Rev. Biol. Trop., 49(2): 535-544, 2001 www.ucr.ac.cr www.ots.ac.cr www.ots.duke.edu

Abondance and distribution of small infauna in mangroves of Missionary Bay, North Queensland, Australia

Sabine Dittmann Zentrom fUr Marine Tropenökologie, Fahrenheitstr. 1, 28359 Bremen, Germany. Fax +49-421-2208 330; sdittmann @uni-bremen.de

Received 21-ffi-2000. Corrected 10-X-2000. Accepted 10-X-2000.

Abstract: To assess the occurrence, spatial distribution and species composition of small infauna on a mangrove shore, core samples were taken along a transeet in Missionary Bay at Hinchinbrook Island, north-east Australia. Three sites were arranged within the mangrove forest and one site was located in an adjacent mudflat The sites were surveyed four times between November 1988 and October 1989. Basedon the records from all samples and sites, 39 taxa were identified. Diversity (H') ranged from 1.18 to 2.~~- Overall, total abondances of small infauna (retained on a 0.25 mm sieve) reached a mean value of 5 477 ind. m , with little varlation throughout the transeet or over time. Species numbers and diversity were higher in the mudflat than at the mangrove sites. The taxonomie composition changed between the mangrove forest and the mudflat: Oligochaeta were more abundant in mangrove sediments, whereas Polychaeta dominaled in the mudflat Of the polychaetes, Capitellidae were almost restricted to the mangrove sites, Sabellidae were recorded frequently at all sites, and Sigambra parva and Myriochele sp. were confined to the mudflat and the mangrove fringe. These species accounted also for · dissimilarities between sites. Multivariate analyses showed a distinct assemblage at the mudflat compared to the mangrove sites. This survey showed that smal! infauna is an abundant component of mangrove sediments, which has been previously underestimated.

Key words: Mangroves, benthic community, infauna, macrobenthos.

Traditionally, the fauna of marine sediments quantified by the use of sieves, and second by is classified into meio- and macrofauna by the the abundance and diversity of infauna use of defmed sieve sizes, whereby or-ganisms intermediate in size between meio- and retained on a 0.5 or 1 mm mesh sieve are refered macrofauna, the so-called "mesofauna" to as macrofauna (Rees 1940, Mare 1942, (Dittmann 1995). Alongi (1989) also put Mclntyre 1969, Rees 1984, Bachelet 1990, forward a concept of a high proportion of Schlacher and Woolridge 1996). Schwinghamer opportunistic, small-sized species in tropical (1981, 1983) bas shown that the distribution of infaunal assemblages. biomass among different size classes of bentbic In mangroves, epibentbic species dominate organisms is a conservative structural feature the macrofauna. Crustaceans and gastropods and relates to pre-dominant life-styles of the size are especially abundant and rich in species groups for microbes, meio- and macrofauna. In (Macnae and Kalk 1962, Macnae 1967, 1968, tropical tidal flats, however, the size range of Sasekumar 1974, Frith et al. 1976, Alongi and bentbic fauna deviates in two ways from the Sasekumar 1992, Guerreiro et al. 1996) and scheme developed by Schwinghamer. First, the mangrove crabs play an essenrial role for leaf abundance of megabenthos, which can not be litter degradation in these systems (Robertson 536 REVISTA DE BIOLOGIA TROPICAL

