A College of Charleston graduate student has completed a study in collaboration with scientists from NOAA’s National Centers for Coastal Ocean Science (NCCOS), to assess the lethal and developmental effects of tire wear particles (TWP) on estuarine fish.
Estuaries are critical ecosystems that provide food, shelter, and nursery grounds for fish and wildlife; estuaries also protect coastal communities from flooding and storm surge and filter runoff from land. This runoff often includes TWP, which are generated through friction between vehicle tires and road surfaces.
TWP can become a significant source of microplastics and are widely distributed in aquatic systems. Tires contain chemical additives such as 6PPD, an antioxidant that prevents cracking and degradation of rubber, and 6PPD-quinone, a toxic product formed when 6PPD reacts with atmospheric ozone. Once in the aquatic system, these chemicals leach into the water and may negatively impact the survival and development of fish.
For the purpose of this study, researchers used sheepshead minnow and spotted seatrout, which are ecologically and economically significant in the South Atlantic and rely on estuarine habitats throughout their life cycles. Scientists collected embryos post-fertilization and exposed them to 6PPD and 6PPD-quinone to assess embryo-larval survival and development. The fish were also exposed to TWP leachate, which are the chemicals in liquid leached from solid material. For the purpose of this experiment, “leachate” refers to chemicals other than 6PPD and 6PPD-quinone. The leachate was made by soaking the tire wear particles in seawater for 48 hours and then filtering them out. The leachate contains all water soluble chemicals from the tire particles.
This research concluded that sheepshead minnow survival was not significantly impacted when exposed to 6PPD, 6PPD-quinone, or the TWP leachate. However, 6PPD and TWP leachate caused delays in hatching. Spotted seatrout were more sensitive, showing reduced hatching success at 6PPD concentrations of 500 µg/L and significant mortality at 6PPD concentrations of 250 and 500 µg/L, as well as at 6PPD-quinone concentrations of 500 µg/L. The researchers measured fish length and eye diameter and discovered that growth for both species was negatively impacted by 6PPD, 6PPD-quinone, and the leached chemicals. 6PPD-quinone was detected in water and sediment samples collected from the Charleston Harbor Estuary, but concentrations were well below the levels posing a risk to estuarine fish.
These findings can inform regulatory agencies of the effects of TWP and support fisheries management efforts aimed at mitigating the impacts of these pollutants.
This work is supported by the Clean Water Act.