Dispersant: rationale for colour coding in Table 4.2

• This evaluation focuses on the levels of exposure and probable impact of dispersants on ecosystem services. No consideration has been given to the beneficial effects of applying dispersants during an oil spill which would disperse the oil, enable more rapid biodegradation and limit potentially greater impacts to shorelines and organisms. These benefits should be considered in a Net Environmental Benefit Analysis.
• The impact on SPUs is proposed to be primarily driven by the overall level of exposure to the dispersant – considering concentration and short-term duration of exposure.
• Exposures are expected to be in the surface mixing zone of marine waters with potential exposure in estuarine waters.
• The exposure scenario consists of dispersant application in the water column separate from any interaction with spilt oil (i.e. off target dispersant spraying).

Table 4.2: Potential impact of dispersant use on specific ecosystem services (green: no impact; yellow: moderate impact; red: severe impact) and potentially impacted service-providing units (SPU)