1986, Micheli, 1993). Meiofauna, on the other elevated part of the mangrove peninsula, about Sample! hand, occurs in low abundances in mangrove halfway along the boardwalk. The mangrove and in 19891 sectimeuts (Alongi 1987a, b, c). Further infaunal canopy was thin bere so that more light reached The mudflat components of mangrove sediments were often the sediment, which was a dry and frrm mud rich November 1 recorded in a qualitative way only or with the in mangrove detritus. Site III was ca. 10 m every sampli use of a 1mm sieve size. Small-sized infauna beyoud the end of the boardwalk. Here, the were taken had not yet been studied in mangrove sediments. sediment was rather soft mud. Site IV was samples frorr These organisms could play an important role in located in a mudflat seaward of the mangrove with piston " the food web of mangrove ecosystems, as small fringe. At this site, the sediment was knee-deep surface area macrofauna can constitute a major food souree mud which also contained shell fragments. extracted to . for juvenile fish and prawns, which use Mudwhelks (mainly Cerithidea cingulata) and were necessru mangroves as nursery sites (Robertson 1988, Theodoxus oualaniensis were abundant on the crab burrows Daniel and Robertsou 1990). Therefore, sediment surface of the mudflat The samples were abundance and distribution of small-sized macrofauna in the mangrove forest was assess the ! infauna were surveyed in mangrove and dominated by sesarmid crabs (Robertson 1986, (mesofauna St adjacent tictal flat sediments. Mieheli 1993). The forest consisted of several he lost by The study sites were arranged along a Rhizophora spp. and Brugiera gymnorrhiza, traditionally transect, as earlier studies on mangrove fauna Ceriops tagal co-occurred at the more elevated (see also Ba have shown clear zonation pattems in relation to site andAvicennia marina grew on the mangrove Woolridge 1S tictal elevation, forest type and sediment fringe towards the mudflat Detailed accounts on size). The aniJ properties (Macnae and Kalk 1962, Sasekumar this mangrove area and environmental under a dissf 1974, Frith et al. 1976, Wells 1983). These parameters of the studied sites are available from contained ma surveys crossed through mangroves into ambient Alongi (1987a, 1988), Boto and Wellington detritus, wh sand- and mudflats and generally showed lower (1984) and Boto et al. (1989). cumbersome. densities and species numbers in mangroves than always record tictal flat sediments (s~e Alongi 1989 and Alongi the lowest 1 and Sasekumar 1992 for further references). polychaetes, g1 Only Frith et al. (1976) found more species in a while most g1 mangrove than mudflat and Schrijvers et al. level with few (1995a) recorded higher macrobentbic densities nemertilles cm in mangrove than sandflat sediments. This study Species presents the fust quantitative records of small­ calculated by t sized infauna from mangrove sediments. 1948). To tes abundances b months, Krusk MATERIALS AND METHOOS Wilcoxon, Ma (Sachs 1992). ~ The study was carried out in the mangroves out using the P of Missionary Bay at Hinchinbrook Island Plymouth Mar (18°13'S; 146°11 'E), North Queensland, (Bray-Curtis si Australia. Four transeet sites were arranged along were made on the boardwalk of the Australian Institute of data in sear Marine Science at Coral Creek (Fig. 1), covering 0 2 I E-=1 Differences in a distance of about 500 m. Site I was ca. 10 m Km tested with ANC inside the forest from Coral Creek. This site was sample groupin frequently inundated and the sediment black and (Clarke 1993). solid mud. The secoud and third sites lay further Fig. I. Location of the study area in Missionary Bay, Hinchinbrook Island, North Queensland. The start (site I) and within the mangrove forest Site II was on a more end point (site IV) of the transeet are indicated in the map. INTERNATIONAL JOURNALOF TROPICAL BIOLOGY AND CONSERVATION 537

