Science Advisory Report  2014/059

Pathways of Effects for Shipping: An Overview

Summary

  • This science advisory report is intended to provide general advice on how shipping activities may potentially impact the marine and freshwater environment. The Pathways of Effects (PoE) models included in this report are general and simply illustrate linkages that may not be universally applicable.  The potential impacts of shipping can be widespread or localised, and may be chronic or acute.
  • The PoE components included in this report (i.e., movement underway, discharge, oil spills, anchoring, and grounding) are independent of time and space constraints, and do not address the frequency, likelihood of occurrence, nor magnitude of potential impact(s) on an ecosystem.  In no way should this advice or the PoE components be interpreted as risk or threat assessments.
  • A suite of stressors resulting from movement underway (i.e. water mixing, substrate disturbance, noise emissions, icebreaking, strikes, wake, and light emission) may lead to changes in habitat, community structure, and the health (fitness) and survival (mortality) of organisms.
  • Operational and incidental or accidental discharges associated with shipping can result in the discharge of aquatic invasive species, debris, oils and other aquatic or atmospheric contaminants, and nutrients (e.g., via grey water, sewage). Such discharges can result in changes to habitat, community structure, the fitness, mortality, and/or function of aquatic organisms.
  • Oil spills are one of the most damaging events in the aquatic environment, affecting multiple species and habitats.  Spill recovery measures are often largely ineffective and long-term chronic ecosystem effects often result.
  • Anchoring may create vertical obstructions in the water column and/or may result in substantial changes to the substrate composition and structure resulting from crushing and/or sediment re-suspension.  Changes to the substrate as a result of anchoring may alter benthic habitats and may result in sub-lethal impacts or an increase in mortality of benthic organisms.
  • Vessel grounding can affect the substrate, habitat, and benthic organisms. Groundings are more likely near shore when approaching ports but could also occur offshore (e.g., where shallow seamounts or ridges are located).
  • The environmental effects of shipping are multifaceted, with potential consequences on all structures and components of the ecosystem.  As such, PoE models can be strongly inter-related leading to linkages at various levels. However, given many of the linkages have limited documentation of varying quality and quantity, predicting the PoEs can be challenging. The PoE components included in this report were developed based on the current state of knowledge with many potential linkages remaining to be thoroughly quantified.

This Science Advisory Report is from the national peer review process on Science Advice for Pathways of Effects for Marine Shipping held October 1-3, 2013 in Ottawa. The Proceedings from this meeting is available on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule.

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