Benthic meiofaunal composition and community structure in the ...

Ocean Sci. J. (2011) 46(2):63-72 DOI 10.1007/s12601-011-0006-y

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Article

Benthic Meiofaunal Composition and Community Structure in the Sethukuda Mangrove Area and Adjacent Open Sea, East Coast of India Balasubramanaian Thilagavathi, Bandana Das, Ayyappan Saravanakumar*, and Kuzhanthaivel Raja Faculty of Marine Sciences, CAS in Marine Biology, Annamalai University, Parangipettai 608502, India Received 9 March 2011; Revised 18 May 2011; Accepted 10 June 2011

© KSO, KORDI and Springer 2011

Abstract − The ecological aspects of meiofaunal communities in the Muthupettai mangrove forest, East coast of India, has not been investigated in the last two decades. Surface water temperature ranged from 23.5 oC to 31.8 oC. Salinity varied from 24 to 34 ppt, while water pH fluctuated from 7.4 to 8.3. Dissolved oxygen concentration ranged from 3.86 to 5.33 mg/l. Meiofauna analysis in this study identified a total of 106 species from the mangrove and adjacent open sea area of Sethukuda. Among these, 56 species of foraminiferans, 20 species of nematodes, 7 species of harpacticoid copepods, 4 species of ostrocodes, and 2 species of rotifers were identified. Furthermore, a single species was identified from the following groups: ciliophora, cnidaria, gnathostomulida, insecta, propulida, bryozoa and polychaete larvae. Meiofaunal density varied between 12029 to 23493 individuals 10 cm/m2. The diversity index ranged from 3.515 to 3.680, species richness index varied from 6.384 to 8.497, and evenness index varied from 0.839 to 0876 in the mangrove area and adjacent open sea. Key words − Mangrove, open sea, meiofauna, diversity

1. Introduction Mangroves create unique ecological ecosystems that host rich assemblages of diverse taxa associated with different habitats. The muddy or sandy sediments are home to a variety of epibenthic or endobenthic macro-invertebrates and meioinvertebrates. Nematodes dominate numerically in the mangrove endofauna, as they do in other benthic environments. They seem to be most successful among other benthic taxa in colonizing the organically enriched oxygen poor environments (Alongi 1987; Olafsson et al. 2000). Meiobenthos occur in all types of sediments and occupy a wide variety of habitats. *Corresponding author. E-mail: [email protected]

They help in the production of detrital organic matter and recycling of nutrients, thereby enriching the coastal waters to support marine benthic production. In particular, those in the mangrove environment play an important role in the food web by recycling of detritus (Camilleri and Ribi 1986). Their community structure and composition are controlled by predation and disturbance by deposit feeders like crabs, gastropods and other macrobenthos (Dye and Lasiak 1986; Wilson 1991). Riverine nutrient discharge may stimulate primary production, and also increase the amount of deposited organic material (Deegan et al. 1986; Nixon et al. 1986). The abundance and biomass of benthic infauna can increase when nutrient loading from river inputs is transformed into food (Montagna and Yoon 1991; Montagna et al. 2002; Semprucci et al. 2010). In return, their abundance is reduced, altering the vertical disturbance in sediments (Hedqvist – Jhonson and Andre, 1991; Coull et al. 1995). Furthermore, exposure time, desiccation, food availability, sediment granulometry, tidal zonation and interstitial water quality are all physical parameters that regulate the abundance of meiofauna, which is highly sensitive to environmental changes. Among these, Nematodes and Foraminiferans are two key groups act as ecosystem bioindicators (Geetanjali et al. 2001; Schafer 1970). The structure of meiofaunal communities in mangrove habitats have been thoroughly investigated in subtropical continents of the world (e.g. Hopper et al. 1973; Decraemer and Coomans 1978; Hodda and Nicholas 1985; Dye 1983. However, there is a paucity of data on meiofauna community structure in India (Ansari et al. 1993; Rao and Sarma 1994) Hence the aim of the present study was study the community composition, density, richness, evenness and

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diversity of meiofauna of Muthupettai mangroves and adjacent open sea.

