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BENTHONIC FORAMINIFERA FROM A MANGROVE SWAMP, WHANGAPARAPARA, G R E A T BARRIER ISLAND

by Murray R. Gregory*

S U M M A R Y

Two distinctive benthonic foraminiferal biofacies can be identified in Whangaparapara inlet. Inter- and sub-tidal mud and sand fiat environments are characterised by an arenaceous/calcareous hyaline assemblage in which rep­resentatives of the latter, (Ammonia beccarii, Elphidium spp. and Discorbis dimidiatus) are generally dominant. Arenaceous species (mostly Miliammina pelita, together with various trochamminids) are typical o f the mangrove swamp environment.

I N T R O D U C T I O N

Foraminifera are unicellular animals that extrude, and move about by means of, granuloreticulose pseudopodia. They differ from other protozoans — e.g. the amoebae with which all students of biology wil l be familiar — in that they possess a test (or shell) that can be organic (tectinous), arenaceous (agglutinated) or calcareous in nature. A few foraminifera do not possess a test. The test may be single- or multi-chambered and is often strikingly beautiful and surprisingly complex (see Figs. 2 and 3). Foraminifera are restricted to marine and brackish waters, and benthonic forms are particularly abundant in shallow coastal seas.

Because of their small size, great morphologic diversity and numerical abundance, and also because they are ubiquitous in fossil and recent marine sediments, foraminifera have been extensively used in stratigraphy. They are also useful in paleoecologic reconstructions. It is indeed unfortunate that whether studying fossil or recent foraminiferal faunas, paleontologists have concerned themselves almost entirely with the abandoned tests. Thus while there is an extensive literature on taxonomy, morphologic diversity and distribution, our understanding of the biology of the foraminifera is quite limited. This is a taxon that attracts little interest amongst zoologists and seldom receives more than a passing comment in standard biology text-books.

While a diverse modern foraminiferal fauna is known from New Zealand (see Eade, 1967) it has not been extensively studied. The more significant contributions to knowledge of the foraminifera of our near-shore environments are Hulme (1964), Hedley et al. (1965 and 1967) Kustanowich (1965), Phleger (1970) and Vel la (1957), although of these, only Phleger records the fauna of mangrove swamps.

*Department of Geology, University of Auckland.

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Foraminifera and Pollution With our growing awareness of the need for environmental protection it is

important to have some understanding of how pollution, and in particular sewage effluent, influences marine life at present. Because they are ubiquitous, abundant and easily identified in near-shore marine sediments, benthonic foraminifera potentially provide a means of demonstrating relationships between marine organisms and pollution. Furthermore, through temporal studies of foraminifera it may be possible to satisfactorily "moni tor" pollution.

Some effects o f pollution on foraminiferal populations and distribution patterns have been demonstrated by Resig (1960), Bandy et al (1964a, 1964b, 1965) and Schafer and Sen Gupta (1969).

Objectives The aim of this study was to identify and record the foraminifera inhabiting a

modern New Zealand mangrove swamp and associated environments.

L O C A L I T Y , S A M P L I N G , T E C H N I Q U E S

During the A . U . F . C . Scientific Camp in August 1972 a number o f sediment samples were collected from a small mangrove swamp at the head of Whangaparapara inlet, Great Barrier Island (Fig. 1). Sampling was restricted to a surficial sediment slice one centimetre in thickness and an attempt was made to collect from obviously different macroenvironments, e.g. mangrove swamp, high marsh, floor o f tidal estuary, intertidal sand or mud flats. For the purposes of comparison several samples were collected near the mouth of Kaitoke Stream on the eastern side of the island. Relevant information on substrate and environment at each sampling locality is summarised in Table I.

A known volume of sediment (about 50cc) was washed thoroughly through a 63/i sieve. After drying, the foraminifera were separated and concentrated by carbon tetrachloride floatation. The species of foraminifera in each sample were identified and their numbers calculated (Table 2). In most samples an attempt was made to identify those individuals living at the time of collection by using the stain, rose Bengal (Walton, 1952). Although this is a widely accepted technique (Phleger, 1960) it has severe limitations and the results are of questionable validity (Boltovskoy and Lena, 1970).