1sula, about Samples were taken on 17 November 1988 RESULTS : mangrove and in 1989 on 3 May, 2 August and 13 October. ght reached The mudflat site IV could not be sampled in Species: Based on the records from all mmudrich November 1988 due to the incorning tide. At samples and sites, 39 taxa were distinguished ca. 10 m every sampling occasion, six replicate samples during this survey, with polychaetes richest Here, the were taken at each site. To extract sediment in species ( 19), foliowed by gastropods (9). te IV was samples from the mud, a cut oti syringe (50ml) Species numbers differed between transeet mangrove with piston was used as a corer. This corer had a sites and most species were recorded in the knee-deep surface area of 6.61 cm·2 and sediment was mudflat (Table 1). Diversity was higher at the fragments. extracted to 5 cm depth. Usually several trials mudflat site than in the mangroves, with ulata) and were necessary to get an entire sediment core, as lowest diversity at site 11. On average, only ant on the crab burrows were often hit with the corer. The two species were found per sample and t1at. The samples were sieved over 0.25 mm mesh size to species densities were low at all sites (Table 1rest was assess the small sized infaunal organisms 1). Species similarity was higher between the :son 1986, (mesofauna sensu Dittmann 1995), which would mangrove sites I, 11 and lil (QS values of of several be lost by the use of larger mesh sizes 0.43 to 0.5) than between the mudflat and morrhiza, traditionally taken for macrobentbic samples mangrove sites I and 11 (QS = 0.29 and 0.3 e elevated (see also Bachelet 1990 and Schlacher and resp.). However, the mudflat and the adjacent mangrove Woolridge 1996 for adequate choice of sieve mangrove site 111 were similar in their counts on size). The animals were sorted alive and counted species composition (QS = 0.46). onmental under a dissecting rnicroscope. The sediment Abondances and distribution: ablefrom contained many small particles of mangrove Abundances of small infauna rarely exceeded Tellington detritus, which made the sorting very 10 ind. 10 cm·2 along the studied transeet cumbersome. Distinguishable species were (Fig. 2). Extrapolating individual densities to always recorded separately and deterrnined to m·:Z (beware of high variations and unknown the lowest possible taxonomie level. For spatial distributions), the overall mean 2 polychaetes, genus or species could be identified, amounts to 5 477 ind m- , varying from 4 796 hlnbrook 2 sland while most gastropods were treated on farnily (site I) to 6 687 ind m· (site lil). level with few species named. Oligochaeta and There was little variation in abundances J nemertines could not be deterrnined further. over time at the single transeet sites (Fig. 2). :L Species similarity between sites was Only at site 11 abundances were significantly calculated by the S!llrensen Index QS (S!IIrensen higher (H-test, p<0.05) in May and August 1948). To test for significant ditierences in than in October, while at site IV abundances abundances between the sites and sampling were significantly higher (H-test, p<0.05) in months, Kruskal-Wallis H-test and the U-test by October than in May. Wilcoxon, Mann and Whitney were applied Comparing abundances of total infauna or (Sachs 1992). Multivariate analyses were carried major taxa at the single months revealed out using the PRIMER software package by the mainly significant differences between the Plymouth Marine Laboratory. Cluster analysis mangrove sites and the mudflat site, while few (Bray-Curtis sirnilarity, group-average linkage) significant differences occurred between were made on double square root transformed single mangrove sites (Table 2). Here, the only data in search of species assemblages. ditierences were recorded in relation to site 11. Ditierences in assemblages between sites were Most of the differences between mangrove and tested with ANOSIM and species discriminaring mudflat sites were due to abundances of sample groupings were analysed with SIMPER oligochaetes and polychaetes. uy Bay, (Clarke 1993). itei) and :map.

j l 538 REVISTA DE BIOLOGfA TROPICAL

TABLE 1 20 Abundance and diversity of sma/1 infauna in a mangrove forest, Missionary Bay.

site I site 11 site lil site IV 15 number of species total 13 11 17 22 10 Polychaeta 8 6 8 10 Gastropoda 3 3 2 4 diversity (H') 1.78 1.18 1.81 2.38 5 species density 1.83 (1.01) 1.5 (1.1) 2.33 (1.52) 2.28 (1.9) 0 Oligochaeta sp. 2 df 1. (46.1 %) 1. (71.4%) 1. (54.7%) 4. (6.6%) Capitella sp. 4 df 2. (15.8%) 4. (3.6%) 4. (5.7%) Capitellidae indet. df 3. (14.5%) 2. (8.3%) 4. (5.7%) 20 Heteromastus sp. df 4. (5.3%) < < < Leitosco/oplos sp. df 5. (4.0%) 5. (2.8%) < 15 Sabellidae indet. sf 3. (4.8%) 2. (8.5%) 3. (8.2%) Cerithidea cf anticipata g 4. (3.6%) < Insecta (mosquito larvae) c < 5. (2.4%) < 5. (3.3%) 10 Oligochaeta sp. 2 df 3. (6.6%) N Amphipoda indet. sdf 5. (2.8%) < ·a 5 Myriochele sp. sdf 1. (31.2%) u Sigambra parva 0 < 2. (21.3%) =""" 0 Holothuroidea indet. df 5. (3.3%) i 2 20 Species numbers, densities (species 6.61 cm· , meao and SD in brackets), diversity and most abundant species of small ~= infauna (0.25 mm sieve) at four sites along the transeet based on records from all sampling dates. Sites I to lil were located ....·;;: within the mangrove forest, while site IV lay in the adjacent mudflat Species taking the first five ranks of abundance at ~ 15 each site are listed with the respective percentages, sorted by rank order starting with site I. Note that several species share 1-1 ranks at some sites. - =species nol recorded at this site, <=species recorded, but ilbundances below rank 5. Trophic modes = (following Fauchald and Jumars 1979 for polychaetes) are indicated by df = subsurface deposit feeder, sdf = surface deposit 10 feeder, sf = suspension feeder, g = grazer, c = camivore, o = omnivore. 5

