Ricardo S. Cardoso

Effect of morphodynamics on the spatial and temporal variation of macrofauna on three sandy beaches, Rio de Janeiro State, Brazil

Three exposed sandy beaches were selected to compare fluctuations in density of the most abundant species, and to verify the influence of spatial and temporal variations on the community structure. Sampling was carried out every three months, from June 1993 to May 1995, on Fora, Prainha, and Boqueirao Beaches. The first two beaches were classified by Deans morphodynamic index (Ω) as intermediate, and the last as reflective. Slope, beach width and median grain size were significantly different among the beaches. Two-way analysis of variance revealed significant differences in species richness only among the beaches. No significant differences in density of the macrofauna between beaches and season were observed. However, Prainha Beach showed a higher temporal variation of the density of the macrofauna (and higher standard deviation) than the other two beaches. Emerita brasiliensis (Crustacea: Decapoda), Excirolana braziliensis (Crustacea: Isopoda), and Pseudorchestoidea brasiliensis (Crustacea: Amphipoda) were the most abundant species. Canonical correspondence analysis calculated the influence of the temporal variation as 27·5%; the influence of the environmental variation on community structure was 20·9%. The results suggest that in spite of the long-term fluctuations in species density, the beaches did not have temporal differences in the species richness and total density macrofauna during the study period.

Biphallia in imposexed females of marine gastropods: new record for Nassarius vibex from Brazil

Imposex is an endocrine disruption syndrome, in which females of marine gastropods develop sexual characteristics of males (penis and/or vas deferens) (Smith, 1971). This syndrome is caused by tributyltin (TBT) or triphenyltin (TPT), toxic organotin compounds found in naval paints used as antifouling system in boats and artificial structures (Gibbs and Bryan, 1987 and Axiak et al., 2003). Quantification of TBT by chemical analysis in water or sediment is very onerous, therefore imposex as a tool to detect contamination by organotin compounds is often used. Five genus of marine gastropods in the Brazilian littoral have already been studied and the occurrence of imposex was related to either mild or severe contamination by TBT (Fernandez et al., 2005 and Limaverde et al., 2007). Nassarius (Mollusca: Gastropoda) is a ubiquitous genus that has been proposed as a bioindicator of TBT pollution (Marshall and Rajkumar, 2003). Here, we report the novel occurrence of imposex in Nassarius vibex (Say) in south Brazil and the biphallia in imposexed females of this species. Specimens of N. vibex were collected at Flexeira beach (22° 56’ S and 43° 53’ W), Itacuruçá Island, Rio de Janeiro state, Brazil, in the intertidal zone at spring low tide in September 2007. Two fixed transects (500 m apart) were established from the lower limit of the swash zone to 10 m above the drift line (supralittoral). Next, ten equally spaced sampling strata parallel to the water line were marked according to a systematic design with stratification. At each stratum, five replicate quadrats of 0.04 m (systematically allocated 3 m apart) were taken to a depth of 25 cm and sieved through 0.7 mm mesh. This beach is exposed to effects of the yachting activities of Itacuruçá Yacht Club (distant 1.1 km) and Sepetiba Harbor (distant 7.3 km), which constituted potential sources of TBT pollution. In the laboratory, shell length (Figure 1a and b) was measured with a vernier caliper, then cracked and opened in a vice, and the individuals of N. vibex removed and examined for sex determination. Individuals having seminal vesicle were identified as males while others with seminal vesicle absent, as females. Females with male sex organs (e.g. penis) were identified as imposexed females. Penis length of males and imposexed females was measured under a stereoscopic microscope and the Relative Penis Length Index (RPLI) and Relative Penis Size Index (RPSI) were calculated according to Gibbs and Bryan (1987). A total of 155 individuals were collected, with 86 males (55.48%, Figure 1c) and 69 females (44.52%). All the females examined present the occurrence of imposex (Figure 1d). Two imposexed females presented biphallia (i.e. double penis, see Figure 1e and f). These

