SOFT BOTTOM MACROBENTHOS AND SEDIMENTS OFF THE BROKEN ISLANDS, NORTHERN

by Bruce W. Hayward,1 Roger V. Grace2 and John McCallum3 'New Zealand Geological Survey, P O Box 30368, Lower Hutt 2274A Birkdale Road, Birkenhead, Auckland 10 382 Exmouth Road, Northcote, Auckland 9

SUMMARY

The soft bottom macrobenthos (exceeding 2 mm in size) and sediments were studied from 34 dredge stations located in a 5 km2 area of sea bed (1-59 m depth) around the Broken Islands, west of Great Barrier Island, northern New Zealand. Six benthos associations and three subassociations are recognised and mapped.

An infaunal bivalve Scalpomactra scalpellum-Dosinia subrosea asso• ciation occurs in clean, well-sorted fine to medium sand in shallow (5-9 m), moderately sheltered bays. Slightly coarser sediment in more exposed portions of bays (5-11 m) has another infaunal bivalve associa• tion, Felaniella zelandica-Talabrica bellula. In areas of greater wave exposure or strong currents (10-15 m), the sandy, shelly gravel substrate is characterised by a rhodolith — "Cucumaria" (holothurian) — Glycymeris laticostata (bivalve) association and rich subsidiary epifauna.

Slightly deeper (11-31 m) in quieter conditions, a slightly shelly, fine sand substrate has a Pupa kirki (gastropod) - Echinocardium cordatum (heart urchin) - Myadora boltoni (bivalve) association. The most prevalent association in the area is that with common Corbula zelandica (bivalve). Within this a bivalve subassociation of Corbula-Limaria orientalis occurs in shelly fine to very coarse sand at 10-20 m depths in moderately exposed portions of two open bays. Two further infaunal bivalve subassociations, Corbula-Venericardia purpurata and Corbula- Pleuromeris zelandica, occur in shelly, fine to coarse sand in quieter conditions at slightly greater depths (23-25 m and 26-32 m). An association characterised by the ophiuroid, Amphiura and the bivalves Saccella bellula, Notocallista multistriata and Cuspidaria willetti occurs in muddy, slightly shelly, fine to medium sand in moderately quiet bottom conditions at 31-59 m depth.

INTRODUCTION

This paper documents the results of an inshore marine dredging programme undertaken during the Offshore Islands Research Group

TANE 31, 1985-86 85 trip to the Broken Islands Group from 28 December 1984 to 5 January 1985. The Broken Islands Group (latitude 36°15'S, longitude 175°25'E) consists of three larger islands (Motutaiko, Rangiahua, Mahuki) and many smaller ones (including the Junction Islands in the east), that lie close to the west coast of Great Barrier Island (Fig. 1). Great Barrier

Fig. 1. Lower. Location of study area, around the Broken Islands, west Great Barrier, northern New Zealand. Upper. Station locations and bathymetry (in metres).

86 Island is situated 80 km northeast of Auckland City at the entrance to the Hauraki Gulf. The 34 dredge stations sampled were located in the large, open bay on the southwest side of the Broken Islands, in the moderately deep, narrow bay between Mahuki and Junction Islands and in the shallow narrow channels between Rangiahua and Motutaiko, Rangiahua and Mahuki and Rangiahua and Great Barrier Islands. The stations sample an area of 5 km2 of sea floor, at depths of 1-59 m (Fig. 1, Appendix I). Bathymetry is based on depths measured in the field with a lead line and adjusted to mean low water spring tide level.

METHODS

Samples were collected using a 4.5 litre bucket dredge (described by Grace and Whitten 1974), hand-hauled from a 4 m dinghy powered by a 7.5 horse power outboard motor. Under ideal conditions the dredge sampled an area of 0.075m2 of sea floor to a depth of 6 cm. Approximately 200 cm3 of each sample was taken for later sedimentary analysis. The remaining bulk of the sample was passed over a sieve with 2 mm openings and live organisms retained on it were sorted fresh, identified, counted and returned to the sea. Three stations struck rock (18, 24, 27) and no sediment was obtained. Insufficient time at the end of the trip prevented full faunal analysis of stations 32 and 34. Sediment grain size analyses were carried out in the laboratory using sieves (Folk 1968, p. 34).

