ENVIRONMENTAL INFORMATION SYSTEM CENTRECentre of Advanced Study in Marine Biology, Annamalai University

Parangipettai - 608 502, Tamil Nadu, India2002

Sponsored byMinistry of Environment & Forests, Government of India, New Delhi

ENVIS Publication Series : 2/2002

MANGROVES OF INDIAState-of-the-art report

Edited by

Prof. T. Balasubramanian(Director & ENVIS in-charge)

Prof. S. Ajmal Khan

Compiled by

Dr. N. Rajendran - Research OfficerDr. S. Baskara Sanjeevi - Research Assistant

Assisted by

Mrs. L. Vijayalakshmi - Assistant ProgrammerMr. V. Swaminathan - Technical Assistant

Mr. B. Senthilkumar - Information AssistantMr. A. Subramanian - Reprography Assistant

Mr. R. Nagarajan - Office Assistant

Front cover : Photo Courtesy Prof. K. Kathiresan

MANGROVES OF INDIAState-of-the-art report

ENVIRONMENTAL INFORMATION SYSTEM CENTRE(for Estuaries, Mangroves, Coral Reefs and Lagoons)

FOREWORD

Mangroves are the salt tolerant forest ecosystems found in tropical andsub-tropical intertidal regions of the world. They consist of swamps, forest-landand water-spread areas. These forest ecosystems support marine fisheries andprotect the coastal zone, thus helping the coastal environment and economy. Theseecosystems are biologically productive, but ecologically sensitive. Realizing this, theMinistry of Environment and Forests, Government of India has taken all necessarysteps to conserve and manage the mangrove ecosystems.

National Seminar on Ecologically Sensitive Coastal Ecosystems, held atthis Centre during March 22-23, 1996, recommended the preparation of State-of-the-art report on mangroves periodically. Ministry of Environment and Forests(Govt. of India) has published a status report for Indian mangroves up to theperiod of 1986. A similar report about the mangroves of India covering the worksfrom 1987 to 1996 was published in 1997 by the ENVIS Centre. The presentreport is an update of the previous one covering works upto the year 2000.

Care has been taken to include as many studies as we could gather, yet itis quite likely that we would have missed some. We would be grateful to all theauthors and users for their suggestions and constructive criticism so that we canimprove the next edition.

I profusely thank Dr. Indrani Chandrasekharan, Director, andDr. D. Bandyopadhyay, Former Director, Ministry of Environment and Forests,Government of India for their sustained support to bring out this report.

My sincere thanks are due to Prof. S. Ajmal Khan, Dr. N. Rajendran andother ENVIS staff for critical evaluation of this report. My special thanks are dueto Dr. K. Kathiresan, Professor of this Centre for preparing the earlier report andfor the suggestions and criticism to the present one. My thanks are also due toProf. K. Krishnamurthy (Retd.) for critically going through the earlier report. Thesupport rendered by Ministry of Environment and Forests, Government of India isgratefully acknowledged.

Prof. T. BalasubramanianDirector and ENVIS in-charge

CAS in Marine BiologyParangipettai - 608 502

CONTENTS

Page No.

1. Introduction 12. Distribution 33. Ecology 84. Microbiology 16

A. Bacteria 16B. Fungi 20

5. Planktonology 23A. Phytoplankton 23B. Zooplankton 26

6. Flora 32A. Flowering plants 32B. Non Flowering plants 36

7. Fauna 39A. Benthos 39B. Molluscs 42C. Crab 44D. Fish/Prawns/Shrimps 47E. Insects 51

8. Biochemistry 70A. Flora 70B. Fauna 77

9. Utilization 8310. Degradation 8811. Conservation and Development 9312. Management of Mangroves 9813. Recommendations 10114. Conclusions 10215. References 104

1. INTRODUCTION

Mangroves are the tidal forests of coastal wetlands, existing in the intertidalzones of sheltered shores, estuaries, tidal creeks, backwaters, lagoons, marshesand mud-flats of the tropical and sub-tropical regions of the world. They form animportant ecological asset and economic resource of the coastal environment. Themangroves are the most productive ecosystems, which can efficiently fertilize thesea, potentially protect the coastal zone and vitally serve as the breeding andfeeding grounds of fishes.

The word Mangroves is used to refer to the plants and also to the forestcommunity. To avoid the confusion, Macnae (1968) proposed Mangal as aterm to refer to the habitat or the forest community and Mangroves to theplant species. The term Mangrove is used as an adjective like mangrove treeor mangrove fauna (Duke, 1992). The word mangroves is usually considered tobe a compound of the Portuguese word mangue (= a type of trees) and theEnglish word groves (= a group of trees). In French, the word manglier is akinto mangue. It is believed that all these words originated from the Malay word,Manggi-manggi(Macnae, 1968). The mangrove forests are sometimes called astidal forests, oceanic rain forests and coastal woodlands.

The mangroves exist under very hostile and inhospitable conditions. Theplants which grow there have to encounter higher salinity, tidal extremes, windvelocity, high temperature and muddy anaerobic soil. No terrestrial plant cansurvive well under these adverse conditions (Kathiresan, 1991; Kathiresan andBingham, 2001). The plants have peculiar adaptations such as support roots,viviparous germination, salt-excreting leaves, breathing roots, knee roots, etc., bywhich the plants are well-adapted to water-logged, anaerobic saline soils ofcoastal environment. Also the mangrove plants have great potential to adapt to thechanges in climate (precipitation and temperature), the rise in sea levels and to theincidence of solar ultravioletB radiation (Rahaman, 1990; Swaminathan, 1991;Moorthy, 1995; Moorthy and Kathiresan, 1996).

Realising the importance of mangroves, the Government of India hasintroduced a scheme for conservation and protection of the mangrove ecosystem,and set up a panel of experts for the mangrove ecosystem. The first meeting ofthe panel was held on 12th October, 1976 at National Institute of Oceanography,Goa and subsequently on 19th April, 1982 in New Delhi. Later, a NationalMangrove Committee was set up in the Ministry of Environment and Forests,

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consisting of mangrove experts. As the first step towards the conservation andprotection of mangroves, a sub-group consisting of Prof. K. Krishnamurthy of thisCentre, Prof. Amalesh Choudhury, Marine Science Department, CalcuttaUniversity and Dr.A.G. Untawale, National Institute of Oceanography, Goa wasset up by the Ministry which brought out a status report on mangroves in Indiaduring 1987.

Several symposia/seminars/workshops on mangroves have been conductedin our Country (Table1). Two major publications viz.,1). The mangroves edited byL.J. Bhosale (1986) and 2). A training manual on conservation of mangrove forestgenetic resources edited by S.V. Deshmukh and V. Balaji (1994) have beenbrought out. Another training manual on the identification of flora and fauna inmangrove ecosystems edited by K. Kathiresan (2000) was brought out. A lecturemanual on UNU-UNESCO international training course on Coastal MangroveBiodiversity was prepared by our staff members in 2000.

Table 1. Symposia/seminars/workshops concerned with mangrove held inIndia

Title of the programme Year Place

National Symposium of Biology, Utilization and Conservation of Mangroves

1985 Kolhapur

National Seminar on Mangroves Awareness in India 1990 Bombay National Symposium on Significance of Mangroves 1990 Pune National Seminar on Conservation and Management of Mangrove Ecosystem with special reference to Sundarbans

1991 Calcutta

A Three Month Trainers Training Programme 1992 Madras Training Programme on Management of Mangroves 1993 Visakhapatnam UNESCO Curriculam Workshop on Management of Mangroves Ecosystem and Coastal Protection

1993 Visakhapatnam

National Seminar on Ecologically Sensitive Coastal Ecosystem

1996 Parangipettai

International Seminar on Mangrove 1997 Visakhapatnam Conservation Assessment & Management Plan Workshop for Indian Mangrove Ecosystem

1997 Goa

All India Co-ordinated Programme on Coastal and Marine Biodiversity: Training and Capacity Building on Coastal Biodiversity (East Coast)

2000

Parangipettai

UNU-UNESCO Sponsored Workshop on Conservation of Mangrove Biodiversity

2000 Parangipettai

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The need was felt for updating the status report as more than a decadepassed since the publication of earlier report and much work was done after that.Hence, a report on mangroves was prepared considering the research workscarried out in India between 1987 and 1996 and published by this EnvironmentalInformation System Centre, Centre of Advanced Study in Marine Biology,Annamalai University, Parangipettai. This report an update till 2000 is publishednow.

2. DISTRIBUTION

The mangroves grow luxuriantly in alluvial soil substrate, which are finetextured, loose mud or silt, rich in humus and sulphides (Rao, 1987) and theydevelop in low lying and broad coastal plains where the topographic gradients arevery small and the tidal amplitude is large. Their distribution is limited by tempera-ture (Duke, 1992) and they prefer moist atmosphere and freshwater inflow, whichbrings in abundant nutrients and silt from terrestrial sources. The mangrovesoccur in sheltered shores as the mangrove seedlings are damaged by waves andcurrents. Repeatedly flooded but well-drained soils support good growth ofmangroves, but impeded drainage is detrimental (Gopal and Krishnamurthy, 1993).

Indian mangroves are distributed in about 6,740 sq.km (Krishnamurthy etal., 1987) which constituted 7% of the total Indian coastline (Untawale, 1987).The area-wise distribution of mangrove forests in India has been reviewed(Deshmukh, 1991a). Status of mangroves along the Arabian sea has beenreviewed (Untawale, et al., 1992). There are three different types of mangroves inIndia viz., deltaic, backwater-estuarine type of mangroves existing in the westcoast (Arabian), characterized by typical funnel-shaped estuaries of major rivers(Indus, Narmada and Tapti) or backwaters, creeks, and neritic inlets. The insularmangroves are present in Andaman and Nicobar islands where many tidalestuaries, small rivers, neritic islets, and lagoons which support a rich mangroveflora (Gopal and Krishnamurthy, 1993).

Of the Countrys total area under the mangrove vegetation, 70% isrecorded on the east coast, and 12% on the west coast. The bay islands(Andaman and Nicobar) account for 18% of the Countrys total mangrove area(Krishnamurthy et al., 1987; Kathiresan, 1995a). The mangroves have a vastexistence on the east coast of India due to the nutrient-rich alluvial soil formed bythe rivers Ganga, Brahmaputra, Mahanadhi, Godavari, Krishna and Cauvery anda perennial supply of freshwater along the deltaic coast. But, the deltas with

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alluvial deposits are almost absent on the west coast of India, only funnel - shapedestuaries or backwaters are present (Gopal and Krishnamurthy, 1993).

