Journal of Foraminiferal Research, v. 44, no. 3, p. 300–315, July 2014
‘‘MONOSPECIFIC’’ AND NEAR-MONOSPECIFIC BENTHIC FORAMINIFERAL FAUNAS, NEW ZEALAND BRUCE W. HAYWARD Geomarine Research, 49 Swainston Rd, St Johns, Auckland, New Zealand e-mail: [email protected]
.80% and 50–80% of the fauna, respectively) by a single species in samples where the full sand-size fraction (.63 mm) has been studied. The international foraminiferal literature contains numerous mentions of such ‘‘monospecific’’ and near-monospecific faunas, particularly in marginal-marine settings (e.g., Murray 1991, 2006), but I am unaware of any previous attempt to summarise their ecological distribution regionally or globally. This review is limited to New Zealand examples and draws from quantitative studies of ,1500 modern faunas and several hundred early Miocene faunas from northern New Zealand (Appendices 1, 2; Fig. 1). Most New Zealand fossil faunas have been selectively picked from coarser size fractions to find biostratigraphically useful species for dating. Sufficient quantitative census data to reliably identify New Zealand fossil ‘‘monospecific’’ foraminiferal faunas (.63 mm) are only available from the early Miocene of the northern North Island (e.g., Hayward & Buzas, 1979; Hayward & Brook, 1994; Hayward, 2004; Hayward et al., 2011a). The diversity and environmental settings of New Zealand modern ‘‘monospecific’’ faunas are likely to be similar to faunas of many mid-latitude temperate countries, although some of the species will be different. Modern tropical and polar regions have additional environments dominated by quite different species that are not touched upon here. The goal of this review is to summarise the distribution of these high-dominance faunas in New Zealand and infer their taphonomic and ecologic drivers to improve paleoenvironmental interpretations of similar fossil faunas.
Thirteen benthic foraminiferal species dominate modern ‘‘monospecific’’ faunas (dead faunas with .80% of one species in .63-mm samples) in New Zealand. These faunas occur in sheltered, often brackish, intertidal or shallow-subtidal environments, never deeper than 25 m. None occurs along exposed coasts or in the open ocean. Seven agglutinated species (Entzia macrescens, Haplophragmoides wilberti, H. manilaensis, Miliammina fusca, M. obliqua, Trochammina inflata, Trochamminita salsa) dominate ‘‘monospecific’’ faunas in salt marshes with varying salinity and elevational ranges. All but H. manilaensis have been recorded comprising 99–100% of at least one fauna. A further six species (Ammobaculites exiguus, Ammonia aoteana, Ammotium fragile, Elphidium excavatum clavatum, E. williamsoni, E. gunteri ) dominate ‘‘monospecific’’ faunas in unvegetated intertidal and shallow-subtidal (,3 m), sheltered estuary, inlet, or lagoon settings. ‘‘Monospecific’’ Amb. exiguus faunas are inferred to have been produced by dissolution of calcareous components. A further 17 species dominate modern near-monospecific faunas (50–80% of one species), 11 at depths ,50 m and six in the open ocean at 50– 4000-m depth. ‘‘Monospecific’’ and near-monospecific faunas are more common in higher latitudes, where overall species diversity is lower. Six species dominate ‘‘monospecific’’ early Miocene faunas in northern New Zealand: Elphidium crispum in a sheltered gravel beach; Nonionella novozealandica in a deep-water (50– 100 m), possibly dysoxic harbour; and three larger, more robust species (Amphistegina aucklandica, Lepidocyclina orakiensis, Miogypsina intermedia) in current- or wave-concentrated beach or shallow-marine deposits. The only bathyal or abyssal ‘‘monospecific’’ fauna is dominated by Amphimorphinella butonensis occurring in a fossil hydrocarbon seep setting. Many of the modern ‘‘monospecific’’ faunas (especially those in salt marshes) are cosmopolitan, whilst most of the fossil and some of the modern faunas are endemic to the New Zealand region. These high-dominance faunas are produced by taphonomic and ecological processes. Taphonomic causes include wave or current concentration by winnowing or transport in high energy, shallow-marine environments and carbonate dissolution in low pH, brackish, salt marsh or deep-sea settings. Ecological drivers include highly specific adaptations that allow species to outcompete all others in stressful (intertidal), strongly variable (high-tidal brackish), or unusual (hydrocarbon seep) environments. Sometimes high test productivity of opportunistic species may result in near-monospecific faunas.
METHODS All samples were washed over a 63-mm sieve and census counts made on 100–300 benthic foraminiferal tests in a whole or split washed sand sample. Many of the modern sediment samples were stained with rose Bengal and only the unstained (dead) tests were included in the census counts. This was done because the majority of the samples used in this review were taken to provide modern analogue data to assist in the paleoenvironmental interpretation of fossil faunas. Excluding live specimens removes much of the seasonality bias. In some studies, however, the stained specimens were recorded (e.g., Hayward, 1982; Hayward et al., 1999b; Southall et al., 2006; Figueira, 2012). These confirmed that in almost all instances the dominant species of the dead ‘‘monospecific’’ or near-monospecific faunas were also dominant in the live fauna. Deeper-water samples (mostly .20 m) obtained from sediment repositories were unstained and the faunas studied were total (live + dead) rather than dead assemblages. Some of the modern sandy samples with low densities of foraminiferal tests have had the fauna concentrated by floating off with sodium
INTRODUCTION In this short review the terms ‘‘monospecific’’ and nearmonospecific refer to dead or fossil benthic foraminiferal faunas that are strongly dominated (Berger Parker Index
‘‘MONOSPECIFIC’’ FORAMINIFERAL FAUNAS
FIGURE 1. Source location of ‘‘monospecific’’ and near-monospecific benthic foraminiferal faunal samples from New Zealand.
