Biogeography and ecological distribution of shallow-water benthic foraminifera from the Auckland and Campbell Islands, subantarctic southwest Pacific

Bruce W Hayward,Rhiannon Daymond-King,Hugh R Grenfell,Ashwaq T Sabaa

doi:10.1144/jm.26.2.127

Abstract

Abstract. One hundred and forty-eight species of benthic foraminifera are recorded from depths shallower than 80 m around the subantarctic Auckland (130 spp.) and Campbell (71 spp.) Islands, southwest Pacific. Comparisons with other circum-polar, subantarctic island groups suggest that they all have relatively low diversity, shallow-water benthic, foraminiferal faunas, with their sheltered harbours dominated by species of Elphidium, Notorotalia, Cassidulina, Haynesina and Nonionella-Nonionellina. More exposed environments are dominated by a small number of species of Cibicides, Miliolinella, Rosalina, Quinqueloculina and Glabratellidae. The extremely low species richness (three species) in high-tidal grass-dominated salt marsh on Campbell Island is similar to that reported from Tierra del Fuego at a similar latitude. The faunas of Auckland and Campbell Islands have their strongest affinities (70–75% species in common) with New Zealand’s three main islands, 460–700 km away. Ten percent of their fauna has not been recorded from mainland New Zealand, reflecting one endemic species and a small element of apparently subantarctic and bipolar-restricted species. Since there have been no shallow-water (<500 m) links to other lands since these two Miocene volcanic islands were formed, it is concluded that most benthic foraminiferal species have arrived in suspension in eddies of surface water, many since the peak of the Last Glacial.

Highlights

Location and setting The uninhabited Auckland (50( 45# S, 166( E) and Campbell (52( 30# S, 169( E) Islands are the southern-most land areas within New Zealand’s Exclusive Economic Zone in the southern SW Pacific Ocean (Fig. 1)
In common with other tropical–subpolar regions, high tidal salt marsh and salt meadow environments are dominated by agglutinated foraminiferal associations (1, 2), whereas most other shelf and bathyal environments have calcareous-dominated faunas (e.g. Murray, 1991; Hayward et al, 1999)
Agglutinated associations are recorded here only from the head of Perseverance Harbour, Campbell Island, similar high tidal environments were not sampled on the Auckland Islands and they will undoubtedly be present there

Summary

Introduction

Location and setting The uninhabited Auckland (50( 45# S, 166( E) and Campbell (52( 30# S, 169( E) Islands are the southern-most land areas within New Zealand’s Exclusive Economic Zone in the southern SW Pacific Ocean (Fig. 1). During the Pleistocene, glaciers flowed down radiating stream valleys on both island groups and eroded out wide ‘U-shaped’ profiles. Most of these valleys were flooded by rising sea-level during each interglacial, forming long, deep (up to 70 m) inlets and harbours (Fig. 1). The average rainfall on both islands is 1000–1500 cm, with precipitation averaging 325 days each year on Campbell Island (Peat, 2003) Much of this rain soaks into the peaty soil beneath the forest or scrub and flows out through the intertidal zone as acidic, tannin-stained seepage

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