2. Materials and Methods Environmental parameters such as temperature, salinity, dissolved oxygen and pH were analyzed following the methods of Strickland and Parsons (1972). A mangrove forest and its adjacent open sea area were chosen for this study. The sites were selected based on their proximities to the open sea (10o20'19.71N, 79o30'50.25E) and the mangrove creek (10o20'49.68N 79o32'13.23E) (Fig. 1). The open sea samples of fauna were collected using a Peterson grab with sampling area of 0.08 m2. Sampling of the mangrove area was conducted at high, mid and low tidal levels in a line transect that ran perpendicular to the water front. While sampling, tree roots, crab holes and mounts were avoided. In each tidal level, triplicate sampling was carried out within a 10-meter2 quadrate. The samples were collected using a 15 cm long core sampler with a diameter of 3.8 cm and sharpened at one end to form a cutting edge. A cork

piston was introduced in the lower end of the tube and the core extruded. On retrieval, the corers were sliced immediately at the length of 3 cm, 6 cm and 9 cm, and each slice was placed separately in small polythene bags and stored in iceboxes. The collected samples were brought to the laboratory and sieved through a 62 mesh sieve. Organisms retained on the sieve were preserved in 5% neutralized formalin and stained with Rose Bengal for easy sorting. Biodiversity indices such as species diversity, richness and evenness were calculated following standard formulae (Shannon and Weaver 1949; Gleason 1922 and Pielou 1966). Sediment texture was analysed to size fraction analysis following the procedure of Udden (1914), later modified by Wentworth (1992). Samples weighing 100 g was taken and sieved through a 62 mesh sieve to separate the mud and clay. Mud and clay were then separated using the pipette method, as described by Lindholm (1987). Statistical analyses and comparative inferences were conducted using various techniques including Margalef’s species richness (d), Shannon– Wiener diversity (H’ log2), Pielou’s evenness (J’), k-dominance curve and Bray–Curtis similarity treatment.

3. Result

Fig. 1. Map showing the study area

The open sea and mangrove creek surface water temperatures varied from 23.5oC to 31.8oC (Fig. 2). Salinity varied from 24 to 34 ppt (Fig. 3), while pH fluctuated from 7.4 to 8.3 (Fig. 4). Dissolved oxygen concentration ranged from 3.86 to 5.33 mg/l (Fig. 5). The water temperature maximum was recorded during summer and minimum during monsoon in the study site. The percentage composition of open sea sand fluctuated between 88.73 and 98.88%. The minimum (88.73%) was observed during monsoon (October 2006) and maximum (98.88%) recorded post monsoon (March

Fig. 2. Seasonal variations of temperature recorded from stations 1 and 2

Benthic meiofaunal composition

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Fig. 3. Seasonal variations of salinity recorded from stations 1 and 2

Fig. 4. Seasonal variations of pH recorded from stations 1 and 2

Fig. 5. Seasonal variations of dissolved oxygen recorded from stations 1 and 2

2007). The silt and clay contents were observed to be high during winter, whereas high percentage of silt was only observed during monsoon. Relatively high percentage of silt and clay were observed during post monsoon and summer, and low percentage of sand was recorded in the open sea (Fig. 6). The percentage composition of clay in the mangrove area fluctuated between 90.26 and 99.72%. The minimum (90.26%) was observed during monsoon (October 2006) and maximum (99.72%) recorded during summer (June 2007). The silt and clay contents were observed to be high during summer and monsoon, whereas high percentage of silt was only observed during monsoon. Relatively high

percentage silt and clay were observed during post monsoon and summer, and low percentage of sand was also recorded in mangrove forest (Fig. 7). Total of 106 meiobenthic species were recorded in open sea and mangrove forest. From the 106 species identified 56 were foraminiferans, 20 nematodes, 7 harpacticoid copepods, 4 ostrocodes, 2 rotifers, while groups such as ciliophora, cnidaria, gnathostomulida, insecta, propulida, bryozoa and polychaete larvae were each represented by a single species. The open sea and mangrove forest meiofuanal percentage composition of foraminiferans ranged from 51.67% to 96.866%, nematodes varied between 1.39% and 1.625,