T H E F O R A M I N I F E R A L F A U N A

O f over 20 species of benthonic foraminifera identified in the material collected, only Ammonia beccarii, Miliammina pelita and Quinqueeoculina seminula were ever numerically dominant although several other species were commonly abundant, (e.g. Discorbis dimidiatus, Elphidium novozealandicum, Elphidium simplex, Haplophragmoides canariense and several trochamminids). Several genera of "Thecamoebians" were also identified. Details of the fauna at each locality are summarised in Table 2, while some of the more important

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Table I:

Sample No. Environment Substrate

1 intertidal flat very coarse sand 2 intertidal flat shelly coarse sand 3 floor of tidal creek muddy coarse sand 4 intertidal flat muddy sand 5 floor of ephemeral streamlet in

mangrove swamp mud 6 amongst mangrove trees mud 7 amongst mangrove trees mud 8 floor of tidal estuary sandy mud 91 marsh behind mangrove swamp mud

10/ at extreme high tide mark mud

11 intertidal rock pool with Corallina shelly sand

12 beach muddy sand 14 tidal estuary clean med. sand 15 tidal estuary clean med. sand 16 exposed beach at low tide mark clean med. sand 17 exposed beach at low tide mark clean med. sand 18 exposed beach at low tide mark clean med. sand 19 exposed beach at low tide mark clean med. sand 20 exposed beach at low tide mark clean med. sand

Table 1: Macroenvironments and substrate types of sampled localities in Whangaparapara Inlet and Kaitoke Beach, Great Barrier Island.

species present are illustrated in Figs. 2 and 3. Synonomies and taxonomic details o f the species recorded are not given. For these the reader is referred to Eade(1967).

Foraminiferal assemblages At least three distinctive foraminiferal assemblages, or associations, can be

recognised in the material studied. To some extent these seem to be environmentally sensitive. 1. A n assemblage of calcareous hyaline species, dominated by Ammonia beccarii, Discorbis dimidiatus and Elphidium is characteristic of inter- and shallow sub-tidal sand and mud flat environments away from the mangrove swamp (stations 1,2,3 and 4). Several other species are persistently present, but in lesser numbers, e.g. Brizalina sp., and Rosalina sp. Mil iol ids and trochamminids are also a significant, although minor, component o f this assemblage. As the mangrove swamp is approached, arenaceous types become increasingly important with Miliammina pelita being particularly conspicuous at stations 3 and 4. 2. A n assemblage dominated by arenaceous species is characteristic o f the mangrove swamp (stations 5-10). The most abundant species in this assemblage is invariably Miliammina pelita, although Jadammina macrescens,

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Sketch Map /4\ W harigapa.rapaTa^^/,1c;

Harbour • Sampling locality

5 0 0

( sca le approx imate )

1000yds I

Sketch Map Kaitoke Beach

(scale approximate)

low t ide m a r k

(approx)

1000yds

Fig". 1 L o c a l i t y M a p

a n d S a m p l i n g S t a t i o n s

Great Barrier Island

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Haplophragmoides canariense, Trochammina inflata and Trochammina spp. are often well represented. Of calcareous hyaline species, Ammonia beccarii and Elphidium novozealandicum occur sporadically and in low numbers, others are extremely rare, e.g. Discorbis dimidiatus (station 5). Representatives of several "Thecamoebian" genera, including Difflugia and Centropyxis are present in considerable numbers at stations 5, 6 and 9. Rare specimens were also present at stations 3 and 4. As these are freshwater organisms, the abandoned lorica (tests) must have been washed in by stream action. 3. Beach samples from Kaitoke (stations 15-20) contain a varied assemblage of porcellaneous and calcareous hyaline species. Quinqueloculina seminula and other miliolids are generally dominant. Most o f the calcareous hyaline species present (e.g. Cibicides sp., Discorbis dimidiatus, Florilus sp. and Rosalina sp.) are attached forms, that have presumably been derived from nearby sub-tidal environments. This assemblage somewhat resembles that o f the Corallina officinalis zone (station 12) described by Hedley et al. (1967). Although arenaceous species (Miliammina pelita and trochamminids) were abundant in the tidal reach of Kaitoke Stream (station 14), none were present in the beach sands. Obviously they did not withstand the battering inflicted upon them by continual wave action in this vigorous environment.

Abundance The foraminiferal population is highly variable. The total population (living

and dead) is greatest in inter- and sub-tidal sand and mud flat environments where it can exceed 30,000/sq.m. It is generally lower in mangrove and marsh environments.

Because of uncertainties with the rose Bengal staining technique, the standing crop (i.e. living population) has not been accurately determined.lt appears to be consistently lower (<1000/sq.m.; in some instances <100/sq.m.) than is generally reported in similar estuarine environments (e.g. Nichols and Norton, 1969; Phleger, 1960, 1963, 1965). Comparable low values are known from Puhoi estuary (Topping, pers. comm.). Reasons for these low New Zealand values cannot even be speculated about at this stage.

Living individuals (i.e. stained by rose Bengal) of most o f the identified species were recognised (Table 2). No " l ive" thecamoebians were observed. It is worthy of note, that distribution patterns of living individuals more or less parallel those of the total population.

The population data collected (Table 2) suggests that the foraminifera identified are not homogeneously distributed. There is some indication of abrupt and erratic spatial variations in the standing crop, total population and even abundance of individual species. It may well be that some species occur in clumps and that foraminifera are indeed "social organisms".

