The appearance of plastic debris results in impaired visually-mediated behavior in a reef fish: Evidence of visual sensory pollution

Macro-plastic debris (MPD) have become ubiquitous pollutants that can negatively impact marine fauna. MPD occur in a wide range of sizes, colors and shapes. The extent to which the visual appearance of MPD can impact organisms that rely on vision is still not well understood, specifically in terms of its potential for causing distraction, masking, and misleading effects. Here, we hypothesized that, much like other disturbances caused by human activities, such as light, sound, and chemical pollution that alter environmental information and impact animal behaviors, the presence of highly visible MPD could disrupt visually-mediated behaviors by causing sensory disruption. For example, MPD that visually contrast against the seascape's background could distract a predator that uses vision to search and catch prey, which may result in mistaken prey identity and reduced hunting efficiency. Prey could also become less contrasted when their color matches that of MPD, thus masking their conspicuousness to predators. Under laboratory conditions, we tested this possibility by measuring the Sergeant major (Abudefduf saxatilis) damselfish's foraging efficiency to consume a set number of crustacean prey (Artemias spp.) in a determined period of time. This was done under each of five treatments, which consisted of a control, white MPD, green MPD and natural fragments of Ulva algae. We also controlled potential interference from chemicals released by MPD by having a treatment of hidden, but submerged, plastic debris. The damselfish's foraging efficiency declined significantly when exposed to white MPD. Specifically, the debris that had the highest contrast in the aquariums and most closely matched the color of Artemias led to the greatest negative impact on fish's foraging efficiency. The visual characteristics of these white MPD appeared to have caused sensory pollution effects, by distorting and/or masking relevant visual information, which led to impaired visually-mediated hunting behavior in this reef fish. To many marine organisms, plastic debris might appear vastly different from natural visual cues, potentially leading to unexpected consequences, which remain incompletely understood.