Habitat-forming cold-water corals show affinity for seamounts in the New Zealand region

Abstract

Determining the distribution of habitat- forming scleractinian corals in the New Zealand region is necessary in order to understand the ecological significance of these taxa and the likely impact of an- thropogenic activities on their persistence. Historical records from early publications, research trawl surveys, commercial fishing bycatch and recent biodiversity sur- veys were compiled for the habitat-forming coral spe- cies Madrepora oculata, Solenosmilia variabilis, Gonio- corella dumosa, Enallopsammia rostrata and Oculina virgosa. These data were used to describe the observed depth, geographic distribution and geomorphic habitat associations of the study corals in the region. A boosted regression trees analysis was also used to identify which of 11 environmental variables best describe the distribu- tion of the 5 species across the New Zealand region, and to predict their spatial distribution. The contribution of the environmental variables differed greatly between species, but consistently identified depth and seamount occurrence as important factors de scribing observed coral species distribution. The models identified that M. oculata, S. variabilis and E. rostrata occurred in deep waters (>1000 m) where seabed slopes were steep, tidal current and orbital velocities were slow, sea surface pri- mary productivity was low, and where seamounts were generally present. By contrast, G. dumosa and O. vir- gosa were found in relatively shallower waters, where sea surface primary productivity was high and tidal current speeds were generally fast. Spatial predictions were consistent with the recorded observations and identified that all species, apart from O. virgosa, were distributed throughout the region a nd were found primarily between ~200 and 2000 m.