TABLE 1. Tidal elevation and bathymetric terminology after van Morkhoven et al. (1986). Bathymetric Depth Ranges (m)
Shelf 0–200 Bathyal 200–2000 Abyssal 2000–5000
Inner 0–50 Upper 200–600 Upper 2000–3000
Mid 50–100 Middle 600–1000 Middle 3000–4000
AMMONIA AOTEANA (FINLAY, 1940) (FIG. 3.2) Outer 100–200 Lower 1000–2000 Lower 4000–5000
Tidal Elevation Terms
HAT MHW MHWS MLW MLWS MSL LAT
highest astronomical tide level mean high-water level mean high-water spring level mean low-water level mean low-water spring level mean sea level 5 mid-tide level lowest astronomical tide level
polytungstate solution (Gregory & Johnson, 1987) before the census count was made. Taxonomic references, descriptions, and figures of all species mentioned in this paper are available in Hayward et al. (1999a, 2010b) for modern species and in Hayward & Buzas (1979) and Hornibrook et al. (1989) for fossil species. The sources of faunal data quoted in this study are given in Appendix 1. Bathymetric nomenclature is given in Table 1. Three species diversity measures are given in Table 2 and follow the recommendations of Hayek & Buzas (2013). 1)
fauna in four samples (S 5 4–5) of unvegetated sandy mud, all clustered around mid-tide level (Fig. 4).
S: This is the total number of species in a sample, which is dependent upon the number of specimens, N, counted. Fisher Alpha Index (a), where S 5 aln(1 + N/a): This is an iterative equation and cannot be solved directly for a. Fisher’s a is the parameter of a log series distribution where species proportions are distributed as a log series independent of N, whereas S is dependent on N. Fisher’s a is often used as a measure of diversity even when the species abundance distribution is not a log series (Fisher et al., 1943; Hayek & Buzas, 1997). Berger-Parker Index (BP): This is the simple proportion of the most abundant species, BP 5 max pi (Berger & Parker, 1970). MODERN ‘‘MONOSPECIFIC’’ BENTHIC FORAMINIFERAL FAUNAS
Listed below are the foraminiferal species (Fig. 2) that comprise $80% of the dead benthic foraminiferal fauna in at least one modern New Zealand sample. AMMOBACULITES EXIGUUS CUSHMAN & BRO¨NNIMANN, 1948 (FIG. 3.1) This cosmopolitan agglutinated species occurs most commonly in New Zealand in slightly brackish, sheltered, shallow-subtidal to mid-tidal harbour and estuarine settings (Hayward et al., 1999a). This species has been recorded only from Ohiwa Harbour (Fig. 1) as a modern ‘‘monospecific’’ fauna (Southall, 2002; Hayward et al., 2004a). Here, in a transect, Amb. exiguus comprises 73–91% of the
The genus Ammonia occurs in ‘‘monospecific’’ faunas in sheltered intertidal and shallow subtidal environments worldwide (e.g., Murray et al., 2006). The dominant species in New Zealand is the South Pacific-restricted Ammonia aoteana (Hayward et al., 2004b) that occurs around the three main islands plus the Chatham Islands but not in the higher latitude cooler environments of the subantarctic islands (Hayward et al., 2007a). In our studies, faunas with 100% A. aoteana have only been recorded from Ohiwa Harbour (Fig. 1) in low-intertidal mud. ‘‘Monospecific’’ Ammonia (BP .80%) faunas (S 5 2–12) have been recorded from around the North Island (Waimamaku Estuary, Kaipara, Mahurangi, Waitemata, Raglan and Ohiwa harbours, Firth of Thames, Pauatahanui Inlet), northern South Island (Nelson Haven, Big Lagoon) and Chatham Islands (Te Whanga Lagoon). Most of these occurrences are in mid-low-tidal mud flats, but in the three coolest locations (Big Lagoon, Te Whanga Lagoon, Pauatahanui Inlet) they are in shallow-subtidal lagoons or inlets at depths of 0.5–3 m at low tide. AMMOTIUM FRAGILE WARREN, 1957 (FIG. 3.3) This cosmopolitan species is a minor component of the brackish, middle reaches of estuaries and lagoons at midtide to shallow-subtidal elevations around both of New Zealand’s main islands (Hayward et al., 1999a). Its highest recorded relative abundances (#78%) occur in Lake Onoke and Big Lagoon on either side of Cook Strait (Fig. 1). In both places, Amt. fragile occurs in shallow lagoons that have highly variable seasonal salinity, ranging from almost freshwater after heavy rain to euryhaline (#40 psu) in the summer dry season (Hayward et al., 2010a, 2011b). The highest recorded relative abundance (78%) essentially qualifies as a ‘‘monospecific’’ fauna, and occurs in the shallow-subtidal (0.5-m depth at low tide) centre of Big Lagoon, Marlborough (S 5 7). ELPHIDIUM EXCAVATUM CLAVATUM CUSHMAN, 1930 (FIG. 3.4) This cosmopolitan subtropical-temperate taxon dominates or co-dominates (30–85%), with A. aoteana or Miliammina fusca in sheltered mid- to high-tide mud flats and low salt marshes in upper harbours or outer estuaries, where salinity is only slightly lower than normal marine (,25–34 psu). To date, it has only been recorded as a ‘‘monospecific’’ fauna (BP 5 82–83%) in mid- to high-tidal muddy sand in the upper parts of Nelson Haven (S 5 3–5). ELPHIDIUM WILLIAMSONI HAYNES, 1973 (FIG. 3.5) This species is distinguished from E. excavatum clavatum by its longer and more numerous septal bridges (Hayward et al., 1997). It dominates (BP #97%) foraminiferal faunas (S 5 3) in non-vegetated, mid- to high-tidal muddy sand in