Population Biology and Secondary Production of Excirolana braziliensis (Isopoda: Cirolanidae) in Two Sandy Beaches of Southeastern Brazil

Abstract The population dynamics and secondary production of the cirolanid isopod Excirolana braziliensis are compared between two distinct sandy beaches. Monthly sampling from June 1998 through July 2000 was carried out at Grumari (a reflective beach with coarse sand and steeper slope) and Restinga da Marambaia (an intermediate beach with fine sand and moderate slope), both located in Rio de Janeiro State (23° S), southeastern Brazil. Sampling was conducted according to a systematic design in which two transects (fixed 500 meters apart) were established, each with 10 equally spaced sampling strata. From each stratum, five replicates (0.04 square meters) were taken. Highest population abundances were observed in spring and summer on both beaches. The beaches differed significantly in physical parameters and the characteristics of their inhabitant populations: (1) Grumari Beach had a steeper slope, coarse sands, and a short swash period; (2) the abundance of total population, fecundity at length, and egg production potential were higher at Restinga da Marambaia; and (3) individual growth of males was higher at Grumari. Mean length at sexual maturity (L50%), mortality, growth of females, secondary production, and mean annual biomass did not show significant differences between beaches. Variations in population parameters of E. braziliensis might be regulated by phenotypic adjustment to local conditions, optimizing fitness, and especially enabling species to adapt to different physical conditions.

GROWTH, MORTALITY, AND REPRODUCTION OF EXCIROLANA BRAZILIENSIS RICHARDSON, 1912 (ISOPODA, CIROLANIDAE) ON THE PRAINHA BEACH, RIO DE JANEIRO, BRAZIL

[With the aim of estimating the growth parameters, mortality, and reproduction of a population of Excirolana braziliensis, monthly samplings were performed in the period from June 1993 to May 1995 at Prainha Beach, Rio de Janeiro, Brazil. The average size at first sexual maturity was estimated to be 6.9 mm (TL) with an average fecundity of 13 embryos per female. There was a significant linear regression between the clutch size and the length of the female. The growth analyses demonstrated that there is seasonality in growth with smaller rates coincident with lower temperatures. This paper discusses the existence of a size gradient, indicated by an increase in total length with decreasing temperatures.Com o objetivo de estimar os parâmetros de crescimento, mortalidade e reproducao de uma populacao de Excirolana braziliensis, amostragens mensais foram feitas no periodo entre Junho de 1993 e Maio de 1995 na Praia da Prainha (Rio de Janeiro, Brasil). O tamanho medio da primeira maturacao sexual foi estimado em 6,9 mm (CT) com fecundidade media de 13 embrioes por femea. Houve uma significativa regressao linear entre o tamanho da ninhada e o comprimento da femea. Foi observada sazonalidade no crescimento, com menores taxas coincidindo com temperaturas mais baixas. Este artigo discute a existencia de um gradiente de tamanho, indicado pelo aumento do comprimento total com a diminuicao da temperatura., With the aim of estimating the growth parameters, mortality, and reproduction of a population of Excirolana braziliensis, monthly samplings were performed in the period from June 1993 to May 1995 at Prainha Beach, Rio de Janeiro, Brazil. The average size at first sexual maturity was estimated to be 6.9 mm (TL) with an average fecundity of 13 embryos per female. There was a significant linear regression between the clutch size and the length of the female. The growth analyses demonstrated that there is seasonality in growth with smaller rates coincident with lower temperatures. This paper discusses the existence of a size gradient, indicated by an increase in total length with decreasing temperatures.Com o objetivo de estimar os parâmetros de crescimento, mortalidade e reproducao de uma populacao de Excirolana braziliensis, amostragens mensais foram feitas no periodo entre Junho de 1993 e Maio de 1995 na Praia da Prainha (Rio de Janeiro, Brasil). O tamanho medio da primeira maturacao sexual foi estimado em 6,9 mm (CT) com fecundidade media de 13 embrioes por femea. Houve uma significativa regressao linear entre o tamanho da ninhada e o comprimento da femea. Foi observada sazonalidade no crescimento, com menores taxas coincidindo com temperaturas mais baixas. Este artigo discute a existencia de um gradiente de tamanho, indicado pelo aumento do comprimento total com a diminuicao da temperatura.]