The deltaic mangroves on the east coast is about 57% (2,738 km2) of thecountrys total area of mangroves. The insular mangroves exist in the Bay islands(Andaman and Nicobar) on many tidal estuaries, small rivers, neritic islets andlagoons, accounting for 20% (383 km2) of total Indian mangroves. However, theextent of mangroves keeps on changing over a period in different states of the eastcoast and the Bay Islands. The satellite data between 1993 and 1997 revealed aconsiderable increase in mangrove cover : 31.13% in West Bengal; 25.4% in BayIslands; and, 12.83% in Orissa and a reduction in mangrove cover in other states:76.7% in Tamil Nadu; and 20.21% in Andhra Pradesh (Kathiresan, 2000).

Intensive and extensive field study on species-wise distribution ofmangroves in 7 estuaries viz., Terekhol, Chapora, Mandovi, Zuari, Sal, Talpona,Galgibag and the Cumbarjua canal of Goa was studied. Natural regeneration ofmangrove in middle Andaman and Goa has been studied (Kumar, 1998, 2000)and various methods of regeneration of mangroves were described (Kumar, 1999).

In Indian mangrove systems, 100% of mangrove species, 92% of otherflowering plants, 60.8% of seaweeds, 23.8% of marine invertebrates and 21.2%of marine fish are threatened. Of 35 mangrove plant species, 9 are criticallyendangered, 23 endangered and 3 vulnerable (Rao et al., 1998). Five hundredspecies of invertebrates occur in Indian mangroves, but only 42 species have beenso for assessd for their conservation status (Kathiresan, 1999a). Recent estimatehas indicated that a total area 6,700 km2 has been covered by mangroves in thecoastal and estuarine area of India, which shared 7% of total world mangroves(Kathirvel, 1996).

The Department of Space (Govt. of India) has mapped the areas undermangroves using satellite data, with 83-90% accuracy. However, the areas undermangroves as calculated from these maps, do not match with earlier data (Table2). According to the Forest Survey of India, Dehradun, total mangrove area is4,827 sq.km as against 6,740 sq.km as reported earlier by the Ministry ofEnvironment and Forests (Krishnamurthy et al., 1987). The figures for the totalIndian Mangrove area varies from time to time. The low value of mangrove areasas shown by satellite data may be due to the following reasons; (a) reduction inmangrove area (b) mangrove areas smaller than 25 ha are not mapped and(c) mixing of mangroves with adjoining forest area especially in the Andaman-Nicobar group of islands (RSAM, 1992).

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The Sundarbans in West Bengal has the largest area of approximately4,250 sq.km (Krishnamurthy et al., 1987; Krishnamoorthy, 1997), which formsthe largest block of mangroves of the world taken together with Bangladesh. It isthe only mangrove forest of the world having among its denizens, the famousRoyal Bengal Tiger (Panthera tigris). The Sundarbans of India cover an area of2,123 sq.km (FSI, 1997). The name Sundarbans may be from the Bengali nameSundari tree i.e. Heritiera fomes or beautiful (Sundar) forests or it may meanboth (Krishnamurthy, 1983). The Sundarbans is famous for its richness anddiversity of mangrove vegetation with dominant species viz., Avicennia spp.,Sonneratia spp., Excoecaria agallocha, Rhizophora apiculata, R. mucronata,Bruguiera gymnorrhiza, Ceriops decandra, Phoenix paludosa etc. (RSAM,1992). The forest is now largely confined to a number of islands situated on theeast of the Matlah river (Scott, 1989). Recently, the working plan maps ofmangrove forest of Sundarbans, West Bengal were updated (Sudhakar et al.,2000).

Table 2. Extent of mangrove cover in India

Andaman and Nicobar Islands harbour a rich diversity of mangroves.Dense mangroves are found on these Islands along the creeks, near bays andlagoons with dominant species - Rhizophora mucronata, Bruguieragymnorrhiza, Avicennia spp., Ceriops tagal etc. Mangroves occupy an area ofabout 770 sq. km (RSAM, 1992). Further information on acreage of mangroveson these islands, is provided by Singh et al. (1986), Rajagopalan (1987) andDagar (1987). Mapping of mangrove has also been carried out on the Andamansand Nicobars by National Remote Sensing Agency (1988). Ranganath et al.(1989) used satellite data to map mangrove distribution on eight Islands

* Status Report, Government of India (1987)** Forest Survey of India (1997)

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(Havelock, Peal, Nicholson, Wilson, John Lawrence, Henry Lawrence, lnglish andOutram Islands) in the Middle Andaman. Bagla and Menon (1989) gave a figureof around 66,261 ha of mangroves in the Andaman-Nicobar Islands. Themangrove areas of south Andaman Islands have also been mapped through remotesensing (Krishnamoorthy et al., 1993). The Andaman and Nicobar Islands,located in the northeast Indian Ocean, occupy 966 sq. km of mangrove cover(Krishnamoorthy,1997; FSI,1997). In the Andaman Islands, mangroves occur in1,150 km area and in the Nicobar Islands, they occur in 35 km2 area. Species ofRhizophora, Bruguiera, Aegiceras and Nypa grow widely and are well preservedin these Islands (Kannan, 1990).

In Orissa, the mangroves are present on the Mahanadi delta, the Brahmani- Baitarani delta and along the Balasore coast with dominant species as Avicenniaspp., Rhizophora mucronata, Excoecaria agallocha, Ceriops roxburghiana etc.(RSAM, 1992). The mangroves near the mouth of the Mahanadi river form acreek network of the Luna, the Jambu, the Kharnasi, the Khola and the Batigharjora creeks. The creeks are arranged parallel to the coast, inundated by dailytides. The Bhitarkanika mangroves are luxuriant due to the beneficial influenceexerted by the Brahmani and the Baitarani rivers and their distributaries and creeksupon the terrain. On Balasore coast, there is no influence of freshwater inflowexcept in the Dhamra river mouth and hence the salinity level remains high exceptin rainy months (RSAM, 1992). The mangroves occur in an area of 211 sq.km(FSI, 1997).

In Andhra Pradesh, dense mangrove vegetation is found towards coastrather than on shoreland because of the dense branching network of creeks, whichexist towards the coast (RSAM, 1992). There are more mangrove vegetation ontidal flats on the western side of the Krishna delta than on its eastern side. Densemangroves are also seen over recent sand / mud spits on the Nizampatnam bay(RSAM, 1992). Sparse mangroves are found on the eastern side of the Krishnadelta.

Mangroves in Tamil Nadu exist on the Cauvery deltaic areas. The totalmangrove area available in this state is around 383 sq.km (Kathiresan, 1998).Pichavaram mangroves that extend between the Vellar and Coleroon estuarineareas, spread to an area of 21 sq.km (Kannan, 1990). Pichavaram has a well-developed mangrove forest dominant with Rhizophora spp., Avicennia marina,Excoecaria agallocha, Bruguiera cylindrica, Lumnitzera racemosa, Ceriopsdecandra and Aegiceras corniculatum (Kathiresan, 1998). It is a highly

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populated region, but the mangrove is relatively well preserved because it enjoysthe status of a Reserve Forest since 1880. These mangroves are noteworthy fortheir beauty, luxuriance and diversity of species (Meher Homji, 1991). Mangrovesalso occur near Vedaranyam, Kodiakarai (Point Calimere), Muthupet, Chatramand Tuticorin (Meher Homji, 1991). From Muthupet to Chattram mangrove area,there is mangrove formation with Avicennia marina, growing in brackish water orshallow lagoons (Kannan, 1990).

Gujarat has got the second largest area of mangroves, according to theremote-sensing data (Table 2). The mangroves on the Rann of Kachchh are pooralong the Kori creek (RSAM, 1992). In the Gulf of Kachchh, dense mangrovesare observed around the Patre creek, the Dide Kabet, Valsura, Navlakhi andKandla and near Mundra jetty. Patches of sparse mangroves are observed nearOkha, Poshitra, Pindhara, Dhani, Narara, Sikka, Jindra, Pirotan and near theJakhau port (RSAM, 1992). The mangrove species - Avicennia officinalis andRhizophora mucronata - dominate on the Gulf of Kachchh. On Saurashtra coast,mangroves occur only in sparse patches along the creeks on the intertidal mudflatsalong the Jafarabad creek and the Buthrani creek. In the Gulf of Khambhat,mangroves are distributed along the coast near the Mahi, the Dhadhar, theNarmada, the Kim and the Sena rivers. A small patch of dense mangroves isfound on the Aliabet Island. In South Gujarat, mangroves exist near the mouth ofthe Kolak estuary and a small creek near Umargam. On the Konai creek,mangroves are present scattered (RSAM, 1992). The mangrove cover extends upto 991 sq.km throughout the state (FSI, 1997).

In Maharashtra and Goa, mangroves exist especially in large patches alongthe Mandovi estuary, the Vasishta estuary, the Savithri estuary, the Kundalikaestuary, the Dharamtar creek, the Panvel creek, the Vasai creek, the Thane creekand the Vaitarana creek (RSAM, 1992). The mangroves occur over an area of124 sq.km and 5 sq.km in Maharashtra and Goa respectively (FSI, 1997).

Mangroves in the Mandovi estuary of Goa have spread to an area of2,000 ha and they have distinct zones, which differ in environment, speciescomposition and growth. Goa once had luxuriant mangrove swamps some 20 kminland from the open sea coast during the recent geological past, when the sealevel was 1 to 3 m lower than at present (Mascarenhas and Chauhan, 1998).

Coastal wetland and shoreline-change mapping of the Maharashtra andKarnataka coast are carried out using IRS LISS II data on 1:15,000 scale.

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Various wetland/landform categories such as mudflat, beach, spit, mangrove,coastal dunes and areas under erosion and deposition have been delineated. Thearea under mangroves is 222.5 sq.km in Maharashtra and 8.7 sq.km in Karnataka.The classification accuracy of wetland maps is 86% at 90% confidence level(Shreedhara et al., 1997; Tikekar et al., 1997).

Present status and management of the mangroves of Uttara Kannada,Karnataka have been reviewed (Sivabalan et al., 1991). Mangroves of Karnatakacover an area of 6,000 ha; of which 1,000 ha are in Uttara Kannada districtalone. About 14 species belonging to 9 genera are extensively distributed in thedistrict. The mangrove forest occurs along the northern coast of Karnataka, in theKalinadi, Gangivali and Agnachini estuaries and at the confluence of the ChakraNadi, Kollur and Haladi rivers near Gangolli (Parnetta, 1993). In general, themangroves are only sparsely distributed along the Karnataka coast around 3 sq.km(FSI,1997).

Distribution of mangroves in Kerala has been described (Basha, 1991). Itis stretching for about 1,000 sq.km a century ago, but is now reduced to justabout 17 sq.km in isolated bits at Kumaragom, Dharmadom, Chettuva, Nadakavu,Pappinisseri, Kunjimangalam, Chageri, Veli etc.