‘‘MONOSPECIFIC’’ FORAMINIFERAL FAUNAS
TABLE 2. Summary of species diversity (Number of species, S; Fisher Alpha Index a; Berger-Parker Index, BP) of New Zealand modern ‘‘monospecific’’ foraminiferal faunas (.80% of one species). Location
North Island: Northland, Bay of Islands Northland, Helena Bay Northland, Whananaki Est. Northland, Waimamaku Est. Northland, Waimamaku Est. Auckland, Mahurangi Hbr Auckland, Kaipara Harbour Auckland, Kaipara Harbour Auckland, Waitemata Harbour Auckland, Manukau Hbr, Puhinui Auckland, Manukau Hbr, Puhinui Waikato, Tairua Harbour Waikato, Tairua Harbour Waikato, Firth of Thames Waikato, Raglan Harbour Bay of Plenty, Ohiwa Hbr Bay of Plenty, Ohiwa Hbr Bay of Plenty, Ohiwa Hbr Bay of Plenty, Ohiwa Hbr Bay of Plenty, Ohiwa Hbr Hawkes Bay, Ahuriri Inlet Wellington, Kapiti Island Wgtn, Pauatahanui Inlet Wgtn, Pauatahanui Inlet Wgtn, Pauatahanui Inlet Wgtn, Pauatahanui Inlet Wairarapa, Lake Onoke South Island: Marlborough, Anakoha Bay Marlborough, Anakoha Bay Marlb, Shakespeare Bay Marlb, Shakespeare Bay Marlb, Shakespeare Bay Marlborough, Big Lagoon Marlborough, Big Lagoon Marlborough, Big Lagoon Marlborough, Big Lagoon Marlborough, Big Lagoon Nelson, Nelson Haven Nelson, Nelson Haven Nelson, Wanganui Inlet Nelson, Wanganui Inlet Nelson, Wanganui Inlet West Coast, Oparara Inlet West Coast, Oparara Inlet Canterbury, Avon Estuary Canterbury, Okains Bay Canterbury, Akaroa Hbr Otago, Shag River Estuary Otago, Purakanui Bay Otago, Purakanui Bay Otago, Purakanui Bay Otago, Purakanui Bay Otago, Purakanui Bay Otago, Akatore Estuary Otago, Pounawea Otago, Pounawea Otago, Pounawea Otago, Catlins Lake Otago, Catlins Lake Southland, Waikawa Hbr. Southland, Waikawa Hbr. Southland, Mokomoko Inlet Southland, Mokomoko Inlet Stewart Island, Port Pegasus Chatham Islands Campbell Island Campbell Island
No. of Samples No. of Species
Small estuary Salt marsh Salt marsh Intertidal mud Salt marsh Intertidal mud Intertidal mud Salt meadow Intertidal mud Salt marsh Salt marsh Salt marsh Salt marsh Intertidal mud Intertidal mud Intertidal mud Intertidal mud Salt marsh Salt marsh Salt marsh Intertidal mud Supratidal pond Intertidal mud Salt marsh Salt marsh Salt meadow Intertidal mud
T. inflata T. inflata H. wilberti A. aoteana H. wilberti A. aoteana A. aoteana T. inflata A. aoteana M. obliqua T. salsa H. wilberti T. salsa A. aoteana A. aoteana Amb. exiguus A. aoteana H. wilberti T. inflata T. salsa A. aoteana T. inflata A. aoteana H. wilberti E. macrescens T. salsa M. fusca
1 1 1 3 1 1 1 1 8 4 1 4 7 1 1 3 5 1 1 1 1 2 3 3 2 1 10
2 5 5 4–9 2 5 8 2 4–12 2–5 3 4–5 2–4 3 8 4–5 2–4 4 5 3 11 1 4–8 6 1–2 4 2–5
0.35 1.11 0.98 0.68–1.92 0.35 1.05 1.91 0.3 0.76–2.86 0.35–0.91 0.53 0.60–0.83 0.30–0.83 0.58 1.80 0.87–1.05 0.40–0.91 0.72 0.90 0.50 2.8 0.15 0.83–2.00 0.98–1.23 0.17–0.31 0.82 0.34–0.97
0.94 0.85 0.84 0.81–0.93 0.99 0.84 0.85 0.86 0.80–0.95 0.91–0.96 0.89 0.88–0.97 0.80–1.00 0.85 0.83 0.90–0.91 0.86–0.95 0.83 0.82 0.89 0.84 1.00 0.81–0.90 0.81–0.90 0.98–1.00 0.89 0.93–0.99
Salt marsh Intertidal sand Salt marsh Salt marsh Salt Marsh Subtidal mud Subtidal mud Intertidal mud Intertidal sand Salt marsh Intertidal sand Intertidal sand Salt marsh Salt marsh Salt marsh Salt marsh Salt marsh Salt marsh Salt marsh Salt marsh Salt meadow Intertidal sand Salt marsh Salt marsh Salt marsh Salt marsh Salt marsh Salt marsh Salt marsh Salt marsh Intertidal mud Salt marsh Salt marsh Salt marsh Salt marsh Salt marsh Salt marsh Subtidal mud Salt marsh Salt marsh
H. wilberti M. fusca H. wilberti T. inflata T. salsa A. aoteana Amt. fragile E. gunteri M. fusca M. obliqua A. aoteana E. clavatum H. wilberti M. fusca T. salsa M. fusca T. salsa H. wilberti H. wilberti T. salsa T. inflata E. williamsoni H. wilberti E. macrescens T. inflata T. salsa T. inflata H. wilberti T. inflata T. salsa M. fusca T. salsa H. wilberti T. salsa H. wilberti T. salsa M. fusca A. aoteana H. manilaensis M. fusca
1 3 1 1 1 1 1 2 2 2 1 2 3 3 4 1 1 2 1 2 1 3 1 1 4 1 1 1 4 1 2 1 6 6 1 2 2 2 2 2
4 3–5 3 4 2 5 7 5–7 4–6 3–4 2 3–5 3 2–5 2–4 1 2 5 4 1–2 2 3 3 4 3 4 3 3 3–5 2 3 2 2–5 1–5 5 2–3 2–5 6 2 2–3
0.92 0.57–1.23 0.52 0.84 0.33 1.0 1.5 0.8–1.7 0.9–1.5 0.5–1.0 0.34 0.57–1.03 0.52–0.57 0.39–1.07 0.39–0.82 0.15 0.35 0.93–1.05 0.78 0.16–0.36 0.30 0.58 0.69 0.83 0.58 0.83 0.51 0.60 0.53–1.11 0.31 0.51–0.56 0.34 0.34–0.96 0.15–1.07 1.07 0.36–0.60 0.35–1.13 1.40–1.41 0.35 0.36–0.59
0.87 0.90–0.93 0.81 0.80 0.99 0.96 0.78 0.78–0.84 0.89–0.91 0.87–0.88 0.82 0.82–0.83 0.80–0.93 0.80–0.85 0.83–0.87 1.00 0.92 0.85–0.88 0.80 0.99–1.00 0.99 0.87–0.97 0.91 0.79 0.80–0.96 0.82 0.85 0.87 0.80–0.87 0.80 0.91–0.92 0.88 0.84–0.89 0.88–1.00 0.81 0.97–0.98 0.94–0.98 0.88–0.89 0.82–0.90 0.97–0.98
FIGURE 2. Sketch of an idealised sheltered estuary, harbour, and lagoon, showing the environmental location of the modern ‘‘monospecific’’ benthic foraminiferal faunas in New Zealand.