TABLE2 0 Differences between abundances of major taxa or total infauna at transeet sites. 20 1-11 1-111 11-111 I-IV 11-IV lii-IV 15 November 1988 total infauna ns ns * 10 Polychaeta * ns ns Oligochaeta ns ns * 5 May 1989 total infauna ** ns ns ns •• * Oligochaeta ** ns ns ns ** • 0 August 1989 Oligochaeta ns ns ns ** ** •• Fig. 2. Meao all October 1989 of small infau total infauna ns ns ns • • ns mangrove, IV Polychaeta ns ns ns • •• • Queensland. SaJ August and ()( November 1988 Significant U-test values at the transeet sites I - IV during the four sampling occasions. Sites I to lil were Iocated within the mangrove forest, while site IV lay in the adjacent mudflat • = p<0.05, ** = p<0.01, ns = not significant.-= site IV not sampled in November 1988. Based o total infaun Polychaeta oe INTENATIONAL JOURNALOF TROPICAL BIOLOGY AND CONSERVATION 539

20 highest abundances in the mudflat Oligochaeta Site I were mainly confined to the mangrove sites (Fig. 15 3). This is also reflected in the share of these taxa on the total individual numbers per site. 10 Polychaeta accounted for most of the individuals at the mudflat site, while Oligochaeta made up 5 46 to 71 % of the individuals at the mangrove sites (Fig. 4). Gastropoda recorded in the 0 infaunal samples occurred in almost the same abundance throughout the transeet Mosquito 20 larvae were recorded in the samples of all sites. Sitell Further taxa (nemertines, bivalves, amphipods, 15 ophiurids, holothurids, pycnogonids, acari) were restricted to the mangrove fringe (site ill) and the 10 adjacent mudflat N '5 5 15 CJ Total infauna =1""'4 0 i 10 nall 20 "CC= lied ·;; Sitem 5 e at .... "CC 15 •are des ~ osit 10 0

N 5 ·a 15 c:J Polycbaeta 0 =1""'4 10 20 ~ Site IV "CC ·;; 5 15 :a ...... = 10 0

5 15 Oligocbaeta 10 Nov. May Aug. Oct.

Fig. 2. Mean abundances and standani deviation (SD) (n=6) 5 of smal! infauna at the transeet sites (1-ill within the mangrove, IV in mudflat) in Missionary Bay, North Queensland. Sampling dates were November 1988 and May, 0 August and October 1989. Site IV was not sampled in November 1988. I 11 m IV Site Fig. 3. Mean abundances and SD (n=24 for mangrove sites I Based on the entire survey, abundances of to m, n=l8 for mudflat site IV) of smal! infauna along a total infauna did oot vary between sites. transeet through a mangrove forest in Misssionary Bay, based Polychaeta occurred throughout the transeet with on samples taken at four dates between November 1988 and October 1989 (see Fig. 2). 540 REVISTA DE BIOLOGfA TROPICAL