3. ECOLOGY

Mangroves have been ecologically well-studied (Gopal and Krishnamurthy,1993) along the Sundarbans (Naskar and Guha Bakshi, 1989), the Andaman-Nicobar Islands (Singh et al., 1986, 1987; Ellis, 1987; Dagar, 1987; Rao andChakrabarti, 1987), the Mahanadi delta (Banerjee, 1987), the Krishna estuary(Prasad, 1992), the Cauvery delta (Kathiresan, 2000) and the Mumbai (Bombay)coasts (Ghosh et al.,1994).

Distribution of mangroves in relation to soil characteristics has been studied.Illustrations are available for Sundarban forests with soil profile diagrams, soilmaps, abundance of mangrove species, the stages of land formation from mean sealevel and the siltation patterns or silting activities of the Ganges delta (Naskar andGuha Bakshi, 1989).

Ninety five percentage of the river bed vegetation in Sundarban mangroveforest is dominated by Porteresia sp. This results in good primary production,turn-over time and transpiration efficiency of this salt marsh grass. The total net

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production is 426 g/m2/yr. Below ground biomass is 53% higher on an averagethan the above ground biomass. Turn-over times for above ground and belowground biomass are reportedly 0.55 and 0.75 yr (Jana et al., 1993).

The level of nutrients is higher in leaf litter of Avicennia marina than that inother components of litter in a tidal creek of Lothian Island of Sundarbans (Ghoshet al., 1990).

Physico-chemical parameters of different mangrove waters have beenstudied (Bava and Seralathan, 1999) more specifically at the eastern and westernsides of the Sundarban mangroves (Matilal et al., 1986). The soils are basicallysimilar on both the sides, except in conductivity, soil texture and NPK ratio.Distribution of the mangrove species in the two sides is however, different. Thewestern side islands are dominated by Avicennia spp. and Acanthus ilicifolius,and the eastern side by Aegiceras majus (Matilal et al., 1986). Ceriops-Phoenixassociation occurs in elevated land areas and Excoecaria species and Ceriopsdecandra exist over the entire forest of the Sundarbans (Matilal and Mukherjee,1989).

In Sundarbans, tigers inhabitat the mangrove zone with predominantspecies of Ceriops and Excoecaria and the habitat is also high in soil salinity(Chakrabarti, 1993).

The distribution of some trace metals in the mangrove flora and fauna ofSundarbans has been studied. Among metals, Zn showed high values in all speciesof plants and animals followed by Cu and Pb (Chakrabarti et al., 1993).

Diurnal changes in temperature, salinity, dissolved oxygen, pCO2, and ionicproduct of calcium carbonate have been studied in virgin and reclaimed mangrovewaters of Sundarbans during monsoonal run off. Surface water of both the placesare undersaturated with respect to oxygen and partial pressure of carbon dioxideremained high. Lower calcium / chlorinity values than those in the open ocean areobtained (Ghosh et al., 1987).

X-ray mineralogical analyses have been made on 107 surface andvibracore samples collected from the Krishna delta to determine whether mineral-ogical assemblages produce distinct criteria for the recognition of modern deltaicsubenvironments. Discriminant function analysis was applied to 69 samples fromeight subenvironments (lagoons, river mouth bar, mudflat, barrier island, mangrove

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swamp, foreshore, tidal creek and channel) with 100% classification success whenthe whole-sample results included estimates of ideal clay-mineral layer types andloss-on-ignition estimate of the organic content. Most of the mineralogical changescan be attributed to grain-size sorting in the subenvironments of the delta. Themajor factors contributing the success of the analysis are associated with quartzenrichment in the subenvironments falling within the marine-dominated part of thedelta and smectite enrichment in the riverine-process-dominated subenvironments(Ferrell et al., 1998).

Sediment characteristics of the Krishna-Godavari deltas have been studied.The deltaic sediments of Godavari are finer than those of Krishna. River channelbar, beach, dunes and paleo-beach ridges consist of predominantly sand. Muddysand is widespread in tidal channels and creeks whereas sandy mud and mud aredistributed in estuary, mangrove swamp, lagoon and bay. The submerged beachridge at a distance of 27 km off Nizampatnam from the present coast in offshoreKrishna delta, contains very coarse sediments (Rao and Swamy, 1991). The siltcontent is high in the sediments on which mangroves grow luxuriantly, in Godavariestuary (Rao et al., 1991).

Diurnal variations in hydrological variables and dissolved inorganic nutrientssuch as phosphate, nitrate, nitrite, ammonia and primary production have beenobserved in three interconnected biotopes including freshwater, marine andmangrove brackishwater of the Kakinada coastal zone. In both marine andmangrove waters the salinity shows bimodal type of oscilation and the dissolvedoxygen content is high in the mangrove waters during day time but decreasesrapidly during the night hours. The highest and the lowest concentrations ofphosphate, nitrate and nitrite are recorded in the mangrove waters and higher infreshwater zone. The concentration of ammonia is relatively high in the mangrovewater. Gross and net primary production in the mangrove water is 4 times higherthan in the marine biotope (Selvam et al., 1992).

The distribution of mangrove plants in the Muthupet mangrove in relation tothe chemical characteristics of the soil with reference to a few important tracemetal has been studied. An attempt has also been made to measure some of theecological parameters used in species zonation. A distinct zonation pattern, in themangrove community has been linked with the variation in edaphic factors, whichare usually associated with the degree of tidal influence (Gunasekaran et al.,1992). Soil salinity is a major factor, responsible for the stunted growth ofAvicennia marina along Ennore backwaters (Selvam et al., 1991).

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The grain size, organic carbon, sedimentary sulphur, calcium carbonate, Fe,Mn, Al, Cu, and Hg are analyzed in Pichavaram mangrove for the mechanismscontrolling the behaviour of metals (Periakali et al., 2000). Spatial and temporalgeochemical variations of various parameters in the water and sediment areexamined in the Pichavaram mangrove area (Ramanathan et al., 1999).

Influence of UV-B radiation on Rhizophora apiculata has been studied interms of chlorophylls, their presence in protein complexes of the chloroplast, PSI,PSII photochemical activities, in vitro absorption spectrum of the chloroplast, invivo and leaf fluorescence and UV absorbing compounds (Moorthy andKathiresan, 1999b).

Seasonal variations in nitrogenous and phosphorus nutrients are noted inmangrove waters of Tuticorin Bay (Manikandavelu and Ramadhas, 1991).

The pattern of accumulation of heavy metals in the tissues of Scyllaserrata collected from Pichavaram mangroves noticed in the laboratory is similarto that observed in the environment: gill > hepatopancreas > muscle (exposed tomercury); hepatopancreas > gill > muscle (exposed to cadmium and zinc)(Narayanan et al., 1997).

Random amplified polymorphic DNA (RAPD) markers are used fordetermining the genetic diversity of Avicennia marina in India (Balakrishna,1995).

Chouldari of South Andaman is analysed for environmental and ecologicalparameters (Damroy, 1995a). The air, surface water, and sediment temperaturesranged from 30 to 34.5C and 29.3 to 33C and 29.3 to 33C respectively. Therange of pH, dissolved oxygen and salinity are from 7.48 to 8.47, 5.69 to 9.00ppm and 30 to 34 ppt respectively. Alkalinity and dissolved carbon dioxideranged from 139 to 172 ppm and 15.5 to 16 ppm respectively. The averageNO2-N content is 0.82 g/l and the average PO4 content is 0.31 g/l. The soil isslightly acidic (6.84) and electrical conductivity is high (14.26 milli mhos/cm).

Manjeri area of South Andaman has been studied for physico-chemicalparameters (Damroy, 1995b). The air and water temperatures ranged from 29.2to 31.5C and 28 to 31C respectively. The pH ranged between 7.4 and 8.2. Thedissolved oxygen and carbon dioxide ranged from 5.8 to 6.4 ppm and 8.0 to 15.3ppm respectively. Salinity ranged between 31.8 and 33.7 ppt. Alkalinity rangedfrom 136 to 153 ppm.

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Andaman mangroves exhibit higher biomass of 214 t/h than any othermangroves of the world (Mall et al., 1991). In Sundarbans, the biodiversity is richin the mangrove zone, situated below the tidal level, over other zones, which arefrequently inundated (Chakrabarti, 1993). To assess the biodiversity effects, acomparative study has been made in monogeneric and mixed mangrove forests ofAndaman Islands. The mixed mangrove forests have high soil respiration rate,faster decomposition rate, and high standing crop biomass (Mall et al., 1991). Thelitter biomass beneath Rhizophora apiculata in Andamans is significantly relatedto rainfall and wind velocity (Dagar and Sharma, 1991). The activities of soilenzymes are important in nutrient cycling and have been assayed in 5 majormangroves of South Andaman (Dinesh et al., 1998).

A comparative study of the interstitial water of the substratum with thecolumn water as regards the parameters-salinity, temperature, pH, nitrate andnitrite and prawn is conducted in the mangrove, coconut grove and culture pondsituated at Vypeen Island, Cochin (Sathyajith and Sampson Manickam, 1993).

Sediment texture and size of Kannur mangroves have been carried out(Badarudeen et al., 1998). The content of sand and mud remains almost constantin landward, intermediate and shallow water profiles in the surface and coresediment of Kannur mangroves. The southern part of the Kannur mangroves showsthe highest average of sand (68%). The mean size varies between 1.83 and5.56 in surface sediments and between 2.3 and 5.6 in core sediments. Thesediments are generally poorly to very poorly sorted, coarse to very fine skewedand lepto to very platykurtic in nature (Badarudeen et al., 1998).

In Cochin mangrove system, Acanthus ilicifolius forms the predominantvegatation (Muralidharan and Rajagopalan, 1993) and the ecological and biologicalfactors that control a Rhizophora dominated community in the Cochin area arealso described (Pretha and Rajagopalan, 1993). The heavy metal and phosphorousfractionation geochemistry and textural aspects of sediments in a tropical mangroveecosystem have been studied. The organic matter concentration ranges from 1.5 to13.4% and it is controlled by the particle size of the sediments. Enhancedconcentrations of heavy metals in the surficial sediments are due to the abundanceof greater surface area of fine particles, high organic matter content andflocculation process (Ramanathan, 1997).

The Bruguiera occurring in the Cochin estuarine system has been studiedwith respect to morphological characters, distribution pattern, tree density,

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phenology, germination and growth of seedlings along with physico-chemicalproperties of the soil, tidal water and litter decomposition rate in that area(Joseleen Jose and Rajagopalan, 1993).

The textural and geochemical aspects, and heavy metal concentrations ofthe sediments of mangrove systems are characterized by the abundance of silt andsand with minor amounts of clay with 5-times greater level of CaCO3. Thisenhanced CaCO3 content of the mangrove sediments is due to the shell miningactivities in the estuarine bed adjoining to the Kumarakom mangroves and it alsocontributes to a substantial lime muds to the mangrove area (Badarudeen et al.,1996).

