Light to intermediate oil sheens increase Manx shearwater feather permeability

Oil pollution has profound negative impacts on the marine environment, with seabirds particularly vulnerable to oiling, due to the amount of time spent on the sea surface foraging or resting. Exposure to oil can affect feather structure and influence waterproofing, buoyancy and thermoregulation. We investigated the effects of surface crude oil on the feather structure of Manx shearwaters (Puffinus puffinus), a seabird species that spends a high proportion of time on the water surface. Sampled body contour feathers were exposed to varying thicknesses of surface crude oil before assessing their resistance to water permeation, increase in mass and clumping of feather barbules. Surface oil as thin as 0.1 µm was enough to increase feather permeability, while greatest impacts on permeability were caused by exposure to dark colour surface sheens 3 µm in thickness. Increases in feather mass of up to 1000% were noted in heavy oiling scenarios due to contact with thicker oil slicks, which may significantly affect wing loading and energetic expenditure.

1. Introduction

Industrialization of the marine environment is continuously intensifying, with all marine habitats affected by at least one anthropogenic influence [1]. This places increased pressure on marine ecosystems through stressors including habitat destruction, overfishing and pollution. Oil spills are one form of environmental pollution that poses both immediate and long-term consequences for marine ecosystems. Large-scale oil spill disasters have been frequently recorded over the past number of decades, including the Exxon Valdez (Alaska, 1989) [2], Sea Empress (Wales, 1996) [3], Prestige (Spain, 2002) [4] and Deepwater Horizon (Gulf of Mexico, 2010) [5]. While not as immediately damaging as an acute large-scale leak, persistent or chronic oil pollution can also impact vulnerable marine populations over much greater time scales. The rapid release of large volumes of oil during catastrophic spill events directs immediate focus on rectifying the incident, whereas cases of persistent and chronic oil pollution often occur on a smaller scale but on a much more frequent basis. Such persistent oil spills can also have a greater long-term impact on marine life than rapid spills like Exxon Valdez [6].

The spread of oil from the point of release is a complex process. The volume of oil spilled, along with the chemical composition and stage of refinement can affect the spread of oil across the water surface, where it can be further transported via wind and water currents [7,8]. Crude oils are notorious for spreading rapidly as a thin film coating on the sea’s surface. The buoyancy and viscosity of such oils make it a highly dangerous substance that can be problematic for a wide range of marine life, particularly those that interact with the sea surface. Natural breakdown of oils through emulsification in water can occur over time, or through human intervention via the addition of emulsifiers or in situ burning. The wider extent of impacts from crude oil spills, however, are not well understood, as slicks can be transported large distances, affecting organisms ranging substantial distances from the original incident.

Extract taken from: Murphy E., Jessopp M., and Darby J., 2022 Light to intermediate oil sheens increase Manx shearwater feather permeability R. Soc. open sci. 9220488220488 http://doi.org/10.1098/rsos.220488