Community structure of macrobenthos in two tropical sandy ... - UFF

Marine Ecology. ISSN 0173-9565 

ORIGINAL ARTICLE 

Community structure of macrobenthos in two tropical 

sandy beaches with different morphodynamic features, 

Rio de Janeiro, Brazil 

Renata Soares Ramalho Fernandes 1 & Abilio Soares-Gomes 2 

1 Programa de Pós-Graduação em Biologia Marinha, Universidade Federal Fluminense, Niterói, RJ, Brazil 

2 Departamento de Biologia Marinha, Universidade Federal Fluminense, Niterói, RJ, Brazil 

Keywords 

Beach morphodynamic; community structure; 

intertidal zonation; soft-bottom benthos. 

Correspondence 

Renata Soares-Ramalho Fernandes, Programa 

de Pós-Graduação em Biologia Marinha, 

Universidade Federal Fluminense, Caixa Postal 

100.644, Niterói, RJ – 24001-970, Brazil. 

E-mail: retfernandes2003@yahoo.com.br 

Accepted: 3 May 2006 

doi:10.1111/j.1439-0485.2006.00093.x 

Abstract 

The macrobenthos of two exposed tropical sandy beaches in Rio de Janeiro 

(Brazil) were compared in relation to density, species richness, and vertical 

zonation. Biological and sediment samplings were carried out in the austral 

winter of 2002 and the austral summer of 2003. The sampling design consisted 

of 10 transects perpendicular to the water line, evenly divided into strata. A 

sampling unit was taken in each stratum with a 0.04 m 2 quadrat sampler. Beaches 

were also compared according to physical features, such as slope, wave 

period, wave height, and grain size. According to Dean’s X morphodynamic 

index the Pontal is a dissipative beach while the Costa Azul is a reflective one. 

The mean grain size ranged from median to coarse sand in Costa Azul, 

whereas in Pontal it ranged from median to very fine sand. Eleven species were 

collected in the two beaches. Crustaceans were the dominant in the Costa Azul 

Beach, while the polychaete Scolelepis squamata dominated the Pontal beach. A 

negative correlation was found between the density of the macrobenthos and 

mean grain size, and beach slope. On the other hand, the Dean’s parameter 

correlated positively with faunal density. Based on the results of ANOSIM, in 

both beaches, two groups of stations were identified, defining an upper and a 

lower beach zone along the vertical distribution of the macrobenthos. 

Problem 

Several environmental abiotic factors have been used to 

explain variations in composition and abundance of 

intertidal macrobenthos, such as mean grain size and 

sorting of sediment grains, wave action, and drainage of 

the sediment column (Salvat 1964; McLachlan et al. 1981; 

Jaramillo & Gonzalez 1991). In relation to biotic factors, 

events related to the life cycle and interactions among 

species (e.g. symbioses) could explain some observed variations 

(Boesch 1973). 

The interactions between tidal regime, wave climate, 

and sediment type produce a range of beach morphodynamic 

types, which span a continuum from microtidal 

reflective beaches, narrow and steep, to macrotidal dissipative 

systems, which are wide and flat, and under conditions 

of large tides, graded into flats (Defeo & McLachlan 

2005). 

Ecological diversity, species richness, overall abundance, 

and biomass of macrobenthic communities inhabiting 

exposed sandy beaches present a clear increasing trend 

from reflective to dissipative conditions (McLachlan 1990; 

McLachlan et al. 1993). 

In oceanic beaches, where strong variation of abiotic 

variables are observed, physical factors are usually more 

important than biological ones in controlling the community 

structure of intertidal benthos. The morphodynamic 

state of the beaches reflects the harshness of these environments 

and could indicate the kind of fauna that 

colonize different beaches (Dexter 1983; Brown & 

160 Marine Ecology 27 (2006) 160–169 ª 2006 The Authors. Journal compilation ª 2006 Blackwell Publishing Ltd

Fernandes & Soares-Gomes 

Community structure of macrobenthos in two tropical sandy beaches 

McLachlan 1990; Jaramillo & McLachlan 1993). Dissipative 

beaches are hydrodynamically more stable than 

reflective ones, harboring a more diverse fauna. The composition 

of these two types of beaches is quite different, 

with polychaetes being predominant in the dissipative 

beaches, and crustaceans being abundant in the reflective 

beaches (Dexter 1984; McLachlan et al. 1993). 

