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

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.


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). Auckland Islands (626 km 2 ) and Campbell Island (113 km 2 ) are separated from New Zealand's South Island by 460 km and 700 km, respectively (Peat, 2003). Both are the partly eroded remnants of Miocene basalt shield volcanoes sitting on uplifted basement and oceanic sedimentary rocks (Cook, 1981) that form seamounts sitting above the 500 m background average depth of the Campbell Plateau.
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 Auckland Islands have a coastal fringe of low rata (Metrosideros) forest that passes upwards into dense scrub. Campbell Island has Dracophyllum scrub and grassland extending down to the shore (Peat, 2003). The average Marjorie (M. K.) Mestayer, conchologist at the Dominion Museum (Wellington), obtained sediment from c. 50 m depth at the Auckland Islands in the 1910s and donated some with its molluscs to Baden (A. W. B.) Powell at Auckland Museum (L13513, F201015). In the 1940s, several natural scientists were stationed on the Auckland Islands to watch for enemy warships (Peat, 2003) and, during their time there, Charles (C. A.) Fleming, Bill (W. H.) Dawbin and Jack (J. H.) Sorenson all took small dredge samples of sediment from Carnley Harbour. These samples, and slides of foraminifera picked from them, were deposited in the collections of the New Zealand Geological Survey (where Fleming was employed as a palaeontologist; F201102, F201162) and Auckland Museum (L6184, L13574). In his study of New Zealand ostracods (including the Auckland Islands), Norcott Hornibrook (1953) used M. K. Mestayer, Fleming and Sorenson material (above), and Paul    Table 1). Many of the old qualitative foraminiferal slides from R. L. Mestayer, M. K. Mestayer, Fleming and Dawbin have been examined during this study, with additional taxa, especially unilocular, being added to the species list (Appendix A).
Recently, the deep-water foraminiferal faunas (deeper than 50 m) have been described and mapped for the Campbell Plateau and surrounding region, including mid-and outershelf depths (>50 m) around Auckland and Campbell Islands (Hayward et al., 2007).

Objectives
The main objective of this study is to document more fully the foraminiferal biodiversity of these distant subantarctic islands, compare their faunal composition with that of mainland New Zealand  and other islands in the subantarctic zone around the world (e.g. Heron-Allen & Earland, 1932;Earland, 1933Earland, , 1935. From these studies it is hoped to provide a better idea of foraminiferal biogeography in the SW Pacific and Southern Ocean and infer modes of dispersal.

Unilocular species
One complicating factor in this study is the highly variable richness and diversity of unilocular lagenid species that sometimes occur in huge numbers in shallow-water subantarctic samples. It is suspected that many of these small, low density species may have been winnowed out of deeper-water sediments and transported into the shallows in suspension (e.g. Murray et al., 1982) and thus do not accurately represent the true living biodiversity near the islands. Because of this, the unilocular records have been removed from species lists before making comparisons between regions.

Samples
Most sediment samples used in this study (Fig. 1,Appendix B) were taken by BWH during a visit to the two island groups in March, 2004. Subtidal seafloor samples were taken by a handhauled surficial grab or small box dredge, which tended to sample the upper 5-7 cm of surface sediment. Intertidally a 10 cm 3 sample of the upper 1 cm of surface sediment was taken with a plastic tube. This set of samples was supplemented by older samples held in the collections of the Auckland War Memorial Museum, and the Institute of Geological and Nuclear Sciences, Lower Hutt (above). Some of these samples consisted entirely of a rich qualitative pick of foraminifera, but, where washed bulk sediment was also present, a new quantitative pick of the foraminiferal fauna was made to produce the total species list (Appendix A). There was no opportunity to distinguish living from dead shells through staining.
Faunal slides (Appendix B) are housed in the collections of the University of Auckland, Auckland War Memorial Museum and Institute of Geological and Nuclear Sciences, Lower Hutt (prefixed by AU, L, and F20, respectively). Census data are available digitally as Appendix C (available online at http:// www.geolsoc.org.uk/SUP18275. A hard copy can be obtained from the Geological Society Library).   Auckland Islands Siphotextularia mestayerae Textularia subantarctica  Auckland Islands Textularia subantarctica Table 2. Species of foraminifera previously recorded from inner shelf depths (0-50 m) around the Auckland and Campbell Islands.
Original name and authority Recorded by Location Name accepted in this study Laboratory processing Samples were washed gently over a 63 µm sieve, and the sand residue dried and microsplit down to an amount containing approximately 200 benthic specimens. All benthic foraminifera were picked from the microsplit, mounted on faunal slides, identified and counted (Appendix C). All taxa were identified to species level. Specimens of planktic foraminifera were counted during picking. Some of the samples from the harbours that were rich in small (63-150 µm) specimens which may have been transported in, were dry sieved over a 150 µm sieve and additional picks of this coarse fraction were made (samples with 'c' suffix).