D I S C U S S I O N

In protected inter-tidal environments near the head of Whangaparapara inlet two distinctive foraminiferal assemblages (or biofacies) have been recognised. Closely comparable assemblages are widely reported from similar temperate

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Table 2: Population Data

Station Number 1 2 3 4 5 6 7

Total population/sq.m. (x lO 3 ) 27.0 >31.0 34.0 >34.0>30.0>40.0>40.0 Standing crop (as a percentage) 29 22 20 4 13 7 5

"Thecamoebians" Difflugia X X X C A x Centropyxis X c A x Other X X ( A

Arenaceous species Haplophra^motdes canariense 1 4 r, 6

(6i Jadammina macrescens 2 6 2 2 5

(x) Miliammina pelita 2 34 28 37 57 59

(4) (1) Textularia sp. .s 1 1 Trochammina inflata 3 5 14 8

( l i (31 Trochammina spp. 5 2 38 20 x

(10) (4) Other X X 2 X

Calcareous hyaline species Ammonia beccarii 18 54 34 27 5

(3) (15) (14) (2) Cibicides sp. ?

Discorbis dimidiatus 32 11 3 2 1 110) (2) 11)

Elphidium novozealandicum 20 23 8 13 6 25 15) (41 (2) (X) (2) (5)

Elphidium simplex 8 3 5

(1) Elphidium spp. X 1

(x) Fissurina spp. 1 Patellinella inconspicua Other X

Porcellaneous species Cyclogyra involvens 6

(x) Quinqueloculina seminula 2

Other miliolids 11 4 2 x 2

expressed as percentage x = present; C = common; A = abundant.

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8 9 10 11 12 14 15 16 17 18 19 20

24.0 25.0 12.0 1 II 15.0 1.0 <1.0 7.4 8.0 2.0 6.0 5 -1 - - 12 - 16 - -

A C A C A X

? X A

?

6 10 9 13

54 46 49 28 31 (5)

1 > X

X 4 14 5 (2)

10 5 6

3 1 X 10

13 14 8 4 29 15 70 50 5 14 (2) (3) (2)

9 3 10 10 7 41 9 10 3

16 29 9 5 14 20 20 (3) (4) <1)

2 4

X 3 2 10

2 1 1

X 15 8 2 12 9 10 15

1

11 20 75 48 70 57 (16)

9 1 50 3 8 4

Table 2: Summary of foraminiferal population data for samples collected from Whangaparapara Inlet, and also near Kaitoke stream mouth, Great Barrier Island.

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estuarine and marsh environments about the world (see Phleger, 1970). A dominantly arenaceous assemblage is typical o f mangrove swamps and high

marsh environments. A dominantly calcareous hyaline assemblage is typical of nearby broad intertidal flat and back-bay environments that have not been colonised by mangroves.

These biofacies were recognisable whether the substrate was sand or mud, suggesting that post-mortem redistribution of tests is o f little significance. The similarity o f living and total population distribution patterns also suggests that little post-mortem redistribution takes place.

A further biofacies, in which porcellaneous and calcareous hyaline species are sub-equally important, and which is devoid of arenaceous species, is associated with high energy beach environments. This assemblage results from trans­portation and redistribution of abandoned tests, that in life are mostly attached forms inhabiting a wave-agitated, near-shore environment.

During fossilization, loss in numbers of foraminifera is considerable. Solution phenomena following post-mortem burial severely depletes the number of calcareous hyaline and porcellaneous species. Similarly, disintegration during post-mortem transport of arenaceous species selectively reduces their numbers. Nevertheless, i f the sediments and associated foraminiferal faunas under discussion were to be preserved in the fossil record, it seems likely that a future paleontologist could interpret the environments of deposition with some degree of confidence.

Unt i l considerable quantitative data on the benthonic foraminiferal populations of all near-shore environments and at a number of localities is obtained, it wil l be impossible to eliminate the "ambient noise" generated by clumped, and seemingly erratic distribution patterns, and hence any attempt to exploit the pollution-monitoring potential o f foraminifera may well be difficult.

Fig. 2: Representative near-shore and intertidal foraminifera, and a Thecamoebian (Difflugea sp.), from Whangaparapara Inlet, and Kaitoke Beach, Great Barrier Island.