Although not so evident as in hard-bottoms, the fauna 

may exhibit a discrete distribution along the beach profile 

in response to abiotic and biotic variables, forming a typical 

zonation pattern worldwide (Dahl 1952; Salvat 1964). 

Zonation is highly dynamic and not sharply defined 

(Defeo & McLachlan 2005). 

The influence of beach morphodynamics and sediments 

on benthic communities and populations was studied, 

among others, by McLachlan (1990, 1996), Jaramillo & 

McLachlan (1993), McLachlan et al. (1993), Borzone 

et al. (1996), Bentes et al. (1997), Defeo et al. (1997, 

2001), Brazeiro (2001), Veloso & Cardoso (2001), Rodil 

& Lastra (2004). Only a few studies were carried out on 

the subtidal portion of the beach (Hill & Hunter 1976; 

Leber 1982; Knott et al. 1983; Borzone et al. 1996), 

because this required an intensive and special sampling 

effort (Borzone et al. 1996). 

The ‘‘swash exclusion hypothesis’’ (SEH) gained wide 

acceptability in explaining the control of species, abundance 

and diversity of the sandy beach macrobenthos by 

swash climate, determined by wave height and beach slope. 

This hypothesis predicts a consistent increase in species 

richness, abundance and biomass from reflective to dissipative 

conditions (Defeo et al. 2001). It is hypothesized that 

only true intertidal species will be affected by the differences 

in beach morphodynamic types (Contreras et al. 2003). 

Gómez & Defeo (1999) formulated new additions to the 

original SEH (postulated at the community level), to 

account for predictions at the population level (reproductive 

sizes, fecundity, growth and mortality rates). They 

argued that in harsh reflective beaches, organisms would 

need to divert more energy to maintenance processes, rather 

than for reproductive growth (Defeo & Martínez 2003). 

The aim of this work was to verify if the above cited 

paradigms are true for two beaches at tropical latitudes and 

to describe the local vertical zonation of their fauna. 

Material and Methods 

Study area 

Both beaches studied (Rio de Janeiro, Brazil) are relatively 

free from anthropogenic impacts, except for human 

recreation, which is especially intense on holidays and 

during summer vacations. Praia do Pontal (22°57¢58¢¢ S) 

is a 700m long and 35m wide intertidal beach, located in 

BRASIL 

Arraial do Cabo Municipality, with a median to fine sand 

granulometry. Costa Azul beach (22°31¢37¢¢) is a waveexposed, 

900m long and 50m wide intertidal beach, 

located in Rio das Ostras Municipality, with a predominance 

of coarse sand (Fig. 1). 

Sampling design 

Sampling was carried out in the austral winter of 2002 

and the austral summer of 2003, during low-spring tides. 

At each beach, two sectors (S1, S2), of 40 m distance, 

were sampled along five transects (T1–T5) perpendicular 

to the water line, from below the swash line and the 

supralittoral vegetation. 

Each transect was divided into 10 strata, equally 

spaced, consistent with the following beach width: Pontal 

beach width 35 m ¼ 3.5 m, the distance between the levels; 

Costa Azul Beach width 50 m ¼ 5 m, the distance 

between the levels. 

A sampling unit was taken in each stratum with a 

0.04 m 2 quadrat sampler, buried to a depth of 25 cm, 

and the macrobenthos were sorted using a 0.5mm-mesh 

sieve. To verify if some species occurred beyond the limits 

of the intertidal zone, a triplicate sample was collected in 

the breaking zone contiguous to each transect, with a 

mean depth of 2 m, using a hand corer of 0.00785 m 2 , 

buried to a depth of 25 cm, and the macrobenthos were 

sorted using a 0.5mm-mesh sieve. 

