First observations on surface activity of sandy beach arthropods at the pristine marine reserve of Rocas Atoll, northeastern Brazil

Abstract

Crustaceans and insects, abundant in the upper zone of sandy beaches, are sensitive to anthropogenic pressures. Thus, to better understand the behavioural changes over time with human impact, studying behavioural and populational parameters in places with pristine conditions is crucial. The Rocas Atoll is one of the first no entry marine reserves in the world, and the first Brazilian marine protected area that harbours unique ecosystems. The aim of the present study was to survey the arthropod fauna associated to the upper zone of a sandy beach at Rocas Atoll, and to study the surface activity of the most abundant species along the transects from the intertidal to the dunes and night/day alternation. Nine arthropod species were observed, including the first record of the marine true bug Halobates sp. (Hemiptera) for Rocas Atoll. Phaleria testacea (Coleoptera), Speziorchestia tucurauna (Amphipoda) and Hecamede sp. (Diptera) represented the most abundant species at the upper zone of Rocas Atoll sandy beaches. Phaleria testacea and S. tucurauna presented marked surface activity predominantly at night time and during low tide. Speziorchestia tucurauna was restricted to the wrack fringe during the entire tidal cycle and the population was represented by a greater number of adults. The high abundance of the fly Hecamede sp. was restricted to daytime and hottest temperatures. This is the first study to assess sandy beach arthropods and their surface activity at Rocas Atoll and provides resources to the understanding of sandy arthropods behaviour under preserved environmental conditions.