Behavioural ecology of sandy beach amphipods on Prince Edward Island’s north shore

Nearly eighty percent of the world’s ice-free coastlines are composed of sandy beaches. These ecosystems are being increasingly exposed to human influence in the form of light pollution at night and recreational activity. Nocturnal creatures such as sandy beach amphipods are expected to be especially affected because they rely on darkness for feeding on stranded seaweeds. Hence, the goals of this study were to 1) explore amphipod composition and abundance through seasonal sampling, 2) evaluate amphipod activity when exposed to artificial light at night in different seasons using laboratory mesocosms, and 3) analyze the effect of intraspecific predation on juveniles. Amphipods were sampled at four north shore beaches over three years in which the talitrid Americorchestia longiconis was identified to be the most populous species and was therefore used in the laboratory studies. Mesocosm trials comparing natural conditions with light pollution at night showed a significant disruption of locomotor activity in the amphipods exposed to pollution. Adults were shown to predate and negatively affect juvenile activity as well. These results suggest that light pollution can reduce the feeding activity and the survival of sandy beach amphipods; especially juveniles which are already exposed to increased predation pressure within their own species