Statistical analyses and diversity measures
Quantitative samples (>63 µm) selected for statistical analysis comprised 16 from Auckland Islands and 21 from Campbell Island -seven Campbell and two Auckland Islands samples were intertidal. Three Auckland and 12 Campbell Islands coarse samples (>150 µm) were also included. Thus the quantitative faunal data consist of census counts of 93 foraminiferal species from 52 samples. The data matrix was transformed by converting counts to percentages of sample totals. A Q-mode cluster analysis dendrogram classification was produced using a Chord dissimilarity coefficient matrix. The mathematical definition of this coefficient is given in Sneath & Sokal (1973). Detrended canonical correspondence analysis (DCCA, Ter Braak, 1985) was used to summarize the percentage faunal data in a two-dimensional ordination plot and relate them to a set of measured environmental and diversity factors (Appendix B). Three indices of benthic foraminiferal species diversity (Appendix B) were determined (Hayek & Buzas, 1997): (1) Fisher Alpha Index, (number of species standardized by number of individuals counted); (2) Information Function, H (a combination of the number of species present and, to a lesser extent, the evenness of species counts); and (3) Evenness, E (a measure of dominance versus evenness of species counts).

Species richness
A total of 148 species of benthic foraminifera, including unilocular species, are recorded here from the Auckland (130 spp.) and Campbell (71 spp.) Islands (Fig. 2). If unilocular species are excluded, there are 113 species from these two groups (Auckland -96 spp., Campbell -64 spp.). This number of species (without uniloculars) is of a similar order to the 53 spp. recorded from around Snares Islands  and the 102 spp. from the Chatham Islands ( Fig. 2; . As happens elsewhere in the world (Gibson & Buzas, 1973;Murray, 1991) there is a decrease in total benthic foraminiferal species richness in shallow water, from warm to cool through the 18( of latitude of the New Zealand region (Fig. 2).

Comparisons between Auckland and Campbell Islands
The main difference between their benthic foraminifera is the greater diversity recorded from Auckland Islands (130 spp.) compared with Campbell Island (71 spp.), partly as a result of the greater variety of habitats sampled and partly because of the rich unilocular fauna present in several historic collections (unilocular species from Auckland Islands=31; from Campbell Island=7). Among the more common New Zealand-wide species that are present at Auckland Islands but absent from the more distant Campbell Island are Scherochorella moniliforme, Trochammina inflata, Patellina corrugata, Rosalina vitrevoluta and four species of Quinqueloculina. Within the harbours the most noteworthy difference is the abundance of Nonionellina flemingi and, to a lesser degree, Haynesina depressula at Auckland Islands, and their near absence from Campbell Island. The harbours in both groups have almost identical diversity, with 61-63 species each in the quantitative samples and, apart from the two species already mentioned, they share the same suite of dominant species. Lack of sampling of salt marsh or brackish environments in the Auckland Islands prevents comparisons between the agglutinated faunas, and the lack of sampling of high energy, shallow-water environments at Campbell Island prevents comparison between faunas characteristic of these.

