Population structure and use of space by ghost crabs (Brachyura: Ocypodidae) on an equatorial, macrotidal sandy beach

Abstract

Ocypodid crabs are important components of sandy beach ecosystems and potential indicators of environmental stress. This is the first study about Ocypode quadrata population on an equatorial, macrotidal, high-energy dissipative beach, located in the Amazon coast. The steady temperature and marked hydrological seasons in this region, along with a wide supralittoral extension, provide exceptional conditions for assessing the effect of rainfall on population structure and across shore distribution. Additionally, von Bertalanffy growth parameters were estimated in order to compare with other studied populations of this crab at higher latitudes (subtropical beaches). Burrow abundance had marked differences between the two hydrological seasons in the Amazon coast, with higher values related to higher rainfall. A bimodal burrow zonation was observed, with a significant relationship between burrow abundance and depth, which shows that burrows are generally less abundant and deeper under drier conditions. Growth parameters were similar to those on some subtropical areas, as opposed to some global, expected ecological trends. Large beach width and local climate were important factors to identify clear population trends, which implies that moisture affects the use of the space by these individuals.