Tane 35: 195 - 205 (1995)
BENTHIC FORAMINIFERA AND OTHER MICROBIOTIC REMAINS
IN WAIMAMAKU RIVER ESTUARY, WEST COAST, NORTHLAND
Chris Hollis' , Emily Jenns, Michael Begbie and Annette Pullin
Department of Geology, University of Auckland, Private Bag 92019, Auckland
SUMMARY
Four associations of brackish foraminifera occur in the Waimamaku River
estuary. In the upper reaches at the extreme limits of marine influence,
Trochamminita salsa is dominant with common Haplophragmoides wilberti
(Trochamminita association). H. wilberti is dominant, and Trochammina inflata
and Miliammina fusca common, above low water in the middle reaches
(Haplophragmoides association). Ammonia beccarii is dominant and M. fusca
abundant subtidally in middle and lower reaches (Ammonia-Miliammina
association), apart from two stations where A. beccarii comprises 90% of the
total fauna (Ammonia association).
Faunas of the lower estuary include numerous normal marine benthic and
planktic species probably carried in at high tide by prevailing on-shore winds and
seas. Reworked foraminifera and radiolarians of Late Cretaceous, Early Tertiary
and Miocene age occur throughout the estuary. Centric diatoms also occur
throughout the estuary and small pennate diatoms were found attached to
microbiotic remains at two stations. Sponge spicules and ostracods are restricted
to the lower reaches.
INTRODUCTION
The Waimamaku River estuary lies on the west coast of Northland, 8km south
of the entrance to Hokianga Harbour and 5km north of the Auckland University
Field Club's field station at Kawerua (Fig. 1). The estuary is at the mouth of the
20km Waimamaku River which drains the largely pastoral Waimamaku Valley.
A full description of bathymetry, sediments and vegetation was included in an
earlier study of the macrofaunal ecology of the estuary (Hayward & Hollis 1993).
Current address: Institute of Geological and Nuclear Sciences, P O Box 30368, Lower Hutt
195
Waimamaku
River
estuary
^
v
(V
Kaikai
Beach
1
i\
/ .
500 m
1
V^-V
/*
1
Fig. 1. Location of sampling stations in Waimamaku River estuary, west coast, Northland (after
Hayward & Hollis 1993).
METHODS
The estuary was sampled in April 1992 as part of an Auckland Museum study
(Hayward & Hollis 1993). 20 sediment samples of about 200cc were collected
by hand from intertidal stations and by hand-hauled bucket dredge from subtidal
stations. 16 of these were selected for foraminiferal study as a Stage III
Paleontology laboratory exercise in Geology Department, University of
Auckland. Each sample was washed with water through 75/xm and 1mm mesh
sieves to remove mud and large pebbles and shells. The remaining sediment was
oven dried at 80°C and split into two portions. One portion was put aside for
later study. The other portion was dry sieved through 150^.m and 300^im sieves.
The 3 resulting size fractions were examined for foraminifera and a
representative pick of at least 100 specimens was made, either by picking 30-50
specimens from each size fraction or, where foraminifera were only rich in one
size fraction, by picking an equal number of trays for each fraction. In the case
of sparse samples, the entire foraminiferal fauna was picked (Stations 1,2,7 and
8). A l l benthic foraminifera were identified and the relative abundance of each
species determined; the relative abundance of planktic foraminifera was
determined; the occurrence and general abundance of other microbiotic remains
196
(ostracod valves, diatom frustules, sponge spicules, reworked foraminiferal and
radiolarian tests) were also recorded (Appendix I). Washed sediment residues and
sample splits, picked faunas and figured specimens (Figs. 3 , 4 ; prefix " A K " ) are
held in the marine collections of the Auckland Institute and Museum.
RESULTS
Benthic foraminiferal associations
Four benthic foraminiferal associations are recognised in the estuary (Fig. 2).
Characterising species are illustrated in Fig. 3a-m.
1. Trochamminita association (Ts). Consists of dominant Trochamminita salsa
with abundant Haplophragmoides wilberti. No other species are present. Occurs
in the upper reaches of the estuary at the extreme range of marine influence.
Sediment is sand or sandy mud.
A n equivalent association is found throughout New Zealand in estuaries at the
extreme limit of marine influence (Hayward & Hollis 1994). Diversity is
typically low, although elsewhere Miliammina fusca is often present.
2. Haplophragmoides association (Hw). Consists of dominant Haplophragmoides
wilberti, with localised occurrences of Miliammina fusca, M. cf. obliqua,
Trochammina inflata and Trochamminita salsa. No other species are present.