BATHYMETRY (Fig. 1)

In the large, open bay on the southwest side of Broken Islands, the seafloor drops rapidly away to 40 m, then slopes more gently down to an almost flat area at 55-60 m depth. Charts indicate that this flat area extends some distance offshore and is the maximum depth reached anywhere in the Hauraki Gulf inside Great Barrier Island. The narrow bay between Mahuki and Junction Islands has a gently sloping floor 25-35 m deep; the bay between Rangiahua and Motutaiko Islands has a gently sloping floor 20-35 m deep; and the bay on the southwest side of Rangiahua Island slopes gently out from 0 to 20 m, before dropping off more rapidly. The narrow channel between Rangiahua and Mahuki Islands is mostly 5-6 m deep, increasing to 10 m at the northeast end; the 1 km long channel between Rangiahua and Great Barrier is consistently 9-10 m deep in most parts.

87 SEDIMENTS

Grain size terminology follows Folk (1968, p. 26-30). Sediment types at dredge stations are listed in Appendix I and their distributions shown in Fig. 2a. The shores of all the islands are fringed almost continuously at intertidal and shallow subtidal depths by a 20-100 m wide zone of rock or of bouldery gravel. Off more exposed parts of the coast on the southwest side of Broken Islands, this zone is fringed by areas of pebble gravel and pebbly coarse sand, down to depths of 40 m. In the mouths of more sheltered bays the sediment is fine sand, whereas the shallower, wave-influenced inshore parts of three bays consists of moderately to well-sorted medium sand. Offshore, away from the rocky island coasts and below wave base, the seafloor is covered in slightly shelly to shelly, slightly muddy to muddy fine sand. The channels between the islands are floored by various sediment types depending on tidal current strengths and depth. The shallows (less than 5 m) of the current-swept channel between Rangiahua and Motutaika are composed of coarse gravel and boulders, fining to coarse sand by 20 m depth. Most of the floor of the narrow channel between Rangiahua and Great Barrier, with its very strong tidal currents, is covered in algal rhodolith gravel, fining to coarse and medium sand by 20 m depth at the southern end. The sinuous, shallow channel between Rangiahua and Mahuki has much weaker currents and is floored by clean, well sorted medium and fine sand, becoming course sand at the west entrance and pebbly medium sand at the east entrance. The map (Fig. 2b) showing the distribution of shell, pebble and rhodolith gravel (greater than 2 mm) clearly shows the influence of strong currents and wave erosion in producing coarse sediment in the channels and around the shore lines. The map (Fig. 2c) showing the distribution of mud also clearly shows the effect of current activity and waves in preventing mud from settling in shallow water.

MACROBENTHIC ASSOCIATIONS

In analysing the live benthic biota (Appendix II) we have attempted to subjectively recognise recurrent sets of taxa, or "associations", that have considerable spatial continuity or have been recognised elsewhere. The associations are named after the dominant or most characteristic taxa. We recognise and map the distribution of six associations and three subassociations within the study area (Fig.3).

88 fine sand medium sand

coarse sand - shell gravel pebble gravel rhodolith gravel rock and boulders

muddy ^xjfk, mud)

>500/,

^ 25-50°/,

15-25%

5-15%

0.5-5%

Fig. 2. a. Distribution of seafloor sediments, Broken Islands. b. Percentage of pebble-size clasts, including shells (larger than 4 mm) in sediments. c. Percentage of mud (finer than 0.0625 mm) in sediments. l. Scalpomactra scalpellum-Dosinia subrosea association Stations: 5, 21, 25 Sediment: clean, fine to medium sand

89 Fig. 3. Distribution of macrobenthos associations, Broken Islands. Depth: 5-9 m Wave energy: moderately low Characterising taxa: BIVALVES. Scalpomactra scalpellum (5, 21, 25), Dosinia subrosea (5, 21). Common associated taxa: GASTROPODS. Zeacolpus pagoda (21, 25),

90 Cominella quoyana (5, 21;, Pupa kirki (5, 25), Epitonium minora (5, 21). This association is confined to sheltered areas on the south side of Rangiahua Island — in a narrow enclosed bay and in the central part of the narrow channel between Rangiahua and Mahuki. The infaunal bivalves that characterise this association are not recorded elsewhere in the study area. Other taxa, occurring in fewer numbers, not found outside this association are the infaunal bivalve, Gari lineolata and the gastropods, Zeacolpus pagoda and Antisolarium egenum. The gastropod, Epitonium minora is also almost entirely confined to this association, occurring elsewhere only in station 2, which is difficult to place in any association. Species diversity and abundance is low in this association with very little other than molluscs present.