Patterns of sandy-beach macrofauna production

Using data available from the literature, patterns of biomass, production and productivity of sandy-beach macrofauna populations were examined, considering environmental (temperature, exposure, grain size and beach slope) and biological variables (life span and mean body mass) and feeding and taxonomic groups. A total of 102 estimates of both production and biomass and 105 estimates of P/B ratios were collected from 52 studies carried out between 42°46′S and 54°05′N, for 83 sandy-beach macrofauna populations. The negative relationship between P/B ratio and beach slope for the supralittoral amphipods agrees with the Habitat Safety Hypothesis, according to which these forms would show higher mortality in dissipative than in reflective beaches. The observed higher production of filter-feeders in exposed than in sheltered beaches suggests that more food is available for filter-feeders in exposed beaches. The higher production of filter-feeders (represented by bivalves and decapods), than of scavengers/predators (peracarids and gastropods) showed the importance of filter-feeders in the food web of sandy beaches. The P/B ratios were strongly related to life span, but weakly or not related to the mean body mass. The high amphipod P/B ratio was attributed to the short life span of these crustaceans; conversely, gastropods showed the lowest P/B ratio, in accordance with their longer life span. The observed differences in biomass, production and P/B ratios within crustaceans and molluscs were attributed to differences in life-history traits and feeding mode.

Population biology and secondary production of the stout razor clam Tagelus plebeius (Bivalvia, Solecurtidae) on a sandflat in southeastern Brazil

The population biology and production of the stout razor clam Tagelus plebeius Lightfoot, 1786 were investigated on an intertidal sandflat on the southeast coast of Brazil (Enseada Beach, Sao Sebastiao, state of Sao Paulo) between April 1997 and April 1998. Two rectangular sites of 50 X 10 m parallel to the waterline were established, site A (upper intertidal level) and site B (middle intertidal level), where the samples were taken in an 0.5 x 0.5 m quadrat. High abundances were recorded in winter and spring, with no significant differences between the sites. The high bivalve abundances were related to the presence of very fine homogeneous sediment with low salinities. Tagelus plebeius had negative allometric growth, characteristic of deep burrowers for the relationships DM/SL and AFDM/SL. Parameters of the modified von Bertalanffy growth function were: L∞ = 67.01 mm, K = 1.73 year-1, t0 = -0.11 year, C = 0.43, WP = 0.96. The instantaneous mortality (Z) was 3.12 year-1, relatively high in comparison to other tropical bivalve populations. Secondary production was 1.53 g AFDM m-2 year-1, with a P/B ratio reaching 1.37 year-1. This high turnover ratio (P/B) was related to a rapid population replacement, connected with the short life span and high mortality of the species.

Environmental effects on the structure of polychaete feeding guilds on the beaches of Sepetiba Bay, south-eastern Brazil

Several studies have been conducted to explain patterns of the abundance, richness and diversity of sandy-beach macrofauna; however, such analyses have ignored the overall functional structure of macrofauna communities. Few studies have examined polychaete feeding guilds on sandy beach environments. To examine the effects of environmental factors on polychaete feeding guilds on sandy beaches, 12 sandy beaches from five islands in Sepetiba Bay were sampled. A total of 24 polychaete morphospecies, grouped among 21 families, were identified in these sandy beaches. The polychaete species were classified into 10 feeding guilds, and the SDT guild (suspended-deposit feeders, discretely motile, with tentacles) was the most abundant feeding guild, with 34.2% of total number of organisms. The highest trophic importance index and index of trophic diversity values were recorded on the sheltered beaches. A canonical correspondence analysis showed that the exposure rate, beach length, and grain size of the beach sediment significantly affected the polychaete feeding guild distribution and abundance. We can conclude that sheltered beaches have a higher diversity of feeding guilds than exposed beaches and that the biological descriptors of the feeding guilds are directly associated with the grain size of the sediment.

