Community structure of macrobenthos in two tropical sandy beaches with different morphodynamic features, Rio de Janeiro, Brazil

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 m2 quadrat sampler. Beaches were also compared according to physical features, such as slope, wave period, wave height, and grain size. According to Dean's Ω 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.

Harvesting effects on tropical invertebrate assemblages in New Caledonia

“…Tropical environments have been explored more recently (Stella et al, 2011), despite some early studies in Asia (Broom, 1982;Lui et al, 2002;Purwoko and Wolff, 2008), America (Vargas, 1988;Fernandes and Soares-Gomes, 2006), the Pacific islands (Dittmann, 1996(Dittmann, , 2000Frouin and Hutchings, 2001) and the Indian Ocean (deBoer and Prins, 2002;Mackie et al, 2005). So far, inventories and quantitative descriptions of invertebrate assemblages in New Caledonia have been limited to very few studies devoted to subtidal communities (Chardy and Clavier, 1988;Garrigue et al, 1998) or to the description of some intertidal populations (Baron and Clavier, 1992;Dumas et al, 2013).…”

Hydrologic interactions of infaunal polychaetes and intertidal groundwater discharge

“…Large-scale studies of communities along estuarine gradients show a positive correlation between biodiversity and salinity (Holland et al 1987, Jorcin 1999, Ysebaert et al 2003, Gimenez et al 2005. At a single site, species distribution can be affected by environmental factors such as grain size (Fernandes & Soares-Gomes 2006), rate of sedimentation (Anderson et al 2004), beach elevation and morphology (McLachlan & Jaramillo 1995), and aperiodic weather-driven tidal events (Brazeiro & Defeo 1996).…”

Variability of macrofauna distribution along a dissipative log-spiral sandy beach in Rio de Janeiro, Southeastern Brazil

“…McLachlan (1996) reported that on a 4-km-long beach in Namibia, the species richness and abundance decreased in the central area of the beach arc where the mean sand particle size increased due to tailings disposal. However, studying two shorter Brazilian beaches (700 and 900 m long), Fernandes and Soares-Gomes (2006) found a significant relationship between species abundance, grain size and beach slope, but not species richness. These results are in agreement with our findings on the relationship between species abundance, species richness and the physical variables.…”

“…Usually, species density is high in the central portions of the beach arc and decreases towards one or both ends (MacLachlan and Brown 2006). The macrofauna distribution alongshore is related to several physical factors, including the presence of freshwater discharge Defeo 2003, Gandara-Martins et al 2014), the morphology and water circulation of the sandy beach (McLachlan and Hesp 1984, Donn 1987, Giménez and Yanicelli 2000, the particle grain size and the slope (McLachlan 1996, Lastra and McLachlan 1996, Fernandes and Soares-Gomes 2006. In addition, biotic factors, such as food availability, settlement behaviour and intra/interspecific competition, also play a role in the alongshore distribution of macrofauna and may interact with the physical variables (Ansell 1983, Defeo and de Alava 1995, Schoeman and Richardson 2002.…”