2. Felaniella zelandica-Talabrica bellula association

Stations: 20, 22 Sediment: clean to slightly muddy, shelly, medium sand Depth: 5-11 m Wave energy: moderate to moderately low Characterising taxa: BIVALVES. Felaniella zelandica (20, 22), Talabrica bellula (22).

Common associated taxa: GASTROPODS. Cominella quoyana (20, 22), Xymene plebeius (22); BIVALVES. Glycymeris laticostata (22), Tawera spissa (20). This association occurs in moderately exposed, shallowish entrances to bays or channels on either side of Mahuki Island. The sediment is slightly coarser and exposure slightly greater than in the areas occupied by Scalpomactra-Dosinia association. Both characterising infaunal bivalves of this Felaniella-Talabrica association are not recorded elsewhere in the study area. Species diversity and abundance is low in this association with very little other than molluscs present.

3. Rhodoliths — "Cucumaria"-Glycymeris laticostata association

Stations: 17, 30, 31, 32, 34 Sediment: sandy, shelly, rhodolith and pebble gravel Depth: 10-15 m Wave energy: moderate to high Current energy: moderate to high Characterising taxa: ALGAE. Rhodoliths (17, 30, 31, 32, 34); Holothurian. "Cucumaria" sp. (30, 31, 32, 34); BIVALVE. Glycymeris laticostata (17, 30, 31, 32, 34). Common associated taxa: POLYCHAETES. Owenia fusiformis (17, 30,

91 31, 32, 34), Marphysa sp. (30, 31), Polydora sp. (30, 31); . Rhyssoplax stangeri (17, 30, 31, 32, 34); GASTROPODS. Cominella quoyana (17, 30, 31), Buccinulum linea (17, 30), Xymene plebeius (17, 31); BIVALVES. Limaria orientalis (30, 31); CRABS. Halicarcinus varius (30, 31), Notomithrax minor (30, 31); HEMICHORDATE. Saccoglossus sp. (30, 31). This association occurs in the strongly current-swept channel between Rangiahua and Great Barrier and off the exposed northwest point of Mahuki Island. The association is confined to high-energy situations in coarse sediment. Pink, finely branched, live rhodoliths are present in all stations and dead white specimens comprise a large proportion of the sediment, especially in the channel. Small, corralline pink holothurians (12-20 mm long), referred to the Cucumaria, are particularly abundant in the rhodolith-dominated sediments of the channel where they reach densi• ties of at least 500 per m2 (stn 31). The rich and diverse fauna in this association reflects the favourable habitats for epifauna within the coarse substrate, as well as for infauna. The three characterising taxa are largely confined to this habitat (Fig. 4). A number of other less abundant species are not recorded elsewhere in the study area and include Polydora sp., Marphysa sp., Saccoglossus sp.; the gastropods, Buccinulum linea, Crepidula costata, Muricopsis octagonus, Taron dubius, and the crabs Liocarcinus corrugatus and Petrolisthes novaezelandiae.

4. Pupa kirki-Echinocardium cordatum-Myadora boltoni asso• ciation

Stations: 13, 23, 33 Sediment: clean to slightly muddy to slightly shelly fine sand Depth: 11-31 m Wave energy: low to moderately low Characterising taxa: GASTROPOD. Pupa kirki (13, 23, 33); ECHINODERM. Echinocardium cordatum (13,23,33); BIVALVE. Myadora boltoni (13). Common associated taxa: POLYCHAETES. Hyalinoecia sp. (13, 23), Owenia fusiformis (13, 23); GASTROPOD. Cominella quoyana (13, 23, 33); BIVALVE. Pleuromeris zelandica (33). This association occurs on three sides of Rangiahua Island, in lower energy situations than the three preceding associations and in finer sediment. Pupa kirki is the most abundant taxon in this association and always occurs in fewer numbers elsewhere in the study area. The two other characterising taxa, Echinocardium and Myadora boltoni, are not recorded outside this association and neither is the tube worm

92 Fig. 4. Distribution of major taxa in the rhodolith - "Cucumaria"-Glycymeris laticostata and Amphiura-Saccella belluIa-Notocallista multistriata-Cuspidaira willetti associations.

Hyalinoecia, the gastropod Neoguraleus sp., nor the bivalve, Gari hodgei. This association has a moderately diverse infauna, mostly of molluscs and polychaetes but with no epifauna except in the slightly shelly sand of station 33.