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Fig. 6. Percentage composition of soil texture in station 1

Fig. 7. Percentage composition of soil texture in station 2

ostracodes varied from 1.12 to 1.19%, harpactcoid copepods ranged from 0.27% to 0.22 at both stations, cumacea varied between 0.02% and 0.24%, tanaidacea ranged from 0.03% to 0.02%, turbularia varied from 0.02% at open sea and mangrove forest, cladocera varied between 0.005% to 0.0165, cnidaria ranged from 0.01% to 0.024%, and polychaete larvae varied between 0.014% to 0.09%. The following group of organisms were only found in the mangrove forest: gnathostomulida (0.008%), propulida (0.008%), bryozoa (0.007%), insecta (0.001%), and ciliophora (0.005%). Meiofaunal density varied between 12029 and 23493 individuals 10 cm /m2. Comparatively, species density in the open sea was higher than the mangrove creek. The twoway ANOVA showed significant variations between seasons (p < 0.05) and stations (p < 0.05). Population density values between the two stations were positively correlated. (r = 0.9411; p >0.001). Foraminifera were the dominant group in terms of abundance and density. The Maximum percentage

in the mangrove area might be due to highly favorable prevailing conditions in this site. The dominant foraminifera in the present study were Cyclammina cancellata, Cibicides sp. Pseudoungeriana sp., Discorbis glabularis, Discorbis sp., Textularia sp., Triloculina sp., Spirillina limbata, Lagena marginata-perforata, Globigerinoides sp., Globigerina sp., Planorbulinella sp., Bolivina abbreviata, Nonion depressulum, Cyclammina sp., Cibicides sp., Rosalina globularis, Hauerina sp., Eponides sp., Ammonia beccari, Neoconorbina sp., Astroratalia trispinosa, Quiqueloculina sp., and Spiroloculina sp. Nematodes were the second dominant group comprised of 20 species. Of these, Daptonema conicum, Theristus sp., Viscosia sp., Oxystomina sp., and Halalaimus sp. were found to be dominant in both study areas. The other groups recorded both in open sea and mangrove area were allogromids, gnathostomulids, ostracods, harpactiocoid copepods, rotifers, cnidarians, turbullarians, tanaidaceans, and polychaete larvae in meager numbers. The Shannon

Table 1. Benthic species diversities, richness and evenness at stations 1 and 2 between 2006 and 2007 Station I Station II Parameters Mon Post mon Summer Premon Mon Post mon Summer Diversity 3.734 3.766 3.801 3.748 3.943 3.988 4.007 Richness 0.854 0.859 0.870 0.857 0.854 0.858 0.864 Evenness 0.970 0.971 0.973 0.970 0.976 0.977 0.978

Premon 3.967 0.863 0.977


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Fig. 8. k-Dominance curves for species abundance data in relation to season in station 1

Fig. 9. k-Dominance curves for species abundance data in relation to season in station 2

Diversity Index (H) values varied from 3.515 to 3.680 in both the open sea and mangrove area. Among the two study sites, maximum diversity index was observed in the mangrove creek, followed by open sea (Table 1). The twoway ANOVA showed significant difference between sites (p < 0.05) but not between seasons. The recorded diversity values between the two study sites are positively correlated. (r = 0.1648; p < 0.1). Multiple kdominance plots facilitated the discrimination of meiobenthos according to speciesrelative contribution to standard stock. The kdominance

plot was also plotted for the seasons (Fig. 8), with the curve not showing much difference between seasons. All the seasons indicated moderate diversity, whereas the curve for the monsoon season showed the lowest diversity in station I, which was lying high (Fig. 8). The k-dominance plot for station II (Fig. 9) shows the highest diversity in all the seasons. Classification analyses (using Bray–Curtis similarity) followed from the resulting dendrogram (Fig. 10 & 11), which was not possible to classify the results according to species, but it was possible for seasons. The station I summer

Fig. 10. Dendrogram showing meiofauna grouping of station 1 during different seasons

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Fig. 11. Dendrogram showing meiofauna grouping of station 2 during different seasons

season showed separation from the remaining samples and station II monsoon season showed separation from other samples.