Soil pH and salinity influence the growth of mangrove plant species:Bruguiera gymnorrhiza is abundant in low saline area and Acrostichum aureumprefers the areas of low pH and salinity in Kerala (Thomas and Fernandez, 1993).

Vertical and horizontal distribution patterns of organic carbon in themangrove sediments have been studied. The concentration of organic carbonvaried from 0.17 to 4.05% in the Cochin mangrove area. Organic carbon has aproportional and patent relationship with the finer fractions (silt + clay) of thesediment. Inconsistent pattern concomitant with the inconsistent concentration inaccumulation of organic carbon in the sediment with regard to vertical as well ashorizontal distribution is discernible in the tidal area of mangrove swamp (SunilKumar, 1996).

The surface sediments of Veli consist of an average concentration of2.75% Na and 1.02% K. The contents of Na and K in the surface (Na = 2.14%;K = 1.48%) and core sediments of Kochi (Cochin) mangroves are almost similar.Kannur mangroves exhibit an average of 2.43% Na and 5.36% of K. The meanenrichments of Na and K in the sediment cores (Kannur mangrove stations) KC1,KC2 and KC3 are 2.93% and 1.8%, 2% and 4.65%, 2.13% and 1.23%,respectively. The enrichment of K over Na in Kannur mangroves can be eitherdue to the contribution from the mangrove vegetative debris or fixation of theseelements in clay minerals of the sediment substratum (Badarudeen et al., 1998).

Textural studies of Tellicherry mangrove sediment of Kerala indicate thatsilty sand is the major textural class in the allochthonous sediments followed bymuddy sand, sandy mud and mud (Reghunadh et al., 1995).

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The heavy metals in the mangrove flora and sediments of three mangrovehabitats along the Kerala coast have been studied. The analysis of heavy metalsindicated a high level of metal pollutants such as Fe, Cu, Zn and Pb in themangrove habitats of Quilon and Veli, as compared to the relatively uncontami-nated areas of Kumarakom (Thomas and Fernandez, 1997).

Distributions of organic carbon (OC) and total phosphorus (P) in thesediments of three mangrove ecosystems reveal comparatively higher concentrationof OC (4%) than that of Veli (2.6%) and Cochin (3.7%). Total P records thehighest concentrations in Kochi (av. 0.395%) compared to Veli (0.055%) andKannur (av. 0.323%) mangroves (Badarudeen et al., 1998).

Effects of heavy metals on growth rate, primary production and chlorophyllcontent of microalgae are examined. Among the heavy metals, copper is the mosttoxic and lead is the least toxic heavy metal to both microalgae and natural popula-tion of phytoplankton (Ithack and Gopinathan, 1995).

The level of nutrients has been studied in several mangrove areas. Thelevels of organic matter and C, N, P in sediments are more in mangroves than inestuary and in sea (Shanmukhappa, 1987). Similarly, the levels of humic acids(dissolved and particulate) are higher in mangrove waters of Karwar than inestuary and sea (Shanmukhappa et al., 1987) and a negative relationship isreportedly noted between dissolved humic acid and salinity (Shanmukhappa andNeelakantan, 1989). The concentration of humic acids in all the three forms(dissolved, particulate and sedimentary) is reportedly highest in the monsoon(June-Sept.), when the salinity is minimum; while the concentration is reportedlylowest in the premonsoon (Feb-May), when the salinity is maximum. Sedimentaryhumic acids (SHA) level is relatively higher than the dissolved (DHA) and theparticulate (PHA) humic acids except in the monsoon when the proportion of PHAexceeds SHA. This has been attributed to the decomposition of the litter from themangrove swamps as well as to the freshwater inflow from the upstream region(Sardessai, 1993).

In the sediments of Talapady lagoon, Dakshina Kannada, high levels ofphosphorus and nitrogen are recorded due to decay of mangrove foliage (Sahoo etal., 1991).

Water and sediments have been studied for distribution of organic carbonand nitrogen in Goa mangroves. Suspended matter ranged from 3 to 373 mg/l

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while particulate organic carbon (POC) from 0.03 to 9.94 mg/l. POC valueshowed significant correlation with suspended matter. Particulate organic nitrogen(PON) values, however fluctuated in the range of 0.01 - 3.4 mg/l. Organic carbonin the sediment (SOC) varied from 1.7 to 54 mg/g with an average value of 45.6mg/g organic matter. The values of total nitrogen in the sediments (STN) rangedfrom 0.3 to 19.3 mg/l. The data indicate that there is marked spatial and temporalvariations in the distribution of organic matter in the mangrove environment. Themangroves and their associated biota contribute major portion of organic matter inthe mangrove environment (Jagtap, 1987).

The Avicennia species are in general more tolerant to salt and organicpollution than other species of mangroves in Ratnagiri, Maharashtra (Sathe andBhosale, 1991).

The life history and chemical composition of Monostroma oxyspermum(Chlorophyceae) have been studied at the mangrove ecosystem of Shirgao creek,Ratnagiri, Maharashtra, Terekhol creek, Goa, and Kali estuary, Karwar. This algacan be easily cultivated on large scale as a food source (Geetanjali Deshmukhe etal., 1998).

The trace metals Cd, Pb, Zn and Cu have been studied in the sediments ofThane creek. Cadmium is low and lead shows a positive correlation with pH ofwater and organic carbon of sediment. Salinity and to some extent sedimentalorganic carbon play a significant role in governing the concentration of copper andzinc, whose fluctations show antagonistic pattern (Athalye and Gokhale, 1989).The nitrogen dynamics of mangroves in Ratnagiri, Maharashtra has been studiedby Waghmode (1987).

Four mangrove biotopes such as, Cochin, Gulf of Kachchh, Killai estuaryand the Andaman-Nicobar Islands, have been comparatively studied for theirecological aspects (Rajagopalan et al., 1986). A study at Thane Railway Bridgeand Basseins creeks system of Mumbai reveals a lower level of dissolved oxygen(DO) (2.7 to 4.0 mg/1) and higher values of BOD and nutrients at Thane. Thisindicates the prevailing unhealthy water quality of the area (Asha Jyothi and Nair,1999a).

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4. MICROBIOLOGYA. Bacteria

Mangroves provide an unique ecological niche to a variety of micro-organisms (Agate, 1991). About 125 species of microorganisms (bacteria, fungi,algae) have been identified (Kathirvel, 1996).

It is interesting to note that the photosynthetic microorganisms behave likeheterotrophs in the mangrove environment. The cyanobacteria and photosyntheticbacteria have to survive in low light or partially dark conditions by utilizing thesuspended organic matter, which are available abundantly in the mangrove waters.This unique heterotrophic adaptation of photoautotrophs, is a mechanism ofsurvival in hostile coastal anaerobic and anoxic conditions of mangrove habitat(Rao and Krishnamurthy, 1994).

The nitrogen fixation by microorganisms has been investigated inmangroves. Nitrogen-fixing bacteria, Azotobacter species are reportedly isolatedfrom sediments of Pichavaram mangroves and their counts are more in themangrove habitat than in marine backwaters and estuarine systems(Lakshmanaperumalsamy, 1987). Three species of Azotobacters viz.,A. vinelandii, A. beijerinckii and A. chroococcum are known and assessed fortheir utility as biofertilizer (Ravikumar, 1995).

The counts of nitrogen fixing bacteria in the rhizosphere of mangrove plantcommunity have been quantified in the Ganges river estuary and the bacterialcounts are high in inundated swamps and low in occasionally inundated ridges anddegraded areas of mangroves (Sengupta and Chaudhuri, 1991). Two halotolerant,nitrogen fixing Rhizobium strains have been isolated from root nodules of Derrisscandens and Sesbania spp. growing along the mangrove swamps of Sundarbans(Sengupta and Chaudhuri, 1990). Hydrocarbonoclastic bacterial isolates have beenreported from mangals of Andaman (Shome et al., 1996).

Nitrogen fixing cyanobacteria such as Aphanocapsa spp., Nodularia spp.and Trichodesmium spp. have been isolated from Pichavaram mangroves(Ramachandran and Venugopalan, 1987; Ramachandra Rao, 1992).

The cyanobacterium has the ability to desalinate the sea water with salinityup to 250 g/1, under laboratory conditions. The cyanobacterium, Phormidiumtenue is promising for desalinization process (Balasubramanian and Kathiresan,1999).

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The standing crop of both epiphytic and benthic cyanobacteria is muchhigher when compared to the planktonic cyanobacteria. Also the standing crop ofepiphytic and benthic cyanobacteria is seasonally high during summer andpremonsoon seasons (Ramachandra Rao and Krishnamurthy, 1994).

Lipophilic extracts of five species of cyanobacteria, isolated from themangroves, have been tested against the bacteria and fungi for their inhibitoryactivity. Extracts of Anacystis dimidiata inhibit 7 strains. Nostoc paludosum andSchizothrix sp. exhibit maximum activity against Bacillus subtilis. Phormidiumfragile does not show any activity against B. subtilis (Ramachandra Rao, 1994).

Phormidium tenue isolated from mangrove and shrimp pond ecosystemshas been studied for optimal culture condition to produce high biomass(Palaniselvam and Kathiresan, 1996).

Seasonal variations of antagonistic actinomycetes have been determined inselected mangrove ecosystems. The highest number of actinomycetes is present inmonsoon. The antagonistic activity of the actinomycetes is shown against 14 testpathogens viz. Vibrio anguillarum, V. cholerae, V. alginoliticus,V. parahaemolyticus, Aeromonas, Pseudomonas, Salmonella-I, Salmonella-II,Escherichia coli, Bacillus, Staphylococcus, Rhodotorula rubra, R. marina andCladosporium. Out of 104 actinomycetes tested for their antimicrobial activity,about 56% exhibit antagonistic effect towards Gram-negative bacteria, 35.6%towards Gram-positive bacteria. 100% of the isolates inhibit the growth of thefilamentous fungi (Cladosporium) and 90% of the isolates are reportedlyantagonistic towards non-filamentous fungi (R. marina and R. rubra) (RathnaKala and Chandrika, 1995).

The cyanobacterium Phormidium tenue has a potential to enhance thegrowth and production of shrimp. For example, in Penaeus monodon, the foodconversion ratio (FCR) is 0.25 when fed with cyanobacterial (Phormidium tenue)diet as against 0.276 with a commercial feed without the cyanobacterium. Proteincontent of the shrimp tissue is also increased by 17.5% in the cyanobacterium-fedshrimp. In Penaeus semisulcatus, the FCR is 2.29 when the shrimp is fed withcyanobacterium-rich diet as against 9.36 with cyanobacterium-deficient one(Palaniselvam and Kathiresan, 1998).