As the sampling device used to sample the surf zone 

was different from the one used to sample the intertidal 

zone, a comparison between both zones was not made. 

However, the surf zones of the two beaches were compared 

so as to test the differences. 

Habitat featuring 

Rio de Janeiro 

45° 44° 43°W 42° 41° 

Fig. 1. Geographic location of the beaches studied. 

Costa Azul 

Pontal 

22°S 

The sediment samples for grain-size analyses were collected 

at each stratum by inserting a 3.5cm diameter 

21° 

23° 

Marine Ecology 27 (2006) 160–169 ª 2006 The Authors. Journal compilation ª 2006 Blackwell Publishing Ltd 161



cylindrical corer to a depth of 15 cm. Samples were 

dried at 70 °C in an oven and sieved through graded 

screens so as to determine mean particle size and sorting 

parameters (Folk & Ward 1957); the sediments were 

classified according to the Wentworth (1922) scale. 

Wave height was estimated by measuring the height of 

the waves with graduated poles against the horizon. 

Beach slope at each site was determined by Emery’s 

(1961) profiling technique, from the average wave height 

(Hb), wave period (T) and sand fall velocity of the particles 

(values estimated using the mean grain size from 

the swash zone and conversion tables given by Gibbs 

et al. 1971). Dimensionless Dean’s parameter (X) (Short 

& Wright 1983) was calculated for each beach as a 

measure of its morphodynamic state: X ¼ Hb/Ws · T. 

The wave period was the time interval between breakers, 

and the swash period was estimated measuring the 

maximum swash amplitude, calculated as the distance 

between the highest and the lowest turning points of 

the up-swash and back-swash, respectively, during a 10- 

min period. 

Data analysis 

The hypothesis that total macrobenthos density and species 

richness were different in the two sectors within each 

beach was tested by the one-way ANOVA 

(T1 · T2 · T3 · T4 · T5). The a posteriori Tukey test 

was adopted to determine if there were significant differences 

among the transects. The one-way ANOVA was also 

adopted to test the differences between the sectors 

(S1 · S2). 

A Student’s t-test was used to compare the total 

abundance of sublittoral macrofauna between the beaches. 

All data were first tested for normality (Kolmogorov– 

Smirnov test) and homoscedasticity (Bartelett test) prior 

to all parametric analyses. 

The data set of each beach were arranged in an ecological 

matrix and analyzed by the Unweighted Pair 

Group Method, Average Clustering and Non-metric 

Multidimensional Scaling Ordination Methods, adopting 

the Bray–Curtis similarity index. To test the hypothesis 

that the strata were different along the vertical distribution 

(levels, zonation), a one-way analysis of similarity 

(ANOSIM) was carried out using the Bray–Curtis similarity 

matrix. 

The samples were pooled for each level/stratum as the 

sum of the species abundance of the five transects for 

each stratum and sector, because the ANOVA results 

showed that there were no differences between the 

transects. 

The relationship between the abiotic and biotic variables 

was determined by the Spearman rank correlation. 

Results 

Well-sorted fine sands predominated at Pontal Beach 

while moderately sorted coarse sand was the main type of 

sediment found at Costa Azul. According to the mean 

Dean’s X index, Pontal is a dissipative beach (X ¼ 

6.120), and Costa Azul is a reflective beach (X ¼ 0.568). 

Table 1 shows the other abiotic features of the two sectors 

at each beach, separated by summer and winter surveys. 

Eleven species belonging to crustaceans, molluscs, polychaetes 

and insects were collected, four of which were 

common to both beaches. At each beach, a set of seven 

species was collected and some species were found only 

in one of the studied periods. 

In Pontal Beach, organisms were collected in all the 10 

levels analysed, while in Costa Azul, organisms were missing 

from levels 9 and 10. 

