Brazilian sandy beach macrofauna production: a review

Brazilian sandy beach macrofauna production: a review     Marcelo PetraccoI,*; Ricardo Silva CardosoII; Thais Navajas CorbisierI; Alexander TurraI IInstituto Oceanográfico da Universidade de São Paulo (Praça do Oceanográfico, 191, 05508-120 São Paulo, SP, Brasil) IIUniversidade Federal do Estado do Rio de Janeiro (UNIRIO) Instituto de Biociências -Departamento de Ecologia e Recursos Marinhos (Av. Pasteur, 458, 22290-240 Rio de Janeiro, RJ, Brasil)     ABSTRACT The state of the art of the studies on the production of Brazilian sandy beach macrofauna was analyzed on the basis of the data available in the literature. For this purpose, the representativeness of the production dataset was examined by latitudinal distribution, degree of exposure and morphodynamic state of beaches, taxonomic groups, and methods employed. A descriptive analysis was, further, made to investigate the trends in production of the more representative taxonomic groups and species of sandy beach macrofauna. A total of 69 macrofauna annual production estimates were obtained for 38 populations from 25 studies carried out between 22º56'S and 32º20'S. Production estimates were restricted to populations on beaches located on the southern and southeastern Brazilian coast. Most of the populations in the dataset inhabit exposed dissipative sandy beaches and are mainly represented by mollusks and crustaceans, with a smaller number of polychaetes. The trends in production among taxonomic groups follow a similar pattern to that observed on beaches throughout the world, with high values for bivalves and decapods. The high turnover rate (P/B ratio) of the latter was due to the presence of several populations of the mole crab Emerita brasiliensis, which can attain high values of productivity, in the dataset. Most of the studies focus on the comparison of production and, especially, of P/B ratio according to life history traits in populations of the same species/taxonomic group. Despite the importance of life history-production studies, other approaches, such as the effect of man-induce disturbances on the macrofauna, should be undertaken in these threatened environments. Descriptors: Sandy beaches, Macrofauna, Secondary production, P/B ratio, Brazil. RESUMO O estado da arte dos estudos de produção da macrofauna de praias arenosas brasileiras foi analisado a partir de informações disponíveis na literatura. Para essa finalidade, a representatividade dos dados de produção foi examinada de acordo com a distribuição latitudinal, grau de exposição e estado morfodinâmico das praias, grupos taxonômicos e métodos empregados. Além disso, foi realizada uma análise descritiva para investigar tendências da produção dos grupos taxonômicos e das espécies mais representativas da macrofauna de praias arenosas. Um total de 69 estimativas de produção referentes a 38 populações da macrofauna foi obtido a partir de 35 estudos realizados entre 22º56'S e 32º20'S. Estimativas de produção foram restritas a populações de praias situadas no sul e sudeste da costa brasileira. A maior parte das populações estudadas habita praias arenosas expostas dissipativas e é representada principalmente por moluscos e crustáceos, com um número menor de poliquetas. As tendências da produção entre os grupos taxonômicos seguiram um padrão similar ao observado em praias ao longo do mundo, com altos valores para bivalves e decápodes. A alta taxa de renovação (razão P/B) dos decápodes foi devido à presença de diversas estimativas para populações do caranguejo Emerita brasiliensis, as quais alcançam altos valores de produtividade. A maior parte dos estudos aborda a comparação da produção e, especialmente, da razão P/B, de acordo com características da história de vida de populações da mesma espécie e/ou com grupo taxonômico. Apesar da importância de estudos com esse enfoque, outras abordagens, tais como o efeito de distúrbios induzidos pelo homem sobre a macrofauna, deveriam ser empregadas nesses ambientes ameaçados. Descritores: Praias arenosas, Macrofauna, Produção secundária, Razão P/B, Brasil.     INTRODUCTION Secondary production is a flow which represents the formation of biomass through the growth of an individual, or collectively in terms of a population, over time (BENKE, 2010). This variable is a composite measure of density, biomass, growth rate, reproduction, survivorship, and development time (BENKE, 1993) and is, therefore, a key parameter in population ecology (SARDÁ et al., 2000). Production analysis also provides a common link between populations and ecosystems as it represents a measure of the population's function at community/ecosystem level (BENKE, 1993). Despite the importance of this functional variable and its several applications to ecological issues, it is often addressed but briefly in most ecology texts and is usually limited to the context of energy flow and trophic-level efficiencies (BENKE, 2010). Moreover, the assessment of secondary production requires expensive and time consuming sampling programs, even at the level of a single population (DOWNING, 1984; BREY, 1990; CUSSON; BOURGET, 2005). Thus, despite the increase in the number of secondary production studies in recent years, this variable is still under-used (BENKE; HURYN, 2010). Sandy beaches dominate the world's temperate and tropical shorelines and are generally characterized by low production, both primary and secondary (DEXTER, 1992; McLACHLAN; BROWN, 2006). However, very high values of secondary production have been estimated for sandy beach macrofauna populations (e.g. GIANUCA, 1985; LAUDIEN et al., 2003). Moreover, Wilson (1999) has indicated the importance of sandy beaches as exporters of productivity to adjacent ecosystems, and also to total coastal productivity due to the great extension of these ecosystems. Therefore, it is important to obtain estimates of sandy beach macrofauna production, especially in Brazil, which has an extensive coastline. Furthermore, species of the sandy beach macrofauna are harvested extensively around the world and play a very important role as food sources for several marine and terrestrial species, including fish and crustaceans of commercial interest (PETERSON et al., 2000; McLACHLAN; BROWN, 2006). According to what is generally observed around the world, Brazilian sandy beaches are frequently subject to various forms of man-induced stress such as oil spills, contaminated freshwater discharges, structures or activities affecting natural sand transport, and balance, among others, which can affect the life history traits of the macrofauna populations of these ecosystems (AMARAL et al., 2003; SCHLACHER et al., 2007; DUGAN et al., 2008; DEFEO et al., 2009). Therefore, estimates of secondary production are a valuable tool for the rational management of aquatic resources and the evaluation of the effects of man-induced stress (DOWNING, 1984; BENKE; HURYN, 2010). In Brazil, several studie (...truncated)