Beyond diving depths: Deepwater macroalgae in the New Zealand region

Abstract

Recent research voyages in the New Zealand region have resulted in new macroalgal specimens and underwater imagery from a range of deepwater habitats in coastal and offshore areas. In addition, targeted surveys have enabled the investigation of the biodiversity of specific island and shelf regions of New Zealand, and assemblages in biogenic habitats, as well as the quantification of biodiversity of offshore areas where the potential for resource utilisation/extraction has been identified. Macroalgal records based on vouchered herbarium specimens were compiled for the New Zealand region, summarising their distribution by depth and region from 29.233° S to 52.55° S. A total of 275 taxa were recorded, with 249 identified to species level from depths greater than 19 m, and 179 species from depths greater than 29 m. Of the 249 species, 8 % were collected solely at depths greater than 29 m, and 6 % were found exclusively at levels deeper than 44 m. Around 17 % of species were found to be recorded across a very wide range of depths (e.g., habitat-forming kelp Ecklonia radiata from shallow subtidal habitats to depths in excess of 90 m). A study off the southwest North Island provided both presence and absence data for macroalgae, and, through sampling and imagery of the seabed, enabled the distribution and habitat associations of macroalgae in offshore benthic habitats dominated by soft sediments at depths of 14 to 97 m to be quantified and documented for the first time. The greatest proportion of sites where macroalgae were recorded (particularly non-geniculate coralline algae) were at depths of 45–59 m where there were either rocky outcrops or robust shell debris. This is the first collation and summary of data on the occurrence of deepwater macroalgae around New Zealand, and serve to identify gaps in sampling and to highlight issues around sampling methods and the different data that they provide. These data now serve as a baseline for subsequent work in New Zealand and for comparison with other deepwater ecosystems.