The Cook Strait Canyon, New Zealand: Geomorphology and Seafloor Biodiversity of a Large Bedrock Canyon System in a Tectonically Active Environment

The multibranched Cook Strait Canyon system (41°S–42°S) deeply incises the bedrock between the North and the South islands of New Zealand, cutting approximately 40km into the continental shelf. Water depths range from 120m on the shelf to 2,700m in the Hikurangi Trough. The geomorphology of the canyons reflects a tidally dominated seaway and intense seismotectonic activity associated with the neighboring active Pacific– Australia plate boundary. The study area covers ~4,500km₂, including the Cook Strait Canyon (~1,800km₂), areas of continental shelf, and deep sedimentary trough. This study uses Kongsberg EM300 multibeam data, 110 sediment samples, ~100 biological samples, and ~200 benthic taxa identified from seabed images and direct samples. Derivative spatially continuous data sets include geomorphic mapping, quantitative backscatter analysis, and sediment distribution, which enabled us to spatially analyze the geomorphic–sedimentary–biologic relationships to characterize the geohabitat and benthic biodiversity of a large, bedrock-incised submarine canyon system.