Taxa restricted to the Subantarctic in the New Zealand region
Here we record fourteen species (other than unilocular) that have not previously been recorded from elsewhere in the New Zealand region -eight from the Auckland Islands, two from Campbell Island and four from both. There are several additional species (Discanomalina coronata, Lagenammina difflugiformis, Rhizammina algaeformis, Siphogenerina dimorpha) that have been recorded occasionally from bathyal and abyssal depths elsewhere in the region but are here recorded from shallower than 80 m at both island groups. A similar phenomenon is known from the shelf around Antarctica, where a number of species occur that are restricted to deeper water in lower latitudes (Mikhalevich, 2004). Haplophragmoides manilaensis -this large agglutinated species with inflated chambers (Pl. 1, figs 1-2) occurs widely in salt marshes around the world. It was described from subtropical conditions in the Gulf of Mexico, but has also been recorded from subantarctic marshes as far south as Tierra del Fuego . Labrospira spiculolega -This distinctive species (Pl. 1, figs 3-4) was described from 120-160 m depth, south of Tasmania  and is here recorded from inner-shelf depths at the Auckland Islands. It may be endemic to shelf depths in the subantarctic region of the SW Pacific. Spiroplectammina biformis (Pl. 1, figs 5-6) -appears to be a widespread, shallow-water, higher-latitude, Northern Hemisphere species (Murray, 1991) with a few rare records from higher latitudes in the Southern Hemisphere. Its type locality is in 100 m of water off Greenland (Parker & Jones, 1865) and it is widespread around the Gulf of St Lawrence (e.g. Schafer & Cole, 1982) and in Scandinavian fiords (e.g. Alve & Nagy, 1986;Hanslik & Nordberg, 2006). It also occurs in higher latitudes in the North Pacific (Murray, 1991) and at King George Island, South Shetland Islands (Gaździcki & Majewski, 2003;Majewski, 2005) in the Southern Hemisphere. Verneuilinulla advena (Pl. 1, figs 7-8) -this small agglutinated species appears to occur in shallow sheltered environments at high latitudes in both hemispheres, with its types from 10-40 m in Hudson Bay, Canada (Cushman, 1922). It has been recorded from abyssal depths at low latitudes . Spirillina obconica -this uncommon species has been recorded from off northern Europe and Florida in the Northern Plate 1. Explanation of Plate 1. Some common and distinctive benthic foraminifera from southwest Pacific subantarctic islands. Scale bar 0.1 mm. figs 1-2. Haplophragmoides manilaensis Andersen, 1953. BWH163/24, AU18127, Campbell Island intertidal MHWN. figs 3-4. Labrospira spiculolega . BWH 169/11, F201106, Auckland Islands 12 m. figs 5-6. Spiroplectammina biformis (Parker & Jones, 1865). BWH 168/14, AU18124, Campbell Island intertidal MHW. Apertural view is slightly oblique. figs 7-8. Verneuilinulla advena (Cushman, 1922). BWH168/22, F201106, Auckland Islands 12 m. figs 9-10. Patellinoides conica Heron-Allen & Earland, 1932. BWH169/12, F202511, Auckland Islands 80 m. Peripheral view is slightly oblique. fig. 11. Cerobertina tenuis (Chapman & Parr, 1937). BWH 169/15, F201106, Auckland Islands 12 m. fig. 12. Cerobertina tenuis (Chapman & Parr, 1937). BWH 169/16, F201106, Auckland Islands 12 m. fig. 13. Elphidium advenum f. limbatum (Chapman, 1907 Hemisphere and from 100-300 m depth off the subantarctic Prince Edward and Kerguelen Islands (Brady, 1884). Laryngosigma williamsoni -this species was described from off the coast of the UK (Terquem, 1878) and has been recorded from a number of European localities. Neolingulina