1. Ammonia beccarii (Linne) Ventral view showing excavate umbilicus with central plug and irregular wedges of calcite extending into it. (x200)

2. Ammonia beccarii (Linne) Umbilical plug and calcite pillars in more detail. (x450)

3. Ammonia beccarii (Linne) Dorsal view showing trochospiral form (x200)

4. Elphidium simplex Cushman Lateral view x250

5. Elphidium simplex Cushman Umbilical area with pustulose growths (x500)

6. Discorbis dimidiatus (Parker and Jones) Umbilical view, thickened plates flanked by deep clefts. Note pores. (x200)

7. Rosalina bradyi Cushman Broad open umbilical area on ventral side (x200).

8. Elphidium novozealandicum Cushman Lateral view. (x240)

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A C K N O W L E D G E M E N T S

I am grateful to Field Club for the chance to participate in their scientific camp and for all assistance so willingly given. Some financial support from the University Grants Committee is acknowledged. I thank Roy Harris for his draughting skills, R . M . Topping, D . McSweeney and M . Speak for assistance with S . E . M . photography and Mrs M . Reynolds for typing at very short notice.

REFERENCES

Bandy, O.L.; Ingle, J.C.; Resig, J.M. 1964a.: Foraminiferal trends, Laguna Beach outfall area. Limnol, and Oceanogr. 9: 112-123.

Bandy, O.L.; Ingle, J.C.; Resig, J.M. 1964b: Foraminifera, Los Angeles County outfall area. Limnol. and Oceanogr. 9: 123-137.

Bandy, O.L.; Ingle, J.C.; Resig, J.M. 1965: Modification of foraminiferal distribution by the Orange County outfall, California. Trans. Marine Technol. Soc. 1: 54-76.

Boltovskoy, E.; Lena, H. 1970: On the decomposition of the protoplasm and the sinking velocity of the planktonic foraminifers. Int. Rev. ges. Hydrobiol. 5: 797-804.

Eade, J.V. 1967: A checklist of Recent New Zealand foraminifera. N.Z. Dept. Sci. Ind. Res. Bull. 182.

Hedley, R.H.; Hurdle, C M . ; Burdett, I.D.J. 1965: A foraminiferal fauna from the Western continental shelf, North Island, New Zealand. N.Z. Dept. Sci. Ind. Res. Bull. 163.

Hedley, R.H.; Hurdle, C M . ; Burdett, I.D.J. 1967: The marine fauna of New Zealand: Intertidal foraminifera of the Corallina officinalis zone. N.Z. Dept. Sci. Ind. Res. Bull. 180.

Fig. 3: Representative near-shore and intertiadal foraminifera from Whangaparapara Inlet and Kaitoke Beach, Great Barrier Island.

1. Difflugia sp. Note the agglutinated test and simple aperture. (x450)

2. Miliammina pelita Saunders Note the finely arenaceous test wall, elliptical shape, simple tooth and quinqueloculine chamber arrangements (x 150)

3. Jadammina macrescens (Brady) The "collapsed" chambers are typical of this species (x400).

4. Trochammina inflata (Montagu) Dorsal view (xlOO)

5. Trochammina inflata (Montagu) Ventral view showing inflated final chamber.

6. Textularia porrecta Brady Finely arenaceous test wall, smooth with distinctive sutures (xl60).

7. Quinqueloculina seminula (Linne) The rounded inflated outline and complete lack of ornamentation is typical (xlOO).

8. Quinqueloculina tenagos Parker A quite coarsely-ribbed specimen (xlOO)

9. Oolina melo d'Orbigny Typical cancellate ornamentation (x360).

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Hulme, S.C. 1964: Recent foraminifera from Manukau Harbour, Auckland, New Zealand. N.Z. Jl. Sci. 7: 305-340.

Kustanowich, S. 1965: Foraminifera of Milford Sound. In T.M. Skerman (Ed.): Studies of a modern fjord. N.Z. Dept. Sci. Ind. Res. Bull. 157: 49-63.

Nichols, M . ; Norton, W. 1969: Foraminiferal populations in a coastal plain estuary. Palaeogeogr. Palacoclimatol. Palaeoecol. 6: 197-213.

Phleger, F.B. 1960: "Ecology and distribution of Recent Foraminifera." The Johns Hopkins Press, Baltimore.

Phleger, F.B. 1965: Patterns of living marsh foraminifera in south Texas coastal lagoons. Bol. Soc. Geol. Mex. 28: 1-44.

Phleger, F.B. 1970: Foraminiferal populations and marsh processes. Limnol. and Oceanogr. 15: 522-534.

Resig, J.M. 1960: Foraminiferal ecology around ocean outfalls off southern California, p. 104-121. In "Waste disposal in the marine environment" Pergamon Press, London.

Schafer, C.T.; Sen Gupta, B.K. 1969: Foraminiferal ecology in polluted estuaries of New Brunswick and Maine. Atlantic Oceanographic Laboratory, Bedford Institute. Rep. A.O.L. 69-1 (unpublished).

Vella, P. 1957: Studies in New Zealand Foraminifera: Pt. I - Foraminifera from Cook Strait. N.Z. Geol. Surv. Paleont. Bull. 28.

Walton, W.R. 1952: Techniques for recognition of living foraminifera Cushman Found. Foram. Res. Contr. 3: 56-60.