Occurs above low tide level in middle reaches (Stations 8, 9, 10 and 14).
Sediment is muddy sand or soil (i.e. organic-rich sediment within rushes).
A n equivalent association occurs throughout New Zealand in moderately
brackish intertidal situations (Hayward & Hollis 1994). It is usually more diverse
(5-6 species, including abundant Miliammina and rare Ammotium and
Pseudothurammina) than observed at Waimamaku. Miliammina cf. obliqua is a
characteristic member of this association, within its known range of Northland
and Nelson (Hayward & Hollis 1994). The species has not been reported
previously from the west coast.
3. Ammonia - Miliammina association (AM). Consists of dominant Ammonia
beccarii, abundant Miliammina fusca and common Haplophragmoides wilberti.
Occurs subtidally from middle reaches to near estuary mouth (Stations 7, 1, 13,
16, 18, 20, 22). Sediment varies from mud through sandy mud to muddy sand.
The ratio of M. fusca to H. wilberti increases towards the estuary mouth (Fig.
2). Diversity increases from 5 species in the middle reaches to 20 species near
the mouth. Although diversity is moderate in the lower reaches, few additional
species occur regularly in the association (e.g. Cassidulina carinata, Florilus
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AM,
subtidal
-
40%
A
, AM,
,
A
>v
^ * i l i P ^ Trochamminita
marginal marine
20
,
AM
Ts
associations-^
19
18
16
15
stations
salsa
benthics
13
Fig. 2. Location of foraminiferal associations and trends in relative abundance of common
benthic foraminiferal species, planktic foraminifera and benthic foraminiferal diversity in
subtidal stations. Ammonia beccarii and most "marginal marine" benthic species have calcareous
perforate tests; Trochamminata salsa, Haplophragoides wilberti and Miliammina fusca have
agglutinated tests.
198
Fig. 3. Common foraminifera of Waimamaku River estuary. Scale bar = 100/un.
a. Trochamminita salsa, Stn 2, AK87509. b. T. salsa, Stn 2, AK87508. c. Trochammina inflata, Stn
10, AK87504. d. T. inflata, Stn 10, AK87505. e. Haplophragmoides wilberti, Stn 10, AK87501. f.
H. wilberti, Stn 10, AK87502. g. H. wilberti, Stn 10, AK87503. h. Miliammina cf. obliqua, Stn 10,
AK87506. i. M. fusca, Stn 7, AK87516. j . M. fusca, Stn 7, AK87515. k. Ammonia beccarii, Stn 7,
AK87519. 1. A. beccarii, Stn 7, AK87520. m. Elphidium excavatum forma excavatum, Stn 20,
AK87526. n. Globigerina falconensis, Stn 22, AK87530. o. Globigerina quinqueloba, Stn 22,
AK87531. p. G. quinqueloba, Stn 22, AK87532.
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Fig. 4. Reworked microfossils and other microbiotic remains from Waimamaku River estuary.
Scale bar = 100/i/ra, unless noted otherwise.
a. Globigerina sp., Stn 20, AK87523. b. Globigerina woodi, Stn 2, AK87511. c. Matanzia varians
Stn 9, AK87541. d. Glomospira charoides, Stn 2, AK87510. e. Bolivinopsis spectabilis, Stn 8,
AK87542. f. Spherical radiolarian (actinommid), Stn 15, AK87539. g. Discoidal radiolarian
(phacodiscid), Stn 15, AK87538. h. Phormocyrtis striata striata, Stn 20, AK87522. i. Dictyomitr
multicostata, Stn 9, AK87540. j . Florilus parri, with pennate diatoms on apertural face, Stn 20,
AK88100. k. Enlargement of apertural face in Fig. 4j. 1. Amphipyndax stocki, with scattered pennate
diatoms, Stn 15, AK875536. m. Enlargement of surface of Fig. 41; scale bar = 10/x/w. n. Centric
diatom, Stn 22, AK87527. o. Centric diatom, Stn 7, AK87512. p. Ostracod, Stn 20, AK87521.
200
parri and Hanzawaia bertheloti).
An equivalent association occurs in moderately brackish low intertidal and
subtidal areas throughout New Zealand (Hayward & Hollis 1994). Usually it
contains a greater abundance of infaunal agglutinated taxa {Ammobaculites,
Reophax, Textularia) and fewer calcareous taxa.
