Damselfish in distress after consuming plastic

Marine microplastic pollution is a growing concern for coral reef ecosystems worldwide. When ingested, plastic may not only cause blockages within the digestive system, but also introduce toxic chemicals like di (2-ethylhexyl) phthalate (DEHP). This chemical can cause an increase in the number of reactive oxygen species (ROS), which damage cells in the body and ultimately lead to death or disease. Usually, the body uses antioxidants to defend itself against high levels of ROS. In addition, eating plastic can also impact the damselfish's daily routine. In fact, it has been reported that damselfish that consumed polystyrene, a plastic particle, had a lower chance of surviving in their reef homes. This may be because fish that have consumed plastic might produce more antioxidants in response to an increase in toxic ROS caused by the plastic. This increase in antioxidant production requires the fish to spend more energy, which could, in turn, make for a desperate and hungry fish willing to take more risks. Amelia Mannering from the University of Otago, New Zealand and her colleagues therefore investigated whether juvenile common tropical damselfish (Pomacentrus amboinensis) that consumed polystyrene experience damage by ROS, leading them to take more risks and leaving them vulnerable to predators.To do so, Mannering and colleagues fed different groups of fish with food containing polystyrene or polystyrene with the toxic chemical DEHP. The team then kept each group of fish in a separate outdoor tank with a dusky dottyback (Pseudochromis fuscus), which regularly dines on damselfish. After 22 h in close proximity with the predator, the researchers counted the surviving damselfish. The team also looked for plastic particles within the damselfish digestive system. Finally, Mannering and colleagues analysed portions of the damselfish's muscle to identify how much damage had been done by ROS released by the plastic into the damselfish's bodies, as well as the amount of antioxidants they produced to defend themselves from the toxins.The team found that fish muscle that came from fish with more plastic particles in their digestive systems showed a higher degree of damage to cells caused by ROS. In fact, the group of fish that consumed polystyrene with DEHP had the highest levels of damage along with more antioxidants promoting healing and repair. This suggests that plastic with DEHP will cause the damselfish to expend more energy to fight off ROS with antioxidants. However, the predatory dusky dotty backs were no more successful at picking off the damselfish that had dined on plastic than fish that had a plastic-free diet, so consuming plastic did not seem to turn the damselfish into daredevils at risk from predators.In summary, Mannering and colleagues confirmed that consuming microplastic damages the body and requires more energy to heal, and further research can lend insight into how this need for extra energy may stunt growth or allow the animals to develop diseases. In general, it is important to understand the potential ecological impacts of marine plastic pollution, such as fewer and smaller fish in the sea, even though these impacts may not be apparent immediately. One thing is for sure – plastic has no place in marine ecosystems.