1 Present address: Madras Research Centre of CMFRI, 68/3, Greams Road, Chennai-6
2 Central Agricultural Research Institute, Port Blair
Introduction
The marine ecosystems of the Andaman and Nicobar Islands are unique in having very high degree of biodiversity and endemism in fauna and flora. The coral reefs of these Islands are one of the richest in the Indian Sub-continent. They not only protect the coastline against sea erosions but also harbour host of animal communities like fishes, molluscs, sponges, echinoderms and other organisms. Commercial fisheries often indirectly depend on coral reefs which serves as nursery grounds for juveniles. Of late, the coral reefs have also come under heavy pressure due to uncoordinated and inconsistent developmental activities on coastal land leading to deforestation, mangrove habitat destruction, and degradation of marine ecosystems.
In the Andaman and Nicobar islands, a total of 733.12 sq. km. of area have been brought under protected areas under Wild Life (Protection) Act, 1972. They include 6 National Parks, and 94 Sanctuaries. The total area of the 6 National Park is 361.79 sq. km. and of which about two third is marine water area. All the National Parks and 91 Sanctuaries are located in the Andaman district, while 3 Sanctuaries in Nicobar district, besides the Great Nicobar Biosphere Reserve.
Mahatma Gandhi Marine National Park
Under the Wildlife (Protection) Act of 1972 the Mahatma Gandhi Marine National Park, Wandoor was notified on 24th May 1983 for the protection of marine life including corals and nesting sea turtles. The Park is located on the South Western coast of South Andaman, in the Bay of Bengal, encompassing 15 islands and several islets of the labyrinth group of islands, like Alexandra, Red Skin, Boat, Hobday, Tarmugli, Grub, Chester, Snob, Bell, Pluto, Malay, Jolly Boys, Riflemen, Twins and parts of Rutland island (Fig.1). The parks boundary runs along the coasts as well as some time along island within the range of latitude between 11°22, 06" and 11° 36 -34" N and longitude between 92° 30.00"W and 92° 40.33' E covering a total area of 281 50 ha (281.5 sq km). The area includes vast stretch of enchanting marine waters, bushy vegetated islands, magnificent coral reefs and sparkling sandy beaches and mangroves.
The park is under the overall administrative control of the Chief Wildlife Warden of the forest department of A&N islands administration. Though the park is uninhabited, there are 8 villages adjacent to the park area with a population of about 3000 (1981 census).
The fishermen of the villages continue to carry out fishing within the park area and are given license by the Fisheries Department. To encourage tourism, two islands in the park viz., Jolly Boys and Red Skin are opened for the tourist to visit during fair seasons.
Coral reef survey
Out of the 15 islands and islets in the Park, Wandoor, five islands were selected for detailed survey. They are Jolly Boys, Red Skin, Tarmugli, Boat and Twins Islands. The islands were selected in such a way so as to have a homogenous representations of all ecosystems in the park area. The Jolly Boys and Red Skin islands are open to tourist and thus subjected to greater disturbances. Tarmugli and Boat Islands are less disturbed while Twins islands is least disturbed due to their far off location and less human interference. Survey stations ranging from 4 to 9 in various islands were fixed so as to cover the maximum perimeter of the islands. Detailed quantitative and qualitative observations were made following live transect and quadrate survey methods.
A total of 99 transects in 33 stations at five islands were surveyed. The total distance covered was about 15,000m in which 1,569 quadrates were sampled to record the occurrence and density distribution of marine flora and various fauna such as hard corals (=live coral), soft coral, dead coral, sponges, fishes, gastropods, bivalves, sea cucumbers, sea stars, sea urchins, crabs, lobsters and sea anemones.
Status of coral reefs
The coral reefs of the Park were mostly of Fringing type. The live coral coverage on the reef and their composition and the list of coral species recorded in five islands are given in Tables 1 and 2.
Jolly Boys Island
This island is located in the buffer zone of the Park and has a total land area of about 17 ha. The coast line vegetation leads to sand and in some places to rocks. The island is not having any mangroves. However uprooted tree trunks are seen along the coastal area in a few places. The surveys were carried out at 6 station. The coral reef is of fringing type and it starts at 30m from the shore in station 1 and at 160 m in station VI.
