Mineral oil, movement and monitoring ecosystem health

Commercial formulations of mineral oils and other forms of lubricants can be released into the environment during the application, use and lifetime of a product. Mineral oil formulations in combination with other materials such as graphene and silicone nanomaterials can be used to prolong the life and use of sporting equipment, such as bikes and boats. Through this, excess material can be released into the environment during application, or during the products subsequent use. Oil is a challenging pollutant to monitor and assess in aquatic environments due to the hydrophobic nature which makes the distribution and movement of oil different to other types of aquatic pollutants, however an important pollutant to understand with the use of oil and advanced material formulations being developed and currently used.In this study, we explored the impacts that different formulations of mineral oil (with and without graphene/silicon) can have on the keystone freshwater species Daphnia magna. Daphnia have been historically used for toxicity testing of chemicals and other materials such as microplastics and nanomaterials, in addition to being used in field studies as indicators of good environmental health. Due to Daphnia’s well established and broad ranging use, they are an excellent species to explore emerging contaminants to compared to the previously established range of responses. Here, Daphnia were exposed to different formulations and concentrations of mineral oil and their acute toxicity was initially assessed, before subsequent studies were undertaken to determine how oil can impact the Daphnia’s behaviour. This was done by recording the Daphnia movement over a 24 hour period and assessing both the vertical migration in the test vessel, in addition to their movement in a 10mL well (in a multiwell plate) for stress indicators (i.e. more spins in the water are behavioural indicators of higher stress). Daphnia are keystone species, and link the algae (primary producers) to high levels of the food web, therefore impacts on their movement could have wider reaching consequences for aquatic ecosystems. Through evaluating Daphnia movement and interaction with the oil in different test vessels we can also explore how they might influence the transport and mixing of oil into their environment and impact the legacy timeframe of oil contamination.