5. Corbula zelandica association

Stations: 3, 4, 6, 10, 11, 12, 14, 15, 19, 28, 29 Sediment: clean to slightly muddy, shelly to slightly shelly fine to very coarse sand. Depth: 10.5-40 m Wave energy: moderate to moderately low Much of the study area at intermediate depths of 10-40 m has highly variable faunas that can be loosely grouped together by the common occurrence of the infaunal bivalve, Corbula zelandica. Most of these stations can be further split into three subassociations, each characte• rised by the co-occurrence of an additional infaunal bivalve. Three stations (6,12,19) do not fall naturally into any of these subassociations. Each is dominated by Corbula zelandica and also has the gastropod, Cominella quoyana in common. The large benthic foraminifera, Liebusella soldanii (12, 19) is not recorded elsewhere in the study area.

93 These three stations all occur on the steep submarine drop-off on the southeast side of the Broken Islands.

5a. Corbula zelandica-Limaria orientalis subassociation

Stations: 3, 4, 10, 15 Marginal stations: 2, 29, 30 Sediment: clean to slightly muddy, shelly, fine to very coarse sand Depth: 10.5-20 m Wave energy: moderate Characterising taxa: BIVALVES. Corbula zelandica (4,10,15), Limaria orientalis (3, 4, 10, 15). Common associated taxa: . Rhyssoplax stangeri (3, 4, 10, 15); GASTROPODS. Cominella quoyana (3, 4, 10), Cominella adspersa (3, 4, 15); Zegalerus tenuis (4, 10, 15); CRAB. Halicarcinus varius (3, 4, 15). This association occurs along the east coast of Rangiahua Island, on the shelf above the steep drop-off. The sediment substrate is poorly sorted and provides a favourable habitat for the diverse infauna and epifauna prsent. Limaria orientalis is dominant with abundances of 200-400 per m2 (Fig. 5). A number of uncommon taxa have been recorded only from this subassociation. These include the coral, Sphenotrochus ralphae; the polychaetes, Armandia maculata, Boccardia polybranchia; the gastropod, Cyclichna thetidis and the bivalves, Cardita aoteana, Modiolarca impacta, Gari stangeri and Glycymeris modesta.

5b. Corbula zelandica-Venericardia purpurata subassociation

Stations: 28, 29 Sediment: clean to slightly muddy, shelly, medium to coarse sand Depth: 23-25 m Wave energy: moderately low Characterising taxa: BIVALVES. Corbula zelandica (28, 29), Venericardia purpurata (28, 29).

Common associated taxa: ALGAE, rhodoliths (28, 29); GASTROPODS. Cominella quoyana (28, 29), Cominella adspersa (28). This association occurs along the east side of Junction Islands at moderate depth. Corbula zelandica is the dominant taxon at both stations followed by large specimens of Venericardia. The fauna is not diverse and mostly infaunal. Live rhodoliths occur in low numbers, reflecting the association's location downslope from the rhodolith — Cucumaria-Glycymeris association. 5c. Corbula zelandica-Pleuromeris zelandica subassociation

Stations: 11, 14

94 Sediment: clean, shelly, fine to coarse sand Depth: 26-32 m Wave energy: moderately low Characterising taxa: BIVALVES. Corbula zelandica (11, 14), Pleuromeris zelandica (11, 14). Common associated taxa: POLYCHAETE. Owenia fusiformis (11, 14); GASTROPODS. Amalda novaezelandiae (11, 14), Cominella quoyana (11, 14). This subassociation occurs east of Rangiahua Island on the seaward side of the Limaria subassociation, around the top of the steep submarine drop-off. At both stations Corbula is more abundant than Pleuromeris. The faunas are not diverse and consist primarily of infaunal molluscs and polychaetes.

6.Amphiura-Saccella bellula-Notocallista multistriata-Cuspidaria willetti association