The live corals in different stations were between 37 and 50%, with 42.3% for the whole island. Corals species diversity was moderately good. A total of 26 species under 17 genera were recorded, of which Acropora and Ponies were dominant, forming 33 and 28% respectively. Soft corals were also available in all stations and were represented by 3 species; maximum coverage (1 2.4%) was in Station 1. Nearly 38% of the reef was strewed with dead corals; a small percentage of them were in 'Bleached' condition caused due to predation of coral polyps by the dreaded crown of thorns (Acanathaster planci).
Red Skin Island
This island is located in the core zone of the Park and has total land area of about 347 ha. The east coast of the island is profusely bordered with mangrove vegetation while the west coast by sand and sheet rocks at few places. Uprooted tree trunks are strewn on the beach. Fairly extensive mangrove swamps are also found on the west, south and eastern parts of the island. Surveys were carried out in 8 stations. The coral reef are of fringing type; generally the reef starts from 80m and extends up to 210 m. In station VII the reef is very close to the shore and its slope suddenly increases from 2m to 7m. Damages to coral reef were seen in Station VI caused mainly due to boat anchorage.
Nearly half (51 %) of the reef area was occupied by luxuriant live corals and at Station VIII it was as high as 62%. A maximum of 18 genera and 26 species of corals were record in the island. Dominant forms were Porites (47%) and Acrqpora (21 %). Soft corals were poorly represented and were found only in 3 out of 8 stations; in Station 1 it formed 4.2%. The dead coral proportion (37%) was more or less similar to that observed in Jolly Boys island.
Table 1: Live Coral Coverage and their composition (%) in the five islands of Mahatama Gandhi Marine National Park
|
Species |
Jolly Boys |
Red Skin |
Tarmugil |
Boat |
Twins |
|
live coral coverage |
42.5 |
51.4 |
45.0 |
40.3 |
52.9 |
|
Composition | |||||
|
Seriatopora |
0.4 |
0.6 |
0.1 |
1.8 |
0.3 |
|
Stylopora |
0.1 |
- |
0.2 |
- |
2.3 |
|
Pocillopora |
0.6 |
0.9 |
1.0 |
0.5 |
0.9 |
|
Acropora |
33.0 |
20.5 |
44.9 |
30.6 |
55.3 |
|
Montipora |
15.6 |
6.4 |
3.4 |
7.4 |
1.5 |
|
Pavona |
0.3 |
1.2 |
0.3 |
- |
0.3 |
|
Pachyseris |
- |
0.2 |
- |
- |
0.3 |
|
Fungia |
0.6 |
0.7 |
0.3 |
0.5 |
- |
|
Herpolitha |
0.1 |
0.1 |
- |
- |
- |
|
Goniopora |
1.3 |
4.5 |
0.5 |
0.5 |
1.2 |
|
Porites |
28.5 |
47.0 |
34.7 |
46.5 |
3.9 |
|
Favia |
0.5 |
2.0 |
0.6 |
0.7 |
0.5 |
|
Favites |
3.6 |
5.2 |
4.8 |
3.2 |
0.8 |
|
Platygra |
0.6 |
0.3 |
0.5 |
- |
- |
|
Leptoria |
0.6 |
0.4 |
2.1 |
0.6 |
- |
|
Hydnopora |
0.6 |
0.1 |
- |
- |
- |
|
Diploastrea |
0.2 |
- |
0.1 |
0.2 |
- |
|
Echinophora |
- |
- |
- |
0.6 |
- |
|
Galaxea |
- |
0.3 |
0.1 |
- |
0.1 |
|
Merulina |
8.0 |
2.4 |
0.6 |
- |
1.5 |
|
Lobophytlia |
- |
1.6 |
- |
- |
0.2 |
|
Millepora |
5.3 |
5.7 |
5.8 |
6.9 |
30.9 |
|
SOFT CORALS |
6.2 |
0.8 |
2.3 |
2.2 |
2.9 |
|
DEAD CORALS |
37.9 |
37.4 |
30.9 |
38.5 |
38.0 |