4. Discussion Environmental factors such as temperature, sediment granulometry and inundation are the main factors influencing the distribution of meiofaunal communities in tropical mangroves (Alongi 1987). Environmental parameters in which a species is exposed have significant impact on its physiology, distribution and population density (Ingole and Parulecar 1998). Temperature is considered to be an important factor controlling meiofaunal density and distribution in the present study since it fluctuated highly with seasonal changes compared to other parameters. The study area was subjected to a wide range of temperature fluctuation (23.5 oC-31.8 oC) which might be the reason for higher density in early post monsoon and low density during monsoon. Kameswara Rao and Balasubramanian (1996), and Ansari and Parulekar (1998), found that the a temperature range of between 20 oC and 35 oC was suitable for high abundance of foraminifera. The high population density of ostracodes recorded in summer indicates favourability towards high temperatures in the present study. Hussain et al. (1996) reported the ostracod population density was higher during elavated temperatures in April. This is normally

attributed to the monsoonal changes in environmental variables (Sunitha Rao and Rama Sarma, 1990; Chandran 1987; Ramana Murty and Kondala Rao 1987). The sediment composition of the study area revealed that sand, silt and clay composition were predominant in the mangrove area, while sand fraction predominated in the open sea. Weak tidal currents, sheltered environment and low energy condition allowed settlement of finer particles in the open sea. Sethukuda, positioned in the creek mouth experiences disturbances by tides and waves, and as such is a high energy environment causing deposition of coarse sediment. Similar findings have been reported earlier by Badarudeen et al. (1996) in the Kumarakam mangrove area, and Chanda et al. (1996) in the Mandovi estuary of West coast of India. Sediment textural analysis showed a strong seasonal variation. Silty sand content was low and clay increased in the open sea in 2006. This may be due to the removal of finer fractions by strong tidal currents and waves created by the cyclonic storm of 2007. Similar observation was made earlier in Tellichery mangroves by Reghunadh et al. (1995). In the mangrove area of this study, there was no change in sediment texture and prevailing high-energy environment enriched the deposition of sand alone. The harpacticod copepods, though observed throughout the year, were abundant only in post monsoon in the present study. Temperature may trigger or terminate reproductive


activities of harpacticoid copepods and determine the development time (Harris 1972). Generally higher ambient temperature results in shore development times for harpacticoid copepods (Nikolas et al. 1991). However, Rao and Sarama (1994) pointed out the harpacticoid copepods densities were reduced during low salinity. This study corroborates the result of the present study where high salinity was observed in the summer which might have supported the high harpacticoid copepods density. However. high pH and low concentration of dissolved oxygen in pre monsoon might also have affected the benthic meiofaunal abundance and diversity. Benthic meiofaunal assemblages recorded were foraminiferans, nematodes, harpacticoid copepods, ostracods, gnathostomulids, turbullarians, cumacea, cnidaria, propulida, rotifera and polychaete larvae. Similar faunal occurrence has been reported earlier in tropical mangrove regions and other parks of India. Sarma and Wilsanand (1994) reported nematodes, harpacticoid copepods, polychaete larvae, kinorhyncha, solenogester, foraminifera, ostracoda, oligochaetes, planaria, and tanaidacea in Shitarkarika mangrove of East coast India. Likewise, Kondala Rao and Ramanamurty (1998) studied the similar faunal in Kakinada Bay, Gautami Godavari estuarine system, East coast of India. Reports similar to this are, by Ingole et al. (1987) in Saphala salt marsh of India, by Ingole and Parulekar (1998) in Siridao beach, West Coast of India, and by Jan Schrijrers (1996) in Gazi bay of Kenya. Sasekumar (1994) reported that nematodes, harpacticoid copepods, oligochaeta, and kinorhyncha were dominant meiofauna in tropical mangroves. It can thus be concluded that mangrove habitat is highly supportive of meiofaunal assemblages even in temperate region with challenging environmental characteristics. Foraminifera were the dominant group in the present study in terms of abundance and density. The percentage composition of foraminifera in the two stations varied from 30 to 70%. The maximum percentage in the mangrove creek might have been due to highly favorable prevailing conditions. The dominant foraminifera in the present study were Cyclammina cancellata, Cibicides sp., Psuedoungeriana sp., Discorbis glabularis, Discorbis sp., Textularia sp., Triloculina sp., Spirillina limbata, Lagena marginataperforata, and Globigerinoides sp. Nigam and Chaturvedi (2000) investigated the foraminifera of Kharo creek, Kachchh, reported 47 species out of which 44 were benthic. Among them, Cibicides sp., Quinqueloculina sp., Triloculina sp., Lagena sp., Globigerinoides, and Spiroloculina sp.