Several types of microorganisms do exist in mangrove biota. The sulphatereducing bacteria have been isolated from the mangrove swamps of Goa (Saxena

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et al., 1988; Lokabharathi et al., 1991). Distribution of phototrophic thionicbacteria in the anaerobic and micro-aerophilic strata of mangrove sediments ofCochin has also been studied (Chandrika et al., 1990).

Phenolic compounds and bacterial counts have been studied in the Cochinmangrove swamps. The diversity of bacteria and their numbers are higher whenphenol concentration is less in the sediment (Imelda Joseph and Chandrika, 2000).

Purple photosynthetic bacteria are reportedly isolated from Pichavarammangrove sediments: two major groups viz., purple sulphur bacteria (family-Chromatiaceae, strains belonging to Chromatium spp.) and purple non-sulphurbacteria (family- Rhodospirillaceae, strains belonging to Rhodopseudomonas spp.)(Vethanayagam, 1991).

Studies on the growth potential of the anoxygenic photosynthetic purplenon-sulphur bacterium Rhodopseudomonas sp. collected from the mudflats of thePichavaram mangroves reveal that this strain grows well in salinities normallyencountered in the marine environment (Vethanayagam and Krishnamurthy, 1995).

Besides sulphur bacteria, the iron oxidizing and iron reducing bacteria doexist in mangrove habitat. This type of bacteria is higher in mining areas of Goathan in non-mining mangroves areas of Konkan (Panchanadikar, 1993). Thesulphate reducing bacteria reduce the activity of methane producing bacteria. Thesemethanogenic bacteria have been studied for the first time for their distribution andecology in mangrove sediments of Pichavaram (Ramamurthy et al., 1990). Thesebacteria are also abundant in marine sediments of Kodiakkarai where Avicenniaspp. are predominant (Mohanraju and Natarajan, 1992). Besides all these types ofbacteria, fungi-like bacteria namely Actinomycetes do exist in the mangrovesediments of Cochin (Rathna Kala and Chandrika, 1993).

The microorganisms inhabiting the rhizosphere and viable counts ofbacteria, fungi, and actinomycetes populations have been estimated quantitativelyand qualitatively. The heterotrophic bacteria identified, belong to five generaAlcaligenes, Flavobacterium, Cytophaga, Vibrio, Aeromonas under the familyof Enterobacteriaceae. The fungi isolated mainly are species of Fusarium,Penicillium, Aspergillus and Rhizopus along Cochin coast. The total microflorashows a seasonal cycle in their counts. The bacterial counts are maximum duringthe postmonsoon months and the counts of the fungi and actinomycetes aremaximum during the monsoon months (Mini Raman and Chandrika, 1993).

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The bacterial load is higher in sediment and water samples than in the gutcontents of the polychaete, Ceratoneries costae, the amphipod, Paracalliopefluviatilis (Devi et al., 1986). The hind gut of Telescopium telescopium harboursmore heterotrophic bacteria (13.37 x 103 CFU/g) than the fore gut (4.42 x 103CFU/g) and mid gut (12.65 x 103 CFU/g). The percentage contribution ofamylolytic, proteolytic and lipolytic bacteria are 53.8%, 23.1% and 23.1%respectively (Prem Anand et al., 1996).

Seasonal variation of total heterotropic bacteria in relation to theconcentration of tannin in water and sediment samples from a mangroveenvironment has been studied. There is a negative correlation with tannin levelsand microbial counts (Kathiresan et al., 1998).

Total coliforms (TC), fecal coliforms (FC), fecal streptococci (FS),salmonellae and vibrios in estuarine, lake and mangrove biotopes of Tamilnadu,east coast of India have been enumerated (Venkateswaran and Natarajan, 1987).

Epiphytic bacteria of mangroves have been studied. The bacteria areattached to the surface of green algae like Chaetomorpha crassa and C. linum(Padmakumar and Ayyakkannu, 1986) and to other plants. These epiphyticbacteria exhibit the lowest population on plant surface of Avicennia marina andSesuvium portulacastrum in premonsoon (Feb-May) and they show the highestpopulation during monsoon (June-Sep) and postmonsoon (Oct-Jan). Leaves of theplant species harbour high counts of Flavobacterium and root and stem of theplants exhibit high counts of Vibrio spp. (Abhaykumar and Dube, 1991).

Bacterial flora of mangrove litter fall and underneath sediments from SouthAndaman has been investigated. Thirty eight bacterial isolates are reportedlypresent in the sediments of Rhizophora, Avicennia and Nypa species. Thecultural, morphological and biochemical features reveal that most of the isolatesbelong to Bacillus spp. (50%). In addition, Aeromonas, Vibrio, Escherichia,Enterobacter, Corynebacterium, Kurthia, Staphyllococcus, Micrococcus andListeria are also present. Most isolates are gram positive (76.3%), motile (87%)and fermentative bacteria range from 6.9% to 82.1% for dextrose. Thirty per centisolates are pigment producers (either diffusible or cell associated). The bacterialisolates show a minimum of 50% resistance against chloramphenicol and amaximum of 100% resistance against polymixin B (Shome et al., 1995). Thepercentage of agarolytic bacteria is reportedly very low (

percentage and other physiochemical characters vary throughout the year (Shomeet al., 2000).

In another study, the bacterial counts are found to be higher on the freshleaves of mangroves than those on leaf litters. The high bacterial counts are alsofound associated with higher leakiness of amino acids and sugar and lowerleakiness of tannins (Kathiresan and Ravikumar, 1995a).

Lytic activity of gut microflora of the prosobranch Telescopiumtelescopium collected from Pichavaram mangroves has been studied. Twoamylolytic, proteolytic and lipolytic strains are selected for analysis of enzymaticactivity when cultured at specified levels of salinity, pH, tannin, Cu and Ni. Allstrains showed maximum enzymatic activity at a salinity range of 10 - 25 ppt, andalkaline pH. Tannin had a clear effect on the enzymatic activity at higherconcentrations. However, all strains showed difference in inhibition of activity atincreasing concentrations of tannin up to 100 ppm (Prem Anand et al., 1996).

The microbial interrelationship in mangrove sediments does exist betweenbacteria and actinomycetes, bacteria and fungi, and fungi and actinomycetes. Theactinomycetes exhibit antibiotic activity against fish pathogens (Rathna Kala, 1995).

B. Fungi

Leaf inhabiting fungi of mangrove plants are known. Khuskia oryzae hasbeen reported for the first time from India, among seven species of fungi that existon mangrove leaf surface of Sundarbans (Pal and Purkayastha, 1992b). There are2 new parasitic fungi namely Pestalotiopsis agallochae sp. and Cladosporiummarinum sp. existing on infected leaves of Excoecaria agallocha and Avicenniamarina (Pal and Purkayastha, 1992a).

Sixteen fungi are isolated from leaves of mangrove plants of Sundarbans,West Bengal and their growth response to tannin, extracellular pectolytic enzyme(PE) activity and degree of inactivation of PE due to presence of tannin are testedin vitro. Tannin (0.2%) inhibited growth of all test fungi, but low concentration(0.05%) stimulated growth of three fungal species. Enzyme activity in culturefiltrates of fungi are also assayed. Phomopsis sp. of Commelinae andP. clerodendrumii show maximum (99%) while Exserohilum rostratum exhibitminimum (13%) reduction in viscosity of their respective culture filterates withouttannin. Among 16 fungi, Chaetomium globosum, Curvularia senegalensis and

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E. rostratum are highly sensitive to tannin with a very low PE activity. Significantinactivation of PE by tannin (0.2%) is recorded for all fungi which is maximum (80- 90%) for tannin sensitive fungi (De et al., 1999).

Ten fungal species isolated from the mangrove leaves of Pichavaram areAspergillus flavus, A. ochraceus, Alternaria alternata, A. tenuissima, Rhizopusnigricans, Penicillum funiculosum, P. expansum, Humicola fuscoatra, Mucorracemosa and Fusarium oxysporum. Alternaria alternata and Rhizopusnigricans are abundant in all the mangrove leaves followed by Aspergillus andPenicillium species and there is a negative correlation found between the fungalcounts and leaf tannins (Sivakumar and Kathiresan, 1990). The fungal counts aremore on mangrove leaf litter than those on fresh leaves. The high fungal counts onleaf litter are associated with low content of tannins and sugars, high level of aminoacids, low leakiness of tannins and sugars, and high leakiness of amino acids(Ravikumar and Kathiresan, 1993).

Fungal activity has been studied in an estuarine mangrove ecosystem ofCochin and 31 fungi species isolated from sediment, 27 from decaying leaves,stems, roots and pneumatophores of the mangroves. A few isolates especiallyAspergillus candidus, show phosphate solubilizing activity by solubilizing insolublephosphorus compounds and making them available to other organisms, thus thefungi play a role in the nutrient regeneration of the ecosystem (Prabhakaran et al.,1987).

Mycological examination of dead wood, prop roots and seedlings ofRhizophora apiculata and R. mucronata collected from Pichavaram mangroveshas yielded 48 fungal species belonging to 36 genera with Ascomycotina beingmost prevalent. The number of fungi recorded on prop roots (44) are muchgreater than that on seedlings (18) and woods (16). The most common andabundant fungus on wood is Lophiostoma mangrovei. Verruculina enalia is mostcommon on prop roots and seedlings. Some of the fungi occur on all the threesubstrates, but their frequency and percentage occurrence on individual substratesvary. Halocyphina villosa, the only Basidiomycete recorded is more abundant onseedlings, while Monodicty spelagica is abundant on wood, the least on seedlings(Ravikumar and Vittal, 1996).

A total of 25 species of fungi, belonging to 15 genera has been isolatedfrom rhizosphere soil of Avicennia officinalis from Alibag, Maharashtra (Nair etal., 1991). The fungal counts in rhizosphere soil are maximum in monsoon andminimum during summer (Nair et al., 1991). Thus salinity affects the fungalpopulations (Venkatesan and Natarajan, 1987).

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Lower groups of aquatic fungi like thraustochytrid species occur indecaying mangrove leaves (Raghukumar and Raghukumar, 1988). Schizochytriummangrovei sp. on decaying mangrove leaves has been described from Goa(Raghukumar, 1988). The thraustochytrids (Thraustochytrium striatum andSchizochytrium mangrovei) kill bacterial cells by developing amoeba-likestructures and the species also behave like fungus in the breakdown of complexorganic molecules (Raghukumar, 1992).

Higher groups of fungi from mangrove woods in Maharashtra coast havebeen reported with 41 species of ascomycetes, 2 basidiomycetes, 12deuteromycetes with predominanace of Massarina velatospora (Borse, 1988).Massarina velatospora and a new mangrove-inhabiting species,M. ramunculicola sp. have been described from dead mangrove wood (Hyde,1991).