Stations: 7, 8, 9, 16, 26 Sediment: muddy, shelly to slightly shelly, fine to medium sand Depth: 31-59 m Wave energy: low Characterising taxa: OPHIUROID. Amphiura sp. (7, 8, 9, 16, 26); BIVALVES. Saccella bellula (8, 16), Notocallista multistriata (26), Cuspidaria willetti (8). Common associated taxa: CORAL. Kionotrochus suteri (8 9); POLYCHAETES. Aglaophamus macroura (7, 16), Lumbriconereis sphaerocephala (7, 16), Pectinaria australis (8, 26); GASTROPODS. Maxacteon cratericulatus (8, 9), Amalda novaezelandiae (7, 9, 26); BIVALVES. Corbula zelandica (7, 8, 9), Chlamys zelandica (9, 26). This association occurs in the deepest water in the study area with the lowest wave energy and muddiest substrate (15-37% mud). It covers the deep, flat seafloor east of the Broken Islands, probably extending a long way offshore, and also occurs at 30 m depth in the south-facing bay between Mahuki and Junction Islands. Amphiura is the dominant taxon occurring in densities up to 1000 per m2 (stn. 8). Live specimens of the three characterising infaunal bivalves are not common but are characteristic of this deep-water, inshore fauna in low number in other parts of eastern Northland. The fauna is moderately diverse, usually with a mixture of infaunal molluscs and polychaetes and a variety of epifauna. A number of less abundant taxa are restricted to this association. These include Kionotrochus suteri, Aglaophamus macroura, Lumbriconereis sphaerocephala, Maxacteon cratericulatus, Cuspidaria willetti and Saccella bellula; the hemichordate, Balanoglossus australiensis; the ophiuroid, Amphipholis squamata

95 and the crab, Pinnotheres novaezelandiae.

DISCUSSION

Two of the six associations in the study area are very distinctive in their overall biotic composition as well as in their characterising taxa. These are the deep, quiet water, muddy substrate Amphiura-Saccella- Notocallista-Cuspidaria association and the shallow, high energy, coarse substrate rhodolith — Cucumaria-Glycymeris association. The other four associations, including the subassociations, are less distinct and inter-grade somewhat often sharing many taxa in common. These associations occupy all the gradations of habitat conditions between the two distinctive end-/member associations. In recognising these less distinct associations, we must determine whether they really are separate entities. Are they a recurring combination of taxa that have considerable spatial extent and/or occur in environments having consistent abiotic attributes? If one examines the individual distributions of many of the more common shallower water taxa in the study area (Figs 5,6), it is obvious that most have spatially discrete distributions that appear to be related to various combinations of sediment grain size, wave and current energy and water depth. Some taxa (e.g. the scavenging gastropods, Cominella quoyana and Amalda novaezelandiae) have wide distributions with moderately even densities. Others with wide distribution (e.g. the infaunal polychaete, Owenia fusiformis; the bivalve, Corbula zelandica) have low background densities but clumps of much greater abundance. Still other taxa (e.g. the chiton, Rhyssoplax stangeri; the bivalve, Limaria orientalis) have more restricted occurrences with high density peaks. A number of less frequently encountered taxa (e.g. Glycymeris spp., Pupa kirki, Venericardia purpurata, Scalpomactra scalpellum, Pleuromeris zelandica, Dosinia subrosea) have very limited, sometimes separated distributions. Examination of all these indicate that in many cases the distributions of several of the more restricted taxa and/or the abundance peaks of one of the more widespread taxa coincide and can be related to the abiotic environmental conditions. Thus for example the peak densities of Venericardia coincide with high densities of Corbula in two adjacent stations in similar environments and are the basis for the Corbula- Venericardia subassociation. In the Scalpomactra-Dosinia association, the total distributions of these two infaunal bivalves plus the gastropod Zeacolpus pagoda coincide in three shallow stations, also with very similar physical attributes. It would seem therefore, that while the distributions of very few taxa exactly coincides with the distribution of any other, there is considerable

96 . . =3&) Corbula ' ^^^^ Limaria " f""^ ^^S, ^-cSi^*^ zelandica orientalis \ I 0 1- 2 m5-1 0 0.1-1 2- 5

Fig. 5. Distribution and abundance (per 1000 cc) of Corbula zelandica, Limaria orientalis, Venericardia purpurata and Pleuromeris zelandica.

Fig. 6. Distribution and abundance (per 1000 cc) of Cominella quoyana, Pupa kirki, Owenia fusiformis and Amalda novaezelandiae. approximate coincidence, density coincidence or peripheral overlap that recurs in similar environmental conditions. This allows the recognition of associations and subassociations even if they intergrade with one

97 another around their margins.