Table 2:List of corals, sponge and flora species recorded in different islands of Mahatma Gandhi MNP, Wandoor, Andamans
|
Species |
Jolly Boys |
Red Skin |
Tarmugil |
Boat |
Twins |
|
Hard live corals Pocillioporidae | |||||
|
Seriatopora hystrix |
+ |
+ |
+ |
+ |
+ |
|
Stylopora pisilata |
+ |
+ |
+ |
+ |
+ |
|
Pocillopora verrucosa |
+ |
+ |
+ |
+ |
+ |
|
Acroporidae |
|
|
|
|
|
|
Acropora gravida |
+ |
- |
+ |
- |
+ |
|
A. hyacinthus |
- |
+ |
+ |
+ |
+ |
|
A. nobilis |
+ |
+ |
+ |
+ |
+ |
|
A. humilis |
+ |
+ |
+ |
+ |
+ |
|
A. efflorescens |
+ |
+ |
+ |
- |
+ |
|
A. palifera |
+ |
+ |
+ |
+ |
+ |
|
Acropora sp |
+ |
+ |
+ |
+ |
+ |
|
Asteropora sp. |
- |
+ |
+ |
- |
+ |
|
Montipora sp |
+ |
+ |
+ |
+ |
+ |
|
Agaricidae |
|
|
|
|
|
|
Pavona sp. |
+ |
+ |
+ |
+ |
+ |
|
Pachysehs sp. |
- |
+ |
- |
- |
+ |
|
Fungidae |
|
|
|
|
|
|
Fungia sp. |
+ |
+ |
+ |
+ |
+ |
|
Herpolitha sp. |
+ |
+ |
- |
- |
- |
|
Poritidae |
|
|
|
|
|
|
Goniopora sp. |
+ |
+ |
+ |
+ |
+ |
|
Ponies sp. |
+ |
+ |
+ |
+ |
+ |
|
Faviidae |
|
|
|
|
|
|
Favia sp. |
+ |
+ |
+ |
+ |
+ |
|
Favites sp. |
+ |
+ |
+ |
+ |
+ |
|
Platygra sp. |
+ |
+ |
+ |
+ |
+ |
|
Leptoria sp. |
+ |
+ |
+ |
+ |
+ |
|
Hydnopora sp. |
+ |
+ |
+ |
+ |
+ |
|
Diploastrea sp. |
+ |
+ |
+ |
+ |
+ |
|
Echinophora sp. |
+ |
- |
- |
+ |
+ |
|
Oculinidae |
|
|
|
|
|
|
Galaxea sp. |
- |
+ |
+ |
+ |
+ |
|
Merulindae |
|
|
|
|
|
|
Merulina sp. |
+ |
+ |
+ |
+ |
+ |
|
Mussidae |
|
|
|
|
|
|
Lobophyllia sp. |
+ |
+ |
+ |
+ |
+ |
|
Symphyllia sp |
+ |
- |
+ |
- |
- |
|
Pectinade |
|
|
|
|
|
|
Mycedium sp |
- |
- |
- |
- |
+ |
|
Milliporidae |
|
|
|
|
|
|
Millepora sp |
- |
- |
- |
- |
+ |
|
SOFT CORALS | |||||
|
Dendrophyllidae |
|
|
|
|
|
|
Turbinaria sp. |
+ |
+ |
- |
- |
- |
|
Sargophytum sp. |
+ |
+ |
+ |
- |
+ |
|
Sinularia sp. |
+ |
+ |
- |
- |
+ |
|
Gorgonia sp. |
- |
- |
- |
+ |
- |
|
Sponges |
|
|
|
|
|
|
Phyllospongia sp. |
|
|
|
|
|
|
Flora |
|
|
|
|
|
|
Sargassum sp. |
+ |
+ |
+ |
+ |
+ |
|
Turbinaria sp. |
+ |
+ |
+ |
+ |
+ |
|
Padina sp. |
+ |
+ |
+ |
+ |
+ |
|
Halemeda sp. |
+ |
+ |
+ |
- |
- |
|
Gracillaria sp. |
+ |
- |
- |
- |
- |
|
Filamentous sp. |
+ |
+ |
+ |
+ |
+ |
|
Sea grass |
+ |
- |
+ |
+ |
+ |
+: PRESENT -: ABSENT
Tarmugli island
This is the biggest island in the park area, having a total land area of 945 ha, located west of Chester and Belle islands. The characteristic feature of the coastline of the island is the presence of very thick mangrove vegetation, sandy beaches, uprooted trees and sheet rocks. Very extensive mangrove swamps are found on the northern side of the island with a few patches of swamps on the east, south eastern and south western parts of the island. Surveys were carried out in 9 stations. Coral reef is patchy/fringing type and starts from 50 m to 150 m from the shore. However, in station VIII ft starts very close to the shore. Damaged dead shells are found at several places inside the sea at Station III. Maximum dead corals up to 70 m from the shore were seen in station IV as well as in station VII at 240 250m from the shores. Damages to the live corals (stag horn) was also seen in this station.
