benthic communities west of slipper island, north-eastern ... · benthic communities wes t of...

16
TANE 20 1974 BENTHIC COMMUNITIES WEST OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roger V. Grace* and Ron F. Whitten f SUMMARY Forty-one dredge samples from sediments west of Slipper Island were analysed for benthic macrofauna, and gross sediment characteristics. Two main faunal associations were recognised. One was characterised by Tawera spissa, and was found in the coarser sediment grades. The other, characterised by Myadora boltoni and Scalpomactra scalpellum, inhabited finer sediment grades. Two additional minor associations were recognised, but not adequately sampled for detailed assessment. The rocky bottom Ecklonia - Carpophyllum community was also briefly described, based on snorkel diving observations. Comparisons were made between the communities found at Slipper Island, and those described from other parts of the New Zealand continental shelf. INTRODUCTION Slipper Island is located in the northern Bay of Plenty (latitude 37?03' S, longitude 175°57' E), 8 kilometres south-east of Tairua, and approximately 4 kilometres east from the closest part of the mainland coast. The samples forming the basis of this paper were collected during the Auckland University Field Club scientific camp in August 1973. The area sampled was bounded by Slipper Island, Rabbit and Penguin Islands, and Watchman Rock. The locations of the 41 stations, and the bathymetry of the area, are indicated on the map in Fig. 1. Depth contours are sketched from unpublished faircharts prepared by the Royal N.Z. Navy from a survey made in September 1971 to October 1972. METHODS Samples were collected using a small dredge (see Fig. 2.), hand-hauled from a 10-foot dinghy with A l A horse-power outboard. The dredge was improvised from scrap materials found on Slipper Island (see footnote). A one-gallon petrol tin with the top cut out, served as the bucket of the dredge. A heavy piece of scrap iron tied to the bottom of the tin with wire, held the Footnote: The original intention of the authors was to undertake a benthic survey using Scuba-diving techniques, but because of illness, Scuba-diving was unwise during the time available for the field work, and an alternative programme for benthic study was devised. *C/o Department of Zoology, University of Auckland, t Department of Geology, University of Auckland. 5

Upload: others

Post on 22-Mar-2020

2 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

T A N E 20 1974

BENTHIC COMMUNITIES WEST OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND

by Roger V . Grace* and Ron F. Whitten f

SUMMARY

Forty-one dredge samples from sediments west of Slipper Island were analysed for benthic macrofauna, and gross sediment characteristics. Two main faunal associations were recognised. One was characterised by Tawera spissa, and was found in the coarser sediment grades. The other, characterised by Myadora boltoni and Scalpomactra scalpellum, inhabited finer sediment grades. Two additional minor associations were recognised, but not adequately sampled for detailed assessment. The rocky bottom Ecklonia - Carpophyllum community was also briefly described, based on snorkel diving observations. Comparisons were made between the communities found at Slipper Island, and those described from other parts of the New Zealand continental shelf.

INTRODUCTION

Slipper Island is located in the northern Bay of Plenty (latitude 37?03' S, longitude 175°57' E), 8 kilometres south-east of Tairua, and approximately 4 kilometres east from the closest part of the mainland coast. The samples forming the basis of this paper were collected during the Auckland University Field Club scientific camp in August 1973. The area sampled was bounded by Slipper Island, Rabbit and Penguin Islands, and Watchman Rock. The locations of the 41 stations, and the bathymetry of the area, are indicated on the map in Fig. 1. Depth contours are sketched from unpublished faircharts prepared by the Royal N.Z. Navy from a survey made in September 1971 to October 1972.

METHODS

Samples were collected using a small dredge (see Fig. 2.), hand-hauled from a 10-foot dinghy with AlA horse-power outboard. The dredge was improvised from scrap materials found on Slipper Island (see footnote). A one-gallon petrol tin with the top cut out, served as the bucket of the dredge. A heavy piece of scrap iron tied to the bottom of the tin with wire, held the

Footnote: The original intention of the authors was to undertake a benthic survey using Scuba-diving techniques, but because of illness, Scuba-diving was unwise during the time available for the field work, and an alternative programme for benthic study was devised.