COMPARISONS WITH OTHER AREAS

Most of the associations recognised in this study, or slight variants ol them, have been recognised previously, elsewhere off north eastern New Zealand in similar environmental settings. The Dosinia-Scalpomactra association has not previously been recog• nised around northern New Zealand. The Felaniella-Talabrica association is similar to the Gari stangeri- Felaniella association that occurs in coarse sand off the Chickens and Rakitu Islands (Hayward et al. 1982, 1984), although no live Gari are present here. All occur in coarse sediment close to rocky coasts with moderate to low wave energy, in 1.5-28 m water depth. An association of rhodoliths — "Cucumaria"-Glycymeris laticostata has not been recognised previously. Beds of rhodoliths, associated with abundant Tawera spissa, have been mapped in similar strong-current- swept channel situations at 4-15 m depth around Great Mercury Island, Cavalli Islands and in the eastern Bay of Islands (Grace & Grace 1976, Grace & Hayward 1980, Hayward et al. 1981). Glycymeris laticostata occasionally occurs in these associations in the coarsest of substrates, but nowhere else have the rhodoliths been associated with abundant holothurians (Cucumaria). The Pupa-Echinocardium-Myadora association is very similar in composition to the Pupa-Pleuromeris-Myadora association at the Chick• en Islands, the Myadora-Scalpomactra association off Slipper Island and northern Great Barrier and the Pupa-Pectinaria association off Great Mercury Island (Grace & Grace 1976, Grace & Whitten 1974, Hayward et al. 1984, in press). All occur in very fine to medium sand in moderately sheltered locations at shallow depths (5-45 m). Although not previously considered to be a characterising species, Echinocardium is common in all these previously named associations. The Corbula-Limaria subassociation has not previously been recog• nised. Limaria orientalis appears to be a fairly recent immigrant to New Zealand and has not previously been found as the dominant taxon in a fauna. The Corbula-Venericardia subassociation is equivalent to the associa• tion in the eastern Bay of Islands and the Venericardia-Talabrica association at the Chickens Islands (Hayward et al. 1981, 1984). The Bay of Islands' and Broken Islands' faunas occur in shelly medium to coarse sand, whereas the Chickens' substrate is sandy shell gravel. All are subject to moderate wave energy. The Broken Islands' stations are at considerably greater depth (23-25 m) than the association is recorded from at the Chickens (12-16 m) or Bay of Islands (1-7 m).

98 The Corbula-Pleuromeris subsassociation has previously been recog• nised off Great Mercury Island (Grace & Grace 1976) where it occurs at similar depths (20-30 m), in similar fine to coarse sand with moderately low wave energy. The Amphiura-Saccella-Notocallista-Cuspidaria association is very similar in composition to the extensive Cuspidaria-Amphiura- Notocallista association that occurs in muddy fine sand at 40-68 m depth off northern Great Barrier and Rakitu Islands (Hayward et al. 1982, in press). It is also similar to the Nemocardium-Notocallista association of fine sediments at 40-53 m depth off the Chickens Islands (Hayward et al. 1984) and the Nemocardium association of fine to very fine sand at 30-40 m depth off the Cavalli Island (Grace & Hayward 1980), although Nemocardium pulchellum itself was not found at the Broken Islands. This association appears to be characteristic of low energy, muddy to slightly muddy very fine to medium sand bottoms at depths of 30-70 m around many parts of northeastern New Zealand. Its lower depth limit is unknown.

ACKNOWLEDGEMENTS

We are grateful to all members of the OIRG trip to Broken Islands for their company in the field and especially to Nigel and Cathy Prickett and Felicity Barnes who helped sort out the live fauna. The manuscript has benefitted from the criticisms of Fred Brook, Alan Beu, and Percy Strong.

REFERENCES

Folk, R.L. 1968: Petrology of sedimentary rocks. Hemphill's, Texas, 170 p. Grace, R.V. & Grace, A.B. 1976: Benthic communities west of Great Mercury Island, north-eastern New Zealand. Tane 22: 85-101. Grace, R.V. & Hayward, B.W. 1980: The macrobenthos of the Cavalli Islands, northern New Zealand. Tane 26: 189-209. Grace, R.V. & Whitten, R.F. 1974: Benthic communities west of Slipper Island, north-eastern New Zealand. Tane 20: 4-20. Hayward, B.W., Brook, F.J., Grace, R.V. & Bull, V.H. 1982: Soft bottom macrofauna and sediments off Rakitu Island, north-east New Zealand. Tane 28: 149-162. Hayward, B.W., Grace, R.V. and Brook, F.J. 1981: Soft-bottom benthic macrofaunal communities of the eastern Bay of Islands, northern New Zealand. Tane 27: 103-122. Hayward, B.W., Grace, R.V. and Bull, V.H. 1984: Soft bottom macrofauna, foraminifera and sediments off the Chickens Islands, northern New Zealand. Tane 30: 141-164. Hayward, B.W., Grace, R.V. and Francis, M.P. in press: Sediments and benthos of northeastern Great Barrier Island, New Zealand. Journal of the Royal Society of New Zealand.

