Assessment of fipronil toxicity to the freshwater midge Chironomus riparius: Molecular, biochemical, and organismal responses.

Fipronil is a phenylpyrazole insecticide that entered the market to replace organochlorides and organophosphates. Fipronil impairs the regular inhibition of nerve impulses that ultimately result in paralysis and death of insects. Because of its use as a pest control, and due to runoff events, fipronil has been detected in freshwater systems near agricultural areas, and therefore might represent a threat to non-target aquatic organisms. In this study, the toxicity of fipronil to the freshwater midge Chironomus riparius was investigated at biochemical, molecular, and whole organism (e.g. growth, emergence, and behavior) levels. At the individual level, chronic (28 days) exposure to fipronil resulted in reduced larval growth and emergence with a lowest observed effect concentration (LOEC) of 0.081 µg L-1. Adult weight, which is directly linked to the flying performance and fecundity of midges, was also affected (LOEC = 0.040 µg L-1). Additionally, behavioral changes such as irregular burrowing behavior of C. riparius larvae (EC50 = 0.084 µg L-1) and impairment of adult flying performance were observed. At a biochemical level, acute (48 h) exposure to fipronil increased cellular oxygen consumption (as indicated by the increase of electron transport system (ETS) activity) and decreased antioxidant and detoxification defenses (as suggested by the decrease in catalase (CAT) and glutathione S-transferase (GST) activities). Exposure to fipronil also caused alterations in the fatty acid profile of C. riparius, since high levels of stearidonic acid (SDA) were observed. A comparison between exposed and non-exposed larvae also revealed alterations in the expression of globins, cytoskeleton and motor proteins, and proteins involved in protein biosynthesis. These alterations may aid in the interpretation of potential mechanisms of action that lead to the effects observed at the organism level. Present results show that environmentally relevant concentrations of fipronil are toxic to chironomid populations which call for monitoring of phenylpyrazole insecticides and of their ecological effects in freshwaters. Present results also emphasize the importance of complementing ecotoxicological data with molecular approaches such as proteomics, for a better interpretation of the mode of action of insecticides in aquatic invertebrates.

Screening of human and veterinary pharmaceuticals in estuarine waters: A baseline assessment for the Tejo estuary.

We investigated the presence of 66 human and veterinary pharmaceuticals from seven therapeutic groups in surface waters of the Tejo estuary. Collection sites covered the entire estuary and included areas near main river inflows and wastewater treatment outfalls, traversing urban, agriculture, aquaculture, and nature reserve areas. Detection of pharmaceuticals was performed via UHPLC-TOF-MS. Pharmaceuticals were found in all sites (32 different compounds in total). Antibiotics, ß-blockers, antihypertensives and anti-inflammatories were the most frequently detected (>90%), with variation in concentrations reflecting the multifaceted nature of estuarine surroundings (accumulated site contamination between 15 and 351 ng L-1). Higher concentrations of antidepressant Sertraline (304 ng L-1), non-steroidal anti-inflammatory Diclofenac (51.8 ng L-1), lipid regulator Gemfibrozil (77.0 ng L-1), antihypertensive Ibersartan (161.9 ng L-1) or antibiotic Doxycycline (128.0 ng L-1), among others, though localized may potentially impact key estuarine functions or services. Ultimately, results provide a baseline for regulatory information and future biota evaluations.