Pinnotherid crabs are typically found associated with many benthic invertebrates. O n sandy beaches of southern Brazil, Pinni.\-apa/u~orziensis RATHBUN, 1918 inhabits burrows of the ghost shrimp Seryio niirirtt (RODRIGUES, 1971). The population dynamics of this crab were studied from monthly samples taken between March 1989 and November 1991 near the Patos Lagoon outlet, southern Brazil (ca. 32"13'S; 52"15'W). There was no correlation between the number and size of the crabs and the size of their respective hosts. Mean densities and incidence reached 3.1 indiv:opening-' (range: 0 to 29) and 83.9%. respectively. Sex-ratios were not significantly different from 1 : 1 for the different size classes and sampling dates. Ovigerous females were found between October and March, showing an average fecundity of 1529 eggs per female. The annual recruitment pattern was bimodal, with a ininor peak in summer and a fall peak that accounted for almost 70% of the population maintenance. Males and females both reached a maximum carapace width of 11.5 mm and had a life span of nearly two years as estimated from fitted VON BERTALANFFY growth curve parameters.

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The aim of this study was to determine the short-term environmental changes caused by the simultaneous passage of a high energy event on two sandy beaches with different morphodynamic states and their influence on the richness, abundance and distribution of the benthic macrofauna. Two microtidal exposed sandy beaches with contrasting morphodynamics were simultaneously sampled before, during and after the passage of two cold fronts in Santa Catarina. The reflective beach showed a higher susceptibility to the increase in wave energy produced by the passage of cold fronts and was characterized by rapid and intense erosive processes in addition to a capacity for rapid restoration of the beach profile. As regards the dissipative beach, erosive processes operated more slowly and progressively, and it was characterized further by a reduced capacity for the recovery of its sub-aerial profile. Although the intensity of the environmental changes was distinct as between the morphodynamic extremes, changes in the composition, richness and abundance of macrobenthos induced by cold fronts were not evident for either of the beaches studied. On the other hand, alterations in the distribution pattern of the macrofauna were observed on the two beaches and were related to variations in sea level, position of the swash zone and moisture gradient, suggesting that short-term accommodations in the spatial structure of the macrobenthos occur in response to changes in environmental conditions in accordance with the temporal dynamics characteristic of each morphodynamic state.
Com o objetivo de avaliar as alterações ambientais de curtoprazo causadas pela passagem de um mesmo evento de alta energia em praias com diferentes estágios morfodinâmicos e sua influência na riqueza, abundância e distribuição do macrobentos, duas praias arenosas expostas e pertencentes aos extremos morfodinâmicos foram simultaneamente amostradas antes, durante e após a passagem de duas frentes frias em Santa Catarina. A praia refletiva apresentou maior suscetibilidade ao incremento de onda causado pelos eventos e caracterizou-se por rápidos e intensos processos erosivos, além de apresentar uma rápida capacidade de restauração do perfil praial. Por outro lado, os processos erosivos operaram de forma lenta e progressiva na porção subaérea da praia dissipativa, que caracterizou-se por uma reduzida capacidade de recuperação do perfil . Embora a intensidade das alterações ambientais tenha sido distinta entre os extremos morfodinâmicos, mudanças na composição, riqueza e abundância do macrobentos, induzidos pelas frentes frias, não foram evidentes para nenhuma das praias estudadas. Por outro lado, alterações na distribuição da macrofauna foram verificadas nas duas praias e estiveram relacionadas com as variações do nível do mar, do posicionamento da zona de espraiamento e dos gradientes de umidade daí decorrentes, sugerindo que acomodações de curto prazo na estrutura espacial do macrobentos ocorrem como resposta às alterações nas condições ambientais de acordo com a di...

This study investigated the effect of environmental factors on the annual average zonation pattern of benthic macrofauna of sub-aerial profile of three exposed sandy beaches of Santa Catarina with different morphodynamic characteristics. Sampling was carried out between March 2000 and March 2001, with monthly frequency on reflective and dissipative morphodynamic extremes and bimonthly frequency on the intermediate state. Results showed that macrobenthic zonation presented marked differences across the morphodynamic spectrum. The main differences observed from reflective to dissipative conditions were: a) increase in the number of species in lower zones of the beach; b) expansion of zones characterized by high water content of sediment and c) increase in the overlapping of zones, mainly on lower levels of the beach. Canonical Correspondence Analysis related these differences to distinctive cross-shore gradients in sediment moisture levels, sediment reworking and mean grain size that exist across the morphodynamic spectrum, showing that it is important to analyze these environmental factors in studies conducted to investigate zonation on microtidal exposed sandy beaches.
Este estudo analisou o efeito dos fatores ambientais sobre a zonação da macrofauna bentônica da porção subaérea de praias arenosas expostas e caracterizadas por diferentes estágios morfodinâmicos em Santa Catarina. As amostragens foram realizadas entre março/2000 e março/2001, a intervalos mensais nos extremos morfodinâmicos e bimestrais no estágio intermediário. Os resultados obtidos demonstraram que a zonação da macrofauna bentônica apresentou as seguintes diferenças, do extremo refletivo para o dissipativo: a) aumento do número de espécies nos níveis inferiores da praia; b) aumento da extensão das zonas faunísticas caracterizadas por elevado teor de umidade do sedimento; e c) aumento da sobreposição das zonas faunísticas, principalmente, nos níveis inferiores da praia. Os resultados da Análise de Correspondência Canônica mostraram que estas diferenças resultam dos distintos gradientes verticais de umidade, remobilização sedimentar e tamanho médio de grão existentes ao longo do gradiente morfodinâmico, demonstrando a importância de analisar estas variáveis em estudos dedicados a investigar os padrões de zonação de praias arenosas expostas e de micromaré