Abstract
Sandy beach fauna is hypothesized to be mainly structured by environmental variables. As such, it is expected that morphodynamic characteristics are limiting factors, and the species pool inhabiting harsher reflective beaches would be a subset of (i.e., nested in) the fauna of nearby dissipative beaches. We investigated the existence of a nestedness pattern in sandy beach assemblages, as well as the contribution of environmental and spatial variables (i.e., factors that potentially affect an assemblage regardless of environmental conditions - typically related to distance between sites and dispersal of organisms) on sandy beach macrobenthic fauna. Dissipative beaches had higher species richness than reflective beaches but we found no nestedness pattern. Furthermore, almost every beach showed exclusive species. Spatial variables exerted stronger influence on macrobenthic assemblages than local environmental variables. Our results therefore suggest that local and small-scale recruitment is the predominant process structuring macrobenthic assemblages. These results bring important implications for sandy beach conservation: given that spatial distance is an important factor structuring macrobenthic fauna and different sandy beaches harbor different pools of species, conservation programs need to focus on sandy beaches across large spatial scales and with varied morphodynamic characteristics in order to preserve coastal biodiversity.
Highlights
Sandy beaches dominate the ocean shores of temperate and tropical coastlines[1,2] and provide habitats for a well-adapted and diversified fauna, as well as key socioeconomic goods and services such as shoreline protection, nutrient cycling and fisheries[3]
It is currently well known that sandy beaches are strongly influenced by environmental variables such as wave action, tides and sediment type[7,8], and that the interaction of these variables determine a morphodynamic continuum from dissipative to reflective beaches[9,10,11]
According to Beach Index (BI) values and beach width, Toque-Toque and Picinguaba were characterized as reflective; Barra do Sahy, Baleia, Flecheiras 1 and 2, Cidade 2 to 4 and Camaroeiro were characterized as intermediary; whereas Cidade 1, Fazenda 1 and 2 and Palmeiras showed dissipative features
Summary
Sandy beaches dominate the ocean shores of temperate and tropical coastlines[1,2] and provide habitats for a well-adapted and diversified fauna, as well as key socioeconomic goods and services such as shoreline protection, nutrient cycling and fisheries[3]. Global diversity patterns in sandy shores seem to validate sandy beach hypotheses and the role of beach morphodynamics as the main explanatory factor structuring intertidal macrofaunal assemblages: a consistent increase in species richness, abundance and biomass is observed from reflective to dissipative conditions[17,18]. For such hypotheses to be valid, the following assumptions need to be fulfilled:
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