Small-scale spatial distribution of ghost shrimp and macrobenthic fauna in an Amazon macrotidal dissipative sandy beach.

Spatial changes in environmental characteristics strongly influence the structure of benthic communities on sandy beaches, where the patterns of occurrence are mainly controlled by morphodynamic characters and biological interactions. Despite being very abundant and extensive, the Amazonian sandy beaches are among the coastal environments less well known to science. On these beaches, the ghost shrimp Lepidophthalmus siriboia Felder and Rodrigues, 1993 is an important component of the intertidal macrofauna. The present study describes the small-scale distribution patterns of L. siriboia and of the macrobenthic communities in a dissipative macrotidal Amazonian sandy beach. Samples were collected in the intertidal zone of two areas: Area 1, next to a tidal channel; and Area 2, away from the tidal channel. In Area 1, with finer sediments, there was a higher burrow density of L. siriboia and higher density and species richness of macrofauna. In both areas, the burrow density of L. siriboia increased towards the sea. The faunal distribution patterns can be explained by changes in flooding and the type of substratum across the shore and alongshore. These findings add to our knowledge of tropical sandy beach ecology and reinforce the idea that tropical macrotidal beaches have a complexity of morphological features, which are drivers of macrofaunal structure. [ABSTRACT FROM AUTHOR]