Multivariate analyses detected distinct %N 100 infaunal assemblages of mangrove and mudflat sites. The mangrove sites were similar to each The st 80 other, only site lil formed a defined cluster in small-sized November as did site I in October. The mudflat of bentbic f 60 site IV gave distinct clusters in the dendrograms differences 1 for May, August (Fig. 5) and October. With the sized infau 40 greater similarities between mangrove sites, the studies sho ANOSIM results (May: R=0.203, p=0.006, mangroves l 20 August: R=0.3I9, p=O.OOO; October: R=0.305, Species p=0.006) show only slightly greater similarities sites were Ie 0 Site I Site U Site III Site IV within than between sites. S. parva, Myriochele from other r sp., indetermined oligochaetes and polychaetes by Alongi a Fig. 4. Percentual share of major taxa on the total of the families Sabellidae and Capitellidae Choudhury individual number (N) of smal! infauna (0.25 mm sieve) contributed most to the dissimilarities between numbers o1 recorded at four transeet sites (1-III within mangrove the mudflat and mangrove sites. mangroves c forest, IV in an adjacent mudflat) between November 1988 and October 1989. in the tropie: August numbers (M IVe Reise I99I, Looking at single species, an oligochaete IVa species and species was most abundant at the mangrove lvb towards the IVe sites, while the first three ranks of abondance at Guerreiro et IVr trend is supp the mudflat site were taken by polychaetes mr along the t (Table I). Rank orders of abondance of species De differed at each site. The species taking the first me presented h five ranks Iisted in Table I comprised 94 % of or species and I the individuals at site 11, about 86 % at site I Ie and mudflat Ie and lil and 74 % at site IV, where the agreement w md remaining I6 species shared rank six. The first world(Day I lla Schrijvers et five ranks comprised only deposit feeders at Dia Theabu site I, but encompassed five different trophic lOb modes at site IV (Table I). Db bere are IO Within the polychaetes, distinct distribution Dd previous re patterns occurred along the transect. la mangrove Capitellidae were almost restricted to the lb Sasekumar De mangrove sites, where they accounted for 45 macroinfaun ld mangroves(! (site lil) to 82 % (site I) of polychaete me abondances, compared to 2 % in the mudflat lf however, Jo Sabellidae were recorded frequently at all sites. o. 10. 20. 30. 40. 50. 60. 70. 80. 90. 100. infauna in Sigambra parva (Pilargidae) occurred almost Bray-Curtls Slmllarlty Queensland exclusively in the mudflat, where it accounted wheremesof for 30 % of the polychaetes, and at site lil Fig. 5. Dendrogram of infaunal samples taken at four highest mac1 transeet sites (I-111 within mangrove forest, IV in an known for t1 nearby (7 %). Myriochele sp. (Oweniidae) was adjacent mudflat) in Missionary Bay in August 1989. The confined to the mudflat and accounted for 43 % letters a-f refer to replicate samples per site, sample IV d Thus, while of the polychaetes recorded bere. was omitted as it contained no individuals. than larget sediments, i recorded fror INTENATIONAL JOURNALOF TROPICAL BIOLOGY AND CONSERVATION 541 i net DISCUSSION The samples were taken at the beginning lflat (November 1988) and end (May 1989) of the :ach The survey presented here identified wet season and during the dry season (August :r in small-sized infauna as an abundant component and October 1989), but no temporal variations lflat of bentbic fauna in mangrove sediments. The relating to seasons were recorded. Abundances illllS differences in the spatial distribution of small­ were lower in October at