viejoensis -this rare, distinctive species has been recorded previously from 40-50 m depth off Peru and Korea . It probably is more widespread and under-reported. Pseudolingulina bradii -an uncommon but distinctive species, described from Indonesia, and also recorded from Hawaii, and 80-1000 m in the South Atlantic (Brady, 1884). Cerobertina tenuis (Pl. 1, figs 11-12) -this appears to be a southern, high-latitude species, with its type locality in upper abyssal depths (2600 m) between Australia and the Auckland Islands (Chapman & Parr, 1937). Bolivina translucens -this is a cosmopolitan species that is often identified under several other names. Fursenkoina cf. riggi -this small distinctive and uncommon species may be restricted to the subantarctic, having been described from the Gulf of San Gorge, southern Argentina (Boltovskoy, 1954) and recorded from Isla de los Estados (Thompson, 1978). Notorotalia aucklandica (Pl. 1, figs 17-19) -appears to be endemic to the Auckland and Campbell Islands. It is morphologically most similar to several New Zealand species of Notorotalia from which it presumably evolved . Patellinoides conica (Pl. 1, figs 9-10) -this species occurs in midto high latitudes in the North and South Atlantic, and was described from the subantarctic region, near the Falkland Islands (e.g. Heron-Allen & Earland, 1932). Heronallenia lingulata -around New Zealand, this small species (Pl. 1, figs 14-16) is restricted to subantarctic Auckland and Campbell Islands plus the Snares Islands. It appears to have a scattered cosmopolitan distribution in deeper water, but occurs in relatively shallow water of higher latitudes in the SW Pacific and southern Australia (e.g. Brady, 1884). A similar distribution is displayed by H. unguiculata which occurs in shallow water at the Auckland and Campbell Islands but at depths >200 m off northern New Zealand (Heron-Allen & Earland, 1922) and northeast Australia .
New Zealand taxa absent from the subantarctic. Notable by their absence from New Zealand's subantarctic islands are a number of species that are common or abundant in shallow water around mainland New Zealand . These include a number of the brackish and high tidal agglutinated species (e.g. Ammobaculites exiguus, Ammoscalaria tenuimargo, Ammotium fragile, Jadammina macrescens, Miliammina obliqua, Trochamminita salsa), with 13-14 species occurring around the two main islands and a combined total of nine at the subantarctic islands (Fig. 3). The abundant shallow-water genus Elphidium is represented by only one species at Auckland and Campbell Islands and two additional species at the Snares, whereas nine species are present at the South Island and 11 off northeast North Island (Fig. 3). In the related genus Notorotalia, five species occur around the main islands, but only two in the subantarctic (including the subantarctic endemic N. aucklandica). Similarly, nine species of Glabratellidae occur off northeast North Island but only four occur in the subantarctic (Fig. 3) -mostly absent are species of Pileolina. The same pattern also occurs in the shallow-water Rosalinidae and the genus Quinqueloculina (Fig. 3). Other notable absences from the subantarctic are New Zealand's most common foraminiferal genus in sheltered harbour settings , Ammonia, and several of the most abundant open-marine species, Gaudryina convexa, Patellinella inconspicua and Trochulina dimidiatus.
A different pattern emerges in the shallow-water members of the Rosalinidae, with similar levels of species richness (13-14 spp.) off northeast North Island and in the subantarctic (Fig. 3).