The polychaete Scolelepis squamata, the crustacean Excirolana 

armata and the insect Phaleria testacea were found 

only at Pontal Beach; the latter species were found only 

in the winter survey. The polychaetes Pisionides indica 

and Hemipodus olivieri, and the mollusc Olivancillaria vesica 

vesica occurred only at the Costa Azul Beach. Hemipodus 

olivieri was found only in winter and O. vesica 

vesica only in summer sampling. 

The dominant species at Pontal, on both surveys, was 

S. squamata while Excirolana braziliensis dominated at 

Costa Azul Beach. At Pontal E. armata co-dominated in 

the winter survey and at Costa Azul, Donax hanleyanus 

co-dominated in winter, while Emerita brasiliensis 

Table 1. Physical characteristics of the beaches studied in winter (W) 

and summer (S). 

physical characteristics/ 

beaches 

Pontal, 

sector 1 

Pontal, 

sector 2 

Costa Azul, 

sector 1 

Costa Azul, 

sector 2 

wave height [m] 

W 1.0 1.0 1.0 1.0 

S 1.0 1.0 0.8 0.8 

wave period [s] 

W 6.0 6.0 16.93 11.93 

S 5.8 5.8 10.2 10.2 

swash period [s] 

W 16.2 15.3 7.4 6.2 

S 14.1 14.5 7.3 7.2 

intertidal slope [1/m] 

W 1:21.4 1:20 1:10.4 1:12.1 

S 1:22.5 1:20.8 1:12.1 1:15 

length [m] 

W 35 35 50 50 

S 35 25 50 50 

Dean parameter X 

W 6.01 6.01 0.48 0.51 

S 6.22 6.22 0.78 0.49 




Table 2. The dominant species of the beaches studied in winter and 

summer. 

winter % summer % 

Pontal beach species 

Scolelepis squamata (Muller, 1806) 41.08 63.65 

Emerita brasiliensis (Schmitt, 1935) 21.40 17.37 

Excirolana armata (Dana, 1853) 32.37 13.37 

Excirolana braziliensis (Richardson, 1912) 4.25 4.62 

Donax hanleyanus (Philippi, 1842) 0.07 0.70 

Pseudorchestoidea brasiliensis (Dana, 1853) 0.55 0.28 

Phaleria testacea (Say, 1824) 0.27 – 

Costa Azul beach species 

Pisionides indica (Aiyar & Alikunhi, 1940) 8.40 0.82 

Emerita brasiliensis (Schmitt, 1935) 20.15 30.23 

Donax hanleyanus (Philippi, 1842) 27.50 19.15 

Hemipodus olivieri (Orensanz & 

– 1.40 

Gianuca, 1974) 

Excirolana braziliensis (Richardson, 1912) 38.10 44.87 

Pseudorchestoidea brasiliensis (Dana, 1853) 5.30 3.56 

Olivancillaria vesica vesica (Gmelin, 1791) 0.36 – 

Table 4. Density of species [ind.Æm )2 ] and total number of individuals 

per beach, in winter (W) and summer (S). 

species PO, W PO, S C.A, W C.A, S 

Scolelepis squamata 3337.6 4602.5 – – 

Pisionides indica – – 192.3 21.36 

Hemipodus olivieri – – – 29.91 

Emerita brasiliensis – – 192.3 200.85 

Donax hanleyanus – – 363.24 213.67 

Olivancillaria vesica vesica – – 68.37 – 

total faunal density 3337.6 4602.5 816.23 465.81 

total number of ind. 781 1077 191 109 

PO, Pontal Beach; CA, Costa Azul Beach. 

co-dominated in summer (Table 2). At Pontal Beach, the 

higher density of intertidal individuals was found in the 

winter survey, and at Costa Azul the higher density was 

found in summer. However, at the breaking zone, the 

opposite pattern was observed with the higher density 

occurring in summer at Pontal Beach, and in winter at 

Costa Azul (Tables 3 and 4). 