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were recorded in the present study, such as Triloculina oblonga, Trochammina inflate, and Quinqueloculina sp., which were also reported in Cochin estuary (Kameswara Rao and Balasubramanian 1996). They identified 78 foraminiferal species that were all benthic. Comparison of these studies with the present one show that few species are found commonly distributed along the West coast of India? and tend to cope with wide fluctuations in environmental variables. Nematodes were the second dominant group comprising of 20 species. Of these, Daptonema conicum, Theristus sp., Viscosia sp., Oxystomina sp., and Halalaimus sp. were found to be dominant. Similar to the present observations, dominance of Riscosia sp., Daptonema conicum, and Halalaimus gracilis in Malaysian mangrove (Sasekumar 1994), Gazi bay (Jan schrijvers 1996) and Pichavaram mangroves, South East coast of India (Sultan Ali 1983) revealed that it might be a common species with cosmopolitan distribution. Ansari and Parulekar (1998) reported that nematodes were the most dominant group in the Zuari estuary, Goa, West coast of India. Maximum percentage composition observed in our two stations in early winter may be due to enrichment of organic materials. The other groups recorded in the present study were allogromids, gnathostomulids, ostracods, harpactiocoid copepods, rotifers, cnidarians, turbullarians, tanaidaceans, and polychaete larvae, which were recorded in meager numbers. Similar reports of mangrove environments are from Malaysia (Sasekuma 1994), Bhitarkanika mangroves, East coast of India (Sarma and Wilsanand 1994), Siridao, India (Ingole and Parulekar, 1998), Kakinada bay, India (Kondalo Rao and Ramanamurty, 1988) and Pichavaram mangroves, South East coast of India (Chinnadurai 2001). Alongi (1989) recorded a mean total meiofaunal density of 1000 to 3000 individual 10 cm2 for most mangrove sites. Nevertheless several studies that dealt with mangrove sediments contained higher density. For example Kandala Rao (1988) indicated about 2130 individual 10 cm2 in Kakinada Bay, Nicholas et al. (1991) counted up to 5000 individual 10 cm2, with maximum 6101 individual 10 cm2 in Gazi Bay, Kenya. In Pichavaram, density ranging from 44 to 2983 individual 10 cm2 was reported by Chinnadurai (2001). Sasekumar (1994) reported the high mean density of 1109 individual 10 cm2 found in the Avicennia sp. forest station. In the present study, the open sea recorded 1020 to 8020 individual 10 cm2 and the mangrove area had 1372 to 9228 10 cm2. Lower density values obtained here may be due to the prevailing arid