Affinities with shallow-water foraminifera of the New Zealand region
Auckland and Campbell Islands have 68-76% of their benthic foraminifera (excluding uniloculars) in common with the South Island and northeast North Island (Table 3). In contrast, a smaller percentage (52-59%) live around the nearer, but smaller, Chatham and Stewart Islands and just 31-32% have been recorded around the Snares Islands (Table 3). An explanation for the low levels of co-occurrence with the Snares is probably the lack of sheltered, harbour or brackish environments there. Explanations for the lower level of co-occurrence with Stewart and Chatham Islands are more difficult. It may reflect the lower number of samples and environments examined around these two island groups.
Of most significance is the observation that 94-98% of the Snares fauna co-occurs around the South and North Islands. This reflects the fact that only one Snares species (Heronallenia lingulata) is restricted to the subantarctic islands, whereas the more distant Auckland and Campbell Islands have 13 species not found further north in the New Zealand region.

FAUNAL ASSOCIATIONS
From the cluster analysis dendrogram we identified 10 faunal associations (Fig. 4, Table 4). Five associations (1-3, 5, 8) are from Campbell Island and six from the Auckland Islands (4, 6-10), with only one association (8) occurring in both places (Fig. 5). With three exceptions, the clustering separated the coarse faunas (>150 µm) from the total sand range faunas (>63 µm), with the coarse faunas from Auckland Islands (assoc. 6) separated from the Campbell Island ones (assoc. 5). The two total faunas (A3, C11) that cluster with the coarse faunas have minimal fine fraction specimens present, and the same is true for the two total faunas (A5, A8) that cluster with the coarse fauna (A6c) forming association 4.

Agglutinated benthic foraminiferal associations
The first-order subdivision in the dendrogram separates faunas that are dominated by agglutinated species and live in Tucker Cove, Campbell Island (assocs 1-3), from all the remaining faunas, which are dominated by calcareous species. Two of the three agglutinated associations (1, 2) occur in high tidal salt meadow composed entirely of the salt-tolerant grass Isolepis cernua. The Haplophragmoides-dominated association (2) occurs in a 20 cm wide (tidal elevation) zone around extreme high water spring (EHWS) with the Miliammina fusca-dominated association (1) present between EHWS and mean high tide level. These two high tidal associations have the lowest diversity ( =0.5-0.6, H=0.2-0.9) but highest level of evenness (E=0.5-0.8) of all associations.
The third agglutinated association (3) is dominated by Eggerelloides scaber and Textularia earlandi, with secondary Paratrochammina bartrami and Spiroplectammina biformis (Fig. 6). This also occurs in Tucker Cove (Fig. 5), but in anoxic organic-rich mud at 4 m depth in the middle of the narrow bay. It has moderate levels of species diversity and evenness (Table 4).

Calcareous benthic foraminiferal associations
A second-order subdivision within the calcareous faunas separates associations 4-8 from 9-10 (Fig. 4). The first of these two groups of associations is restricted in occurrence to the muddy sand and sandy mud on the floor of the relatively sheltered,   Island  100  73  32  59  57  68  71  64  Auckland Islands  47  100  31  55  52  74  76  96  Snares Islands  38  55  100  75  74  94  98  53  Subantarctic Islands  47  71  40  53  49  74  77  Norman and Smith Harbours in the Auckland Islands. This association has subdominant Sigmoilopsis elliptica, Trifarina angulosa and Eilohedra vitrea and has the highest species diversity in the study ( =6.9, H=2.3). Association 6 (Notorotalia aucklandica) is limited to the slightly more exposed, shallower (10-17 m) Port Ross, in the northern Auckland Islands. Association 5 (Elphidium advenum) is restricted to Campbell Island and consists of all the coarse faunas throughout Perseverance Harbour, at depths of 4-40 m, plus the total fauna (C11) from mid-tidal level on the muddy sand beach in Tucker Cove (Fig. 5). Association 8 (Cassidulina carinata) contains all the total faunas (>63 µm) from the same samples as association 5, plus the total faunas from two samples (A2, A4) at 10-18 m depth in Port Ross, Auckland Islands. The main difference between these two associations is in the relative abundance of small Cassidulina, which comprises 40-70% of the total faunas and less than 2% of the coarse faunas and, to a lesser extent, the greater abundance of small Eilohedra vitrea in the total faunas.
The second of the two calcareous groups occurs in cleaner sands from more exposed, wave-or current-swept locations around the Auckland Islands. Association 9 (Pileolina radiata) is known from one sample at 9 m deep from just inside the western entrance to Carnley Harbour (Fig. 5) where big swells and strong currents sweep over the seafloor. Subdominant are Quinqueloculina suborbicularis and Notorotalia aucklandica. It has relatively low species diversity and the lowest evenness of all the associations (E=0.24) as a result of the strong dominance by P. radiata. Association 10 (Rosalina irregularis) occurs in three samples at 0-8 m depth from either side of Enderby Island (Fig. 5). The samples from the north side (A15-A16) are not in situ and comprise sand washed up onto the rocks by storms, but are considered representative of the fauna in the shallow subtidal just offshore. Subdominant in this association are P. radiata, Miliolinella subrotundata and Quinqueloculina incisa (Fig. 6).

