Benthic Ecology of Glory Cove, Stewart Island

Transactions of the Royal Society of New Zealand : Biological Sciences, Volume 11, Issue 5, 15 July 1969, Page 73

Benthic Ecology of Glory Cove, Stewart Island

E.J. Batham

By

Portobello Marine Biological Station, Portobello, New Zealand.

[.Received by the Editor, August 9 , 1968.]

Abstract

Glory Cove, near the south end of New Zealand, is a small sheltered bay with a bottom of sandy mud. Five dredge hauls and three trawl hauls indicate that its benthic ecology is relatively uniform. The red alga Lenormandia chauvinii is dominant over most of the bottom. Echinoderms are especially in evidence, 17 species being recorded, with Echinocardium cordatum and the holothurians Amphicyclus thomsoni and Chiridota nigra each present in at least three-quarters of the samples. Of infaunal lamellibranchs, Paphirus largillierti and Tawera spissa are present in moderate numbers. Abundant epifaunal molluscs include Terenochiton inquinatus, Micrelenchus micans, Chlamys radiata and Maoricolpus roseus, though the shells of the latter frequently house hermit crabs. Eunice australis and the amphipod Maera inaequines abound.

Introduction

Two days of intensive bottom sampling of Glory Gove, during the Munida- Port Pegasus 1967 Expedition, gave a relatively uniform picture of its benthic ecology. At the present stage, when little has to date been published on New Zealand benthic ecology (Powell, 1937; Skerman, 1964; Ralph and Yaldwyn, 1956; Hurley, 1959; Fleming, 1952), but when much work is in active progress, it is felt that an account of Glory Cove can usefully be presented.

Methods

Field work was carried out from the University of Otago’s 46ft research vessel Munida. The trawl used was a 4ft-wide Agassiz beam trawl, with fin mesh, and with a removable bottom-sampling box in each runner, after the pattern of one used by the New Zealand Oceanographic Institute. The dredge was an 1 Sin-wide Salpa dredge with curved, angled jaws and with a sacking bag that quickly filled with substrate. This was washed gently out on to the deck with a hose, and the animals removed as they appeared. Because the bottom biota was very rich, the Agassiz trawl was hauled each time for less than the usual 10 minutes the writer normally standardises on. In one haul (Mu 67-38), after approximately one minute on the bottom, the trawl bag was so full that difficulty was encountered in getting it on board and only half of the large catch was methodically sorted. Familiar species were identified and recorded on deck; others were brought back and subsequently

identified, with extensive help by specialists. Numbers or approximate numbers were recorded during catch sortings. These are accurate for large species (where a dash in Table II indicates definite absences), but are approximations only, and probably well below actual numbers, for smaller recorded species, such as Terenochiton and

Podarke angustifrons. Tiny animals, such as smaller crustaceans, molluscs and polychaetes, have been omitted; the aim being to give a broad preliminary picture in semi-quantitative terms rather than to present an extensive faunal list or a precisely quantitative study.

Eight bottom samples were analysed by Dr W. A. Hodgson, Otago University Geology Department. Standard grain size analysis was carried out, the sand fractions from 1 to 4 <£ being sieved into \ <£ fractions. Grain size distribution of silt and clay fraction was determined by the pipette method (Krumbein and Pettijohn, 1938). Results were plotted as cumulative frequency curves, and from these the values for Md, M (f> , etc., were calculated, following the method of Inman (1952).

Physical Environment

Glory Gove is a small, fairly sheltered, deeply indented bay which runs off the south-east of Paterson Inlet, Stewart Island, at the south end of New Zealand (Figs. 1,2). It lies at latitude 46° 58' south, longitude 168° 10' east. Its depth is mostly between 6 and 15 metres. Its opening is miles from the entrance of Paterson Inlet to the open sea of Foveaux Strait. It is not exposed to open ocean wave action. Bottom sampling was carried out on February 9 and 15, 1967. A surface salinity sample on the second day, after some rain the previous night, gave

a reading of 34.46° / 0 0, as compared with a nearly open ocean surface reading of 34.81°/oo off the SE of Stewart Island a few days earlier. In other words, Glory Cove is close to full offshore salinity; the limited run-off from the surrounding low country presumably not normally reducing its salinity significantly. Glory Cove surface sea temperatures at 9 a.m. were 14.2°G (air 12.7°G) on 15.2.67, and 13.8°C (air 12.7°G) on 16.2.67. These may be compared with 9 a.m. surface sea temperatures taken from the end of the Portobello Marine Station wharf, five miles from the opening to Otago Harbour, on the same dates. These latter were rather warmer, namely 16.0°C (air 15.0°C) on February 15, and 15.4°G (air 16.1 °C) on February 16, 1967.