POPULATION BIOLOGY OF NASSARIUS VIBEX (SAY, 1822) ON A SHELTERED BEACH IN SOUTHEASTERN BRAZIL

ABSTRACT Nassariids have a worldwide distribution and are most often found in sheltered embayments in tropical, subtropical, and temperate zones occurring in intertidal and subtidal areas. Species of this genus are scavengers, constituting a major link in the energy flow between carrion, independent of trophic levels, and the environment. The aims of this study are to compare the distribution pattern and the population biology (growth and mortality) of males and females of Nassarius vibex. Sampling was carried out monthly, at spring low tide, from September 2007 through February 2009 at Flexeiras Beach, located in Rio de Janeiro state (22°), southeastern Brazil. Sampling was conducted according to a systematic design in which biological samples were taken along 6 transects spaced equally and perpendicular to the shoreline. On each transect, 10 equally spaced sampling units (SUs) were established: the first (SU1) at the waterline, the second last (SU9) on the drift line, and the last (SU10) 3 m above the drift line (supralittoral). Highest population abundances were observed in spring for both sexes. There were significant differences in abundance among the levels in both sexes. Females of N. vibex had lower abundance, grew faster, and had higher mortality and shorter life spans than males. Variations in the population parameters of N. vibex might be regulated by phenotypic adjustment in local conditions, food availability, and, apparently, in this case, by exposure to organotin compounds inducing to the imposex.

Heavy metal contamination in sandy beach macrofauna communities from the Rio de Janeiro coast, Southeastern Brazil

We evaluated concentrations of eight heavy metals Cr, Zn, Pb, Ni, Cu, Cd, Co and V, in tissues of representative macrofauna species from 68 sandy beaches from the coast of Rio de Janeiro state. The links between contamination levels and community descriptors such as diversity, evenness, density and biomass, were also investigated. Metal concentrations from macrofaunal tissues were compared to maximum permissible limits for human ingestion stipulated by the Brazilian regulatory agency (ANVISA). Generalized linear models (GLMs) were used to investigate the variability in macrofauna density, richness, eveness and biomass in the seven different regions. A non-metric multidimensional scaling analysis (n-MDS) was used to investigate the spatial pattern of heavy metal concentrations along the seven regions of Rio de Janeiro coast. Variation partitioning was applied to evaluate the variance in the community assemblage explained by the environmental variables and the heavy metal concentrations. Our data suggested high spatial variation in the concentration of heavy metals in macrofauna species from the beaches of Rio de Janeiro. This result highlighted a diffuse source of contamination along the coast. Most of the metals concentrations were under the limits established by ANVISA. The variability in community descriptors was related to morphodynamic variables, but not with metal contamination values, indicating the lack of direct relationships at the community level. Concentration levels of eight heavy metals in macrofauna species from 68 sandy beaches on Rio de Janeiro coast (Brazil) were spatially correlated with anthropogenic activities such as industrialization and urbanization.

Crustaceans composition in sandy beaches of Sepetiba Bay, Rio de Janeiro, Brazil

A crustacean survey was made in Sepetiba bay, Rio de Janeiro state, southeastern Brazil. Twelve sandy beaches were sampled on five islands in this embayment. A total of 3024 individuals were collected, belonging to 21 species, which are grouped in 16 families, seven infraorders, seven suborders, and four orders. Isopods, followed by amphipods and tanaids, showed the highest abundance, amounting to over 92% of the dominance of crustaceans. The main species were Excirolana armata , Excirolana braziliensis (isopods), Atlantorchestoidea brasiliensis (amphipod), and Monokalliapseudes schubarti (tanaid), which together accounted about 80% of crustaceans of the beaches studied. Excirolana braziliensis had the highest frequency. The majority of species found are typical of sandy beaches, with large spatial distribution.