4. Ammonia association (A). Consists of dominant A. beccarii (89% and 92%),
with relatively high diversity but all other species are rare. Occurs at two stations
(15 and 19) in mid channel in lower reaches of the estuary. Sediment is muddy
sand. This association differs from the Ammonia-Miliammina association only by
the much reduced abundance of M. fusca and absence of H. wilberti. The lower
station also contains the single miliolin specimen encountered in the study.
A similar "Ammonia" association, widely distributed around New Zealand in
marginal marine subtidal areas (Hayward & Hollis 1994), differs by having a
greater abundance of elphidiids {Elphidium excavatum, E. advenum, Haynesina
depressula) and common infaunal agglutinated species (as above).
Trends
The dominant factor controlling the distribution of foraminiferal associations
is salinity. Trends observed in subtidal stations (Fig. 2) which are related to a
seaward increase in salinity are:
• Agglutinated species decrease from 100% to 30%;
• Calcareous perforate species increase from 0 to 70%;
• Diversity increases from 2 species to 20;
• Planktonic foraminifera increase from 0 to 10%.
The second factor controlling foraminiferal distribution is tidal level. Trends
from high tidal to subtidal stations, as evident from a transect from Station 10 to
7 and also from Station 14 to 15 (see Appendix I), are:
• Agglutinated species Trochammina inflata and Haplophragmoides wilberti
decrease in abundance;
• Other agglutinated species (Miliammina fusca, Textularia earlandi) tend to
increase;
• Ammonia beccarii and other calcareous species increase;
• Diversity increases from 2-4 species to 5-12 species.
Planktic foraminifera
Planktic foraminifera are present in all subtidal stations in the lower estuary
(Stations 15-22) and comprise 10% and 14% of the total foraminiferal fauna in
Stations 22 and 19 (Fig. 3n-p). Planktics are usually absent in brackish waters
201
and rarely greater than 15% on the inner shelf (Hayward 1986). However, high
numbers (up to 40%) have been reported previously from intertidal sediments at
Kawerua to the south (Hayward 1979, 1986). As at Kawerua, it seems likely that
the planktic tests have been concentrated and carried into the estuary by
prevailing on-shore winds and seas. The abundance of planktics in Station 22
suggests that high seas may cross the beach and empty into the backwater at high
tide. It is very likely that many of the normal marine benthic foraminifera present
in the estuary have also been carried in by strong seas or winds, particularly
small taxa such as Cassidulina, Hanzawaia, Gavelinopsis, Nonionella, Bulimina
and Virgulopsis.
Reworked foraminifera and radiolarians
Samples from the upper reaches of the estuary contain high numbers of
reworked foraminifera (Fig. 4a-e), either Late Cretaceous to Paleocene benthic
taxa (Ammodiscus, Bolivinopsis spectabilis, Glomospira charoides, Matanzia
varians) or Miocene planktic species (Globigerina woodi). Reworked radiolarians
occur throughout the estuary (Fig. 4f-i, 1). These are mainly spherical or
discoidal spumellarians of indeterminate age but rare specimens of LateCretaceous-to-Early-Paleocene (Amphipyndax stocki, Dictyomitra multicostata)
and Eocene species (Buryella tetradica, Phormocyrtis striata striata) were
encountered. Late Cretaceous and Early Tertiary microfossils have probably been
derived from argillaceous limestones and mudstones of Motatau and Mangakahia
Complexes (Northland Allochthon) which outcrop throughout the Waimamaku
Valley from about 2km upstream of the estuary mouth. Miocene planktic
foraminifera probably come from sandstones of the Otaua Formation which
outcrops 1.5km upstream of the mouth (adjacent to station 2).
Diatoms, sponge spicules and ostracods
Large centric diatoms occur throughout the estuary (Fig. 4n, o), while sponge
spicules and ostracods (Fig. 4p) are restricted to the lower reaches (below Station
14).
Because all samples were sieved through a 15pm sieve, isolated smaller
diatoms were not retrieved. However, S E M examination of foraminiferal and
radiolarian tests turned up two interesting occurrences of small pennate diatoms.
A cluster of diatoms was observed on the apertural face of a specimen of Florilus
parri (Fig. 4j, k). The final chamber was broken and it appeared that the diatom
frustules adhering to the apertural face may represent the foraminifer's last meal.
In most foraminifera digestion takes place in food vacuoles situated in the final
chamber. If the diatoms had attached after the foraminifer had died, the frustules
would not be restricted to the apertural face.
