INTRODUCTION:

Microbial diversity has received particular attention in environment studies since 1960s, but its functional significance in ecological processes is still a subject of debate and analysis. The ecological importance of fungal diversity in marine ecosystem has been often under estimated or completely ignored, even though fungi represent a wide range of nutritional groups such as saprobes pathogens and symbionts, that form an integral part of the coastal ecosystems.

Mangroves are salt tolerant vegetation that grows in inter tidal regions of rivers and estuaries sediment deposition and availability of sheltered areas are to essential pre – requisites for establishment of mangroves. Mangroves are also referred to as “Tidal forests” and belong to the category of tropical wetland rain forest Eco – system. Mangroves occur almost exclusively in the tropical regions of the world covering an area of around 200, 000sq.km in 30 countries.

Ecologically mangroves are colonizers, creating land forms out of sea. Mangroves perform a number of vital ecological functions like nutrient, recycling, maintenance of hydrological regime, coastal protection, fish – fauna production, Protecting coastal zones from erosion, storms and flood and also in supplying food and shelter for large number of fishes.

Driftwoods are one of the important and interesting object for the study of fungal colonization as their origin is unknown and can be drifted to any part of the coast by wind in the break down of driftwood and thus in the nutrient cycles of marine habitat. They get exposed to sunlight and atmosphere at a frequent interval due to tidal variation.

MATERIALS AND METHODS:

Physico chemical characteristics of soil:

To find out the moisture content known weight of the soil was dried at 40⁰C in a hot air oven till complete evaporation of water molecules and re-weighed. The weight loss was expressed in terms of percentage of moisture content. The sediment samples were mixed in distilled water(1:2w/v) well and the pH of soil suspension determined with a pH meter(Elico, India). Electrical conductivity (EC) was determined (Systronics India, Model 631E) (Jackson,1973).

Temperature was measured in field itself by inserting a standard thermometer. color was also recorded. Dried sample were ground well and subjected to sieving through a set of standard sieve plates. Based on the proposition of different sized particles, soil texture was also ascertained. Organic carbon content was determined by wet ashing method in K₂Cr₂0₇ solution as described by ElWakeel and Riely (1956). Total organic matter was estimated by rapid titration method of Walkey and Black (1934). The distilled, digested soil samples in boric acid was titrated against N/50 sulphuric acid using bromo cresol green indicator and from the titrimetric value the nitrogen content was calculated as described by Sankaran (1966). To estimate the available phosphorous content, the phosphate was extracted in ammonium fluoride solution and to this solution ascorbic acid reagent was added.

The solution was read in calorimeter using filter against the potassium di hydrogen phosphate standard, and the available P – content was calculated multiplying dilution factor as described by Olsen (1954). The samples were extracted in neutral ammonium acetate solution as described by Sankaran (1966) and the available potassium was estimated by using flame photometer.

Isolation of fungi from driftwoods:

The driftwood samples were collected in sterile polythene bags and sterilized 50% seawater was added to each bag in order to maintain moisture condition. The bags were tied with a string and incubated at room temperature for 7 days.

After incubation, the wood samples were taken out from the bags and allowed to air dry. Then the wood samples were examined under dissection microscope for the development of ascocarps, basidiocarps, pycnidia or conidia. The reproductive structure were transferred with a needle to a microscopic slide, torn apart in a drop of water to expose the spores and carefully squeezed under a color glass.

Morphology and septation of ascospores/basidiospores conidia were used for their identification. In some cases, asci and sterile element of the ascocarps such as paraphyses and pesudoparaphyses of the fruit bodies were used as character for identification. The fungi were identified with standard manuals of Marine Mycology-The higher fungi (Kohlmeyer and Kohlmeyer, 1979) and the publication (Kohlmeyer and Kohlmeyer, 1992).