Purakanui Inlet, Otago (Fig. 5), where freshwater inflow is minimal and salinity is usually close to 35 psu. ELPHIDIUM GUNTERI COLE, 1931 (FIG. 3.6) This cosmopolitan species occurs in sheltered intertidal environments in the northern half of New Zealand (north of 42uS). It dominates two ‘‘monospecific’’ faunas (BP #84%, S 5 5–7) at low-tide level on the fringes of the central part of Big Lagoon, Marlborough (Fig. 6), at the southern limits of its distribution. ENTZIA MACRESCENS BRADY, 1870 (FIGS. 3.7, 3.8) This cosmopolitan, fragile-shelled, agglutinated species (previously identified as Jadammina macrescens; see Filipescu & Kaminski, 2011) is one of the more common
species in high salt marshes around both main islands of New Zealand. It forms ‘‘monospecific’’ faunas (S 5 1–4) in near-normal-marine salinity salt meadows on the edge of Purakanui Inlet (Fig. 5) and in the more brackish rush vegetation at the head of Pauatahanui Inlet, where E. macrescens reaches relative abundances of 98–100% of the foraminiferal fauna. HAPLOPHRAGMOIDES MANILAENSIS ANDERSEN, 1952 (FIGS. 3.9, 3.10) In New Zealand, this species only occurs in the subantarctic, on Campbell Island (Hayward et al., 2007a), where it occupies the same niche in the high salt marsh as occupied everywhere else by H. wilberti. Here, it reaches relative abundances of 82–90% (S 5 2) at MHWS level and above.
‘‘MONOSPECIFIC’’ FORAMINIFERAL FAUNAS
FIGURE 3. Scanning electron micrographs of the species that dominate ‘‘monospecific’’ benthic foraminiferal faunas in New Zealand. Catalogue numbers are of the New Zealand Fossil Record File (Xnn/f), Auckland Museum (AK), U.S. National Museum (USNM), GNS Science (other formats). Scale bar 5 100 mm. 1–17 are Recent specimens; 18–25 are early Miocene. 1 Ammobaculites exiguus, Waitemata Harbour, BWH114/5; 2 Ammonia aoteana, Waitemata Harbour, RC1/2; 3 Ammotium fragile, Waitemata Harbour, BWH117/8; 4 Elphidium excavatum clavatum, Nelson, AK76435; 5 Elphidium williamsoni, Aotea Harbour, AK76438; 6 Elphidium gunteri, Waitemata Harbour, AK78053; 7, 8 Entzia macrescens, Pauatahanui Inlet, BWH60/13; 9, 10 Haplophragmoides manilaensis, Campbell Island, BWH163/24; 11, 12 Haplophragmoides wilberti, Waitemata Harbour, AK130792; 13 Miliammina fusca, Kaipara Harbour, BWH91/54; 14 Miliammina obliqua, Nelson, AK76415; 15, 16 Trochammina inflata, Purakanui Inlet, AK92416; 17 Trochamminita salsa, Pauatahanui Inlet, BWH56/3; 18 Amphimorphinella butonensis, Mathesons Bay, R09/f184, BWH120/3; 19 Amphistegina aucklandica, Waiheke Island, R10/f9001, FP4836; 20, 21 Elphidium crispum, Waiheke Island, R11/f23, FP4353; 22 Lepidocyclina orakiensis, Hokianga, O06/f9569; 23 Miogypsina intermedia, Kaipara, Q08/f9913, USNM 243424; 24, 25 Nonionella novozealandica, Waiheke Island, R10/f9513, BWH52-12, BWH52-13.
HAPLOPHRAGMOIDES WILBERTI ANDERSEN, 1953 (FIGS. 3.11, 3.12) This species is one of the most common agglutinated foraminifera of high-salt-marsh settings (Fig. 4) around New Zealand and in many other parts of the world (Murray, 2006). It can also live in lower relative abundances down to low-tide level in non-vegetated mud in more brackish parts of estuaries. In New Zealand, H. wilberti (80–99%) has been recorded in at least 29 ‘‘monospecific’’ faunal samples (S 5 2–6) from high-tidal marshes, mostly in rush vegetation. These marshes occur right around the North Island (Waimauku and Whananaki estuaries, Tairua and Ohiwa harbours, Pauatahanui Inlet) and South Island [Wanganui Inlet, Anakoha and Shakespeare bays, Avon Estuary, Okains Bay, Purakanui (Fig. 5) and Mokomoko inlets, Pounawea, Waikawa Harbour]. MILIAMMINA FUSCA (BRADY, 1870) (FIG. 3.13) This cosmopolitan species is the most abundant agglutinated foraminifera in brackish environments around New Zealand and on its subantarctic islands. It is restricted to
brackish environments (,10–30 psu) but can extend from ,MHW to shallow-subtidal depths in vegetated and nonvegetated substrates. It tends to dominate more brackish intertidal estuarine and harbour environments below ,MHW (Fig. 4). We have recorded over 50 samples with ‘‘monospecific’’ M. fusca faunas (S 5 1–6) from around all three main islands of New Zealand, with 30 of these having 90–100% M. fusca. The most extensive development of this ‘‘monospecific’’ fauna is in the shallow-subtidal to intertidal unvegetated muddy sand of unusual Lake Onoke (Fig. 1), which alternates over weeks to months between a brackish lake and tidal inlet (Hayward et al., 2011b). Other localities with .90% M. fusca are salt marshes in Ohiwa Harbour, Wanganui and Oparara inlets (#100%), Shakespeare Bay, Big Lagoon (Fig. 6), Catlins Lake, Port Pegasus, Campbell Island, and non-vegetated intertidal mud at Anakoha Bay (Fig. 1). MILIAMMINA OBLIQUA HERON-ALLEN & EARLAND, 1930 (FIG. 3.14) This Southern Hemisphere agglutinated species is restricted to the northern half of New Zealand (north of 42u S)
FIGURE 4. Transect through the intertidal zone at Ohiwa Harbour, Bay of Plenty (Fig. 1), showing the tidal-elevation-related zonation of the dominant foraminifera and the unusual number of ‘‘monospecific’’ and near-monospecific faunas (data from Southall, 2002; Hayward et al., 2004a).
FIGURE 5. Air photo of Purakanui Inlet, Otago (Fig. 1), showing quantitative modern foraminiferal sample sites and samples where ‘‘monospecific’’ and near-monospecific faunas occur (data from Hayward et al., 1996, and unpublished). Small dots are sample sites without ‘‘monospecific’’ or near-monospecific faunas.