Glory Cove is surrounded by slightly hilly land, forest-clad to the water’s edge around its western half, and by coastal scrub on a low neck of land along its southeast margin. Its shores have no habitations, but a small jetty attracts visitors by summer tourist launch. Thus, except immediately below the jetty, it is presumably practically unmodified. The shore consists of rocky outcrops, stones and small beaches.

The bottom of Glory Cove is mostly sandy mud, with an abundance of organic matter, chiefly in the form of faeces. Some samples had a considerable amount of shell gravel, predominantly of the shells of Maoricolpus roseus. Lamellibranch shells of several species were found in much smaller numbers, and a few shells of the brachiopod Magasella sanguinea were present.

Size analyses of bottom samples associated with the eight biological stations are summarised in Table I and some of them are shown graphically in Fig. 3. The sand/silt/clay ratios show most samples to consist of sandy mud, two of mud. Apart from station Mu 67-38, samples show a trend from coarsest in shallowest water to finest in deepest, which is reasonable for an enclosed bay. The high S s <£ values

indicate that all samples are very poorly sorted, presumably because neither wave action not currents are effective in sorting bottom sediments in such a site. Data in Table I and Fig. 3 suggest that current activity is unimportant, and that wind-wave action controls sediment distribution. The s/s/c ratios show the same relations as the median shows.

The dominant biological fraction of sediments in the innermost part of the Cove consists of Foraminifera, whereas near the entrance it is primarily molluscan shell hash, with echinoid spines and test fragments.

Biological Data

Results are tabulated in Table 11. This lists species occurring in at least two of the stations sampled, and of which at least three specimens were present. This list is not exhaustive, but covers more than 95 percent of the bulk of the living material sampled.

Most of the cove floor was dominated by Lenormandia chauvinii, a flat more-or-less dichotomously branching red alga, some plants of which were attached to the turret shell Maoricolpus roseus. Macrocystis pyrifera was locally abundant, usually with Spirorhis and encrusting bryozoans on its fronds. Carpophyllum flexuosum was dense sublittorally below the jetty. Dichotomising Codium plants, chiefly C. fragile, with a little C. dichotomum, were fairly frequent. A few other red algal species were present in small amounts in one or another sample. No other greens were sampled sublittorally, and the only other brown noted was a slender Cystophora (probably a form of C. retroflexa ) in small quantities.

Of animals, Echinodermata was the group represented unusually strongly, in numbers of specimens, bulk of organisms, and numbers of species. Some 17 species were taken, many in considerable numbers. Three snorkel dives to about 10-12 ft below low tide, near the jetty, showed three large echinoderm species— Evechinus chloroticus, Stichopus mollis and Coscinasterias calamaria —all in abundance, individuals of each species lying scattered about 1m from each other. This was where rocky reefs ran out to a sandy bottom. In the eight stations worked, the khaki cucumariid holothurian Amphicyclus thomsoni proved more abundant than Stichopus. Whereas the occasional specimens of A. thomsoni taken off Otago have been unadorned, all from Glory Cove, and almost all from Port Pegasus, Stewart Island, were covered with scraps of shell and alga. Not infrequently, from two to six of these holothurians were found sticking closely together, in a common covering. Whether the curious habit of covering themselves serves as camouflage, protection against light, or other function, is not known. An even more abundant though slightly smaller holothurian was Chiridota nigra, a wine-coloured apodous species with pale spots. Two smaller, pinkish-coloured apodous holothurians present in several hauls, but not always distinguished from one another in the field, were Trochodota dendyi and Trochodota dunedinensis. The khaki heart urchin Echinocardium cordatum was conspicuous in most catches. Pectinura gracilis, a small grey-brown brittle star with barred arms, was because of its size less conspicuous than the larger echinoderms, but present in numbers at practically all stations. Echinoderm species taken in too small numbers to be included in Table II were: Aliostichaster polyplax, Pentagonaster pulchellus, Chiridota gigas, and a tiny white brittle star, Ophioceres huttoni.