RESULTS AND DISCUSSION:

Totally 23 physicochemical parameters were analyzed in the present study (Table – 1). Physico – chemical conditions of the mangroves environs, where the fungi were isolated were analyzed. Parameters such as moisture, temperature, pH, electrical conductivity (EC), organic carbon, organic matter, available nitrogen, available phosphates and available potassium were taken with phosphorous and available potassium was taken into consideration for the present investigation as these parameters are reported to influence the fungal population (Swart, 1958; Ramanathan 1977). These parameters are responsible for population dynamics of micro organisms in the mangrove environment, which coincided with those in other mangrove along the east coast. (Shanmukhappa 1987 and Rangarao 1988). Muthupet mangroves exhibit the tropical characteristic features of the mangroves.

Table.1-Physico-chemical analysis of soil

S. No	Name of the parameter	Analytical value
1.	pH	5.68
2.	Electrical conductivity (dsm^-1)	0.37
3.	Colour	Brown
4.	Texture	SCL
5.	Lime status	NIL
6.	Organic carbon (%)	0.25
7.	Organic matter (%)	0.50
8.	Available Nitrogen (Kg/ac)	82.6
9.	Available Phosphorus (Kg/ac)	5.5
10.	Available Potassium (Kg/ac)	85.0
Available Micronutrients
11.	Available Zinc (ppm)	0.84
12.	Available Copper (ppm)	0.20
13.	Available Iron (ppm)	2.15
14.	Available Manganese (ppm)	4.01
Soil Fractions
15.	Fine sand (%)	22.25
16.	Coarse sand (%)	42.62
17.	Silt (%)	14.95
18.	Clay (%)	20.18
19.	Cat ion exchange capacity (c. Mole. Proton⁺ /kg)	19.60
Exchangeable bases (c. Mole. Proton⁺ /kg)
20.	Calcium	9.50
21.	Magnesium	5.80
22.	Sodium	0.15
23.	Potassium	0.04

Diverse filamentous fungi were recovered on the driftwood of Muthupet mangroves along the East Coast of India (Table-2 ;Plate-1).

Table.2-Fungi isolated from Driftwood

S. No	Name of the fungi
1.	Aigialus sp.
2.	Alternaria sp.
3.	Anthostomella sp.
4.	Aspergillus oryzae
5.	A. luchuensis
6.	A. ochracaeus
7.	Bathyascus avicenniae
8.	Camerosporium sp.
9.	Coniothyrium obiones
10.	Corollospora sp.
11	Curvularia indica
12.	C. pallescens
13.	Didymosphaeria sp.
14.	Fusarium semitectum
15.	Halocyphina villosa
16.	Halosarpheia sp.
17.	H. obonnis
18.	Lignincola laevis
19.	Periconia sp.
20.	Sarvoryella lignicola
21.	Sphaerulina albispiculata
22.	Trematosphaeria mangrovei
23.	Verticillium tenerum

In the present investigation, totally 23 fungal species were identified from driftwoods. The fungal species are Aigialus sp, Alternaria sp, Anthostomella sp, Aspergillus oryzae, A. luchuensis, A.ochracaeus, Bathyascus avicenniae, Camerosporium sp, Coniothyrium obiones, Corollospora sp, Curvularia indica, C. pallescens, Didymosphaeria sp, Fusarium semitectum, Halocyphina villosa, Halosarpheia sp. H. obonnis, Lignicola laevis, Periconia sp Sarvoryella lignicola, Sphaerulina albispiculata, Trematosphaeria mangrovei, Verticillium tenerum.

The abundance of this group of fungi on marine and mangrove substrates has been reported by Hyde and Jones in 1988, and this might be due to their spores show adaptation to the marine ecosystem by way of production of appendages, which provide buoyancy in water, entrapment and adherence to substrates, as reported in mangrove wood (Aleem, 1980), driftwood (Prasannarai et al., 1999).

Hence it could be concluded that there is no uniformity in the diversity of marine fungi and their distribution pattern in different geographical regions. Extent of salinity, kind of substrates, position of inter tidal region, nature of floor, pH and oceanic region affect the occurrence and diversity of marine fungi in the mangroves ecosystem. They are dependent on the nature of substrate and temporal regions that favour the colonization, growth and substrate possession of the fungi.

REFERENCES:

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Received on 19.07.2011 Accepted on 18.08.2011

Asian J. Pharm. Ana. 1(3): July-Sept. 2011; Page 53-55