The live coral density at Tarmugli island was not uniform; its coverage varied between 20% in Station 1 and 58% in Station IX. The overall coverage for the island was 45%. A total of 26 coral species under 17 genera were recorded during the survey; Acropora (45%) and Porites (35%) were the dominant forms. Only one species of soft coral (Sargophytum) was recorded in 7 out of 9 stations; its percentage coverage in Station III to V were between 4.2 and 4.9. Of the five islands surveyed, the percentage proportion of dead coral was lowest (31 %) in this island; it was as low as 14% in Station IV.
Boat island
This island is situated in the core zone of the park, on the south of Tarmugli, Belle and on the west of Malay island. The total land area of the island is about 180 ha. Fairly extensive mangrove swamps are found both on the northern and south-western part of the island. Sheet rocks are present on the south eastern and north western parts of the island. Coastal vegetation leads to sandy as well as rocky beaches and in some areas uprooted tree trunk are lying on the sandy beaches. The survey was carried out in 6 stations. Coral reefs are patchy/fringing type and ft starts very close to the shore in Station 11 and extends up to 250 m in station VI.
As compared to other islands in the park, live coral (40%) coverage was lowest in Boat island. Species diversity was also low; only 24 species under 14 genera were recorded. Porites (46.5%) and Acropora (31%) were dominant. However, the maximum dead coral coverage (39%) was also observed in this station. In Station V, nearly half of the reef region was with dead corals. Soft corals were found in four stations, with coverage ranging from 1 to 8%.
Twins island
As the name implies it represents two small islands situated side by side in east west directions in the southern most core area of the park, far away from rest of the Labyrinth group of islands. The total land area of Twins islands is about 49 ha. In the eastern Twins island, the coastal vegetation leads to sheet rocks, edged rocks and sandy beaches while in the western Twins island mostly to vast stretches of sandy beaches and edged rocks. In some places uprooted tree trunks were seen. This island is an important breeding ground for Turtles. Large number of turtles were seen swimming in the sea and their foot prints were observed on the sandy beaches.
Among the five islands, live coral coverage was highest (53%) in Twins island. In 3 out of 4 station, its proportion was over 50%. In Station 11 and III, they formed nearly 57% substaratum coverage. Coral species diversity was moderately good, with 25 species under 15 genera. The dominant coral was Acropora (55%) followed by Millepore (31 %). Though Millepore was recorded in all the 5 islands, its density distribution was very high in Twins island. Soft corals (Sargophytum sp and Sinularia sp) were recorded only from Station 1. Among the dead corals which formed 38%, a small proportion were in Bleached' condition.
An overall analysis revealed that nearly 47% of the reef in the Park were with live and luxuriant corals in varying density; soft corals from about 3%. A total of 31 coral species under 25 genera were recorded. Acropora, Porites and Millepora were the dominant coral forms in the park region. Soft corals were relatively more in number in Jolly boys and Twins islands than in other islands and they were represented by four genera.
Based on species diversity and substratum coverage with live corals, the status of coral reef of the park area may be broadly categorised as 'Fair' in Jolly Boys, Tarmugli and Boat islands and as 'Good' in Red Skin and Twins islands.
Associated fauna of coral reefs
Among the reef inhabiting invertebrate fauna, the major groups found in order of abundance were Gastropods (35%), Bivalves (25%) and Echinoderms (25%). Conus, Cyprea, Lambis, Trochus, Blood clam, Pearl oyster, Rock oyster, Giant clam, Sea urchin and Holothurian were the commercially important forms found in varying densities. Fairly high density of invertebrate fauna were found at Red Skin, Twins and Boat islands. Gastropods' and Echinoderms were more common in Twins island, while Bivalves in Red Skin island. A total of 31 species of Gastropods, 26 species of bivalves, 3 species of Cephalopods and 16 species of Echinoderms were recorded from the park area. Crabs, lobsters and sea anemones were observed in small numbers only.