*C/o Department of Zoology, University of Auckland, t Department of Geology, University of Auckland.

5

Page 2: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

trailing edge of the dredge on the seabed. To the leading edge of the bucket, a bridle was attached, made from old clothes-line wire. The bridle was shackled to a length of chain about 1.5 metres long. This was further weighted with scrap iron, to help hold the front of the dredge on the seabed, and thus ensure a good bite. A length of anchor warp attached to the chain was held by the operator in the boat. The dredge was carefully designed so that it would bite into the bottom equally well in either of its two stable positions on the seabed.

Efficiency tests carried out on the beach, and in shallow water observed by snorkelling, showed that the dredge took a bite into the sediment to an even depth of 6 centimetres, across the 17 centimetre width of its track. The bucket was filled after the dredge had travelled forwards about 50 centimetres. Thus, it was possible to estimate the area of the seabed sampled during each dredge haul, and hence make pseudo-quantitative assessments of the benthic macrofauna. In practice, however, the dredge never came up more than 7/8 full, because when lifting the dredge clear of the seabed a small amount of sediment fell out before the bucket reached an upright position. The area sampled by the dredge was estimated as 0.074 sq.metre when it arrived at the surface 7/8 full. If the dredge arrived at the surface only partly filled, adjustments to the quantitative estimates could be made by calculating by proportion the area of the seabed sampled.

After hauling, the sediment in the sample was briefly described using a grain size comparator, and the sample was passed over a sieve with approxi­mately 2 millimetre openings. The sieve was also improvised, made from a 5-pound peach tin, with many holes punched in the bottom with a nail. Care was taken to flatten out all the rough edges around the holes, so as to avoid damaging the more delicate members of the fauna. The fauna retained on the sieve was identified and counted, then returned to the sea. Where field sorting was impractical, the sieved sample was placed in a plastic bag and sorted on shore, the fauna then being returned alive to the sea. Estimates of the volume of residue remaining on the sieve after sorting were also made, to give an indication of the quantity of sediment coarser than 2 millimetre particle size.

Sampling stations were precisely located using a sextant to measure horizontal angles between fixed points on the shore.

RESULTS

A full list of data is presented in Appendix Table 1. This includes faunal counts in their raw state, species numbers, estimates of the area covered by the dredge, summary of sediment characteristics, and estimates of the volume of residue.

Key to Fig. 3: 1. Tawera spissa, 2. Glycymeris modesta, 3. Gari stangeri, 4. Diplodonta zelandica, S.Cominella quoyana, 6. Pervicacia tristis, 7. Zegalerus tenuis, 8. Nucula nitidula, 9. Anthochiton stangeri, 10. Hermit crab, 11. Polychaete (approx. life size).

Key to Fig. 4: l. Myadora boltoni, 2. Scalpomactra scalpellum, 3. Pupa kirki, 4. Pervicacia tristis, 5. Myadora striata, 6. Gari lineolata, 7. Cominella quoyana, 8. Astropecten polycanthus (juv.), 9. Polychaete (approx. life size).

6

Page 3: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

Fig. 3. Some important animals from the Tawera spissa community.

Fig. 4. Some important animals from the Myadora boltoni - Scalpomactra scalpellu, community.

Page 4: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

Sediments. Sediment distribution is indicated in Fig. 5. The coarse sediments contain

a high proportion of molluscan fragments, whereas the medium to fine sands appear to have only small quantities of bioclastic material. Fauna.

The most prominent components of the fauna are the molluscs. Of the 20 species of gastropods present, 16 species are carnivores, 2 are herbivores, and 2 are suspension feeders. Sixteen species of suspension-feeding bivalves, and 2 species of deposit-feeding bivalves were found. The chitons were represented by only 3 species.

The identification of polychaetes is difficult in the field, but some of them were identified because of their characteristic appearance or behaviour.

Five species of Crustacea were identified, although the commonest group, the hermit crabs, could not be specifically identified in the field, with the exception of large specimens of Stratiotes setosus.

Five species of echinoderms were found in the dredge samples. Shell residues from 5 stations were found to support 29 species of live

bryozoans, which were positively identified by subsequent microscopic examina­tion.

