Extreme physical conditions usually limit the meiofauna occurrence and distribution in highly hydrodynamic environments such as reflective beaches. Despite sediment grains of the upper layers being constantly resuspended and deposited, the high energy of the swash zone besides depositing coarse sediments allows an ample vertical distribution of meiofaunal organisms. The effect of physical, chemical and sediment variables on the vertical distribution of meiofaunal organims and nematodes was analysed on two reflective exposed beaches. Sampling was conducted at three sampling points on each beach in the swash zone. The sediment collected was divided into four 10-cm strata (0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm). The statistical differences between strata due to factors previously established (i.e. meiofaunal composition, density of most abundant taxa) were tested using a hierarchical PERMANOVA applied under similarity and euclidian distances. An inverse relation among average grain size, content of organic matter and sediment sorting was evident. Coarser sediment characterized the upper layers, while at deeper layers the sediment was very poorly sorted and presented a higher content of organic matter. A similar pattern in the vertical distribution of meiofaunal and nematofaunal composition and density was detected. The lowest densities were associated with the first stratum (0-10 cm), highly affected by hydrodynamics. The vertical distribution of organisms was statistically different only when the interaction among factors was considered. This result suggests that zonation and vertical distribution of meiofaunal organisms are determined by the within-beach variability. Descriptors: Reflective beach, Vertical distribution, Spatial distribution, Meiofauna, Nematoda, Sediment. AbstrAct Mariana de Oliveira Martins*, Tito Cesar Marques de Almeida, Maikon Di DomenicoA ocorrência e distribuição da meiofauna em ambientes com alta energia hidrodinâmica, tais como praias refletivas, são normalmente limitadas por extremos físicos. Apesar de as camadas superficiais do sedimento serem afetadas, a alta energia na zona de espraiamento e a presença de areia grossa possibilitam que a meiofauna tenha ampla distribuição vertical. Para testar o padrão de distribuição vertical da meiofauna e de nemátodos em relação às variáveis físicas, químicas e sedimentológicas, duas praias refletivas expostas foram analisadas. As coletas ocorreram na zona de espraiamento em três pontos de cada uma dessas praias. O sedimento coletado foi dividido em quatro estratos de 10 cm (0-10, 10-20, 20-30 e 30-40 cm). A diferença entre os estratos foi analisada com o uso de PERMANOVA com modelo hierarquizado. A análise foi aplicada em matrizes de similaridade e de distância euclidiana, para estudo da composição da meiofauna e densidades específicas de táxons mais abundantes, respectivamente. O padrão granulométrico evidenciado caracterizou-se pela relação inversa entre o tamanho médio do grão e o teor de matéria orgânica aliado ao grau de selecionamento. Sedime...

The distribution of the benthic macrofauna of Itapocoroy Bay, Santa Catarina on Brazilian south coast and the factors that influence it were analyzed within 50 sampling stations determined in a grid, covering the whole extent of this area. Two temporal sampling were done -one in July 2010 and the other in February 2011. Numeric describers of the community were associated with sediment characteristics, depth, salinity and temperature according to multivariate statistical analysis. A total of 4338 organisms were collected With 97 species identified and classified in Polychaeta, Crustacea and Mollusca. Four faunal assemblages were found, and their spatial distribution was mainly related to depth and sediment characteristics. The first assemblage was the deepest and showed higher concentration of fine sediments, dominated by Kinbergonuphis sp. The second assemblage located under the mussel farm showed high heterogeneity of sediments and was dominated by Ampelisca spp. The third assemblage, shallower and with pebble concentration, was dominated by species of the Syllidae family. The fourth assemblage was characterized by well sorted sediment with high percentage of sand, dominated by Prionospio sp. 1. Although this bay is a sheltered site, the distribution of sediments showed that high energetic hydrodynamics processes operate inside it, which is able to avoid the formation of biodeposits. Nevertheless, the constant supply of organic matter and shell fragments accumulation from mussel farms are a source of stress, increasing the abundance and diversity values near the mussel farms.