Application-rate-dependent impacts of a fire retardant on zooplankton community structure of temporary ponds

In the present study, we employed dry sediments in a temporary-pond microcosm experiment to evaluate the response of the zooplankton community after exposure to different application rates of the commercially available fire retardant, Fire-Trol 934. Application rates were selected to reflect ranges used during fire control/prevention operations in grasslands and shrublands in Mediterranean areas. Results show loss of water quality in terms of increased nutrient (total phosphorus and total nitrogen) concentrations, electrical conductivity and water colour. The magnitude of water-quality impact depended on FRC application rate and was most severe in the highest application rate treatment. The zooplankton community was significantly affected by the FRC treatments. In the control, a diverse assemblage of cladocerans, rotifers and ostracods developed, whereas the zooplankton community in all FRC treatments was depauperate, consisting only of a few species of rotifers. The lack of cladocerans, which are effective grazers of phytoplankton, could negatively affect ecosystem functioning and foster eutrophication effects through excessive algal growth, at least during the first weeks after temporary ponds fill with winter rains.