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climate in the study area. Species diversity is a simple and useful measure of a biological system. Sanders (1968) and Redding and Cory (1975) found a high level of agreement between species diversity and the nature of the environment and, hence, regarded the measure of species diversity as an ecologically powerful tool. Moreover, Pearson and Rosenberg (1978) proposed that the use of diversity indices is advantageous for the description of faunas at different stages of succession. Sanders (1968) postulated that species diversity is mainly controlled by fluctuations in the environment which lead to less diversity. Species diversity in the present study recorded a minimal fluctuation of between 3.734 (monsoon) and 3.801 (summer) between stations and seasons. The pattern of lower species diversity during monsoon and higher diversity values in summer recorded in the study area is in conformity with the earlier observations made in Vellar (Chandran 1987) and Coleroon estuaries (Devi 1994). In this study, richness of benthic macro-fauna was at maximum during the post-monsoon season (0.870). Similar observation was reported in the Sundarban mangrove by Parulekar et al. (1980). The low richness recorded in this study during monsoon (0.854) might be due to riverine freshwater outflow which induces low saline conditions, which in turn affects the distribution of meiobenthos. Maximum diversity and richness recorded during summer at the study sites might be due to stable environmental factors, such as salinity, which play an important role in faunal distribution. Shillbeer and Tapp (1989) stated that the mangrove environment is far more dynamic than the marine environment. Hence, a wider range of temporal variation in the diversity of meiobenthos, as recorded in the study area, could be naturally expected. Sheltered regions with muddy sediments rich in detritus generally are characterized by high meiofaunal densities (Heip et al. 1985; Coull 1988; Giere et al. 1988, Chimadurai and Ferando 2003). The composition of meiofauna in areas with different mangrove cover is apparently related to grain size, and probably to some extent with oxygen condition. Sediment with higher silt and clay content is a characteristic feature in areas with Avicennia marina which covers mainly inhabitation by burrowers such as nematodes and higher density meiofauna. Sediments with a median particle size smaller than 125 mm are usually dominated by burrowers (Coull 1988). Sanders (1958) and Wieser (1960) observed that fine/mud sediment with large amounts of detritus support rich meiofauna densities. Kondalarao and Ramanamurthy

(1988) reported that clayed silt sediment of mangroves supported high population densities of meiofauna. The present study concludes that, the open sea region is more enriched in nutrients and benthic organisms compared to the Sethukuda mangrove creek. This is based on the fact that Avicennia marina is the predominant species in the mangrove area, which determines the particles size present in the sediment, mainly inhabiting burrowers such as nematodes and higher density of meiofauna.

Acknowledgement We thank the Director and Dean, Faculty of Marine sciences, Annamalai University for providing facilities. The authors acknowledge financial assistance from Sethusumathram Canal project and MOES, Government of India.

References Alongi DM (1987) Inter estuary variation and intertidal zonation of the free-living nematode communities in tropical mangrove systems. Mar Ecol Prog Ser 40:103-114 Alongi DM (1989) Ecology of tropical soft-bottom benthos: a review with emphasis on emerging concepts. Rev Biol Trop 37(1):85-100 Ansari ZA, Parulekar AH (1998) Community structure of meiobenthos from a tropical estuary. Indian J Mar Sci 27:362-366 Ansari ZA, Parulekar AH (1998) Community structure of meiobenthos from a tropical estuary. Indian J Mar Sci 27:362-366 Ansari ZA, Gauns MV (1996) A quantitative analysis of the fine scale distribution of intertidal meiofauna in response to food resources. Indian J Mar Sci 25:259-263 Ansari ZA, Sreepada PA, Matondka SGP, Parulekar AH (1993) Meiofaunal stratification in relation to microbial food in a tropical mangrove mudflat. Trop Ecol 34 (2):63-75 Badarudeen A, Damodaran KT, Sajan K, Padmalal D (1996) Texture and geochemistry of the sediments of a tropical mangrove ecosysted, southwest coast of India. Environ Geol 27:164-169 Camilleri JC, Ribi G (1986) Leaching of dissolved organic carbon (DOC) from dead leaves, formation of flakes from DOC and feeding on flakes by crustaceans in mangroves. Mar Biol 91:337-344 Chandra MN, Shirodkar PV, Singbal SYS (1996) Studies on organic carbon, nitrogen and phosphorus in the sediments of Mandovi estuary, Goa, India. J Mar Sci 25:120-124 Chandran R (1987) Hydrobiological studies in the gradient zone of the Vellar estuary, IV. Benthic fauna. Mahasagar 20(1):1133