Other minor components of the fauna included small numbers of species from 8 major taxonomic groups.

DISCUSSION

Sediments. The distribution of sediments appears to be related to the depth, and to

water energy characteristics of the environment. Storm waves from the south-east, together with the tides, create "high energy environments" in the vicinity of the channels between the islands. This prevents deposition of fine sediments, and allows very coarse sediments to accumulate in the channels. These coarse sediments consist largely of shell fragments derived from dense beds of bivalves, particularly Tawera spissa, in nearby areas.

With increasing depth to the north-west, the influence on the seabed of both currents and wave action is much reduced, because of a combination of shelter from surrounding islands, probable slower tidal currents away from channels, and depth of water. This allows the accumulation of medium sands.

The finest sediments, in South Bay and Stingray Bay, appear to result from two slightly different sets of circumstances. In South Bay, an extensive subtidal bed of the eel grass Zostera capricorni has a sand-binding effect, trapping quantities of fine sand. In Stingray Bay, fine sand has accumulated, probably as a result of the considerable shelter from wave action offered by Slipper Island.

Fauna. The analysis of the fauna has been approached from the classical point of

view of selecting the most obvious, most numerous, or characteristic species to define benthic communities. For this purpose, the term "community" is used to

8

Page 5: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

apply to a recurring combination of species of organisms, in a characteristic biotope, and with a considerable degree of continuity in space.

An examination of the data has allowed us to define two major and two minor soft bottom communities. A brief assessment of the rocky bottom community is also included. Each of the communities recognised is defined and discussed below. The distribution of the communities is shown in Fig. 6.

1. Tawera spissa Community

Stations: 2 ,3 ,7 , 11, 13,21,22,23,27,29,30,36,37,38,39. Marginal stations: 14,40.

Biotope Sediment: Coarse sand to shell gravel. Depth: Mainly 5 to 10 metres. Energy: Moderate to high.

Characterising Species Number of stations Tawera spissa 12

Associated species Polychaetes 14 Cominella quoyana 12 Pervicacia tristis 11 Zegalerus tenuis 7 Diplodonta zelandica 1 Anthochiton stangeri 6 Cominella adspersa 6 Gari stangeri 6 Glycymeris modesta 6 Nucula nitidula 6 Hermit crabs 6 Amalda novaezelandiae 4 Maoritomella albula 4 Ischnochiton maorianus 3 Amalda australis 3 Limatula maoria 3 Myadora striata 3 Scalpomactra scalpellum 3 Trochodota dendyi 3 Amphipholis squamata 3

This community occurs in two areas; a small area close to Home Bay, and a larger one to the south-east. The centre of abundance of Tawera spissa appears to be near stations 27 and 39, which are partly sheltered by Penguin Island. Estimated densities of Tawera at these stations are 5,500 and 4,700 per square metre at stations 27 and 39 respectively. The Tawera in this vicinity, however, are not adults, averaging approximately 10 to 15 millimetres in length. Adult Tawera are found further to the east around stations 22, 23 and 36, and to the west at station 38. At these stations, the most frequent length of Tawera is

9

Page 6: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

about 22 to 25 millimetres. The bed of Tawera off Home Bay appears to contain mainly adult specimens.

The observed distribution of size groups of Tawera could have arisen in any of three ways:

1. The sheltered area behind Penguin Island may be a "nursery" area, where Tawera larvae settle, but migrate to other areas as they grow.

2. There may have been a good spatfall in the areas where large Tawera occur, followed by a more recent successful spatfall only in the area where the smaller specimens occur.

3. The Tawera may all be roughly the same age, but those closer to the channels have grown to a large size more rapidly because of better food supply. Without long term monitoring of the populations, it is not possible to say which of these processes is in operation.

The associated species listed are mostly species normally found in fairly coarse sediments. However, the carnivores Cominella quoyana and Pervicacia tristis range over a variety of sediment types, and are both found fairly commonly in the Myadora - Scalpomactra community as well as in the Tawera community.