Distribution of benthic foraminiferal associations (Fig. 5)
The DCCA ordination (Fig. 7) shows that there are four separate groups of associations. , Fisher Alpha Index (number of species standardized by number of individuals counted); H, Information Function (a combination of the number of species present and, to a lesser extent, the evenness of species counts); E, Evenness (a measure of dominance versus evenness of species counts); EHWS, extreme high water spring; MT, mid-tide.  (1, 2), whereas most other shelf and bathyal environments have calcareous-dominated faunas (e.g. Murray, 1991;. Although 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. 2. Restricted bay head. This shallow subtidal association (3) is unusual and unique in the New Zealand region, where  Fig. 7. Two-dimensional ordination of benthic foraminiferal faunal samples from the Auckland (prefixed by A) and Campbell (prefixed by C) islands, produced by Detrended Canonical Correspondence Analysis using the census data of species with >5% relative abundance in at least one sample. The common species (>5% in at least one sample, three-letter abbreviations) are plotted. Vector axes (arrows) show the correlation of faunal distribution patterns with some environmental and diversity factors. The sample associations (1-10) are those identified from the cluster analysis (Fig. 2) subtidal substrates dominated by agglutinated foraminifera (usually M. fusca and Trochamminita salsa) are restricted to low salinity environments at the head of estuaries . Here in Tucker Cove at the head of Perseverance Harbour there is sometimes a thin low salinity surface layer, but subtidally salinity is only slightly lower than normal marine values. Here the water is commonly tannin-coloured from all the freshwater seepage from the peat soils and the sediment on the subtidal floor of the cove is chocolate brown and anaerobic. Anaerobic, acidic conditions are inferred, which might favour this agglutinated assemblage and dissolve the shells of any calcareous taxa. Partly dissolved shells are frequently encountered in other samples in Perseverance Harbour. 3. Exposed coasts. The two associations (9-10) which occur in relatively shallow, wave-and current-swept, sandy environments around the Auckland Islands have distinctively different faunal compositions than the other associations (Figs. 6, 7). Although not recorded from Campbell Island, they may be present there as no samples were available for study from similar environments around this island. 4. Sheltered harbours. Five calcareous-dominated associations (4-8) occur within the glacially incised harbours of the two island groups. All share in common the presence of Elphidium advenum and Notorotalia aucklandica, but the common co-occurrence of Nonionellina flemingi separates out associations 4 and 7, which are confined to the more sheltered southern and central harbours of the Auckland Islands at depths of 17-80 m. The faunas in muddy sand at 0-40 m depth in Perseverance Harbour, Campbell Island (associations 5, 8) differ from those in similar environments in the Auckland Islands by the abundance of Cassidulina carinata (faunas >63 µm) or E. advenum (>150 µm). In the relatively shallow depths (10-17 m) near the more exposed mouth of Port Ross, northern Auckland Islands, N. aucklandica reaches its greatest relative abundance and characterizes the separate association 6 (Fig. 6). The vectors on the DCCA ordination (Fig. 7) indicate a strong correlation of the distribution of faunal assemblages and species with depth (long vector arrow), with depth increasing from bottom right to top left. This trend parallels the expected increase in planktic foraminiferal percentage with increasing distance from shore  and also an unusual trend of decreasing evenness (E) in faunal structure. Both species richness and absolute abundance of benthic foraminifera (specimens g 1 sediment) show an increasing trend with increasing water depth (Fig. 7). The short vector for sand percentage indicates that grain size has little influence on faunal composition.