Chinnadurai G, Fernando OJ (2006). Meiobenthos of Cochin mangroves (Southwest coast of India) with emphasis on freeliving marine nematode assemblages. Russian J Nematol 14(2):127-137 Chinnadurai G (2001) Meiofauna of Pitchavaram mangrove, southeast coast of India. MS Thesis, Annamalai University, India, 85 p Coull BC (1990) A member of the meiofauna food for higher t rophic levels? Trans Am Microsc Soc 109:233-246 Coull BC, Greenwood JG, Fielder DR, Coull BA (1995) Sub tropical Australian juvenile fish eat meiofauna: experiments with winter whiting sillago maculata and observations on other species. Mar Ecol Prog Ser 125:13-19 Decraemer W, Coomans A (1978) Scientific report on the Beigian expedition to the Great Barrier Reef in 1967. Nematodes, 13. A description of four known species from in and around mangroves on Lizard Island. Aust J Mar Freshwat Res 29:509-541 Devi LP (1994) Ecology of Coleroon estuary: Studies on benthic fauna. J Mar Biol Ass India 36(1-2):260-266 Doan C, Thanh NV (2000) Free living nematodes at the brackish water estuary of the Thi Vai river (Dong Naiprovince). J Biol 22:6-9 Dye AH, Lasiak T (1986) Microbenthos, meiobenthos and fiddler crabs: trophic sediment tropical mangrove sediment. Mar Ecol Prog Ser 32:259-264 Dye AH (1983) Composition and seasonal fluctuations of meiofauna in a southern African mangrove estuary. Mar Biol 73:165-170 Geetanjali, Malhotra SK, Malhotra A, Ansari Z, Chatterji A (2001) Role of nematodes as bio indicators in marine and freshwater habitats. Curr Sci 82(5):505-507 Gleason HA (1922) On the relation between species and area. Ecology 3:156-162 Harris RP (1972) Reproductive activity of the interstitial copepods of a sandy beach. J Mar Biol Ass UK 52:597-624 Hedqvist-Johnson K, Andre C (1991) The impact of the brown shrimp, Crangon crangon. on soft bottom meiofauna: an experimental approach. Ophelia 34:41-49 Hodda M, Nicholas WL (1985) Meiofauna Associated with Mangroves in the Hunter River Estuary and Fullerton Cove, South-eastern Australia. Aust J Mar Freshwat Res 36:41-50 Hopper BE, Fell JW, Cefalu RC (1973) Effect of temperature on life cycles of nematode associated with mangrove (Rhizophora mangle) detrital system. Mar Biol 23:293-296 Hussain SM, Ragothaman V, Manivannan V (1996) Distribution of ostracoda in waters off Tuticorin, southeast coast of India. Indian J Mar Sci 25:78-80 Ingole BS, Parulekar AH (1998) Role of salinity in structuring the intertidal meiofauna of a tropical estuarine beach: field evidence. Indian J Mar Sci 27:356-361 Kameshwara RK, Balasubramanian T (1996) Distribution of

