A seafloor bioregionalisation for New Zealand

Marine habitats and ecosystems are under increasing pressure from human activities. Well-designed Marine Protected Area (MPA) networks can be highly effective tools for conserving biodiversity and associated ecosystem functions and services. Adequate coverage of biogeographic regions – i.e., large regions that represent broad-scale biodiversity patterns that are relatively homogeneous (stable over space and time) with distinct environmental conditions and biological contents – in a MPA network is seen as key to ensure that protected areas are representative. Building on a recent spatial classification of ‘seafloor communities’ in the New Zealand marine environment (a 75-group classification termed the New Zealand Seafloor Community Classification), a range of broader classifications (i.e., 4–20 groups) were assessed for their suitability to represent seafloor bioregions. Following analysis of within- and between-group classification strength using analysis of similarities (ANOSIM), and visually exploring the geographic patterns at different classification levels, the 9-group classification was defined as the New Zealand Seafloor Bioregionalisation. Bioregions were defined and described in terms of their characterising marine environmental conditions. Here we provide justification for the use of a 9-group classification to provide broad-scale geographical units which complements the higher resolution communities identified in the New Zealand Seafloor Community Classification. We discuss the use of the New Zealand Seafloor Bioregionalisation for incorporating bioregional representativeness in future marine spatial planning processes and the management of human activities. The New Zealand Seafloor Bioregionalisation provides more relevant information for spatial planning within New Zealand waters than global or ocean-basin scale bioregionalisations, primarily due to the large amount of nationally relevant data used and applied at a fine spatial resolution.