the elevated the sized infauna further confirmed previous mangrove site 11, but higher at the mudflat site the studies showing a distinct macrofauna of in the same month compared to the other 106, mangroves and mudflats. sampling dates. Without further studies it will 105, Species numbers recorded at the transeet not be possible to relate this finding to any ties sites were low, but within the range of records seasonality in abundances or population 1ele from other mangroves and tidal flats compiled dynamics of species occurring at the respective ~tes by Alongi and Sasekumar (1992). Nandi and sites. Temporal variations in infaunal numbers dae Choudhury (1983) also found low species rarely showed consistent patterns with een numbers of macrofauna in mudflats near monsoon elimate (Nandi and Choudhury 1983, mangroves of the Sunderbans. Other tidal flats Alongi 1989, Alongi and Sasekumar 1992), in the tropics, however, have very high species although species-specific responses to dry and numbers (Macnae and Kalk 1962, Day 1974, wet seasons were reported by Vargas (1989, IVe Reise 1991, Dittmann 1995). The number of 1996) and Broom (1982). Daniel and IVa species and species diversity tends to increase Robertson (1990) related temporal differences Yb towards the lower intertidal (Vohra 1971, in epibenthos of mangrove waterways to Vc Guerreiro et al. 1996, Dittmann 2000). This hydragrapbic changes with the wet- and dry vr trend is supported by the distribution of species season. Alongi (1988) reported seasonal lU Ie along the transeet through the mangroves differences of microbial biomass, chlorophyll­ Ie presented here. The richness of polychaete a and further sediment factors in the low- and 11 species ~d their high species number in sand­ mid intertirlal region of the study site in and mudflats adjacent to mangroves are in Missionary Bay. Thus, the availability of food agreement with records from other parts of the for small-sized infauna could have varied over ld world (Day 1974, Frith et al. 1976, Wells 1983, the year at the different transeet sites. I Schrijvers et al. 1995a. Guerreiro et al. 1996). Several factors have been proposed to la lb The abundances of small infauna recorded regulate infaunal densities in mangrove b here are 10 to over 60 times higher than sediments: physical farces, competition with d previous records of macrobenthos from epifauna, predation by epifauna, poor quality mangrove sediments (see Alongi and of food and chemical defense by mangroves Sasekumar 1992) and only camparabie to (Alongi 1989, Alongi and Sasekumar 1992). macroinfaunal densities from East-African These factors could also account for the mangroves (Schrijvers et al. 1995a). They are, differences in spatial distribution and species c however, lower than abu;Qflances of small composition found along the transeet and are infauna in other tidal flis of the North discussed in the following. Queensland coast (Dittmann 1995, 2000), Sediment properties vary with tidal where mesofaunal abundances even exceed the elevation and forest type and thus affect the ~r highest macrobentbic abundances previously distribution of meio- and macrofauna in ID te known for tropical tidal flats (Vargas 1987). mangroves (Alongi 1987a, Guerreiro et al. d Thus, while small infauna is more abundant 1996). The oxic layer, judged by the colour of than larger macrofauna in mangrove the sediment, was slightly thicker in the mudflat sediments, it does not reach abundances than at the mangrove sites. Bioturbation and recorded from tidal flats. oxygen production by a microphytobentic layer 542 REVISTA DE BIOLOGIA TROPICAL