99 APPENDIX I. Station data

Station Depth Sediment1 Sample Assoc (m) vol. (cc) 1 1 m. sand 4000 . 2 7.5 f. sand 1200 5a 3 14 Sh, f. sand 2400 5a 4 10.5 Sh, c. sand 4000 5a 5 5.5 f. sand 3600 1 6 32 si M, si Sh, f. sand 3200 5 7 47 M, Sh, f. sand 2800 6 8 55 M, Sh, f. sand 2800 6 9 59 M, Sh, m. sand 4000 6 10 17 si M, Sh, vc. sand 2800 5a 11 26 Sh, c. sand 3600 5c 12 40 Sh, m. sand 2800 5 13 30 f. sand 1600 4 14 32 Sh, f. sand 3600 5c 15 20 Sh, c. sand 1200 5a 16 44 M, Sh, m. sand 3200 6 17 15 S, Sh, P, gravel 3200 3 18 38 rock - - 19 20 si M, Sh, vc. sand 1600 5 20 11 Sh, m. sand 3200 2 21 5 Sh, m. sand 3600 1 22 5 si M, Sh, m. sand 3600 2 23 31 si M, f. sand 1600 4 24 24 rock - - 25 9 m. sand 3200 1 26 31 M, si Sh, f. sand 2400 6 27 28 rock - . 28 25 si M, Sh, m. sand 2800 5b 29 23 Sh, c. sand 2800 5b 30 11 S, Sh, gravel 2400 3 31 10 S, Sh, R, gravel 2400 3 32 10 S, Sh, R, gravel - 3 33 11 si Sh, f. sand 3200 4 34 10 S, R, gravel - 3

'si = slighty, M = muddy, Sh = shelly, S = sandy, P = pebbly, R = rhodolith, f M = medium, c = coarse, vc = very coarse.

APPENDIX II. Species counts from Broken Islands dredge stations. For each taxon, the stations at which it occurs alive is given, followed in brackets by the number of live individuals present in the sample. Where no figures in brackets are given, information is qualitative only. ALGAE Corallina officinalis 2, 4 Coralline "rhodoliths" 17, 28, 29, 30, 31, 33 FORAMINIFERA Liebusella soldanii 12(1), 19(4) BRYOZOA membraniporiform 7, 9, 17, 31

100 PORIFERA cream sponge 4(1) yellow sponge 26(2) COELENTERATA Culicia rubeola 7(15), 31(3) Edwardsia sp. 4(1) Kionotrochus suteri 8(2), 9(2) Sphenotrochus ralphae 4(3) small cream anemone 4(2) hydroids 9(3) POLYCHAETA Aglaophamus macroura 7(1), 16(1) Armandia maculata 3(1) Boccardia polybranchia 10(300) Euchone sp. 4(14), 14(1), 22(1), 25(1) Glycera sp. 9(1), 17(1) Hyalinoecia sp. 13(1), 15(1), 23(2) Hydroides norvegicus 9(3) Lumbriconereis sphaerocephala 7(1), 16(1) Marphysa sp. 30(4), 31(2) Owenia fusiformis 4(27), 10(25), 11(2), 12(18), 13(2), 14(1), 17(3), 22(5), 23(50), 26(5), 28(1), 30(1), 31(4) Pectinaria australis 8(1), 26(2), 33(1) Polydora sp. 30(1), 31(1) Cirratulidae 14(1), 15(1), 31(1) Maldanidae 5(1), 7(1), 9(6), 31(1) Nereidae 3(2), 4(1), 17(9), 30(1), 31(6), 33(1) Sabellidae 16(1) Spionidae 14(1), 23(4) Syllidae 3(12), 4(10), 6(1), 10(7), 11(3), 12(1), 15(4), 16(1), 17(21), 20(1), 30(20), 31(3), 33(1) Terebellidae 3(3), 10(1), 12(1), 14(1), 30(1), 31(1) unidentified 1(3), 5(1), 6(120), 7(2), 8(5), 9(5), 10(100), 11(6), 14(4), 16(5), 17(30), 19(1), 20(8), 21(1), 22(5), 23(100), 25(2), 26(50), 28(1), 29(6), 31(6), 33(3) NEMERTEA black 4(1), 11(1) orange 3(2), 4(1), 6(1), 11(1), 14(1), 31(1), 33(2) pink 8(1) red 30(1) white 9(1) yellow 10(1) SIPUNCULA unidentified 8(1), 13(1) POLYPLACOPHORA Acanthochitona zelandica 3(1), 30(2) Guildingia obtecta 31(1) Notoplax cuneata 8(1), 10(1) Onithochiton neglectus 3(4), 28(1) Rhyssoplax stangeri 3(2), 4(2), 10(1), 15(4), 17(17), 30(4), 31(7) GASTROPODA Amalda novaezelandiae 6(1), 7(1), 9(1), 10(1), 11(1), 14(2), 17(1), 23(1), 25(2), 26(4), 28(1) Antimelatoma buchanani maorum 14(2), 28(1)