‘‘MONOSPECIFIC’’ FORAMINIFERAL FAUNAS
FIGURE 6. Air photo of Big Lagoon at the mouth of the Wairau River, Marlborough (Fig. 1), showing quantitative modern foraminiferal sample sites and samples where ‘‘monospecific’’ and near-monospecific faunas occur (derived from Hayward et al., 2010a). Small dots are sample sites without ‘‘monospecific’’ or near-monospecific faunas.
in slightly brackish (,20–33 psu) high salt marsh and salt meadow above MHW. It has been recorded as a ‘‘monospecific’’ fauna (S 5 1–5) in three localities—Kaipara Harbour salt marsh (BP 5 100%), Puhinui salt marsh (#96%) in Manukau Harbour, and in Big Lagoon salt marsh (Fig. 6). TROCHAMMINA INFLATA (MONTAGU, 1808) (FIGS. 3.15, 3.16) This cosmopolitan species occurs around New Zealand’s two main islands in the more saline (.,30 psu) high salt marsh settings, often in association with E. macrescens or M. obliqua. ‘‘Monospecific’’ T. inflata faunas (S 5 2–5) have been recorded from high-tidal rush and salt meadows above MHW in the North Island (Helena Bay, Kaipara and Ohiwa harbours, Pauatahanui Inlet) and South Island (Shakespeare Bay, Shag River Estuary, Akatore Inlet, Pounawea). It has also been recorded (76–94%) in high-tide mud at the head of a tiny creek estuary on Urupukapuka Island, Bay of Islands, and as a pure monospecific fauna (BP 5 100%) in a supratidal, brackish pond on Kapiti Island (Fig. 1). TROCHAMMINITA SALSA (CUSHMAN & BRO¨NNIMANN, 1948) (FIG. 3.17) This agglutinated species is common around the three main islands of New Zealand, but has only sporadic recorded occurrences elsewhere in the world. It is the foraminiferal species most tolerant of low salinity (,5–20 psu) and highest tidal settings. Live specimens are restricted to elevations above MHW and the species occurs as a ‘‘monospecific’’ fauna (BP .80%, often 100%) in salt meadows or grass above MHWS (Fig. 4) in many localities (S 5 1–5) in the North Island (Waimamaku Estuary,
Manukau, Tairua and Ohiwa harbours) and South Island [Shakespeare Bay, Big Lagoon (Fig. 6), Okains Bay, Akaroa and Waikawa harbours, Oparara, Akatore Estuary, Wanganui, Purakanui (Fig. 5) and Mokomoko inlets, Catlins Lake, and Pounawea]. This is the most commonly encountered foraminiferal species forming pure monospecific faunas, always occurring at the highest elevation of foraminifera in a salt marsh, usually above HAT. ADDITIONAL SPECIES COMPRISING .50% MODERN FAUNAS
A further 11 modern species that live in shallow (0–50 m), normal-marine salinity environments have been recorded from around New Zealand in relative abundances .50% of the dead benthic foraminiferal fauna. These are in order of decreasing abundance: Pileolina radiata Vella, 1957—an endemic species comprising 75% of a fauna from 9-m water depth in a currentswept channel at the entrance to Carnley Harbour, Auckland Islands (Hayward et al., 2007a); Cassidulina carinata Silvestri, 1896—small specimens (63–150 mm) of this species comprising 53–70% of 13 faunas in 4–40-m water depth in the shelter of Perseverance Harbour, Campbell Island (Hayward et al., 2007a); Elphidium advenum (Cushman, 1922)—comprising 67% of a mid-tidal sand fauna in sheltered Perseverance Harbour, Campbell Island (Hayward et al., 2007a); Quinqueloculina seminula (Linnaeus, 1758)—comprising 66% of a fauna in 0.5 m of water at low tide in the normalmarine-salinity outer part of Queen Charlotte Sound; Haynesina depressula (Walker & Jacob, 1798)—comprising 63% of a fauna in muddy sand at 20-m water depth in
the relatively sheltered western side of the Firth of Thames at Matingarahi; Elphidium charlottense (Vella, 1957)—comprising 50– 60% of faunas in low-tidal and shallow-subtidal beach sand in the Cavalli Islands and Bay of Islands (Fig. 1); Bolivina neocompacta McCulloch, 1981—comprising 57% of a fauna in muddy sand at 1-m subtidal depth near the centre of sheltered Pauatahanui Inlet, Wellington; Nonionellina flemingi (Vella, 1957)—an endemic species comprising 56% of a fauna in muddy sand at 22-m depth in sheltered Camp Cove, Carnley Harbour, Auckland Islands; Rosalina bradyi (Cushman, 1915)—comprising 54% of a fauna in shallow-subtidal gravel 0.5 m below low tide at Port Pegasus, Stewart Island. The gravel is among seaweedcovered rocks which may be the substrate for R. bradyi; Zeaflorilus parri (Cushman, 1936)—an endemic species comprising 53% of a fauna in the entrance channel to Purakanui Inlet, Otago (Fig. 5); and Rosalina irregularis (Rhumbler, 1906) – comprising 51% of a fauna washed up into rock pools by large swells on the exposed northern side of Enderby Island, Auckland Islands. Six species that live at mid-shelf and greater depths (50– 4000 m) have been recorded with relative abundances .50% around New Zealand (Hayward et al., 2010b, 2013). In order of decreasing abundance these are: Cassidulina carinata Silvestri, 1896—in the New Zealand region this cosmopolitan species being the one that most commonly occurs as a strong dominant, with records of 60– 75% relative abundance at middle-bathyal–middle-abyssal depths (700–4000 m) and 50–60% at mid-outer-shelf depths (50–200 m); Globocassidulina canalisuturata Eade, 1967—comprising 73% of a fauna at mid-bathyal depths (900 m) on the southern end (55uS) of Macquarie Ridge, south of the South Island (Fig. 1); Alabaminella weddellensis (Earland, 1936)—comprising 70–72% of three faunas at mid-outer-shelf depths in Poverty Bay (Culver et al., 2012); Cassidulina reniforme Norvang, 1945—comprising 68% of a fauna at middle-abyssal depths (3550 m), west of Fiordland (Fig. 1); Trifarina angulosa (Williamson, 1858)—comprising 61% of a fauna at lower-bathyal depths (1300 m) swept by strong bottom currents on the edge of the Bounty Plateau (47uS), east of Stewart Island; and Bolivina robusta Brady, 1881—comprising 50% of a fauna at upper-bathyal depths (350 m) on Pukaki Rise (49uS), southeast of Stewart Island.
