Macroalgae of the Balleny Islands and western Ross Sea, Southern Ocean

The known macroalgal flora of the Balleny Islands, Southern Ocean, has more than doubled as a result of expeditions to the area over the past 8 years and their subsequent study is reported here.

The samples collected as part of a benthic survey at Borradaile Island, one of the Balleny Islands group, during the 2006 Tiama expedition have been analysed to provide an assessment of benthic community structure. We provide a quantitative assessment of shallow water macrofaunal community composition and seafloor sediment characteristics, and a more qualitative assessment of seafloor habitat structure and epifaunal/floral community composition. The Borradaile Island sites were located in a high energy environment, sediments had relatively high organic and chlorophyll a content, and considerably lower concentrations of degraded plant material (phaeophytin) than noted in previously surveyed southern Ross Sea locations. This could be a reflection of the higher light levels and the large amount of algal detritus noted at the higher latitude Borradaile sites. Borradaile Island macrofaunal diversity was within the range noted for the more southern sites; macrofaunal abundance, however, was more variable. Epifaunal diversity was very low at the Borradaile Island sites, with the seastar Odontaster validus the only large epifaunal taxon found. In contrast, the Borradaile Island dive sites had high macroalgal diversity. Although not observed at the Borradaile Island dive sites, the Tiama voyage researchers noted shallow water areas with high diversities of encrusting organisms. This study has provided the first analysis of shallow water benthic communities of the Balleny Islands. While it has shown some interesting similarities and contrasts in benthic diversity with other coastal Ross Sea locations, this information from Borradaile Island may not be representative of the entire Balleny area, and further surveys from other sites within the Balleny group are recommended.

In 2005, Ministry of Fisheries (MFish) scientists and Ministry of Foreign Affairs and Trade (MFAT) personnel prepared a paper for submission to CCAMLR justifying a Marine Protected Area (MPA) designation for the islands. To collect data in support of the MPA proposal, MFish commissioned a month-long targeted research voyage to the Balleny Islands in February 2006, using the yacht Tiama, (“Balleny Islands Ecology Research Voyage”; ZBD2005-01). MFish also obtained additional samples from the Balleny Islands during a 7-week voyage to the Ross Sea using Tangaroa (“Ross Sea Biodiversity”; ZBD2005-03). In 2004, Tangaroa sampled 49 sites in the Ballenys region as part of a BioRoss voyage (TAN0402 - Biodiversity of deepwater invertebrates and fish communities of the North Western Ross Sea), The Tiama and Tangaroa voyages were very successful, providing important ecological information and specimens from the Balleny Islands area, and supplementary information for the Antarctic Working Group Research Programme. The Tiama voyage included a survey of shallow water benthic faunal communities and habitats using the methods developed for NIWA’s coastal Antarctic research project, ICECUBE (ZBD2001-02). To our knowledge this is the first quantitative sampling of shallow water benthos around these islands.

The objectives of this study were (1) to describe and characterise macroalgae diversity from the Balleny Islands and the Western Ross Sea, and (2) to describe and quantify benthic community structure from one location at the Balleny Islands. This report describes the macroalgal collections obtained on recent and earlier voyages and expeditions to the region as well as presenting an analysis of results of the Tiama’s shallow water benthic survey. The diversity of macroalgal and benthic communities and habitats are compared to that of other Ross Sea locations.