Massarina armatispora sp. a new intertidal ascomycete has been isolatedfrom mangrove wood (Hyde et al.,1992). Other ascomycetes isolated frommangrove woods are Rhizophila marina, Trematosphaeria striatispora,Lineolata rhizophorae, Caryosporella rhizophorae, Passeriniella savoryellopsisand Hypoxlon ocenicum (Chinnaraj and Untawale, 1992). Most of the wood-rotting fungi contain laccase, one of the major lignin-modifying enzymes(Raghukumar et al., 1994).

Enzyme activity shows positive and significant relationships with organicnutrient forms like organic C, P and S, which indicate that soils with higher organicC stimulate microbial activity and therefore, provide a more conducive environmentfor enzyme synthesis and its accumulation in the soil matrix of the mangroves(Dinesh et al., 1998).

Physiological studies on strain variations have been made in Pestalotiopsisversicolor, isolated from the mangrove plant, Ceriops decandra growing indifferent localities of Sundarbans (Bera and Purkayastha, 1992).

Most of the fungi collected from Maharashtra coast are decomposers ofmangrove plants (Ramesh and Borse, 1989). Fungal succession on decomposingpneumatophore of mangrove plants, can be divided into three groups: group1-sugar digesting fungi are mainly comprised of zygomycotina which are pioneercolonizers; group-II-cellulose decomposing fungi consist of various ascomycotinaand deuteromycotina, and most efficient ones are Chaetomium spp., Fusarium

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spp., Humicola spp. Penicillium spp., and Trichoderma spp.; group III-lignindecomposing fungi include Alternaria alternata, Graphium spp., Preussia spp.,Trichoderma lignorum, Trichurus spiralis and Truncatella truncata.

Laboratory studies on decomposition of leaves of Rhizophora apiculatahave been carried to assess the role of thraustochytrid fungi in the marine detritalsystems. There are two phases of fungal dynamics in the first phase between0 and 21 days; in the first phase, cellulase producers are formed (Cladosporiumherbatum, Fusarium moniliforme, Cirrenalia basiminuta andHalophytophthora vesicula); in the second phase between 28 and 60 days,Xylanase producers (hypomycetes) are formed; and in all ages of detritus, pecticenzymes, amylase and protease are uniformly produced by the fungi (Raghukumaret al., 1994).

The thraustochytrid, Schizochytrium mangrovei grows well on bothphases of detritus. Fusarium moniliforme and Halophytophthora vesiculacause an increase in detrital protein. All the fungal species enhance the aminoacids and Halophytophthora vesicula reduces the phenolics of the decomposingorganic matter (Raghukumar et al., 1994). Cirrenalia pygmea, a mangrovefungus, has been grown at various salinities and analysed for its amino acidcomposition (Ravishankar et al., 1996).

5. PLANKTONOLOGY

A. Phytoplankton

The mangrove waters are more productive than the backwaters andestuaries (Bhattathiri, 1992). In Kakinada coast, the productivity is four timeshigher in mangroves than that in the adjacent marine waters (Selvam et al.,1992). This is attributed to high production of plankton in the mangove waters asthe phytoplankton are one of the initial biological components, from which energyis transferred into higher organisms through food web. Biomass and production ofphytoplankton of various sizes are important factors, which regulate the availabilityand diversity of organisms at higher trophic levels.

Statistical methods to obtain diversity indices, richness indices andevenness of phytoplankton and zooplankton separately have been used andrelated them to the ecological parameters in mangrove ecosystems in Cochin area(Shajina and Balan, 1993).

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Marine phytoplankton of the mangrove delta region of West Bengal havebeen investigated. They show a taxonomic account of 46 taxa of bacillariophyceae,dinophyceae and cyanophyceae (Table 3). The predominant genera found almostround the year are Coscinodiscus, Rhizosolenia, Chaetoceros, Biddulphia,Pleurosigma, Ceratium and Protoperidinium (Santra et al., 1991).

Table 3. Plankton species reported in Sundarban mangrove areas

Source : Santra et al. (1991)

In Pichavaram waters, the phytoplankton of 5-10 m size are importantcontributors to the primary production (Kawabata et al., 1993). There are 82species of phytoplankton in Pichavaram which constitute 67 species of diatoms, 12species of dinoflagellates and 3 species of blue-green algae. The diatoms form thebulk with 72% of the census followed by the dinoflagellates with 15% (Kannanand Vasantha, 1992). Another estimate for the same area reports totally 84species of phytoplankton comprising 74 species of diatoms, 5 species ofdinoflagellates, 4 species of blue green algae and 1 species of green algae. Thephytoplankton popuation density has ranged from 25 to 15,84,893 cells/l during1980-81 and from 12 to 50,11,872 cells/l during 1981-82. Generally, the density

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is high during summer and post-monsoon seasons and low during monsoonperiods (Chandrasekaran, 2000). A positive relationship exists between thephytoplankton and the finfish and shrimp juveniles. This indicates that phyto-plankton could be one of the major factors influencing the temporal fluctuations ofthe populations of fish juveniles in this mangrove biotope (Table 4)(Chandrasekaran, 2000).

Table 4. Checklist of phytoplankton collected during the study period atPichavaram mangrove

Source : Chandrasekaran (2000)

Amongst phytoplankton, Ceratium sp., Coscinodiscus sp., Pleurosigmasp., Chaetoceros sp. and tintinids are predominant. Among the zooplankton,

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copepods are the most dominant, followed by nauplius, protozoea and zoea ofcrustaceans, lucifer, Oikopleura sp. chaetognaths, planktonic gastropods, fish eggsand siphonophores in Manjeri area of South Andaman (Damroy, 1995b).

The phytoplankton analysis has been made on the native species(autochthonous) and migrants (allochthonous). Species which occurred more than90% are considered as autochthonous species and the rest of the occurrences arerelated to allochthonous species. Such autochthonous species are Biddulphiamobiliensis, Coscinodiscus jonesianus, Bacteriastrum delicatulum,Chaetoceros lorenzianus, Coscinodiscus centralis, C. eccentricus, Gyrosigmabalticum, Navicula rostellata, Pleurosigma elongatum and P. directum(diatoms) and Ceratium furca, Peridinium depressum and Provocentrummicans (Dinoflagellates) (Chandrasekaran, 2000).

The dominant allochthonous consitituents are Chaetoceros compressus,Eucampia zodiacus and Rhizosolenia setigera among diatoms; and Ceratiumtripos and Dinophysis caudata among dinoflagellates. Freshwater species such asAnabaena, Nostoc, Oscillataria, Spirogyra, Navicula and Synedra are seen onlyduring the freshwater influence in the biotope associated with monsoonal floods(Chandrasekaran, 2000).

B. Zooplankton

The population density of zooplankton varies from 11 to 22, 13,094organisms/1 for the year 1980-81 and from 15 to 22, 84,020 for the year 1981-82. Major peaks of abundance are noted during post-monsoon and summerseasons and the lowest population density during monsoon (October-December)(Chandrasekaran, 2000).

Totally 47 species/groups of zooplankton have been recorded in thePichavaram mangrove area. Calanoid and cylopoid copepods are the mainconstituents of the macroplankton and the dominant species are Acroporasouthwelli, Eucalanus elongatus, Oithona rigida, O. brevicornis andPseudodiaptomus aurivilli. The major components of microzooplankton aretintinnids represented by 10 species. Of these, Dictyocysta seshaiyai,Tintinnopsis tubulosa, T. tocantinensis, T. cylindrica, T. minuta,T. uruguayensis, Tintinnidium primitivium are most common numerically. Thelarval population consists mainly of polychaete larvae, nauplii of copepods, prawnlarvae, nauplii and cypris of cirripedes and veligers of gastropods and bivalves and

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fish larvae. Besides the above forms, rotifers, ctenophores, chaetognaths, siphono-phores, hydrozoan medusae and pteropods are also recorded (Chandrasekaran,2000).

Natural phytoplankton communities in Pichavaram have been documentedwith predominance of Nitzschia closterium, Pleurosigma spp., Thalassionemanitzschioides and Thalassiothrix frauenfeldii (Mani, 1989, 1992). Thirty onespecies have been identified as bloom formers with a predominance ofRhizosolenia alata f. gracillima in Pichavaram mangrove waters (Table 5) (Mani,1994). Phytoplankton in Chorao (Goa), west coast are higher in bottom layer thanon the water surface and they also show alkaline phosphatase activity (Desai,1988).

Zooplankton constitute one of the important intermediate steps in the foodpyramid of mangrove waters. Distribution and abundance of zooplankton havebeen studied in Hooghly and Saptamukhi river waters, West Bengal (Kundu et al.,1987).

Zooplankton in Godavari mangrove ecosystem are composed of 27groups. In Krishna mangroves, maximum number of groups (22) are observed insummer period and minimum number of groups (6) are recorded in flood period(Ramanamurthy and Kondala Rao, 1993).

Community structure of zooplankton at 4 locations, 2 in the coastal watersoff Bombay and 2 in interior Thane-Bassein creek system has been studied(Vijayalakshmi et al., 1999). Copepods are the major herbivore community,contributing 76-83% of total zooplankton population. Decapods are relativelymore in the outer (av.11%) than in interior zone (av.7%). Population density ofcarnivores are 2-4 times more in the polluted interior segment.

Metal concentrations in the zooplankton have been studied. Among themetals, Cu and Zn contribute 60-89% of the total elements accumulated. Ingeneral, concentration of Zn is higher than Cu in different groups. Also levels ofZn in polluted locations are 2 times higher than in the outer zone. The concen-trations of metals are higher in gelatinous organisms, which include a variety ofcarnivores. Metal concentration in copepods is lower than carnivores. The lowestconcentration of metals in decapods is attributed to the effective elimination of apart of the concentrated metal through periodic moulting (Vijayalakshmi et al.,1999).

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Table 5. Bloom-forming phytoplankton species and their cell surface area(m2), number of cells required to attain bloom level and themaximum bloom concentration recorded at Pichavaram mangrovesduring 1984-86

Source : Mani (1994)

The daytime planktonic composition is rich with phytoplanktonic communityand detritus, which is the main source of food for the organisms living in themangrove ecosystems. The temperature and salinity reflect the conditions of thehabitat, while the plankton have direct relationship with the nature of tide, strengthof the current and direction of flow. Higher displacement volumes of about 0.73,0.75, 0.85 ml/m3 are recorded during night with numerical abundance of 27053,17401 and 18688 no./m3 respectively. The detritus constitute about 50-60%during the low tide period. Among the zooplankton, copepods, larvae of molluscsand polychaetes contribute to the bulk of zooplankton component (Mohan andSreenivas, 1998).

