Effects of a fire-retardant on oviposition habitat selection and larval development of the mosquito Culiseta longiareolata

1. Fire retardants are composed of fertilising salts that are commonly used for fighting wildfires. These chemicals have various effects on individual arthropod species and aquatic communities. 2. This study investigated the effects of four treatments of a prevalent fire retardant [FR CROS 134 (FR), applied at concentrations of 0, 3.8 × 10², 7.6 × 10² and 11.4 × 10² mg litre⁻¹] on oviposition habitat selection (OHS) by Culiseta longiareolata and Culex laticinctus mosquitoes in an outdoor mesocosm. Additionally, larval development of C. longiareolata was examined in response to this fire retardant. 3. The results demonstrate that OHS increased in both species, whereas survivorship (0–86.7%) and time to metamorphosis (5.4–23.1 days) of C. longiareolata were not affected by any of the treatments. However, cyanobacterial biomass increased and heterotrophic bacteria decreased in response to the addition of FR. 4. It was found that FR applications can have unintended consequences which can increase OHS by female mosquitoes. The growing use of fire retardants worldwide, and especially in Israel, justify evidence-based assessment and environmental management of their use. This study is a first critical step in filling the knowledge gap with respect to the impact of FR on aquatic ecosystems.