According to the cluster and MDS analyses (Figs 2 and 

3) there were three groups of stations at Pontal and two 

at Costa Azul. On the other hand, when applying the 

ANOSIM test, only two of these groups were statistically 

significant for both the beaches (global R ¼ 1.0). 

Comparing the intertidal zones, the Pontal Beach showed 

a higher species richness than Costa Azul. However, species 

richness at the breaking zone at the Costa Azul Beach 

Fig. 2. Cluster analysis and n-MDS ordinations. Above: Pontal Beach 

winter; Below: Pontal Beach summer. 

Table 3. Density of species [ind.Æm )2 ], and total number of individuals per beach, in winter (W) and summer (S). 

species PO, W [m )1 ] PO, W [m )2 ] PO, S [m )1 ] PO, S [m )2 ] C.A, W [m )1 ] C.A, W [m )2 ] C.A, S [m )1 ] C.A, S [m )2 ] 

Scolelepis squamata 1636.6 3140 2651.2 4545 – – – – 

Pisionides indica – – – – 1150 230 150 30 

Hemipodus olivieri – – – – 200 40 250 50 

Emerita brasiliensis 1150.6 1315 1446.6 1240 2550 550 5300 1105 

Excirolana braziliensis 259 370 288.7 330 4920 1040 795 1640 

Excirolana armata 2030 2400 1114.1 955 – – – – 

Pseudorchestoidea brasiliensis 70 40 87.5 50 500 115 416.6 130 

Ocypode quadrada – – – – 25 5 – – 

Donax hanleyanus 323.7 5 – – 3325 750 2950 700 

Olivancillaria vesica vesica – – – – 50 10 – – 

Phaleria testacea 35 20 70 20 – – – – 

total density 5504.9 7290 5658.1 7140 12720 2740 9861.6 3655 

total number of ind. 1458 1428 548 731 

PO, Pontal Beach; C.A, Costa Azul Beach. 




stratum 8, at about 40 m from the water line. According 

to the ANOVA results, the density of E. braziliensis did 

not differ significantly between the sectors or periods 

(P > 0.05) (Fig. 4). 

According to the results from the Student’s t-test, the 

abundance of macrobenthic fauna was significantly different 

in the sublittoral zone between Pontal and Costa Azul 

(P < 0.05). At Pontal Beach, the macrobenthic fauna were 

more abundant in summer, whereas at Costa Azul they 

were more abundant in winter. 

The Spearman rank correlation analyses revealed a significant 

positive relationship between mean grain size and 

beach slope (P < 0.005), and between omega (X) and 

macrofaunal density (P < 0.005). Conversely, significant 

negative correlations were found between mean grain size 

and macrofaunal density (P < 0.005), and between beach 

slope and macrofauna density (P < 0.005) (Table 5). 

Discussion 

Fig. 3. Cluster analysis and n-MDS ordinations. Above: Costa Azul 

beach winter. Below: Costa Azul Beach summer. 

was higher than at Pontal. At Costa Azul the species richness 

increased from the higher to the lower intertidal 

zone, while at Pontal, the higher species richness occurred 

at the intermediate levels (c. 23 m from the water line). 

On both beaches the total macrobenthic fauna did not 

differ significantly between intra-sector transects (S1 – 

T1 · T2 · T3 · T4 · T5; P > 0.05) and (S2 – T1 · T2 · 

T3 · T4 · T5; P > 0.05). Also, no significant differences 

were found between inter-sectors (S1 · S2; P > 0.05) as 

well as between the two sampling periods (P > 0.05). 

At Pontal Beach, S. squamata occurred from the sublittoral 

zone to stratum 7, at approximately 24 m distance 

from the water line. The distribution of E. brasiliensis ranged 

from the sublittoral to stratum 5, peaking at stratum 

4 (c. 14 m distance from the water line). Excirolana 

armata and E. braziliensis occurred from stratum 4 to 

stratum 7, and from stratum 5 to 10, respectively. 

