Offshore oil and gas, and operational sheen occurrence: is there potential harm to marine birds?

Abstract

Hydrocarbon discharges into the ocean, both regulated and accidental, occur from offshore drilling and production operations, and can result in oil sheen (≤3 μm thick) and slick (>3 μm thick) formation, potentially harming marine birds. Sheens may commonly occur around offshore oil and gas platforms in Atlantic Canada, however, there is little information on regularity of occurrence. Further, there are few direct studies on potential impacts of sheens, associated with offshore oil and gas operations, on marine birds. We reviewed potential sources and frequency of hydrocarbon accumulation on sea surfaces from offshore oil and gas operations in Atlantic Canada, and the likelihood of overlap with marine birds. We conducted a literature review on lethal and sub-lethal effects of low levels of oil contact and ingestion on marine birds, focusing on studies that describe measured dosages of oil. We extrapolated from these data on low-dose oil exposure to link possible effects to marine birds resulting from exposure to sheens. We found that sheens occur around production operations in Atlantic Canada at allowable levels of oil concentrations in produced water. Frequency and extent of occurrence cannot be estimated from current monitoring practices. While immediate lethal effects to seabirds likely are not common from external oiling of feathers from sheens, added stressors, such as cold weather, can result in external oiling from sheens having significant impact on seabird metabolic rate and can be ultimately lethal. Ingestion of small amounts of oil, doses that realistically could be expected from exposure to sheens, in some cases resulted in sub-lethal effects to adult seabirds, primarily affecting metabolic rate, sub-lethal health impacts, and reproductive output. Nestlings and eggs do not come in direct contact with sheens, yet these life stages are highly sensitive to oil, and transfer of oil from adults exposed to sheens likely is above tolerance levels at times. Negative effects to reproductive output from small doses of ingested oil could be causing undetected impacts on marine birds and marine bird populations. Lack of standardized monitoring of marine bird contact with sheens and potential harm makes assessments of magnitude and extent of impact problematic.

Deepwater Horizoncrude oil reduces aerobic capacity of birds

“…Additionally, similar effects on RMR have been observed in other taxa (e.g., fish) 59 . It is worth noting that several studies have found that external oiling caused the opposite response to occur, whereby oiled birds increased RMR 22 to maintain body temperature as a compensatory response to external oiling damaging feather integrity and reducing insulation 60,61 . The differences in RMR responses highlights the potential for external and internal exposure to have substantially different effects on metabolic processes.…”

A Physiologically Based Oiling Model (PBOM) to Predict Thermoregulatory Response in Birds

“…As oil and/or water penetrate the plumage, an equal volume of air in the plumage is displaced until the plumage reaches saturation. Whereas the effects of oiling on feather microstructure are well documented (O'Hara and Morandin 2010; Morandin and O'Hara 2014, 2016), the rate at which oil may displace air from the plumage is not well understood. Variables were introduced into the PBOM to adjust the rate at which feathers are compromised and the rate at which the volume of air in the plumage is displaced by oil and/or water.…”

“…From literature cited by French et al (1996) and French‐McCay (2009), as well as studies published since that time (e.g., O'Hara and Morandin 2010; Morandin and O'Hara 2014, 2016), it is apparent that numerous variables can affect the physiological response of birds after oiling. The variables captured in the PBOM as they relate to receptors (i.e., birds), their exposure to oil, and ambient environmental conditions, are presented diagrammatically in Figure 1.…”

Experts’ opinions on threats to Leach’s Storm-Petrels ( Hydrobates leucorhous ) across their global range

“…Leach's Storm-Petrels spend most of their time at sea in contact with the ocean surface, either to feed or rest. This makes them vulnerable to hydrocarbons discharged from vessels or offshore platforms and to more voluminous oil spills (Fraser et al 2006, Wilhelm et al 2007, Ellis et al 2013, Morandin and O'Hara 2016.…”