Several of the more important species in this community are illustrated in Fig. 3. 2. Myadora boltoni - Scalpomactra scalpellum Community

Stations: 4, 5, 6, 8, 9, 10, 12, 15, 16, 24, 26, 28, 32, 33, 34, 35, 41 Marginal stations: 14, 17,40.

Biotope Sediment : Medium to fine sand. Depth: Mainly 5 to 15 metres. Energy: Low

Characterising species Myadora boltoni Scalpomactra scalpellum

Associated Species Polychaetes Pervicacia tristis Pupa kirki Myadora striata Cominella quoyana Astropecten polyacanthus

Tawera spissa Diplodonta zelandica Gari lineolata Hermit crabs Echinocardium cordatum Antisolarium egenum This community occurs in a large area bounded

main area occupied by the Tawera community.

Number of stations 15 8

12 1 1 8 8 7 6 5 4

4 4 3

by Slipper Island and the

10

Page 7: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

Myadora boltoni is widespread, but never reaches high densities, the maximum number per dredge haul being 5 at stations 15 and 33. Scalpomactra scalpellum is also widespread with low densities, but the total number of occurrences of Scalpomactra is somewhat lower than that of Myadora boltoni.

The roving carnivores Pervicacia tristis and Cominella quoyana belong equally well to this community and the Tawera community.

There is a tendency for Pupa kirki to occur more commonly at the northern edge of the area sampled, perhaps indicating a subtle sediment change not detected by our crude sediment analysis.

All specimens of the starfish Astropecten poly acanthus found in the dredge samples were very small juveniles up to 5 millimetres in diameter, but adults almost certainly occur in this community.

Apart from an occasional small specimen of Tawera spissa, most of the associated species are normally found in medium to fine sandy sediments. Several of the species are illustrated in Fig. 4. 3. Zostera capricorni - Nucula hartvigiana Community

Stations: 19,20. Marginal station: 17.

Biotope Sediment: Fine sand. Depth: 0 to 5 metres. Energy: Low to moderate.

Characterising Species Number of stations Zostera capricorni 3 Nucula hartvigiana 3

Associated species Polychaetes 3 Cominella adspersa 2 Hermit crabs 2 This community was not defined satisfactorily because of insufficient

sampling. The inclusion of the eel grass Zostera capricorni was, however, a very distinctive feature of the samples.

The nut shell Nucula hartvigiana is commonly associated with Zostera on harbour flats. The tube worm Owenia fusiformis was found at station 20, and is known to be common in Zostera beds elsewhere.

An extensive subtidal bed of Zostera occurs in South Bay, and was clearly visible from the dinghy, and aerial photographs. This particular occurrence of the Zostera — Nucula association is the deepest known to the authors, as it extends to a depth of about 5 metres. 4. Paphies subtriangulatum Community Stations: 1, 18,25,31. Biotope

Sediment: Medium to fine sand. Depth: Mainly intertidal. Energy: Moderate to high.

I 1

Page 8: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

Characterising Species Number of stations Paphies subtriangulatum 1

Other Species Present Amalda australis 1 Cominella adspersa 1 Divericella huttoniana 1 Pycnogonida 1 This community was also difficult to define satisfactorily, because of the

small number of samples. The distribution of the community indicated on the map is defined more by inference than any empirical method, as the type of habitat occupied by this community is well known from other districts.

Although the tuatua Paphies subtriangulatum turned up in only one of the dredge samples, it was seen on occasions on the beaches at Home Bay and South Bay. This community has few species and usually small numbers of individuals. 5. Ecklonia radiata - Carpophyllum spp. Community.

Biotope Substrate: Hard Rock. Depth: 0 to 5 metres. Energy: Moderate to high.

Characterising Species Ecklonia radiata Carpophyllum flexuosum Carpophyllum plumosum

Associated Species Coralline paint Cliona celata Cellana stellifera Charonia capax Cookia sulcata Thais orbita Jasus edwardsi Plagusia chabrus Evechinus chloroticus Asterocarpa caerulea This community was readily observed from the boat because of the clear

water. Snorkel diving enabled some of the more characteristic organisms to be determined.