In situ versus transported specimens
Most faunas picked from the coarser fraction (>150 µm) cluster separately (assocs 5, 6) from the faunas from the total sand fraction (>63 µm). The coarse fraction faunas have lower species richness (mean =2.4-2.9) than the total faunas (mean =4.1-6.9) but all have a similar range of dominance and evenness (Table 4). Thus, the main difference between the two size fractions is the additional presence in the total faunas of numerous small, low density shells of C. carinata, E. vitrea, S. elliptica, Bolivina and a diversity of unilocular species. Do these small specimens live in situ in these sheltered harbour settings, or have they been winnowed out of seafloor sediment by strong currents or large Southern Ocean swells outside the harbour and transported into the harbours in suspension with the incoming tide or onshore winds? This latter method of displacement has been documented in the English Channel (Murray et al., 1982) and elsewhere around New Zealand (Reid & Hayward, 1997).
The strongest hint that at least some of these small lightweight specimens have been transported in, comes from the size range of C. carinata. In situ populations contain a mix of juveniles and adults (up to 400 µm), but in these harbour samples (particularly from Campbell Island), only populations of juveniles (<150 µm) are present. The other common species (above) represented only by small specimens do not have large adults and thus could be in situ or displaced. It is strongly suspected that most E. vitrea, S. elliptica and many of the unilocular specimens have also been transported in from midouter shelf depths offshore, where they are relatively abundant (Hayward et al., 2007). Thus, the coarse fraction faunal compositions (dominated by E. advenum, N. flemingi, N. aucklandica and Haynesina depressula) are considered to reflect more correctly the in situ fauna of the sheltered harbours.

Biogeographical affinities with other subantarctic island groups
It is not possible to make detailed comparisons of the faunal composition with other subantarctic island groups beyond the SW Pacific, because the taxonomic concepts and names used in earlier studies (e.g. Chapman, 1909;Heron-Allen & Earland, 1932;Earland, 1933Earland, , 1935 are incompatible with this study. A full and consistent review of the fauna from all islands is required for detailed biogeographical analysis and this is well beyond the scope of this study. It is possible, however, to make some general comparisons.
In terms of species richness, the relatively low diversity of the inner-mid shelf (<80 m) benthic foraminiferal fauna (including uniloculars) of the Auckland Islands, 51( S (130 spp.) and Campbell Island, 52( S (71 spp.) is of a similar order to that recorded from the same depth range around South Georgia, 54( S (60 spp. from three samples; Earland, 1933), Tierra del Fuego, 53( S (75 spp. from one sample; Heron-Allen & Earland, 1932) and Isla de los Estados, 54( S (76 spp. from 36 samples; Thompson, 1978). The Auckland and Campbell Islands have a significantly higher species richness from that recorded around Macquarie Island, 54( S (19 spp. from one sample; , Kerguelen Islands, 50( S (33 spp. from 13 samples;  and Falkland Islands, 52( S (33 spp. from ten samples; Brady, 1884;Pearcy, 1914;Cushman & Parker, 1931;Heron-Allen & Earland, 1932). The species lists for all these islands are undoubtedly incomplete and would be expanded with more exhaustive sampling. The main conclusion that can be drawn, however, is that species richness at inner-shelf depths around the subantarctic islands is relatively low, akin to that around the shores of Antarctica (e.g. Stockton, 1973;Delaca & Lipps, 1976;Gaździcki & Majewski, 2003;Majewski, 2005), but considerably lower than around southern temperate, subtropical and tropical islands (e.g. Murray, 1991;. The larger subantarctic islands (Auckland, Campbell, Kerguelen, South Georgia, Falklands, Estados, Fig. 8) all have similar nearshore topography, with a mix of exposed rocky coasts and more sheltered, glacially carved harbours. At the generic level their shallow-water foraminiferal faunas have considerable commonality (Heron-Allen & Earland, 1932;Earland, 1933;Thompson, 1978; this study). The more sheltered harbours have a dominance of Elphidium, Cassidulina, Haynesina depressula, Nonionella-Nonionellina and the Southern Hemisphere-endemic genus Notorotalia. In all places, Trifarina angulosa becomes common in deeper parts of the inner shelf (>30 m). In sandier, more exposed locations the faunas are usually dominated by Cibicides, Rosalina, Quinqueloculina, Pileolina-Glabratella and Miliolinella subrotunda. Numerous, small, unilocular foraminifera have been recorded from the shallows around all these island groups. A number of rarer species appears to be common to all of the larger subantarctic islands, e.g. Patellina corrugata, Cornuspira involvens, Tubinella funalis. Ammonia and Pyrgo appear to be absent from all except South Georgia (Heron-Allen & Earland, 1932) and Isla de los Estados (Thompson, 1978).
High-tidal marsh faunas have not been reported from most other subantarctic islands. The marsh fauna from Campbell Island, 52( S, 3 spp. (associations 1, 2), is of similar low diversity to that recorded from salt marshes on Tierra del Fuego, 52( S, 5 spp. . They have two species in common (H. manilaensis, M. fusca) although the dominants differ (Trochammina inflata, Jadammina macrescens at Tierra del Fuego).