could have contributed to the higher diversity properties. Along the transect, a greater diversity and higher abondances of polychaetes in the of trophic modes at the mudflat than the Para ev; mudflat Alongi (1987a) recorded little varlation mangrove sites could reflect a wider range of posición de e: in sediment properties (% silt, grain size, water availab1e resources outside of the mangroves. In manglar, se kJ content) at a mid- and low-intertidal site in fact, 1ow abondance of protozoa, microalgae and transecto en I; Missionary Bay, which relate to my transeet meiofauna recorded in mangrove sediments de Australia S y un sitio se 11 sites I and IV. However, he measured higher provide a poor quality of food there (Alongi tios se mueslrl values of total organic matter as well as organic 1987a, 1988, 1989), contrasring with a high octubre de 191 C and N at the mid-intertidal site, which would density of meiofauna and an abondance and tras y sitios, SI correspond with the distribution of oligochaetes productivity of bentbic diatoms in tropical tidal varió de l.l81 and capitellids. Oligochaetes and capitellid flats (Swennen et al. 1982, Guerreiro et al. infauna pequei ron un valor pt 1996, Dittmann 1995, 2000). polychaetes were most abundant at the por todo el traJ mangrove sites and their occurrence is often A1ongi and Sasekumar (1992) discuss that y la diversidall re1ated to muddy sediments rich in organic tannins leaching from mangrove detritus could los sitios de ffil matter (Pearson and Rosenberg 1978). These regulate infaunal densities as it was shown for tre el bosque d findings from Missionary Bay are therefore in meiofauna (Alongi 1987c). However, tannin más abundante Polychaeta d01 accordance with records of Schrijvers et al. concentrations increase with depth (Boto et al. Capitellidae es (1995a), who found a correlation of 1989) and it is unlikely that the lower values Sabellidae se 11 macrobentbic oligochaetes with % mud and near the sediment surface could inhibit the gambra parva . organic matter in mangrove sediments. small infauna occurring there. do y al borde ' Interactions between endo- and epifauna While the infauna of the mangrove sites at para las diferen mostraron Ul'l c' have rarely been studied in mangrove forests, the studied transeet were more similar to each paración con Ie therefore their effect on the abondance and other, the mudflat site differed in abondances la infauna pequ distribution of small infauna cannot be fully and species composition and was distinguished manglar, y que assessed. Most mangrove crabs feed on leaves, from the other sites by multivariate analysis. microbes, detritus and carrion, while few These distinct faunal compositions corroborate species are classified as carnivore (see Alongi findings from macrobentbic surveys in other and Saselcumar 1992, Schrijvers et al. 1996). Indo-Pacific mangroves, which showed a Alongi, D.M. l Juvenile penaeids prey upon small macrofauna defined fauna for sand- and mudflats and a meioben~ (Robertson 1988). Small infauna could indeed fauna peculiar to mangroves (Day 1974, Biol. 95: provide a rich food souree for juvenile fish and Sasekumar 1974, Frith et al. 1976, Schrijvers Alongi, D.M. 1 prawns, as they are easily accessible at the et al., 1995a, Guerreiro et al. 1996). The zo nation sediment surface where they occur in great agreement between the cited macrobentbic tropical m numbers. Given the higher abondance of small surveys and the records of small infauna 103-114. than 1arger infauna, trophic interactions and presented here substantiates that mangroves Alongi, D.M. I food webs of mangrove ecosystems have to be and tidal flats constitute two different habitats. tannins ' further studied. estuaries. The uptake of bacteria and microalgae by Alongi, D.M. I fiddler crabs and gastropods (Dye and Lasiak ACKNOWLEDGEMENTS biomass i 1987) could imply a food competition with Ecol. 15:! infauna and indeed, Schrijvers et al. (1995b, This study was carried out during a 1996) found a density increase of meiobentbic postdoctoral fellowship funded by the German Alongi, D.M. benthos: , oligochaetes in exclusion cages as well as a Science Foundation (DFG grant lil 02-Di concepts.l resource competition between epibenthos and 396/1-2). I am gratefu1 to the Australian amphipods. In my study, amphipods occurred Institute of Marine Science for its hospitality Alongi, D.M. &, p. 137-171 only at the mangrove fringe and mudflat, but it is and providing excellent research facilities. My TropiealM not known whether tbis distribution resu1ts from thanks also go to the crew of the "Harry Studies , competitive interactions or is due to sediment Messel" and D. Alongi, K. Boto, F. Mieheli and Washingtol INTENATIONAL JOURNALOF TROPICAL BIOLOGY ANO CONSERVATION 543

