Short-term effects of hurricane events on the bioindicator species Ocypode quadrata inhabiting an island in essence free of anthropogenic disturbances

Abstract

The effects of high-energy weather events may be most dramatic on coast dominated by sandy beaches, characteristic habitat of the Atlantic ghost crab. This study evaluates the impact of two hurricanes over Ocypode quadrata populations based on the hypothesis that natural disturbances may bring on a decrease in crab burrow size (population structure) and/or a significant decline in the burrow density (relative abundance). Densities of crabs, estimated via burrow counts and their size, evaluated according to burrow opening diameter, were quantified at six sites around Isla de Aves, before (July) and after (November) two major hurricanes (Irma and Maria) that hit the coastal areas on islands of the Caribbean Sea in 2017. Six 2 × 2 m areas were sampled at each site. The results reveal an effect on the size structure, while the population density did not present any evident change between the pre and post-hurricane moments. The decrease in the diameter of the burrows after the passage of the hurricanes, suggests that the larger crabs could have been removed during this event followed by an arrival of new recruits into the ghost crab population. The results suggest a short-term resilience to the impact of extreme climatic events in terms of population density, a scenario that could had been favored by several conditions. Isla de Aves has sandy beaches exposed to ocean currents, which favor the transport of larvae and the recruitment of juveniles. The availability and quality of food, due to its characteristics of being a main nesting site for sea turtles (mainly green turtle); therefore, it offers various resources in abundance (e.g., turtle eggs). As well as the characteristic of being an island practically free of anthropogenic disturbances.