According to the results from the ANOVA, the density of 

S. squamata, E. brasiliensis and E. braziliensis did not differ 

between sectors or periods (Two-Way ANOVA factors 

sector and periods P > 0.05). The density of E. armata 

was higher in the winter (P < 0.05) but did not differ 

between sectors (P > 0.05). 

At Costa Azul, the highest density of E. brasiliensis 

occurred in stratum 1, at about 5 m distance from the 

water line. Donax hanleyanus ranged from strata 1 to 5, 

about 15 m above the water line. Its density was statistically 

different between the two sectors but did not differ 

between the seasons. Excirolana braziliensis occurred from 

stratum 2, at about 10-m distance from the water line, to 

Grain size and swash period are the physical factors that 

control community structure. Grain size often tends to be 

coarser at reflective rather than at dissipative beaches, as 

a result of intense wave action in the former (McLachlan 

1990; Defeo et al. 1992; McArdle & McLachlan 1992; 

Borzone et al. 1996). The physical features of both beaches 

studied in this work are in accordance with these 

statements; the Pontal Beach has a slight slope and fine 

grains, while the Costa Azul Beach has a steeper slope 

and coarser grains. 

Dexter (1983) and Borzone et al. (1996) showed that 

the density of the macrofauna was negatively correlated to 

mean grain size. In addition, Defeo et al. (1992) found a 

negative correlation between beach slope and macrofaunal 

density, concluding that both slope and grain size are 

factors determining beach macrofaunal structure. According 

to McLachlan (1990), the abundance of macrofauna is 

best correlated with Dean’s parameter. On the other hand, 

Jaramillo & McLachlan (1993) observed that grain size 

was the sediment factor that best correlated with variations 

of macrofaunal abundance in Chilean beaches. For 

those beaches, slope, grain size, and the Dean parameter 

were positively correlated with macrofaunal density. 

Some authors, when comparing morphodynamic types, 

found an increase in the abundance of macrofauna, from 

reflective to dissipative beaches (Brown & McLachlan 

1990; Defeo et al. 1992; Borzone et al. 1996; Brazeiro 

1999). Jaramillo et al. (2001) however, stated that the 

morphodynamics was not always a useful predictor of 

sandy beach community structure. 

McArdle & McLachlan (1992) observed that variations 

in swash, a factor that is related to slope, lead to changes 

in the distribution of macrofauna. According to Bowman 




Fig. 4. Variation in the number of individuals and slope along the water level. 

Table 5. Spearman Rank Correlation between abiotic and biotic variables 

of the beaches studied. 

variables R P significance 

grain size versus faunal density )0.8982 0.0046 * 

grain size versus intertidal slope )0.7785 0.0279 * 

grain size versus species richness 0.2191 0.6021 n.s. 

Intertidal slope versus faunal density 0.9048 0.0046 * 

Intertidal slope versus species richness 0.5361 0.1710 n.s. 

X versus density 0.8675 0.007 * 

X versus richness 0.3061 0.418 n.s. 

n.s., not significant. 

*P < 0.05. 

& Dolan (1985), beaches that have slight slopes and long 

swash periods are more favourable for filterfeeding 

animals. The difference in the abundance of the 

sandy crab, E. brasiliensis between the beaches in this 

study, corroborates these ideas. The swash period at 

Pontal Beach was two times that at Costa Azul Beach, 

where the abundance of E. brasiliensis was very low, thus 

in agreement with the SEH, proposed by McLachlan et al. 

(1993). 

At Costa Azul Beach, where the animals were more 

exposed to wave action, crustaceans were the dominant 

taxa, whereas the polychaete S. squamata dominated at 




Pontal Beach. Along the Brazilian coast, S. squamata 

occurs in beaches along São Paulo and Paraná State coasts 

(Amaral 1979; Amaral et al. 1990; Shimizu 1991, 1995; 

Omena & Amaral 1997), and it is the most characteristic 

macrofauna species, both in abundance and frequency 

(Souza & Gianuca 1995; Borzone et al. 1996). Similarly, 

Barros et al. (2001) found that S. squamata was the most 

representative species on a dissipative beach of the Paraná 

State coast, representing 70% of the total macrofauna 

abundance. 

