Goa - The threats are as given below:
(1) Barnacle infestation : Plantations and young plants are being damaged by the attachment of barnacles to their stem and the damage is more pronounced along Panaji-Ponda Highway, from Panaji to Ribandar. The plant affected generally is Rhizophora mucronata, which probably is due to its rough bark, thereby providing a good substratum for their attachment. Seedlings of Rhizophora mucronata in this area have suffered severe casualty in past. This affect is, though there, but is less pronounced in other river estuaries.
(2) Conversion of mangrove areas : It has been observed that mangroves in private areas / khazan lands face threat due to conversion of these lands for human habitation, aqua culture, agriculture and other developmental activities. Reclamation of these areas results in damage to saplings and small mangrove plants in general. Sporadic incidents of felling of trees illegally for conversion of land have also been reported, though damage due to this is almost negligible.
(3) Unauthorized felling : Cutting of branches of mangroves for firewood purpose is sometimes reported and very little damage may be there due to such cuttings. Cutting of bigger mangrove trees for timber, however, is not reported.
(4) Insect attack / diseases : There are some species of insects or borers, which cause considerable damage to the stems and therefore to the mangroves of Goa. Besides, insect attack on the leaves of Rhizophora mucronata has been observed to take place regularly, which some times results in total damage to young plants. Also, insect attack on Avicennia alba is observed at a regular interval of 5 years, where the larvae of the insect eat all the leaves of the plants and make them leafless and causes severe damage to young crop. Fungal attack on the leaves of plants has also been observed, mainly on the leaves of Sonneratia alba, and other species also found to have been attacked by fungus.
(5) Fishing : In the entire State, fishing using dragnets is common. This results in damage to the young regeneration and plantations. Besides, such fisherman find mangrove regeneration an obstacle in their fishing activity and they uproot / damage the young crop and this is one of the major threats to the mangroves of Goa.
(6) Barge movement : Considerable barge movement is there in Mandovi & Zuari rivers, which carries ores to Marmugao Port. Due to the strong wave action caused by the movement of these barges, young regeneration / saplings gets uprooted. Besides, erosion on the river banks is caused and trees / sapling of mangroves there are also affected. However, other estuaries not having barge movement do not have such problem.
(7) Inadequate infrastructure for protection : The Forest Department, Goa is a small department and have limited staff and resources. This inadequate infrastructure poses some difficulty in protecting all the mangroves scattered all over the State. However, the quantum of problem due to this factor is quite limited.
(8) Pollution : Oil slicks, solid waste deposition etc. causes pollution to the mangrove habitat and thereby affects them adversely. The threat due to pollution is again very limited in the State.
MANGROVE FLORA & FAUNA
There are more than 59 species of mangroves in the world of which 45 are found in India. Dr. Untawale has recorded 53 species in India. The flora and fauna of mangrove ecosystem in India are as follows:
The flora and fauna (mangroves) recorded in Goa are as under :
These species are found in different zones depending upon water salinity. The salinity varies with the distance from sea and tide. Ceriops tagal is found today only in Terekhol river.
Mangroves play an important role
as feeding and nursery ground for a large number of organisms
which from the marginal marine and freshwater habitats. It
is estimated that as much as 90% of tropical marine fish species
pass some stages of their life cycle in mangrove estuary.
Fauna associated with mangroves of Goa are as under:
Work done by Forest Department, Goa
Goa forest department has done pioneering work in the establishment of mangrove nurseries and plantations. The first mangrove nursery was established at Charao during 1985. Plantationa have also been taken up in 1985 at Chorao. Govt. of Goa has constituted a State Level Steering Committee on mangroves for its management and development. 15 mangrove species have also been declared as protected species in 1990 and all mangrove areas has been put under CRZ-I category.
Mangrove management plan was prepared
for five years (1991-1992 to 1995-96). There after work has
been taken up on annual basis. Recently managment plants have
been prepared for 1999-2000 to 2001-2002. During the management
plan period and annual plans the plantations have been taken
up at following places:
Year Location Area
Thus an area of 846.6 ha. has been afforested till 1998-99. The actual area covered after 1995-96 is national because it is in terms of number of seedlings. The total cost of raising the plantation is Rs. 42.2 lakhs. The plantation survival is not hundred percent because of various reasons and one of the main reason is the biotic interference though fishing and barge movement. As per F.S.I. report 1997, there is an increase of 5 sq.kms. in forest cover of Goa due to increase in mangrove forest and it almost conforms to the mangroves plantations raised by the department.
The plantation in Goa have been raised both by seedlings and propogules. The mature propogules of the steering committee took place on 29/06/99. It has been agreed to prepare the mangrove management plan and projects on Chorao mangrove complex and coral reef.
The mangrove management plan for 1999-2000 has been prepared and it envisages the following activities:
1.Conservation and development
4.Education and Extension
5.Research and Protection
The total financial projection for the management plan period is Rs. 140 lakhs. The Chorao mangrove complex inter alia also includes awareness education extension, research and protection activities and total cost is projected at Rs. 84 lakhs.