contains 86% (Hayward et al., 2011a). This may be an extinct species that was endemic to hydrocarbon seep environments where it sometimes formed ‘‘monospecific’’ faunas. AMPHISTEGINA AUCKLANDICA KARRER, 1864 (FIG. 3.19) ‘‘Monospecific’’ faunas dominated by large, robust specimens (,300–800-mm test diameter) of extinct A. aucklandica occur quite commonly in early Miocene coarse sedimentary rocks around Auckland. Some of these appear to be near in situ in pebbly sandstone (R09/f58, S09/f4) close to the base of the transgressive Waitemata Group sequence (Kawau Subgroup) in association with inner-shelf macrofossil assemblages and sedimentary facies (Kawau Subgroup; Hayward & Brook, 1984). Others occur in coarse volcaniclastic sandstone and gritty breccia (Parnell Grit; Ballance & Gregory, 1991) within the bathyal Waitemata Group turbidite sequence, and were transported in subaqueous debris flows downslope into bathyal depths of the basin from the shallows around an active volcanic island (Hayward & Buzas, 1979). Living Amphistegina do not occur today around New Zealand, which is now cooler than it was in the early Miocene. Today, faunas dominated by large, thick-walled Amphistegina are characteristic of high energy and high light environments on the shallow (0– 30 m), exposed, outer-reef slope of tropical islands (e.g., Cushman et al., 1954; Todd, 1976; Hallock et al., 1986), and this is the inferred environment, without the coral reefs, for many of the New Zealand early Miocene occurrences. ELPHIDIUM CRISPUM (LINNAEUS, 1758) (FIG. 3.20)
EARLY MIOCENE ‘‘MONOSPECIFIC’’ BENTHIC FORAMINIFERAL FAUNAS
‘‘Monospecific’’ faunas (R11/f8, f23) of robust E. crispum (BP 5 80–89%) occur in two thin, coarse-sand horizons within thick pebble and cobble shelly conglomerate overlying the greywacke basement of the early Miocene Kawau Subgroup at Fossil Bay, Waiheke Island, Auckland (Hayward & Brook, 1994). This shell-bearing conglomerate lies between non-marine basal carbonaceous conglomerate and macrofossil-rich inner-shelf sandstone near the base of the transgressive Waitemata Group sequence (Eagle et al., 1995). Today, E. crispum only occurs in the warmest northern parts of New Zealand, but is far more common in subtropical and tropical shallow, normal-marine environments elsewhere around the world (Murray, 2006). Morphologically, it is similar to the southwest Pacific, modern endemic E. charlottense, which occurs in greatest relative abundance (20–50%) on slightly sheltered, normal-marine salinity beaches in intertidal and shallow-subtidal (0–3 m) sand and pebbly sand (e.g., Hayward, 1981, 1982). A similar beach setting is inferred for these early Miocene faunas.
AMPHIMORPHINELLA BUTONENSIS KEYZER, 1953 (FIG. 3.18)
LEPIDOCYCLINA ORAKIENSIS (KARRER, 1864) (FIG. 3.21)
Three early Miocene samples (R09/f84, f85, f86), strongly dominated by extinct A. butonensis, occur in bathyal mudstone in the lower part of the Waitemata Group sequence at Mathesons Bay, Auckland (Fig. 1). Two samples in close proximity to a concretionary calcareous mound (inferred to be the site of a fossil methane seep) contain 94–95% A. butonensis and one from 5-m away at the same stratigraphic level
A 3-m thick bed of uncemented foraminiferal limestone (Hokianga Orbitolite Bed; Chaproniere, 1984) occurs within the early Miocene Otaua Group at Omapere, Hokianga Harbour, Northland (Fig. 1). The foraminiferal limestone is composed of a ‘‘monospecific’’ fauna of the extinct New Zealand endemic, larger foraminifer L. orakiensis with tests mostly 2–10 mm, but up to 30 mm, across. This species
‘‘MONOSPECIFIC’’ FORAMINIFERAL FAUNAS
presumably had algal symbionts and lived in clear, shallow subtropical marine environments. The orbitolite deposit was probably concentrated by currents that winnowed away finer sediment and other foraminifera and was deposited in a shallow-subtidal or even beach setting. MIOGYPSINA INTERMEDIA DROOGER, 1952 (FIG. 3.22) At Pakauranga Point, Kaipara Harbour (Fig. 1), there is a 20-m thick early Miocene unit of coarse volcanic sandstone with interbeds of well-sorted, coarse-grained foraminiferal sandstone (Waitakere Group, Pakauranga Miogypsina Sandstone; Jones, 1969). The foraminiferal sandstone beds are composed of ‘‘monospecific’’ faunas of large (1–5-mm diameter), robust M. intermedia. Like other larger calcareous foraminifera, this extinct cosmopolitan species is inferred to have had algal symbionts, and lived in clear, current-swept, shallow-marine, tropical-subtropical environments that no longer occur in the temperate New Zealand region. In these beds the Miogypsina tests are often imbricated and clearly deposited by relatively strong currents that have winnowed the finer sediment and most smaller foraminifera. A shallow, inner-shelf or beach paleosetting is inferred (e.g., Jones, 1972). NONIONELLA NOVOZEALANDICA CUSHMAN, 1936 (FIGS. 3.23, 3.24) Three early Miocene ‘‘monospecific’’ faunas (R10/f12, f79, f81) dominated by the extinct New Zealand endemic species N. novozealandica (BP 5 82–95%) occur in macrofossiliferous muddy sand in the lower parts of the transgressive Waitemata Group sequence at Double U Bay, Waiheke Island, Auckland (Hayward & Brook, 1994). The most morphologically similar modern New Zealand species is the endemic Nonionellina flemingi, which is widespread in quiet innershelf to mid-bathyal depths (20–500 m). It occurs in greatest relative abundances (30–60%) in muddy sediment at inner mid-shelf depths (20–100 m) in quiet, sheltered embayments and deep inlets on Great Barrier, Stewart, and Auckland islands (Hayward et al., 1994, 2007b; Hayward & Grenfell, 1994). A similar, perhaps slightly dysoxic, setting is inferred for these early Miocene faunas, which is supported by the associated macrofossils (Eagle et al., 1995). DISCUSSION INFLUENCE OF SIZE FRACTION STUDIED This study is confined to census counts of faunas from the .63-mm sample fraction. The larger the grain size studied the more frequent are ‘‘monospecific’’ faunas, because diversity decreases as smaller-sized species are removed. This is evident in samples from the subantarctic islands, where both .63 mm and .150 mm fractions were separately studied using quantitative counts of similar test numbers (Hayward et al., 2007a). One sample from 42 m in Carnley Harbour, Auckland Islands, has a diverse fauna in the .63-mm size (a 5 5.2), but a low diversity ‘‘monospecific’’ fauna dominated by Nonionellina flemingi (BP 5 85%) in the .150-mm size (a 5 1.1). A sample with 65% Cassidulina carinata in the .63-mm size (a 5 4.7) in Port