Cirolanidae crustaceans were abundant at both the beaches 

studied. At Costa Azul, E. braziliensis was the most 

abundant species, and at Pontal, E. armata was the second 

most abundant species, coexisting with the hippidean 

E. braziliensis. Defeo et al. (1997), comparing the different 

beaches along the Uruguayan coast, concluded that 

E. braziliensis and E. armata prefer fine sandy habitats, 

although E. braziliensis seems to be more eurytopic, also 

occurring at high densities in coarse sandy habitats. The 

lower abundance of E. braziliensis at Pontal Beach compared 

with Costa Azul might suggest a competitive interaction 

with E. armata. 

Defeo et al. (2001), showed that E. brasiliensis was 

more abundant at dissipative beaches, corroborating the 

‘swash exclusion hypothesis’, which predicts a consistent 

increase in species richness, abundance and biomass from 

reflective to dissipative conditions (Defeo et al. 2001). 

Conversely, it has been hypothesized that only true intertidal 

species will be affected by differences in beach 

morphodynamic types (Contreras et al. 2003). 

In the present study, Pseudorchestoidea brasiliensis was 

found in both dissipative and reflective beaches. Gianuca 

(1983) has found that this crustacean was more abundant 

in dissipative beaches. On the other hand, it has been 

demonstrated that P. brasiliensis was more typical of 

reflective beaches (Cardoso & Veloso 1996). Gómez & 

Defeo (1999) suggested that P. brasiliensis was more resistant 

to immersion, desiccation and least prone to predation 

at reflective beaches. These results show that this 

species is able to successfully colonize beaches that are 

morphodynamically distinct. However, in this study, 

P. brasiliensis was found at low densities at both the beaches 

studied. Barros et al. (2001) suggested that the 

absence of some species in the beaches could be associated 

with a high level of recreational activities (i.e. tramping) 

and the usual practice of removal of artificial and 

natural detritus from those beaches. Studies have shown 

that some species can be eliminated or have their population 

densities reduced as a result of the increase of recreational 

activities in beach ecosystems (Moffet et al. 1998). 

The total abundance and dominance of species were not 

different between winter and summer surveys. The same 

has been found in beaches along the Paraná State coast in 

Southern Brazil, where crustaceans dominated or co-dominated 

together with polychaetes, regardless of the period 

(Barros et al. 2001). Therefore, the absence and/or the low 

abundance of some species can also be related to their life 

cycle. Monthly and annual fluctuations in population density 

are common among sandy beach macrofauna, where 

peaks in abundance are often a consequence of variations 

in recruitment rates (Souza & Gianuca 1995). 

Species richness in this study was low and similar to 

that recorded in the exposed Chilean beaches (Jaramillo 

et al. 2001), when compared with the west coast beaches 

of the United States, South Africa, Australia, and Oman. 

Otherwise, the macrofaunal density in the Chilean 

beaches is often higher than at other localities. Those high 

densities, in the majority of the cases studied, were largely 

a result of great densities of the sand crab Emerita 

analoga, that could reach 50% of the total density in the 

different types of beaches in Chile (Jaramillo & Lastra 

2001). Similar results have also been found by Dugan 

et al. (2000) along the California beaches. At Pontal 

Beach, densities were comparable with those of the Chile 

and California beaches, but are attributed to the high 

density of the polychaete S. squamata. 

Dahl (1952) and Salvat (1964), among others, have 

proposed a vertical zonation pattern for sandy beach 

assemblages. For Brown & McLachlan (1990) it was possible 

to recognize two vertical zones: a subaerial or resurgence 

zone and a subaquatic or retention zone. However, 

there are controversies about a global pattern of zonation 

in sedimentary beaches. Defeo et al. (1992) were not able 

to recognize a unique pattern for five beaches studied in 

the coast of Uruguay. In addition Brazeiro & Defeo 

(1996) demonstrated that zonation at dissipative beaches 

could exhibit either a seasonal or a short-time variation. 