Other animals important in the present association will not be considered so much in their systematic order. The turret shell Maoricolpus roseus was abundant. Of a sample of about 100 shells, approximately equal numbers were living, contained hermit crabs, or were empty. The more abundant hermit was Pagurus traversi, here occurring almost entirely in Maoricolpus shells, though one was in a Melagraphia aethiops shell, and several w r ere free amongst the algae. With these latter, one was

(dom. —dominant; abund. —abundant; pc. —pieces; c.—circa.)

tempted to wonder whether the dull pink colour of the soft abdomen had protective value in a red algal habitat. In smaller numbers in the Maoricolpus shells was the hermit Pylopagurus cooki, characterised in the field by its deep blue maxillipeds. A single specimen was taken at Glory Gove of a vermilion hermit crab with mauve first antennules ( species as yet unnamed). This is the commonest offshore shelf hermit crab species in Otago waters.

Eunice australis was the most conspicuous polychaete, coming up either free or in flaccid shelly tubes. The tiny tan chiton Terenochiton inquinatus and the small pink trochid Micrelenchus micans were both generally abundant. The red-shelled Chlamys radiata, at times with the purple sponge lophon laevistylis on one valve, was conspicuous amongst the epifauna. Infaunal lamellibranchs of “ cockle ” type shell were Paphirus largillierti and Tawera spissa. Although both were present in the majority of catches, neither was taken in great density. Other infaunal lamellibranchs were Tellina huttoni, Leptomya retiaria and Diplodonta globus, the last coming up in a dense, khaki-coloured covering of fibrous material.

Grabs other than hermits included the small camouflage crab Notomithrax minor and a little hymenosomid. A large apricot-coloured amphipod, Maera inaequipes, was abundant. Several smaller species were present in limited numbers.

Ascidians were not at all in general evidence, with the exception of an orange compound species. This was abundant both on algae in one trawl haul, and on rock and tins below the jetty. A stout apricot nemertine about scm long was in the majority of hauls, and a larger wine-coloured species was taken at one station. A single live brachiopod, Magasella (Terehratella) sanguinea, was taken. No coelenterates were seen sublittorally. Infaunal polychaetes seemed relatively sparse. This was probably partly due to the sampling methods used, though even allowing for this they certainly did not show the density met with in some New Zealand benthic habitats.

Of fish, spotties (the wrasse Pseudolabrus celidotus) were seen in numbers during diving and from the vessel, their near-absence from catches reflecting their quick escape response rather than their sparseness. Acanthoclinus trilineatus and Syngnathus blainvillianus were not infrequent. Both were of the dull red colour of the dominant Lenormandia. Several species of Tripterygiid abounded. Pending formal descriptions of New Zealand sublittoral Tripterygiidae, Mr J. Moreland’s manuscript names have been used for them.

Comments

No obvious correlations were apparent between slight differences in bottom sediments and the species occurring at given stations. Rather, the picture shown by the data is of a relatively uniform sandy-mud environment, with a number of species occurring repeatedly in samples. This suggests that a reasonably typical picture is given of the sea bottom of Glory Cove. Deeper-sampling gear would doubtless have revealed more polychaetes and lamellibranchs, whilst finer sorting would have increased the species list of small animals. Aqualung diving would be expected to show which species are particularly associated with the probably patchy algal covering; and also which are entirely on the substrate, which totally or partially buried. Concurrent Otago studies by several workers, using an assortment of methods, are showing what very different pictures of benthic ecology emerge when different sampling techniques are used.

It does not seem useful at this juncture to compare the results obtained here with the very few other New Zealand benthic ecology studies that have been published to date, as so much more work is at present under way. The particular impression gained in the present instance is of the unusual wealth of echinoderms at Glory Cove.