101 Antisolarium egenum 5(1) Buccinulum linea 17(1), 31(2) Cominella adspersa 3(1), 4(3), 12(1), 15(2), 22(1), 28(3), 33(2) C. quoyana 2(2), 3(2), 4(8), 5(2), 6(2), 10(3), 11(2), 12(1), 13(2), 14(1), 17(1), 20(1), 21(5) 22(2), 23(2), 28(3), 29(2), 30(2), 31(1), 33(2) Crepidula costata 17(1) Cyclichna thetidis 4(1) Duplicaria tristis 2(1), 4(1), 11(1) Epitonium minora 2(1), 5(1), 21(1) Maxacteon cratericulatus 8(2), 9(3) Muricopsis octogonus 30(1) Neoguraleus sp. 33(1) Pelicaria vermis 6(1) Phenatoma rosea 12(1), 23(1) P. zealandica 6(1), 25(1) Proxiuber sp. 4(1) Pupa kirki 3(2), 5(3), 6(1), 13(4), 23(5), 26(1), 33(3) Taron dubius 17(1) Trochus tiaratus 6(1) Xymene plebeius 17(1), 22(1), 31(1) Zeacolpus pagoda 21(1), 25(1) Zegalerus tenuis 4(1), 9(1), 10(3), 15(1), 16(1), 17(2), 21(1), 26(2) BIVALVIA Cardita aoteana 3(1) Chlamys zelandica 3(1), 9(2), 26(1), 30(2) Corbula zelandica 4(4), 6(13), 7(1), 8(1), 9(1), 10(4), 11(1), 12(1), 14(10), 15(3), 19(4), 23(1), 28(12), 29(6) Cuspidaria willetti 8(1) Dosinia subrosea 5(1), 21(1) Felaniella zelandica 20(3), 22(1) Gari hodgei 33(1) G. lineolata 5(2) G. stangeri 4(1) Glycymeris laticostata 17(3), 22(1), 30(2), 31(4) G. modesta 10(1) Limaria orientalis 3(16), 4(10), 10(9), 15(8), 29(1), 30(4), 31(1) Modiolarca impacta 3(1) Myadora boltoni 13(1) Notocallista multistriata 23(1), 26(1) Nucula nitidula 5(1), 9(1), 12(2), 13(1), 14(2) Pecten novaezelandiae 9(1), 14(2), 15(2), 17(1) Pleuromeris zelandica 11(1), 14(4), 26(1), 33(8) Saccella bellula 8(1), 16(1) Scalpomactra scalpellum 5(2), 21(2), 25(1) Talabrica bellula 22(1) Tawera spissa 4(1), 15(2), 20(1) Tellina huttori 5(1), 26(1) Venericardia purpurata 3(1), 9(3), 28(3), 29(3), 31(1) CRUSTACEA Alpheus sp. 30(1) Eoalia sp. 9(1) Halicarcinus varius 2(1), 3(10), 4(1), 9(1), 15(2), 30(7), 31(3) Liocarcinus corrugatus 31(1)

102 Notomithrax minor 3(1), 9(1), 10(1), 30(1), 31(3) Petrolisthes novaezelandiae 17(1) Pinnotheres novaezelandiae 9(1) Amphipoda 20(2), 23(1), 30(3) Caprellidae 2(1) Isopoda 4(2), 17(1), 30(1) unidentified hermits 2(1), 4(1), 5(2), 7(2), 14(3), 17(4), 33(1) INSECTA Philanisus plegejus 2(1) ECHINODERMATA Amphipholis squamata 7(1) Amphiura sp. 7(1), 8(38), 9(35), 16(13), 26(2) "Cucumaria" 30(2), 31(20), 33(1) Echinocardium cordatum 13(2), 23(1), 33(1) Ophiuroidea 2(1), 31(11) CHORDATA Agnesia sp. 4(2) Balanoglossus australiensis 7(1) Saccoglossus sp. 30(3), 31(5) unidentified compound ascidian 7(2), 9(4), 26(1) unidentified simple ascidian 7(1)

103