The possible use of sandhoppers as bioindicators of environmental stress on sandy beaches

Several studies have addressed the biology and behavioural adaptations of sandhoppers, common and widespread inhabitants of sandy beaches in temperate areas. The increasing stress (both natural and anthropogenic) to which beaches are subject around the world has posed the question of the choice of good bioindicators to monitor changes in sandy beach ecosystems and propose management options for their conservation. Sandhoppers carry out their whole life cycle on the same beach throughout the year, so they may integrate the effects of environmental changes over a yearly time scale in population features. Moreover, throughout their life cycle, sandhoppers occupy various zones of the beach, from the intertidal zone up and behind the dunes, integrating the local spatial scale that is of interest for the management of sandy beaches. Comparisons among populations from beaches subject to different stressful factors have been conducted over a wide geographical scale (that of the species distribution) and a large base of data exists. Population characteristics, such as seasonality of the life cycle, age structure, sex ratio and genetic variation, as well as behavioural and physiological traits, have shown a potential for their use as suitable bioindicators of environmental stress on beaches. In this study, following the hypothesis of Møller and Swaddle we propose the level of fluctuating asymmetry as a bioindicator of mechanical stress during the critic phases of development.