The outline of this community on the map was clearly defined by reference to aerial photographs.

The sea urchin Evechinus chloroticus occurred commonly only in the absence of dense beds of Ecklonia.

The densest beds of Ecklonia appeared to be those along the western side of Slipper Island. On the north-west side of Penguin Island, Carpophyllum plumosum and C. flexuosum were often in greater abundance than Ecklonia radiata.

As well as supporting a large number of invertebrate species, the rocky bottom is a suitable habitat for a number of reef-dwelling fishes.

12

Page 9: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

Fig. 5: Distribution of sediments.

13

Page 10: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

Bryozoan fauna. The following living Bryozoa were recovered from the dredge samples

(station numbers in brackets), and subsequently identified:

Aetea anguinea (38) Arachnopusia unicornis (38) Arthropoma circinata (38) Beania discodermiae (38) Bicrisia edwardsiana (38) Calloporina angustipora (38) Chaperia acanthina (3,22,27,38) Chaperia cervicornis (27,38) Crepidacantha crinispina (38) Disporella cf. fimbriata (22) Escharoides angela (22,38) Eurystomella foraminigera (38) Fenestrulina malusii (38) Hippoporina cincta (22,27,38) Hippothoa bougainvillei (3,38)

Inversiula fertilis (38) Lichenopora novaezelandiae (38) Microporella cilliata (22,38) Microporella hyadesi (38) Opaeophora monopia (38) Osthiomosa bicornis (23) Osthiomosa eatonensis (22,23,38) Parasmittina trispinosa var. aotea (38) Parasmittina unispinosa (38) Rhynchozoon larreyi (22,23,27,38) Smittina maplestonei (3,38) Smittina smittiella (27) Steganoporella neozelanica var. magnifica (38) Umbonula bicornis (38)

Most of the Bryozoa encrust dead molluscan shells, especially those of Tawera spissa. Pebbles were very rare in the dredge samples, and none of those found were encrusted by Bryozoa. At station 38 an unidentified hydroid, attached to a valve of a dead Glycymeris laticostata, supported several colonies of Lichenopora novaezelandiae and Bicrisia edwardsiana.

The most common species found encrusting Tawera spissa were Chaperia acanthina, Rhynchozoon larreyi and Hippoporina cincta. The large valves of Glycymeris laticostata recovered from stations 22 and 38 were encrusted predominantly by Escharoides angela, Steganoporella neozelanica var. magnifica and Hippoporina cincta.

Diversity of species. The number of species in each sample is indicated in Appendix Table 1.

For this purpose, all species of bryozoa, and all species of polychaetes are grouped together.

Because of variation in sample size, distribution of number of species must be interpreted with caution. Nevertheless, a clear pattern of species diversity can be seen.

In general, species diversity is greatest in the Tawera community, where most samples have between 10 and 20 species, with a maximum of 21 species at station 22.

The Myadora — Scalpomactra community has lower diversity than the Tawera community. Most samples contain between 5 and 10 species, but towards the north of the area sampled, diversity is even lower.

Samples in the Zostera - Nucula community have 5 or 6 species. This community was poorly sampled, however, and it is likely that more species occur here than these samples indicate.

14

Page 11: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

Diversity is lowest in samples from the unstable sands of the Paphies community.

It appears that the coarser sediment and higher energy environment in the Tawera community gives greater opportunity for more species than in the other communities.

Comparison with other areas in New Zealand.

1. Tawera spissa community. This community, or variations of it, is widespread on sandy or shelly areas

of the New Zealand continental shelf. There is an obvious affinity with the "Venus" communities recognised by McKnight 9. McKnight describes four variations of "Venus" communities, and the variation which best fits the community at Slipper Island appears to be the Tawera spissa - Venericardia purpurata community. Although Venericardia is absent from the Slipper Island samples, McKnight suggests that Tawera tends to be dominant in shallow areas, but less important in deeper parts. The Tawera community at Slipper Island is at the shallow end of the depth range given by McKnight for his Tawera -Venericardia community.