Beach species could have their distribution altered in 

response to environmental changes such as beach width 

and slope, position of the swash zone, food availability, 

and competition (Brazeiro & Defeo 1996; Giménez & 

Yannicelli 1997). 

At Pontal Beach, our results pointed out three groups 

of stations corresponding to biological zones: a lower 

zone, where S. squamata was a conspicuous species, an 

intermediate zone, characterized by the high abundance 

of E. brasiliensis and E. armata, and a higher zone, where 

E. braziliensis was the characteristic species. At Costa 

Azul, only two zones could be distinguished: a lower zone 

characterized by E. brasiliensis and D. hanleyanus, and a 

higher zone by E. braziliensis. When zonation patterns 

were tested using ANOSIM, only two zones were evident 

at both beaches; a zone located in the lower portion of 

the beach, encompassing intertidal migratory species, and 

a zone where those migratory species were excluded. 

These results are in agreement with Brown & McLachlan 




(1990), who suggested that the only valid zonation 

scheme might be a division of the air-breather, high-shore 

assemblages from the water-breather, lower shore assemblages. 

Giménez & Yannicelli (1997) suggested that on beaches 

with a steeper slope, E. brasiliensis and D. hanleyanus 

could define the zones more properly, while the high 

zone was characterized by E. braziliensis. 

Species that depend upon swash have their distribution 

limited to reflective beaches because on those beaches the 

slope is steeper and the swash is shorter. Correlation analysis 

between swash and slope suggested that slope controls 

zonation patterns on sandy beaches. At Costa Azul, 

the steep slope might act as a barrier hindering the migration 

of species that occupy the lower zone. As a result of 

the fast water drainage at the intermediate zone, only 

organisms adapted to dry sand such as E. braziliensis can 

persist. 

At Pontal Beach, P. brasiliensis and E. brasiliensis cooccur 

in the supralittoral zone. The occurrence of these 

cirolanid isopods at higher levels on the coast is opposite 

to the pattern proposed by Dahl (1952). The same occurrence 

was also reported by Jaramillo (1978), Gianuca 

(1983), Defeo et al. (1992) and Brazeiro & Defeo (1996) 

for temperate sites in South America. 

Defeo et al. (1997) studied the distribution of E. armata 

and E. braziliensis, and observed that when these species 

co-occur, E. braziliensis is found in lower densities and 

occupies the high mediolittoral zone, above the zone where 

E. armata occurs. The same was observed in the present 

study at Costa Azul. 

Few studies of beaches include samples taken in the 

sublittoral zone. Some studies showed that the sublittoral 

assemblages are more structurally variable than intertidal 

ones (Borzone et al. 1996). Hill & Hunter (1976); Leber 

(1982) and Knott et al. (1983). In our study the results 

were contradictory. At Pontal, the density of S. squamata 

was higher in the sublittoral zone while the richness of 

species was lower, while at Costa Azul, the species richness 

was higher in the sublittoral zone. 

Hill & Hunter (1976), Leber (1982) and Knott et al. 

(1983) concluded that species composition between the 

intertidal and sublittoral zones differs. Contrary to those 

results, no exclusive species were found in the sublittoral 

zones at Costa Azul and Pontal. 

Fleischack & Freitas (1989) studied the sublittoral portion 

of several beaches and suggested an inverse relationship 

between species diversity and turbulence in the 

sublittoral zone. Barros et al. (2001) studied six beaches 

of the Paraná state coast (South Brazil), and found that 

higher values of species diversity occurred in a reflective 

beach. The same was found in our study, where the 

diversity was higher in the reflective beach of Costa Azul. 

The reflective beaches, being more stable, possibly also 

have more stable macrofaunal assemblages, but this test 

would need careful temporal sampling, considering the 

great variability in time and space of these environments 

(Barros et al. 2001). 

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