The fish assemblage on the reef region was moderately high at Twin island, followed by Red Skin, Tarmugli, Boat and Jolly Boys islands. Pomacentrids represented by 5 species were the dominant group in all the island. Lutjanids, Acanthurids and Chaetodontids, each represented by 6 species were more common than other groups. An overall analysis showed that Angle fishes formed 32%, Snappers and Fusiliers 19%, Surgeon fish 18%, Coral fish 12%, Spine foots 4% and Wrasses 3%. The other fish groups such as Breams, Reef cods, Parrot fishes and Gobis were represented by 2% each. Out of the 55 fish species recorded in the park area, many of them were of highly priced ornamental fishes and important tuna live bait fishes.
The algal coverage in the park was generally poor ft was represented by Turbinaria, Sargassum, Padina, Halemeda and Gracillaria. Filamentous algae was found attached on the dead corals in all the islands. Sea grass was found in good patches at Station VI of Tarmugli island, suggesting that ft could be the feeding ground for Sea cow, Dugon dugon.
Among sponges, Phyllospongia sp was the only species recorded in all islands, but in small numbers. Its occurrence was relatively more in Red Skin and Jolly Boys islands.
General remarks
The sea water quality of the park area in respect of temperature, salinity, dissolved oxygen and pH were in optimal range, free from oil and other pollutants, with very high clarity and transparency, inspite of several fishing and tourist boats ply within the park area. The shores of these islands were also unpolluted; litters were not observed even in Jolly Boys and Red Skin Island which are opened to tourist.
Several factors like predation by crown of thorns, siltation of coastal waters, effluent discharge, unfavourable environmental conditions, human interference, etc. are stated to be the responsible factors for the damage and destruction of corals. As far as the Park is concerned, human interference and crown of thorns infestation, have definitely caused damages to coral and coral reefs. In some areas like Station VI of Red Skin island, corals in the reef slope were badly damaged, mostly due to boat anchorage. Shell collection activity also caused considerable damage to corals at Station 11 of Twins island and Station III of Tarmugli island. Tourist activity like trampling, overturning the coral blocks, Snorkelling and Scuba diving have damaged the corals at Station III in Jolly Boys island.
Wood (1989) had observed significant and localised damages to corals by crown of thorns in the park area. However, James et al (1 990) had stated that 'predation by Acanthaster might have played some role in the death of corals but this is not of an alarming state at present". As is well known that some of the reef inhabiting animals like fishes, sea urchins, shrimp, polychaete and molluscs also feeds to a limited extent, on the coral tissues and cause damage to coral colonies. However, the prey-predator inter-relationship and mechanism of coexistence of corals and coral inhabiting the organisms of the Park have not been studied.
Though there are several reports about the damage and death to corals due to siltation and effluent discharges in the inshore areas of South and Middle Andaman, (Dorairaj et al 1987, Wood 1989, James et al 1990), these problems have not been encountered in the Park area, except at a few coastal areas near the New Wandoor and on the west coast of Rutland island. The strong monsoonal winds and cyclones also appear to exert strong influence on reef flats, turning them into rubble banks. The exposed reef are normally affected by tidal emersion due to prolonged exposure. The tidal amplitude in the Andaman is 2.5 m. At times of prolonged exposure, the corals tend to extrude the zooxanthellae and the loss of tissue give way for algal growth and thus widespread damages are likely to be caused due to unfavourable environmental factors.
Environmental awareness campaign need to be organised, particularly in the bordering villages of the Marine National Park Wandoor, to educate and to create an awareness among the general public, the need for protecting the coral reef and preserving the valuable 'germplasnm' of the National Park.
References
Dorairaj, K. R. Soundararajan and N.T. Singh. 1987. Corals of Andaman and Nicobar islands: a status report. Central agricultural research institute. 29 pp.
Dorairaj, K., R. Soundararajan and 1. Jagadis. 1994. Fishes of Andaman Islands check list. Spi. Publ. CARI Port blair. 66 pp.
James, D.B., C.S. Gopinatha Pillai and g. Gopakumar. 1990. A case study of infestation of acanthaster planci in andaman waters. Mar. Fish. Infor. Serv. T& ese/'106: 1-3
Pillai, C.S.G. 1983. Coral reefs and their environs. In: mariculture potential of Andaman and Nicobar islands - an indicative survey. Cmfri bulli., 34: 36-43.
Wood, E. 1989. Corals: wandoor marine national park, sane awareness series 4, INTACH, A&N Chapter, 14pp.
