Science Advisory Report 2017/013

Application of a framework to assess vulnerability of biological components to ship-source oil spills in the marine environment in the Pacific Region

Summary

• In support of the development of a timely and informed response to ship-source oil spills in the Pacific region, DFO Science developed the ‘National Framework to Assess the Vulnerability of Biological Components to Ship-source Oil Spills in the Marine Environment’ (hereafter termed the ‘framework’) which was reviewed through a CSAS National Peer Review in March 2016 (Thornborough et al., 2017).
• The framework uses a structured method to identify the biological components most vulnerable to a ship-source oil spill utilising a suite of criteria and a screening and ranking process. DFO’s Oceans Branch requested that Science Branch provide an adaptation and application of this framework to the Pacific region.
• The scope of the framework is limited to considering only the direct effects of oil. It was not designed to incorporate potentially significant indirect and food web effects such as consumption of contaminated food sources (e.g. contaminated plankton impacts on baleen whales), or cumulative effects from multiple stressors. Furthermore, this application is limited to marine biological components within DFO’s jurisdiction in the Pacific region. However, it serves as an example of a method that could be applicable to biological components in other jurisdictions (e.g. marine birds).
• All marine biological components within DFO’s mandate in the Pacific region are represented by sub-groups containing one or more species. The sub-groups described for the Pacific region application of the framework were developed through iterative changes in parallel with scoring. The proposed sub-groups are considered appropriate to represent the suite of on-shelf biota in the Pacific region, while also providing sufficient discrimination for scoring the vulnerability criteria.
• Some biological groups in the framework required considerable changes to sub-group breakdown when adapted for the Pacific region (i.e. marine fishes and marine algae/plants), whereas other biological groups required little to no changes (i.e. marine mammals, marine reptiles, marine invertebrates). Modifications to the sub-groups outlined in the framework were clearly stated and justified to facilitate comparable exercises in other regions.
• The following major changes were made to three of the vulnerability criteria in this pilot application of the framework to the Pacific region:
1. Two criteria in the sensitivity category (‘loss of insulation’ and ‘reduction of feeding/photosynthesis’) were merged into a single criterion named ‘mechanical sensitivity (reduction in feeding/ photosynthesis/insulation)’ because both criteria capture impacts to energetics.
2. Within the exposure category of criteria, site fidelity was moved from the aggregation/concentration criterion to the mobility criterion to capture mobile species with very limited home ranges.
3. The name of a criterion within the exposure category was expanded from ‘interaction with sediment’ to ‘seafloor or vegetation interacting’ to address the fact that oil can also persist in consolidated sediments and result in exposure.
• Scoring the chemical sensitivity (impairment due to toxicity) criterion was challenging due to the breadth and conflicting nature of the literature on this topic. As a consequence, all sub-groups were given a precautionary score of 1*, based on a broad evaluation of toxicity on a whole oil basis, rather than a function of the constituents of the oil.
• The modified scoring criteria, and screening and ranking methods outlined were considered valid for use in the Pacific region to identify an appropriate list of sub-groups most vulnerable to a ship-source oil spill, and may also be applicable to framework adaptation in other regions.
• The screening and ranking method selected for this application required sub-groups to fulfil at least 1 exposure and 1 sensitivity criterion, and then be ranked based on the vulnerability score (total score over all criteria). The method was selected because the ranked complement of sub-groups was most consistent with the scientific literature. It differs from the framework method where scores were ranked based on recovery score.
• Relative vulnerability rankings of sub-groups were based on total additive scores across the three vulnerability criteria categories (exposure, sensitivity, and recovery). It is important to note that the unequal number of criteria in each of the vulnerability categories may result in unequal weighting of those categories in the total score (vulnerability score). It is recommended that further iterations of this approach look carefully at how the relative rankings are estimated to avoid unintentional bias in specific categories.
• Important knowledge gaps were identified throughout the application of the framework, and are summarized in a gap analysis.
• The geospatial representation of the outcomes of this framework will provide a foundation and a useful collaborative tool to inform marine spatial planning and response efforts in the Pacific region.

This Science Advisory Report is from the September 14-15, 2016 Evaluation of Pacific Region application of a National Framework to assess the vulnerability of biological components to ship-source oil spills in the marine environment. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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