Acknowledgments

I am deeply indebted to the New Zealand Golden Kiwi Lottery Science Committee, for the grant for the research vessel Munida that has opened the way for a greatly expanded southern New Zealand biological programme. I express my appreciation to the vessel’s skipper (Mr Bill Tubman) and crew (Mr Stan Deans), for the very helpful way they looked after us during the expedition and, together with Mr Dallas Clark, for assistance in sorting catches. Dr W. A. Hodgson (Otago University Geology Department) analysed the bottom samples, and Dr J. Jillett (Portobello Marine Biological Station) made the salinity measurements with a Cronulla inductive salinometer. My thanks go to the following for identifications of specimens within the groups named: Dr P, Bergquist, Auckland University (some sponges), Dr J. Forest, Paris (hermit crabs), Mr J. Moreland, Dominion Museum (fish), Dr D. Pawson, Smithsonian Institution, while temporarily back at Victoria University of Wellington (holothurians and ophiuroids), Mr W. Ponder, Dominion Museum (most molluscs), and Mr S. Rainer, Portobello Marine Biological Station (polychaetes, amphipods).

Literature Cited

C. A., 1952. A Foveaux Strait oyster-bed. N.Z. Jl Sci. Technol. 34, B, 2: 73-85. Hurley, D. E., 1959. Some features of the benthic environment in Cook Strait. N.Z. Jl Sci. Tech. 2,1: 137-47. Inman, D. L., 1952. Measures for describing the size distribution of sediments. /. Sedim. Petrol. 22: 125-45. Krumbein, W. G.; Pettijohn, F. J., 1938. Manual of Sedimentary Petrography. New York, Appleton-Gentury. Powell, A. W. 8., 1937. Animal communities of the sea-bottom in Auckland and Manukau Harbours. Trans. R. Soc. N.Z. 66: 354—401. Ralph, P. M.; Yaldwyn, J. C., 1956. Sea floor animals from Otago Harbour. Tuatara VI, 2: 57-85. Skerman, T. M., ed., 1964. Studies of a southern fiord. Bull. N.Z. Dep. sclent, ind. Res. 157.

E. J. Batham, Portobello Marine Biological Station, Portobello, New Zealand.

* The parameters in first column are defined as follows; </> or phi: minus the log of the diameter in mm to the base 2; Md: median diameter in phi units; M <f>: mean diameter in <P units, being effectively a measure of current strength; S <t>: Inman’s approximation to standard deviation in phi units, giving measure of sorting ( the better the sorting, the lower being the value) ; a </>: measure of skewness ( a low value indicating a relatively symmetrical distribution); sand/silt/clay (or S/S/C) ratio, regarding 4 0 as boundary of sand and silt, 6 4> as boundary of silt and clay.

* May have been present in more stations than recorded.

Description Md* M ■©-* Station Depth S (f) a <p Sand/ Silt/ Clay Station Depth mud sandy O' pro 03 03 OS OS Mu 22 HH £ 1 g O a rf o mud sandy 03 03 .! tOO)^ O o 03 co 00 On CO O-i CO CO Oi ro Mu 67-37 22 mud 05,0 ►f* iCO On On 67-19 42 mud O 3 KS O OS 05 Ol Ir 4 i— 1 • • * . 'JOI 01^^010 Mu 67-18 32-36 feet U ►f». ' • • • . • Mu 67-18 32-36 feet sandy Mu 67-38 36 feet £ggg Mu 67-38 36 feet mud 6.26 6.66 Mu 67-39 36 feet 2.34 0.17 9.5 36 54.5 Mu 67-39 36 feet sandy mud Oi O CO OS o Mu 67-17 30-55 feet r 4>Mu 67-17 30-55 feet t "5 sandy OS OS OS 4*. P ks os On On 67-20 feet )utermost

Table I. —Size analysis results of eight Glory Cove bottom samples.

