Earthquakes have the potential to trigger submarine mass transport processes that transfer substantial amounts of sediment and organic carbon from the continental margin to deep-sea environments. This presentation will review the evidence that such events have had a significant and persistent impact on deep-sea community structure and function across the world’s oceans. While long-recognised, a detailed understanding of these impacts has been thwarted by the rare opportunity to study benthic communities soon after the occurrence of large mass transport events. An earthquake in New Zealand in November 2016 provided for such an opportunity. The earthquake caused significant local and regional ground-shaking that resulted in submarine mass slope failure in the Kaikōura Canyon and the devastation of one of the world’s most productive benthic ecosystems. This event also led to the initiation of a turbidity current and the deposition of sediment >600 km from source at abyssal depths. A series of cores, grabs and camera transects were collected in Kaikōura Canyon itself, and along the path of the turbidity current in the Hikurangi Channel. Data from this sampling were compared to data collected from previous samples in Kaikōura Canyon, which allowed for the quantification of the initial physical and chemical effects on the seafloor environment, including carbon sequestration, as well as changes in benthic community structure. The impacts of earthquake-triggered mass transport events are likely to be similar to those caused by the activities of proposed deep-seabed mining. The last part of the presentation will draw parallels between the two types of disturbances, and based on what we know about the effects of earthquake-initiated events, consider with what confidence we can predict the extent of the local and regional impact on biodiversity from any future seabed mining.
Keynote speaker
Ashley Rowden
Principle Scientist
NIWA
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