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Zooplanktonic larval recruitment of Coleroon estuary occurs due to theinflux of Pichavaram mangrove waters during low tide and to the influx of coastalwaters at hightide (Ayyakkannu, 1989). There are 35 species of rotifers (Table 6)belonging to 17 genera in Pichavaram mangrove waters with three predominatspecies viz., Brachionus angularia, B. calyciflorus and B. forficula(Govindasamy and Kannan, 1991).

Table 6. Species composition of rotifers encountered from the Khan sahibcanal of the Pitchavaram mangrove area

* New distributional records to Porto Novo; # New distributional record to IndiaSource : Govindasamy and Kannan (1991)

The population density, species diversity, species evenness and speciesrichness of zooplankton have been studied in the Pichavaram mangroves. Thezoo-plankton density varies from 200 to 61650 individuals/litre, with the maximumin summer season. Out of 55 species of zooplankton recorded, the copepods arethe dominant group (36.5%) (Table 7) (Karuppasamy and Perumal, 2000).

A planktonic larvacean tunicate has been recorded for the first time fromthe mangrove waters of Sundarbans (Singh and Choudhury, 1992a). Zooplanktoncommunity of the fringing mangroves along the upper reaches of Mandovi andZuari estuaries of Goa has been studied. This reveals that the standing stock(biomass) values in the mangroves are low as compared to estuarine and neriticbiotopes (Goswami, 1992).

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Table 7. Zooplankton species recorded in different stations at Pichavarammangrove waters

Forty six species of copepods have been identified, of which, 40 belong toCalanoida with an overall dominance of Acartiidae. Acartia spinicauda, A.centrura and Centropages dorsispinatus are the common species throughout theyear at all locations (Table 8). Eucalanus subcrassus and Paracalanus aculeatusare more abundant in the outer zone, while A. tropica is very common in theinterior region. Hyposaline species, Pseudodiaptomus binghami malayalus exists

Source : Karuppasamy and Perumal (2000)

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from the interior locations particularly during the monsoon months (June-September) (Neelam Ramaiah and Nair, 1997).

Table 8. Copepod species reported at the mangrove waters of Goa

Source : Neelam Ramaiah and Nair (1997)

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Microzooplankton of Parangipettai with special reference to Tintinnida(Protozoa: Ciliata: Tintinnida) have been documented (Krishnamurthy et al., 1995).Species composition and abundance of tintinnids and copepods have been studiedin Pichavaram mangroves. Tintinnids are the dominant microzooplankters with 50species and densities ranging from 60 to 44,990 invididuals/m3. The mostimportant genera are Tintinnopsis and Favella (Godhantaraman, 1994;Krishnamurthy et al., 1995). They also found 40 rotifer species in 17 genera.Except for rotifers, whose populations peaked in the premonsoon and monsoonmonths, the microzooplankters are most abundant in the summer, correspondingwith highest phytoplankton abundance. Copepods are the most abundant group inthe mangrove mesoplankton. In the Pichavaram mangrove waters, copepodsdensities reach 80740 individual/m3. The genera Acartia, Acrocalanus(Calanoida), Macrosetella and Euterpina (Harpacticoida) and Oithona(Cyclopoida) are the most abundant (Godhantaraman, 1994).

6. FLORA

A. Flowering Plants

The Indian mangroves comprise approximately 59 species of higher plantsbelonging to 41 genera and 29 families (Deshmukh, 1991a). Of these, 32 speciesbelonging to 24 genera and 20 families are present along the west coast. Thespecies viz., Sonneratia caseolaris, Suaeda fruticosa, Urochondra setulosahave been reported only from the west coast. An annotated check list of Indianmangroves has been prepared by this ENVIS Centre in 1999.

The mangrove flora in the Cochin backwater consists of 10 speciesbelonging to 9 genera and 7 families. Rhizophora mucronata, Avicenniaofficinalis, Acanthus ilicifolius, Derris trifoliata and Acrostrichum aureumoccur widely. Rhizophora mucronata is the most dominant species, followed byAvicennia officinalis and Acanthus ilicifolius (Sunil Kumar and Antony, 1994).

The east coast of India and Andaman Nicobar Islands have high speciesdiversity. There are 45 species in 27 genera of mangroves in the bay islands(Deshmukh, 1991b). The species like Ceriops decandra, Xylocarpus spp.,Lumnitzera littorea, Nypa fruticans, Phoenix paludosa and Cerbera manghasare limited to east coast. The common species in Indian coastline are Rhizophoramucronata, R. apiculata, Ceriops tagal, Bruguiera gymnorrhiza, Lumnitzeraracemosa, Sonneratia apetala, Acanthus ilicifolius, Avicennia marina,

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A. officinalis, Excoecaria agallocha and Acrostichum aureum (Deshmukh,1991b).

Manjeri mangrove area of Andaman is dominated by species ofRhizophora, Avicennia, Bruguiera, Lumnitzera and Sonneratia. The mangrovesarea that is facing the seafront is less influenced by influx of freshwater (Damroy,1995b).

Totally thirty-seven species of exclusive mangroves and about 25 speciesassociated with mangroves occur in the coastal and inland regions in India (Dagar,1995). Thirty two species of mangrove and mangroveassociate species belongingto 26 genera and 18 families are reportedly present in Godavari and Krishnamangrove ecosystems (Ramanamurty and Kondala Rao, 1993). Another surveyreports 45 species coming under 37 genera belonging to 6 families (Venkanna,1991). It is interesting to note that Prosopis chilensis, grows in association withSonneratia and Acanthus (Venkanna, 1991).

The typical mangroves, such as, Lumnitzera racemosa, Bruguieragymnorrhiza and Rhizophora apiculata are rarely found in the Godavari Delta(Umamaheswara Rao and Narasimha Rao, 1988). Mangrove flora of AndamanIslands has the dominat species of Rhizophora apiculata, R. mucronata andAvicennia marina (Mall et al., 1985; Jagtap, 1985). The Nicobar Islands ofAndaman sea have 10 major species with predominance of Rhizophora stylosaand Bruguiera gymnorrhiza (Jagtap, 1992).

There are 47 species of mangroves and 37 species of otherangiosperms in the deltaic regions of the Ganges, Mahanadi, Godavari, Krishnaand Cauvery rivers, situated along the east coast of India alone (Untawale andJagtap, 1991).

A rare mangrove species, Scyphiphora hydrophyllacea (Rubiaceae) isreportedly existing in Andhra Pradesh (Venkanna, 1991). Acanthus ebracteatushas been recorded only from the Andaman and Nicobar Islands (Deshmukh,1991a).

In Andaman Islands out of 32 principal species of Indian mangroves, 13species are found in the west coast, 23 species are in the east coast and 27species are found in Andamans, contributing 87% of the total species of Indianmangroves flora (Singh et al.,1990).

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The fallen leaves from the trees are colonized by microbes which in turnare eaten by protozoans. The enriched biomass of microbes along with organicdetritus, gives rise to rich particulate organic matter and this forms 90% of thefood for crabs, worms, shrimps and small forage fishes, which in turn form prey tojuveniles of large fishes of Pichavaram mangroves (Kathiresan, 1991).

A new species, Rhizophora x annamalayana, has been described, as ahybrid between R. apiculata and R. stylosa from Pichavaram mangroves(Kathiresan, 1995b, 1999b). Previously this species was called as R. lamarckii, ahybrid between R. stylosa and R. apiculata (Lakshmanan and Rajeswari, 1983;Muniyandi and Natarajan, 1985). But the Rhizophora stylosa is not existing inPichavaram (Kathiresan, 1995b). Bruguiera cylindrica (Rhizophoraceae) hasbeen recorded for the first time from the west coast, while it is common on theeast coast (Bhat and Untawale, 1987).

For evaluating baseline status of mangroves and halophytes around thethermal station in Mumbai, studies have been carried out during construction phaseof the power plant at banks of three creeks, namely Dahanu, Danda and Savta.Altogether 7 species of vegetation are recorded, of which Avicennia marina andAeluropus sp. are widely present. Average height and density of different plantsvary between 0.34 and 1.65 m and 8 and 125 per 100 m2 respectively. Diversityindices of the plants vary from 0.67 to 1.47, indicating presence of less number ofspecies and their uneven distribution in different study zones. Plantation andsurvival of mangrove seedlings on both banks of Savta creek have also beenrecorded (Ghosh et al., 1996).

A few unusual morphological features have been observed in Avicenniaalba, Bruguiera gymnorrhiza, B. cylindrica and Ceriops decandra, inmangroves of the Karnataka coast. The features are the aerial roots on trunk up to65 cm above the ground level, regular dichotomous branching system and notpenetrating the mud or becoming prop like structures as in other mangrove taxa(Rao et al., 1987).

Studies of leaf anatomy for 13 species of mangroves, belonging to 11genera and 9 families have led to construct a taxonomic key (Seshavathram andSrivalli, 1989). Besides leaf anatomy, chromosomal diversity has also been studiedin three species of Heritiera, H. fomes, H. macrophylla and H. littoralis fromBhitarkanika on the Mahanadi delta of Orissa. The chromosome number is2n = 38 with minute variation in chromosomal length among the three species.

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These minutes structural alterations in chromosomes, with regard to chromosomelength and chromosome volume play an important role in establishment andadaptability of the species (Das et al.,1994).

Twelve true halophytic plants have been studied for their unique foliaranatomical organizations. All of them have thick cuticular, leaf surface coveringwith sunken stomata in seven species. The stomatal frequency (no/sq.mm) and thepore size (sq. m) are comparatively lower in halophytes than mesophytes. All thespecies have distinct salt glands over leaf surface as desalination mechanism. Thecarbon fixation mechanism is typical C3 type with distinct photorespiration (AlokeBrahma and Santra, 1993).

Forest structure has been studied in terms of canopy height, tree diameter,mean stand diameter, basal area, basal cover, relative density, relative dominanceand stand density in Pichavaram (Kathiresan et al., 1994) and in Coringamangrove forest, Godavari delta. There is a definite trend in the distribution ofmangroves from the mouth of the estuarine region to the inland waters (Azariah etal., 1992).

Phenology of mangroves from the west coast of India has been studied(Jagtap, 1986; Mulik, 1987; Mulik and Bhosale, 1989). The flowering inmangroves is controlled by an interaction of temperature and photoperiodcondition besides longitudinal differences. In all the mangrove species along theGoa coast, extensive flowering is noticed from March to June and extensivefruiting from April to July. Flowering and fruiting are generally poor or absentfrom September to January (Mulik and Bhosale, 1989). The floral biology hasbeen examined in relation to pollinators in five mangrove species of the Godavariestuary in southern India (Aluri, 1990). In Aegiceras corniculatum andLumnitzera racemosa, flowers self pollinate and their pollen and nectar serve asfood resource to the insects; whereas Avicennia officinalis and Acanthusilicifolius need pollen vectors for their reproduction through outcrossing (Aluri,1990).