Other parallels are found in the Tawera - Glycymeris formation in the Auckland Harbour 1 1 , and the Tawera - Dosinia community at the entrance to the Whangateau Harbour6, and some of the Tawera beds at Whangarei Heads 1 0. Very dense beds of Tawera (over 7000 per square metre) were found at Mimiwhangata by Ballantine, Grace and Doak 1 , with a number of associated species similar to those found at Slipper Island.

2. Myadora boltoni - Scalpomactra scalpellum community. There appears to be no clear-cut parallel to this community, recorded for

other parts of the New Zealand continental shelf. One of the variations of McKnight's s "Venus" communities, the Scalpomactra scalpellum - Maorimactra ordinaria community, occurs on a similar substrate and has some faunal similarity with the community at Slipper Island. The depth range given by McKnight, "mainly 20 to 60 metres but also much deeper", and many differences in species composition, indicate that the two communities are not the same. The community at Slipper Island probably represents a shallow water variation of McKnight's Scalpomactra scalpellum - Maorimactra ordinaria community. McKnight encountered difficulty in trying to subdivide this community, because of differing sampling techniques and sample volumes, and an inherent variation in the abundance of Scalpomactra scalpellum, McKnight suggests that strictly comparable samples will be needed before a sound basis for subdivision can be established.

3. Zostera capricorni — Nucula hartivigiana community. This community is well known from sheltered harbour flats on the New

Zealand mainland, where it is usually associated with several other species of molluscs, and some characteristic Crustacea 1 0 . Subtidal occurrences of this community in offshore areas appear to be rare.

15

Page 12: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

Fig. 6: Distribution of communities.

16

Page 13: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

4. Paphies subtriangulatum community. The tuatua, Paphies subtriangulatum, occurs on most open coast sandy

beaches throughout New Zealand, and is subject to extreme fluctuations in population density. Most of the associated fauna occurs at such low densities that it is difficult to sample quantitatively.

This community is described more fully from other areas in New Zealand by Knox 8 and Morton and Mi l l e r 1 0 .

5. Ecklonia radiata - Carpophyllum spp. community. The large brown kelp Ecklonia radiata forms extensive forests on rocky

bottoms off much of the hard shoreline of the North Island. It becomes less common towards the south. Ecklonia radiata is often accompanied by Carpophyllum plumosum, or C. flexuosum, particularly in shallow water.

Several subdivisions of this community can be recognised, but are beyond the scope of this paper.

Discussions of various aspects of subtidal Ecklonia forests are given by Bergquist2, Doak 3 , Dromgoole 4, 5 and Grace.7

ACKNOWLEDGEMENTS

The authors wish to thank the Marine Research Laboratory, Leigh, for use of their 10-foot dinghy, Mr D.A. Saies for the loan of the outboard motor, and Mr Richard Willan for identification of some molluscs. The authors also wish to thank their wives for retrieving the dredge by Scubadiving, after the dredge rope was accidentally cut by the outboard at an early stage in the sampling programme.

REFERENCES

•Ballantine, W.J., Grace, R.V. and Doak, W.T. 1973 "Mimiwhangata Marine Report." Limited circulation report for New Zealand Breweries Ltd. 98pp.

2Bergquist, P.L. 1960 The marine algal ecology of some islands of the Hauraki Gulf. Proc.N.Z.Ecol.Soc. 7:43-5.

3Doak, W.T. 1971 "Beneath New Zealand Seas." Reed, Wellington. 113pp. 4Dromgoole, F.I. 1964a The ecology of the sublittoral boulder beaches at Little Barrier

Island. Tane 70:70-8. sDromgoole, F.I. 1964b The depredation of Ecklonia radiata beds by the sea urchin

Evechinus chloroticus. Tane 10: 120-22. 6Grace, R.V. 1972a "The Benthic Ecology of the Entrance to the Whangateau Harbour,

Northland, New Zealand." Ph.D. thesis, University of Auckland. 205pp. 7Grace, R.V. 1972b Sublittoral zonation of dominant organisms at Red Mercury Island,

north-eastern New Zealand. Tane 18:57-66. 8 Knox, G.A. 1969 Beaches. Chapter 32 In Knox, G.A. (ed.), "The Natural History of

Canterbury." Reed, Auckland. 620pp.