Ross, Auckland Islands, has the .150-mm size (a 5 2.4) dominated (BP 5 56%) by another species, Notorotalia aucklandica. Faunas from Perseverance Harbour, Campbell Island, with 53–70% Cassidulina carinata in the .63-mm size (a 5 2.2–6.0) have only 0–2% of this species in the .150-mm size (a 5 0.4–4.5), which have ‘‘monospecific’’ faunas dominated by Elphidium advenum (BP 5 44–99%). Higher diversity in size fractions with a wider size range (i.e., .63 mm rather than .150 mm) is well documented (e.g., Hayward et al., 2003; Mojtahid et al., 2009; Scho¨nfeld et al., 2013), but switching from one strongly dominant species to another in different size ranges is unexpected and requires special explanation, such as post-mortem processes (see below). LIVING OR DEAD ‘‘MONOSPECIFIC’’ FAUNAS All faunas reported here were dead or total samples and, thus, they are the combined death assemblages from a number of seasons and years. Comparison of the unstained faunal composition with the stained (live) component from salt-marsh and inlet studies invariably shows that they are similar (e.g., Hayward, 1982; Hayward et al., 1999b; Southall et al., 2006; Figueira, 2012), and the ‘‘monospecific’’ classification of the dead fauna could usually be applied to the live fauna as well. This might not be the case where some species are highly seasonal, with different species ‘‘blooming’’ at different times of the year and dominating the faunas in succession (e.g., Basson & Murray, 1995; Buzas et al., 2002). This situation has not been encountered in this review. ‘‘MONOSPECIFIC’’ FAUNAS PRODUCED BY POST-MORTEM PROCESSES Some examples of ‘‘monospecific’’ faunas recorded here have undoubtedly had the dominant species secondarily concentrated by post-mortem processes. Perhaps the most prevalent is the winnowing of smaller tests by current or wave action and maybe also the size sorting of the remainder into drift or beach deposits strongly dominated by larger and more robust foraminiferal specimens. There are no obvious cases of concentration in our recorded modern ‘‘monospecific’’ and near-monospecific faunas, but two faunas with .50% of one species are likely to have had the dominant species concentrated by winnowing. These are the Pileolina radiata fauna found in a strong, current-swept channel at the Auckland Islands and the Zeaflorilus parri fauna in a strong, tidal, current-swept entrance channel to Purakanui Inlet (Fig. 5). Pileolina radiata commonly lives in such current-swept environments (Hayward, 1982) and appears to be adapted to them with its plastogamic reproduction. In this case, the tests of smaller species have likely been winnowed away. Zeaflorius parri lives in innershelf sand off exposed coasts. All the specimens in the entrance channel are somewhat abraded, and these are inferred to have been carried in by tidal inflow currents and concentrated after their death. In Perseverance Harbour, Campbell Island, we have an example of secondary deposition and concentration (53– 70%) of small, low density tests of C. carinata. They are inferred to have been winnowed out of offshore bathyal
sediment by bottom currents, carried in suspension (e.g., Foster & Battaerd, 1985) into the harbour by the incoming tide and winds, and deposited at slack water in the calm, deep waters inside (Hayward et al., 2007a). The New Zealand fossil record seems to have more examples of current-concentrated deposits of ‘‘monospecific’’ faunas of larger foraminifera and here includes the examples above of Amphistegina, Elphidium crispum, Lepidocyclina, and Miogypsina. Dissolution of calcareous tests in low pH conditions may lead to the concentration of the remaining, more resistant foraminiferal species (e.g., Murray & Alve, 1999a, b). This has sometimes been inferred in fossil abyssal-hadal samples at and below the calcium carbonate compensation depth, creating faunas strongly dominated by resistant, thickwalled calcareous species such as Oridorsalis umbonatus (Reuss, 1851), Nuttallides umbonifera (Cushman, 1933), and Globocassidulina subglobosa (Brady, 1881) (e.g., Hayward et al., 2004c). Salt-marsh sediment and brackish water can also have lower pH, resulting in the dissolution of calcareous tests and a greater concentration of agglutinated species (e.g., Alve & Murray, 1999; Hayward et al., 2006c; Grenfell et al., 2007). In New Zealand salt marshes, calcareous species only live in the lower fringes, where they often dissolve soon after death (e.g., Hayward et al., 1997, 1999b; Figueira, 2012), and this process may contribute to the common occurrence of the near-monospecific Miliammina fusca faunas. The agglutinated species Ammobaculites exiguus generally lives in association with more numerous calcareous species at brackish, shallow-subtidal to mid-tidal levels below the extent of salt marshes. Where the pH of the low salinity, low density water that bathes the usually intertidal site is low, the dominant calcareous component may be completely dissolved away leaving near-monospecific Amb. exiguus faunas. This is the likely explanation for these faunas recorded here from mid-tide levels in Ohiwa Harbour and for M. fusca-dominated near-monospecific faunas in Anakoha Bay, Marlborough Sounds (Hayward et al., 2010c). ENDEMIC VS. COSMOPOLITAN Approximately 10% of New Zealand’s living, shallowwater foraminifera (,50 m depth) are endemic to the region (Hayward et al., 1999a). A similar proportion (8%) of the ‘‘monospecific’’ (BP .80%) faunas are endemic, but a larger proportion (18%) of all the faunas in shallow water with BP .50% are dominated by endemic species (E. charlottense, P. radiata, N. flemingi, Z. parri). Most of the remaining species are cosmopolitan, except for three of the ‘‘monospecific’’ species, A. aoteana, M. obliqua, and T. salsa, which appear to be far less common elsewhere, with the former two apparently restricted to the Southern Hemisphere. GEOGRAPHIC DISTRIBUTION OF MODERN ‘‘MONOSPECIFIC’’ FAUNAS In shallow water (,50 m), species diversity decreases from warmer northern coasts (304 spp.) to cooler southern (260 spp.) and subantarctic shores (130 spp.) around New Zealand (Hayward et al., 2010b). With their lower overall
