LAUSR

Temperature is one of the more important factors affecting metabolism and fitness of aquatic ectothermic animals. The present study aimed, therefore, at quantifying and comparing the oxygen consumption rates of several subtropical macrobenthos organisms living in two South African estuarine systems. Oxygen fluxes were measured in the laboratory at an individual level for temperatures ranging between 16 and 30 °C. The metabolic response differed significantly among taxa, developmental stage, and microhabitat, with higher activation energy for the animals from the permanently open estuary compared to the one from the temporarily open/closed system. The invasive snails showed an exceptional higher metabolic performance at higher temperatures compared to the other organisms collected within the temporarily open/closed system. The results suggest that estuaries experiencing prolonged closure with stable environmental conditions and lower biodiversity host the least performing native species. Setting this pattern in a future global change scenario, this study highlights that longer closures of the estuarine mouth caused by changing rainfall regimes and increased freshwater abstractions from catchments are likely to create the ideal conditions for the proliferation of more adaptable invasive species in temporally open/closed subtropical estuaries.