Innermost Outermost No. of out of 8 Outermost No. of out of 8 Station: Mu Mu Mu Mu 67-38 Mu 67-39 Mu 67-17 Mu 67-20 stations Mu 67-18 Mu 67-38 Mu 67-39 Mu 67-17 Mu 67-20 stations metres: 7 13 10-11 11 11 , 9-17 9-11 at which 7 13 10-11 11 11 9-17 9-11 at which Gear: Dredge Dredge Dredge Trawl Dredge Dredge . Trawl Dives found: Trawl Dredge Dredge Trawl Dredge Dredge Trawl Dives found: ALGAE ' ; ( chauvinii Harv. Lenormandia catch 1/5 dom. dom. dom. scraps. c.20 pc. dom. 7 1/5 catch dom. dom. dom. scraps c.20 pc. dom. 7 C S. Gray catch 1/10 — few pc. A — 1 4 4 1/10 catch — — few pc. — 1 4 4 (L) 3 — — — — — — Z c.90 pc. — — — — — — 2 PORIFERA Callyspongia 2. 3 9 6 1 - — — 4 2 3 9 6 1 — 1 4 (Pallas) — — — 4 — 1 3 — — — 4 — 3 ingalli — — ' . — 6 1 1 — — — 1 1 lophon 2 2 6 9 2 NEMERTINA apricot 2 ] 4 — — 2 5 2 1 4 — — 2 5 POLYGHAETA Quatrefages australis Eunice c.5 100s 10s 100s 4 5 7 100s 7 Kinberg ? few 1 5 15 7 5* (Haswell) 1 2 1 , 3* (McIntosh) c.20 few 2* angustifrons few 1 2* AMOLLUSC (Reeve) c.50 c.50 10s 3 few 6 100s 6 and 100s c.30 1 c.20 5 100s 5 (Suter) Mtcrelenchus micans 5 few 100s 10s 3 few 7 few 7 (Gray) tenuis 1 3 2 Martens) 5 — ' — 1 — — — 2 5 — — 1 — — — 2 (Philippi) — 1 — 5 — — — 2 — 1 — 5 — — — 2 Pleurobranchaea ,3; — ' — 1 — — 2 3 — — 1 — — 2 sp. 1 3 2 (Hutton) Chlamys — — 4 5 ' — 4 16 4 — — 4 5 — 4 16 4 (Philippi) 5 2 -Tfew 1 1 — 6 2 2 -rfew 1 1 — 6

Table ll.—Occurrence of species in eight hauls and several snorkel dives at Glory Cove. This list includes only species observed on at least two occasions, including a total of at least three specimens.

globus j 1 1 2* 3 i 2* (Deshayes) spissa 1 7 1 — — ■ 2 1 6 3 2 1 6 Hutton) 15 1 1 2 4 A. Solemya 1 — 10 — — — — ■. 2 CRUSTACEA (Costa) 1 few c.20 100s i 10 few 7 Maera 8 I* si traverPagurus 6 3 12 20 i 5 2 7 cooki Pylopagurus 4 11 few 3* dark small, 3 3 2* N (Filhol) 1 2 — — 1 — . — 2 4 ECHINODERMATA (Pennant) ' 3 11 1 — 7 — 2 1 6 ) — — — — 4 i — 2 3 3 (Hutton) 1 26 — 10 21 — 1 — 5abund. 5 (Hutton) — — 7 1 7 11 2 5 6 nigra 5 54 few - 5 ii 3 4 7 (Parker) 31 28 c.12 CL i Q 6* J dendyi vJ O 31 28 — c.12 5 1 3 — 6* gracilis — 4 100s 15 53 3 3 100s 7 Clark Ophiomyxa — 17 few 4 few 5 2 few 5 magellanica 5 18 — ' — ' — 2 regularis — 42 ■ — — 2 2 (Gray) — 1 - — — 2 — — 1 3 3 (Farquar) 3 2 2 ASCIDIACEA compound Orange 100s 1abund. 1 bicornuata Cnemidocarpa 9 3 2 ? Pyura 1 2 2 PISCES and — ■ — — 1 — — , — 1 1 Griffin 8 3 4 7 4 5* and Eyd. Syngnathus 2 2 i 1 4* Griffin ? Callogobius 1 i 2* mud Tripterygiid, 2 4 33 , 1 4* 1 1 4* yellow, 4 O 1 4* 1 4 * 1