:er diversity RESUMEN Bachelet, G. 1990. The choice of a sieving mesh size in the quantitative assessment of marine macrobenthos: a t than the Para evaluar Ja presencia, distribución espacial y com­ necessary campromise between aims and :r range of posición de especies de Ja infauna pequeila en una costa de constraints. Mar. Environm. Res. 30: 21-35. ngroves. In manglar, se tomaron rouestras con barrenos a Jo largo de un oolgaeand transecto en Ja bahfa Missionary, isla Hinchinbrook, noreste Boto, K.G. & J.T. Wellington. 1984. Soil characteristics sediments de Austtalia Se arreglaron tres sitios en el bosque de manglar and nutrient status in a northern Australian mangrove re (Alongi y un sitio se localizó en un banco de lodo adyacente. Los si­ forest. Estuaries 7: 61-69. tios se muestrearon cuatro veces entre noviembre de 1988 y ith a high octubre de 1989. Basado en los registros de todas Jas roues­ Boto, K.G., O.M. Alongi & A.L.I. Nou. 1989. Oissolved :lance and tras y sitios, se identificaron 39 táxones. La diversidad (H') organic carbon-bacteria interactions at sediment­ 1pical tidal varió de 1.18 a 2.38. Entre todo,Jas abundancias totales de Ja water interface in a tropical mangrove system. Mar. ~iro et al. infauna pequeila (retenida en un tarniz de 0.25 mm) alcanza­ Ecol. Progr. Ser. 51. 243-251. ron un valor promedio de 5 477 ind. m·2, con poca variación por todo el transecto o por tiempo. Los mimeros de especies scuss that Broom, M.I. 1982. Structure and seasonality in a y Ja diversidad fueron más altos en el banco de lodo que en Malaysian mudflat community. Estuar. Coast. Shelf itus could los sitios de manglar. La composición taxonómica cambió en­ Sci. 15: 135-150. •hown for tre el bosque de manglar y el banco de lodo: Oligochaeta fue :r, tannin más abundante en los sedimentos del manglar, mientras que Clarke, K.R. 1993. Non-parametrie multivariate analyses ioto et al. Polychaeta dominó en el banco de lodo. De los poliquetos, of changes in community structure. Aust. I. Ecol. 18: Capitellidae estuvo casi restringida a los sitios del manglar, 117-143. er values Sabellidae se registró con frecuencia en todos los sitios y Si­ hibit the gambra parva y Myriochele sp. se confinaeon al banco de Jo­ Oaniel, P. & A.I. Robertson. 1990. Epibenthos of do y al horde del manglar. Estas especies contaron también mangrove waterways and open embayments: 'e sites at para Jas diferencias entre los sitios. Los análisis multivariados Community structure and the relationship between r toeach mostracon un conjunta diferente en el banco de lodo en com­ exporied mangrove delritus and epifaunal standing paración con los sitios del manglar. Este estudio mostró que stocks. Estuar. Coast. Shelf Sci. 31: 599-619. mdances Ja infauna pequeila es un componente abundante de sitios de tguished manglar, y que ha sido previamenie subestimado. Oay, J.H. 1974. The ecology of Morrumbene estuary, malysis. Moçambique. Trans. Roy. Soc. S. Afr. 41:43-97. roborate REPERENCES in other Oittmann, S. 1995. Benthos structure on tropical tidal flats of Australia. Helgoländer Meeresunters. 49: :>wed a Alongi, O.M. 1987a. Intertidal zonation and seasonality of 539-551. s and a meiobenthos in tropical mangrove estuaries. Mar. Biol. 95: 447-458. ' 1974, Oittmann, S. 2000. Zonation of bentbic communities in a brijvers tropical tidal flat of north-east Australia. J. Sea Res. Alongi, O.M. 1987b. lnter-estuary varlation and intertirlal )). The 43: 33-51. zonation of free-Jiving nematode communities in bentbic tropical mangrove systems. Mar. Ecol. Progr. Ser. 40: & infauna 103-114. Oye, A.H. T.A. Lasiak. 1987. Assimilation efficiencies tgroves of fiddler crabs and deposit feeding gastropods from Alongi, O.M. 1987c. The influence of mangrove-derived tropical mangrove sediments. Comp. Biochem. abitats. tannins on intertirlal meiobenthos in tropical Physiol. 87: 341-344. estuaries. Oecologia 71: 537-540. Fauchald, K. & P.A. Jumars. 1979. The dietof worms: A Alongi, O.M. 1988. Bacterial productivity and microbial study of polychaete feeding guilds. Oceanogr. Mar. biomass in tropical mangrove sediments. Microb. Biol. Ann. Rev. 17: 193-284. Ecol. 15: 59-79. ing a Frith, O.W., R. Tantanasiriwong & 0. Bhatia. 1976. Alongi, O.M. 1989. Ecology of tropical soft-bottorn erman Zonation of macrofauna on a mangrove shore, benthos: a review with emphasis on emerging 02-Di Phuket Island. Phuket Mar. Biol. Cent., Res. Bull. concepts. Rev. Biol. Trop. 37: 85-IOO. :ralian 10: 1-37. 1itaJity Alongi, O.M. & A. Sasekumar. 1992. Benthic Communities, s. My p. 137-171. In A.I. Robertson & O.M. Alongi (eds.). Guerreiro, J., S. Freitas, P. Pereira, J. Paula & A. Macia. Tropical Mangrove Ecosystems. Coastal and Estuarine 1996. Sediment macrobenthos of mangrove flats at Harry Studies 41. American 'Geophysical Union, lnhaca Island, Mozambique. Cab. Biol. Mar. 37: li and Washington, O.C. 309-327. 544 REVISTA DE BIOLOGfA TROPICAL

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