The most common sandhopper found in the sandy beaches of the Brazilian coast, Atlantorchestoidea brasiliensis, has suffered from activities related to human recreation, which include removing the vegetal wrack from beaches. It is known that macrophyte beach deposits are the main food source of sandhoppers. The aims of the present study were to: (1) evaluate the variation in food availability as vegetal deposits at two levels of the beach, (2) understand how variations in amphipod demography are correlated to variations in beach vegetal wrack abundance, (3) evaluate how meteorological (precipitation, air temperature and humidity, solar irradiation, wind speed and direction) and biological (beach vegetal wrack and amphipod demography) parameters are correlated, and (4) evaluate the genetic composition and diversity of the amphipod population at two localities with different degrees of disturbance over a 2 year period. Seasonal and inter-annual variations were observed in beach vegetal deposits and amphipod demography. Vegetal deposits were most abundant during the summer and at the high level of the beach; they were positively correlated with air temperature and negatively correlated with air humidity. Amphipod demographic parameters (size, weight, and % juveniles) measured using active amphipods showed a significant correlation to the variation pattern of the vegetal wrack. The percentage of active juveniles was strongly correlated with air humidity. No genetic differentiation was found between amphipods for different localities and years. Demographic composition of active A. brasiliensis amphipods over time was strongly correlated with beach vegetal wrack and debris variation, suggesting the importance of beach vegetal wrack on amphipod demography and growth. (c) 2019 Elsevier B.V. All rights reserved.