17

Page 14: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

A P P E N D I X T A B L E 1 S T A T I O N D A T A .

1 2 3 4 S 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

ft a ms IMS ms c i ms m i m i ms ms mi CI m i I!1S ms ft Is CI 1/3 7 8 7.8 1/3 7/8 2'3 M K & 7/8 % 2/3 4 7/8 1/8 1/8 %

2.8 7.4 7.4 4 3 4.3 2.8 7.4 5.7 4.3 6 4 6 4 6 4 7.4 6.4 5.7 4 J 4 1 7 4 2.8 2.8 6.4 ? 250 SI) JO a HI 15 25 10

I JO 1 2 10 3 5 1 4 6 4 1 4 1

1

1 2

5 1 4 6 1

2 1 1 3 1 1 3 2 2 3 1 1

I 2 I I 3 1 2 1 3 2 1

1

2 2 2 7

I 1

2

2 5 3 2

1 2 ]

17 18 19 20

Page 15: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

STATION NUMBER Sediment code (see key) Proportion of dredge Tilled. Sample area estimate (sq. metre x 100) Shell residue volume (ml) GROUP and SPECIES P O R I F E R A Tethya ingalli1

HYDROZOA unidentified hydroid N E M E R T E A unidentified, black B R Y O Z O A P H O R O N I D A Phoronis sp P O L Y C H A E T A (total) Aglaophamus macroura Armandia mac uia ta Axiothella australis Euchonr ip. Eulalia sp Lank* conchilega Lepidonotus polychrome unidentified Maldanid unidentified Nereids Owenia fusiformis other unidentified M O L L U S C A A M P H I N E U R A Acanthochiton zelandicus Anthochiton stangeri Ischnochiton maorianus G A S T R O P O D A Amalda australis Amalda novaezelandiae Antiguraleus sp. Antimellatoma buchanam maorum Antisolarium egenum Axymene corticatus Cominella adspersa Cominella quovana Epitonium phillipinarum Maoncrypta costata Maoritomella albula Marginella pygmaea Pervicacia tristis Phenatoma novaezelandiae Philine angasi Pleurobranchaea novaezelandiae Pupa kirki Risstiina achatina Xymene pusilla Zegalerus tenuis B I V A L V I A Diplodonta zelandica Divancella huttoniana Dosinia maoriana Can lineolata (ian stangeri Glycymeris modesta Hunkvdora australica novozelandica Limatula maoria Myadora boltoni Myadora striata Notocorbula zelandica Nucula hartvigiana Nucula nitidula Paphies submangulata Pecten novaezelandiae Scalpomactra scalpellum Soleteliina nitida Tawera spissa CRUSTACEA Tan aid ace a Locarcinus corrugatus Paramithrax minor Elamina sp. Halicarcinus varius unidentified Hymenosomatid Stratiotes setosus unidentified hermits Balanus trigonus P Y C N O G O N I D A E C H I N O D E R M A T A Trochodota dendyi Amphipholis squamata Astropecten polyacanthus Echinocardium cordatum Fellaster zelandiae C H O R D A T A H E M I C H O R D A T A Balanoglossus australiensis A S C I D I A C E A unidentified, simple unidentified, compound C E P H A L O C H O R D A T A Epigonichthys hector!

T O T A L N U M B E R Of̂ SPECIES

S T A T I O N N U M B E R

Page 16: Benthic communities west of Slipper Island, North-eastern ... · BENTHIC COMMUNITIES WES T OF SLIPPER ISLAND, NORTH-EASTERN NEW ZEALAND by Roge Vr. Grace* and Ron F Whitte. n f

9McKnight, D.G. 1969 Infaunal benthic communities of the New Zealand continental shelf. N.Z.JI mar.Freshwat.Res. 3:409-44.

1 0 Morton, J.E. and Miller, M.C. 1968 "The New Zealand Sea Shore." Collins, London. 638pp.

1 1 Powell, A.W.B. 1937 Animal communities of the sea-bottom in Auckland and Manukau Harbours. TransM.SocJV.Z. 66":354^01.

20