71

foraminifera in the Cochin estuary. J Mar Biol Ass India 38(1-2):50-57 Kondala RB, Ramanamurthy KV (1988) Ecology of intertidal meiofauna of the Kakin Bay (Gautam-Godavari Estuarine System), eastcoast of India. Indian J Mar Sci 17:40-47 Lai Phu Hoang LP, Thanh NV, Ulrich SP (2005) Preliminary investigating result about the meiobenthic invertebrates in Can Gio mangrove, Ho Chi Minh City. In: The 4th National Conference on Life Sciences, Hanoi State Medicine University, November 3, pp 169-172 Lindholm RC (1987) A practical approach to sedimentology. Allen and Unwin Inc 276 p Mc Gregor SB (1991) Seasonal and ontogenetic changes in meiofauns in the diets of post Metamorphic flatfish. MS Thesis, University of Alasks, Fairbanks, 78 p Nguyen DT (2004) Biodiversity of nematodes in Ha Long Bay, Vietnam. MS Thesis, Ghent University, Belgium, 75 p Nicholas WL, Elek JA, Stewart AC, Marples TG (1991) The nematode fauna of a temperate Australian mangrove mudflat: its population density, diversity and distribution. Hydrobiologia 209:13-27 Nigam R, Chaturvedi SK (2000) Foraminiferans study from Kharo creek, Kachchh (Gujarat), North west coast of India. Indian J Mar Sci 29:133-138 Ólafsson E (2000) Meiobenthos of hypersaline tropical mangrove sediment in relation to spring tide inundation. Hydrobiologia 426:57-64 Parulekar AH, Dhargalkar VK, Singbal SYS (1980) Benthic studies in Goa estuaries. Part III. Annual cycle of macrofaunal distribution, production and trophic relations. Indian J Mar Sci 9:189-200 Pearson TH, Rosenberg R (1978) Macrobenthos secession in relation to organic enrichment and pollution of the marine environment. Oceanogr Mar Biol Ann Rev 16:229-234 Pielou EC (1966) The measurement of diversity in different types of biological collection. J Theor Biol 13:131-144 Ramana Murty KV, Kondalarao B (1987) Survey of meiofauna in the Gautami odavari estuary. J Mar Biol Ass India 29(12):37-44 Rao DG, Sarma ALN (1994) Seasonal abundance and breeding cycles of meiobenthic Copepods at Parikud island in Chilka lagoon (Bay of Bengal). Indian J Mar Sci 23:217-220 Redding JM, Cory RL (1975) Macroscopic benthic fauna of three tidal creeks adjoining the Rhode river, Maryland. Water Resources Investigation Report, USA, pp 39-75 Reghunadh K, Sushadevi KP, Sajan K (1995) Texture of Tellicherry mangrove sediments, southeast coast of India. Indian J Mar Sci 24:91-93 Sanders HL (1968) Marine benthic diversity: a comparative study. Am Naturalist 102:243-282 Sarma ALN, Wilsanand V (1994) Littoral meiofauna of Bhitarkanika

72


mangrove of river Mahanadi system, eastcoast of India. Indian J Mar Sci 23(4):221-224 Sarma ALN, Wilsanand V (1996) Meiofauna of the outer channel of Chilka logoon, Bay of Bengal. Indian J Mar Sci 25:302-306 Sasekumar A (1994) Meiofauna of a mangrove shore on the west coast of peninsular Malaysia. Raffles Bull Zool 42:901-915 Schafer CT (1970) Studies of benthic foraminifera in the Restigarche estuary: faunal distribution pattern near pollution sources. Maritime Sediments 6:121-134 Schrijvers J (1996) Meiobenthos of Ceriops and Rhizophora mangroves at Gazi bay, Kenya: human impact. Academia Analecta 58(1):97-114. Shannon CE, Weaver W (1949) The Mathematical Theory of Communication. University of Illinois Press, Urbana, 117 p Shillbeer N, Tapp JF (1989) Improvements in the benthic fauna of the Tees estuary after a period of reduced pollution loadings. Mar Pollut Bull 20(3):119-123

Strickland JDH, Parsons TR (1972) A practical hand book of seawater analysis. Bull. Fisheries Research Board of Canada, 167 p Sultan Ali MA, Krishnamurthy K, Prince Jeyaseelsn MJ (1983) Energy flow through the benthic ecosystem of the mangroves with special reference to nematodes. Mahasagar 16(3):317325 Sunitha RG, Rama Sarma DV(1990) Meiobenthos of Gothavari estuary. Indian J Mar Sci 19:171-173 Thanh NV, Gagarin VG (2004) New species of the genera Chronogaster (Araeolaimida: Chronogasteridae) from Vietnam (Nematoda). Zoosystematica Rossica, 12:145-149 Wentworth CK (1992) A scale of grade and clastic sediments. J Geol 30:377-392 Wilson WH (1991) Competition and predation in marine soft sediment communities. Ann Rev Ecol Syst 21:221-241