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In the second occurrence the same types of pennate diatoms were observed
to be randomly scattered over the reworked tests of Cretaceous-Paleocene
microfossils — the radiolarian Amphipyndax stocki (Fig. 41, m) and the
agglutinated foraminifer Bolivinopsis spectabilis (Fig. 4e). In this case, the
diatoms may have attached themselves during life or they may have become
cemented during early stages of diagenesis within the sediment. Diagenetic
cementation seems likely because the frustules do not appear restricted to one
side of the radiolarian test and it also appears that some of the frustules are losing
detail because of etching or overgrowth of silica.
CONCLUDING REMARKS
Two features distinguish these brackish foraminiferal associations from similar
ones reported elsewhere in New Zealand and overseas (Hayward & Hollis 1994).
1. Only 5 species are common in the estuary: Trochamminita salsa,
Trochammina inflata, Haplophragmoides wilberti, Miliammina fusca and
Ammonia beccarii. Other species characteristic of brackish environments were not
recorded and are therefore very rare or absent, i.e. Ammotium fragile,
Ammobaculites exiguus, Jadammina macrescens. Three other characteristic
species are unusually rare: Reophax moniliforme, Elphidium excavatum and E.
gunteri.
2. Normal marine species are more common than usual in brackish
associations, i.e. Cassidulina carinata, Florilus parri, Hanzawaia bertheloti. It
is likely that these species and other normal marine foraminifera do not usually
live in the estuary but are carried in by strong westerly swells.
Flori/^-dominated faunas, with common Ammonia, Cassidulina and Hanzawaia,
have been reported living in intertidal pools at Kawerua (Hayward 1979).
ACKNOWLEDGEMENTS
We are grateful to the Auckland Institute and Museum for supplying the samples used in this
study. We thank members of the 1994 paleontology class who assisted in preparing and picking
samples and identifying the faunas; Louise Cotterall for drafting Fig. 1 and part of Fig. 2; Sue
Courtney and Barry O'Connor for assistance with SEM photography. We also thank Jack
Grant-Mackie, Hugh Grenfell and Bruce Hayward for reading the manuscript and suggesting
improvements.
REFERENCES
Hayward, B.W. 1979: An intertidal Zostera pool community at Kawerua, Northland and its
foraminiferal microfauna. Tane 25: 173-186.
Hayward, B.W. 1986: Abundant planktic foraminifera in intertidal sediments, Kawerua, Northland.
Tane 31: 1-12.
203
Hayward, B.W. & Hollis, C.J. 1993: Ecology of Waimamaku River estuary, north of Kawerua,
North Auckland. Tane 34: 69-78.
Hayward, B.W. & Hollis, C.J. 1994: Brackish foraminifera in New Zealand: A taxonomic and
ecologic review. Micropaleontology 40: 1K5-222.
APPENDIX I. Relative abundance (%) of benthic foraminifera in representative picks (x = <
0.5%), percentage of planktic foraminifera and approximate abundance of other microbiotic
remains in Waimamaku estuary stations. Abbreviations - depth: H T = high tide, M T = mid
tide, L T = low tide, otherwise in metres below low tide; sediment: S = sand, mS = muddy
sand, M = mud, sM = sandy mud, pM = pebbly mud; approximate abundance: C = common,
F = few, R = rare.
BENTHIC FORAMINIFERA
Cribrostomoides jeffreysii
Haplophragmoides wilberti
Miliammina fusca
Miliammina cf. obliqua
Reophax moniliforme
Textularia earlandi
Trochammina bartrami
Trochammina inflata
Trochammina sorosa
Trochamminita salsa
Ammonia beccarii
Bolivina pseudoplicata
Bolivina spathulata
Bulimina submarginata
Cassidulina carinata
Cibicides marlboroughensis
Elphidium advenum
Elphidium charlottensis
Elphidium excavatum
Elphidium gunteri
Evolvocassidulina orientalis
Florilus parri
Fursenkoina fusiformis
Gavelinopsis spp.
Gyroidina neosoldanii
Hanzawaia bertheloti
Haynesina depressula
Lagena sulcata
Nonionella turgida
Oolina tasmanica
Quinqueloculina sp.
Virgulopsis turris
Total
Count
PLANKTIC FORAMINIFERA
OSTRACODS
DIATOMS
SPONGE SPICULES
R E W O R K E D FORAMINIFERA
Ammodiscus sp.
Bolivinopsis spectabilis
Glomospira charoides
Matanzia varians
Planktics
R E W O R K E D RADIOLARIANS
undet. spumellarians
Amphipyndax stocki
Dictyomitra multicostata
Buryella tetradica
Lychnocanium sp.
Phormocyrtis striata striata