Dispersal and geological history
The Campbell Plateau has been submerged continuously since at least the Eocene, 35 million years ago, well before the eruption and formation of the volcanic Auckland and Campbell Islands (Adams et al., 1979;Adams, 1983;Cook et al., 1999). Therefore, there has never been a shallow-water connection (<500 m) between the islands or across to mainland New Zealand that would have aided progressive dispersal of shallow-water benthic foraminifera. Thus, all the intertidal and shallow-marine foraminifera that now live around the Auckland and Campbell Islands must have arrived by dispersal across the Southern Ocean. Only one species (Notorotalia aucklandica) has inhabited these island shores for sufficiently long to have evolved into a distinct endemic species. Some species that do not occur around mainland New Zealand, may have reached these islands after long journeys in the Subantarctic Current from far distant lands, such as Kerguelen Islands or even South America.
The majority of species (c. 70-75%) share their geographical distribution with mainland New Zealand and show that this is by far the most usual dispersal route (possibly in both directions). The route from mainland New Zealand to the Auckland and Campbell Islands is contrary to the main net surface current direction of the Subantarctic Current (SW to NE). Surface currents commonly have large mobile eddies that at certain times could sweep larval stages, juveniles or even floating logs from southern New Zealand down to the islands, or the reverse. The best evidence that this happens comes from the shared distribution patterns themselves. The most likely source for many of the dispersed foraminifera is the southwest coast of the South and Stewart Islands, where currents associated with the Subtropical Front sweep southeastwards in the direction of the Auckland Islands before swinging northeast in the vicinity of the Snares Islands (Fig. 1). This would have been particularly emphasized during glacial periods when sea-level was c. 100 m lower than present.
During the last 2-3 million years, sea surface temperatures around the Auckland and Campbell Islands have seldom, if ever, been any warmer than they are today. During the many glacial periods, sea surface temperatures could have been 2-5( C colder than today (e.g. Weaver et al., 1998) and could potentially have killed-off island populations of some intertidal and shallow-marine species. A further contributor to a hypothesized lower diversity foraminiferal fauna during glacials, could have been the much lower sea-levels, when there is unlikely to have been many sheltered shallow-water environments similar to the present fiord-like harbours. Thus, it is suggested that a sizeable proportion of the present shallow-water benthic foraminiferal fauna of the islands has probably arrived by dispersal from mainland New Zealand and recolonized their shores only since the Last Glacial peak, 18 000 years ago.

APPENDIX A: Foraminiferal list
Appendix A provides a taxonomic list of all foraminifera recorded here from the Auckland (A), Campbell (C) and Snares (S) Islands, shallower than 100 m, with references to easily accessible published figures that best portray the species as interpreted by us. Generic classification largely follows Loeblich & Tappan (1987), with the ordinal classification after Loeblich & Tappan (1992). The original descriptions of these species can be found in the Ellis & Messina world catalogue of foraminiferal species on www.micropress.org.

APPENDIX A.1: Benthic foraminifera
Order Astrorhizida Lagenammina difflugiformis (Brady, 1879); Jones, 1994, pl. 30, figs 1-3. A, C Rhizammina algaeformis Brady, 1879;Jones, 1994, pl. 28 Alpha is the Fisher Alpha Index (number of species standardized by number of individuals counted). H is the Information Function (a combination of the number of species present and, to a lesser extent, the evenness of species counts). E is the Evenness (a measure of dominance versus evenness of species counts). EHWS, Extreme high water spring level; MHW, mean high water; MHWN, mean high water neap; MHWS, mean high water spring level; M.T., mid-tide level