The members of mangrove vegetation produce large quantities of pollengrains that are liberated into the ocean where the conditions are favourable fortheir preservation and fossilization. Therefore, the pollen studies reveal theconditions of the mangrove vegetation in the past (Kumaran, 1991).

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Pollen studies have been made in marine quaternary sediments of ChilkaLake (Gupta and Khandelwal, 1992) and in the Andaman sea (Venkatachala etal., 1992). From the pollen studies, the climatic evolution and sea level changescan also be understood in any region (Caratini, 1992). Pollen studies indicate thatthe species like Rhizophora existed in Muthupet swamp of Tamil Nadu, some 200years ago and today this area is monospecific with Avicennia marina (Azariah etal., 1992). There has been a decline in pollen representation of the arborescentgenera-Sonneratia and Rhizophora and an increase in the herbaceous taxa suchas Suaeda due to selective wood cutting, grazing in the mangrove forest and thewidespread development of freshwater damming. Tertiary sediments of landlockedareas of India have yielded core mangrove plants, which indicate the existence ofseashore, still more inland than the present coastline at Rajahmundry, Kachchh andRajasthan (Bonde, 1991).

The chemical composition and productivity of the grass Porteresiacoarctata from intertidal zone of Cheemaguri creek in western part of Sundarbanshave been studied. Average total biomass production of the grass in a tidal creekis 260 g/m2/year (dry wt.). Of the total production, leaves, stems, understems androots contribute 29.6, 40, 23.9 and 6.4% respectively. Throughout the season,maximum rate of production is during monsoon (0.86g/m2/year) and is higher thanthe below ground production (79g/m2/year). About 666-kcal/m2/year solar energyis utilized by the plant to produce 177g/m2/year organic carbon (Ghosh et al.,1991).

B. Non Flowering Plants

Marine algal resources from mangroves have been studied. A total of 32taxa of benthic algae - 13 species belonging to Cyanophyceae, 12 toChlorophyceae, 6 to Rhodophyceae and only 1 to Xanthophyceae - are recordedfrom Sundarban delta (South 24-Parganas) of West Bengal (Table 9) (Pal et al.,1988).

Survey and distribution pattern of 67 blue-green algal species in varioussaline habitats of West Bengal have been studied (Table 10) (Santra et al., 1988).

The number of cyanobacteria varies in the same area of mangroves : 13species (11 genera; Ramachandran, 1982), 19 species (14 genera, 4 families;Ramachandra Rao, 1992) and 24 species (Palaniselvam, 1995; Krishnamurthy etal., 1995) in Pichavaram mangrove forests.

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Table 9. Species of algae reported in the Sundarban delta

Phormidium tenue isolated from mangrove and shrimp pond ecosystemshas been studied for biomass production. This species grows well underlaboratory conditions in the marine nutrient (MN) medium incorporated with urea(92 g/l), superphosphate (24.7 g/l) and potash (4.94 g/l), maintained at asalinity of 40 x 10-3, pH 8 and light intensity of 160 J/s. Under field conditions, thespecies does not require any addition of nutrients to the MN medium, but onlyshaded condition and 15 cm of water depth for better biomass production(Palaniselvam and Kathiresan, 1996). During the culture period, the levels ofpigments and photo-chemical activities have also been studied. The trend is similarbetween the fluorescence excitation of pigments and the production of biomassand that is also similar between the fluorescence emission and the level of pigmentssuch as, phycocyanin and phycoerythrin; but the pattern is not alike between thelevels of pigments, their capacity to transfer energy and biomass production arehigher in salinity 40x10-3 than in 18 and 100x10-3 grown cultures. Thus biomassand pigment characteristics are highly dependent on salinity and age of culture(Palaniselvam et al., 1998).

Source : Pal et al. (1988)

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Table 10. Blue-green algal species reported in the mangrove and coastalareas of Sundarbans

Source : Santra et al. (1988)38

Sixteen genera and 22 species have been listed from Bhitarkanikamangroves, Paradeep port area, estuaries of Subarnarekha, Debi, Kusabhadra,Rushikulya and the backwaters of Konarka and Gopalpur coast of Orissa state.The common species are Enteromorpha compressa, E. intestinalis, Ulvafasciata, Chaetomorpha aerea and C. antennina, Rhizoclonium kernerioccurring commonly attached to pneumatophores in the mangroves, Cladophorauncinella in the littoral sandy beds of all the estuaries and Gracilaria verrucosain restricted patches in the estuaries of Mahanadi and its distributaries.Cyanobacterial species are Aphanocapsa, Chroococcus, Hydrococcus,Dermocarpa, Microcoleus, Lyngbya, Oscillatoria and Calothrix from thecoastal mud flats (Adhikary, 2000).

7. FAUNA

Mangroves support rich faunal resources (Rao, 1987). The importance ofmangrove ecosystems for its potential for fisheries and aquaculture in Sundarbanshas been described (Chakraborty, 1995). Among invertebrates, more than 500species of insects and Arachnida, 229 species of crustacea, 212 species ofmolluscs, 50 species of nematodes, and 150 species of planktonic and benthicorganisms are known from Indian mangroves (Gopal and Krishnamurthy, 1993).

Vertebrate fauna is represented by 300 species of fish, 177 species ofbirds, 36 species of mammals. Twenty two species of molluscs, 50 species ofnematodes, and 150 species of planktonic and benthic organisms are also knownfrom Indian mangroves (Gopal and Krishnamurthy, 1993). Forty one species ofinvertebrates and 52 species of fishes have been assessed, and four species of theinvertebrates and only one species of fish are categorized as endangered(Anonymous, 1997).

The fauna of Sundarbans has been investigated in detail (Naskar and GuhaBakshi, 1987; Mandal and Nandi, 1989; Ghosh et al., 1990).

In the Sundarbans, faunal biodiversity is higher in the vegetational complexsituated below the tidal level than other zones, which are above the tide level oroccasionally inundated (Chakrabarti, 1986).

A. Benthos

Fifty three species of macrozoobenthos from six different intertidalbiotopes of Sagar Island in Sundarbans through six consecutive seasons have been

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measured by using Shannon-Weavers method of diversity index and correlatedwith the major ecological parameters of the study sites viz., salinity, dissolvedoxygen, pH, temperature, organic carbon and texture of the substratum(Chakraborty et al., 1992).

There are 17 species of stylet-bearing nematodes in Sundarban mangroves(Sinha et al., 1987; Sinha and Choudhury, 1988). Studies of meiobenthos ofmangrove mudflats of Thane creek, south of Bombay Harbour Bay have revealeda dominance of nematodes (78.35%) with insignificant seasonal variations (Goldinet al., 1996).

Acanthamoeba rhysodes is a predominant intertidal benthic gymnamoebain the mangrove ecosystem of Sundarbans of lower deltaic Bengal (Bhattacharyaet al.,1987).

Macrobenthos in the Sundarban mangroves have been studied. The mostcommon forms are polychaetes, sipunculids, crustaceans, molluscs, nemarteans,gobiids and actiniarians. Polychaetes are the dominant taxa in the creekenvironment, whereas in the mangroves, sipunculids are the most abundant group(Patra et al., 1988, 1990).

Meiofaunal studies have been carried out in mangroves. The meiofaunareduces with increasing depth in the sediment (Ansari et al., 1993). The reducingenvironment is characterized by high population of nematodes, turbellarians andharpacticoids. The meiofaunal taxa are significantly correlated with interstitial waterof the sediment and to the microbial density in mangrove mudflats (Ansari et al.,1993). There are 13 groups and 22 species of harpacticoid copepods (18 generaand 8 families) of meiofauna in the Kakinada Bay (Gautami-Godavari estuarinesystem) (Kondala Rao and Ramanamurty, 1988). There are 11 major faunal taxa,of which nematodes are dominant in the Bhitarkanika mangrove sediments (Sarmaand Wilsanand, 1994).

Surface sediment samples, collected within 4 to 13.5 m water depth fromKharo creek Kachchh have been studied for their foraminiferal content. There are47 foraminifera species, of which 44 are benthic and 3 planktonic. The faunashows a positive relationship between angular-asymmetrical form and clay fractionin the sediments (Nigam and Chaturvedi, 2000).

Depth-wise distribution of macro-invertebrates in sediments of intertidalareas of Cochin mangroves has been studied. The fauna is mainly composed of

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polychaetes, crustaceans and molluscs. At all tidal levels, the macro-fauna tends toconcentrate at the top 0-5 cm layer substratum (65%) and to substantiallydecrease towards deeper levels. The polychaete, Marphysa gravelyi is abundantbelow 10 cm depth. The aggregation and coexistence of organisms are perceptiblein the top layer (0-5 cm) of soil (Sunil Kumar, 1997).

Community structure and distribution of macro-zoobenthos in aquaculturepond in relation to environmental factors have been compared with the macrofaunaof mangroves in the surrounding area. Macrofaunal density is 8918/m2 and 5254/m2 in the pond and mangrove habitat respectively. Polychaetes dominate in thepond (43.91%) and mangroves (41.23%) followed by molluscs and crustaceans.The rich population density and species composition in the prawn ponds,compared to mangroves, is related to the variability in substrate characteristics(Sunil Kumar, 1998).

Structure, composition and seasonal distribution of macrobenthic fauna inthe intertidal areas of the mangrove ecosystem of Cochin backwaters have beenstudied. The benthic fauna is mainly represented by polychaeta, crustacea andmollusca. The diversity is higher at Cochin barmouth than at interior areas.Maximum macrofaunal density and dry weight recorded are 8970/m2 and 567.86g/m2 respectively. Polychaete constitutes the bulk quantity in all the stationsstudied. Detritivorous benthos are found to be common at all stations and welladopted mangrove habitats (Sunil Kumar, 1995b).

Ecological studies on the polychaete fauna of the mangrove areas ofCochin have been made. There are 33 species of polychaetes belonging to 20genera, and 10 families (Table 11). Among the polychaetes, Marphysa gravelyi,Paraheteromastus tenuis, Nereis glandicincta, Dendronereides heteropoda andDendronereis aestuarina are found to be the more dominant species. Faunaldistribution in relation to the type of sediment shows high species diversity andrichness in the sandy substratum, followed by clayey sand (Sunil Kumar andAntony, 1993; Sunil Kumar and Antony, 1994; Sunil Kumar, 1995a). Studies onbiodiversity of soil dwelling organisms in Indian Mangroves have been reviewed(Sunil Kumar, 2000).

In Pichavaram mangroves, there are 44 macroinvertebrates mostly ofestuarine fauna which includes four polychaetes, one bivalve, nine gastropods,three tanaids, four isopods, four amphipods, one cirripede,