diversity, it is perhaps not surprising that a disproportionate number of faunas from subantarctic Auckland and Campbell islands are ‘‘monospecific’’ or near-monospecific in composition compared to those farther north. For example, four (C. carinata, E. advenum, N. flemingi, P. radiata) of the five near-monospecific faunas in normal salinity inner-shelf depths only occur in the subantarctic. Those faunas occupying intertidal and shallow-subtidal (,5 m), sheltered, non-vegetated substrates are more evenly distributed. The diversity of salt-marsh foraminifera also decreases from warmer northern areas to cooler southern parts (Hayward et al., 1999a), but this diversity decrease mostly involves rarer species and thus the distribution of ‘‘monospecific’’ salt-marsh faunas is not strongly skewed towards the cooler south. Haplophragmoides manilaensis faunas only occur at Campbell Island, but this species has not been recorded elsewhere in New Zealand. Similarly, Amt. fragile, E. gunteri, and M. obliqua only occur as ‘‘monospecific’’ faunas from the north end of the South Island northwards because these species’ geographic ranges do not extend further south (Hayward et al., 1999a). In bathyal and abyssal depths, the diversity of benthic foraminifera also decreases from northern to southern parts of the New Zealand region (207 to 169 spp. at bathyal depths and 168 to 150 spp. at abyssal; Hayward et al., 2013). Four (G. canalisuturata, C. reniforme, T. angulosa, B. robusta) of the six modern deep-water, near-monospecific faunas cited above, do so in the southern, lower diversity part of the region. ECOLOGICAL DISTRIBUTION OF MODERN ‘‘MONOSPECIFIC’’ FAUNAS ‘‘Monospecific’’ faunas (dominant .80% of fauna) are most abundant in New Zealand and globally in salt-marsh environments at or above high-tide level (Sen Gupta, 1999; Murray, 2006). In this review, 50% of the modern ‘‘monospecific’’ faunas (E. macrescens, H. manilaensis, H. wilberti, M. fusca, M. obliqua, T. inflata, T. salsa) are recorded from these stressed habitats that may suffer: temperature extremes when the tide is out; extremes of dryness especially at higher sites that may not be inundated by the tides for several months on end; and sometimes, extremes of salinity, from weakly hypersaline (,40 psu) to hyposaline or even fresh water after heavy rain, when the tide is out. No other salt-marsh species is recorded here comprising .50% of faunas (5 near-monospecific). All the above species have agglutinated tests. All of the remaining species that dominate modern ‘‘monospecific’’ faunas (i.e., Amb. exiguus, A. aoteana, Amt. fragile, E. excavatum clavatum, E. williamsoni, E. gunteri) occur in paralic environments without vegetation, mostly at mid- to low-tidal elevations, but extending down to ,3 m subtidally. They occur in sheltered harbours, estuaries, inlets, and lagoons, where salinity fluctuates, usually within a brackish range of ,20–32 psu. This group comprises two agglutinated species and four calcareous ones. No additional near-monospecific faunas (50–80% for one species) have been recorded in these sheltered, slightly brackish intertidal to shallow-subtidal settings. Of the calcareous
‘‘MONOSPECIFIC’’ FORAMINIFERAL FAUNAS
taxa, the dominance of Ammonia or Elphidium has been attributed to differences in interstitial oxygen or phytodetrital food sources (Sen Gupta et al., 1996; Thomas et al., 2004). The majority of the shallow-water, near-monospecific faunas (B. neocompacta, C. carinata, E. advenum, H. depressula, N. flemingi, Q. seminula, R. bradyi) occur subtidally in sheltered, normal-marine-salinity harbour settings. Three of the other near-monospecific faunas (P. radiata, R. irregularis, Z. parri) occur in the same general setting or in intertidal rock pools, but are inferred to have been concentrated by current or wave transport. Three somewhat unusual sheltered inlets or lagoons have enhanced numbers of ‘‘monospecific’’ or near-monospecific foraminiferal faunas. Purakanui Inlet (Fig. 5) is almost entirely intertidal, but is unusual in having a small surrounding catchment with only one tiny freshwater stream flowing into it at its head (Hayward et al., 1996). Thus most habitats are bathed in normal-salinity ocean water that is flushed out twice a day. Here, there are two near-monospecific faunas in the intertidal sand (E. williamsoni, Z. parri) and five ‘‘monospecific’’ faunas in the hightidal salt marsh (H. wilberti, E. macrescens, M. fusca, T. inflata, T. salsa). The occurrences of two of the latter are probably influenced by lowered salinity in the mouth of the small creek (M. fusca) and in high-tidal seepage (T. salsa). Large, shallow, subtidal (up to 2-m deep) Big Lagoon (Fig. 6) is separated from the sea by a narrow boulder bank and linked through a long, narrow channel to the estuarine mouth of the large Wairau River. At different times, this channel transports freshwater, brackish water, or normal marine water into the lagoon during floods or high tides (Hayward et al., 2010a). During summer neap tides, evaporation can raise salinity in the lagoon towards 40 psu. Four ‘‘monospecific’’ and one near-monospecific faunas occur in the intertidal to subtidal sand (A. aoteana, Amt. fragile, E. gunteri) and in the surrounding salt marsh and ponds (M. obliqua, T. salsa). Lake Onoke, southern North Island (Fig. 1), has the largest proportion of ‘‘monospecific’’ or near-monospecific faunas in New Zealand. This unusual lake alternates every few months between a low-salinity, brackish lake, cut off from the sea by a temporary boulder barrier, and a tidally flushed, intertidal to shallow-subtidal inlet (Hayward et al., 2011b). The muddy sand floor has a consistent ‘‘monospecific’’ M. fusca fauna, whereas most of the surrounding elevated (MHW and above) salt marsh has a ‘‘monospecific’’ or near-monospecific T. salsa fauna. These faunas and the low diversity in Lake Onoke reflect the low salinity, especially when there is no tidal exchange with the sea. No ‘‘monospecific’’ faunas (dead or total) have been recorded from mid-shelf or greater depths (.50 m). The closest are some near-monospecific modern and Late Quaternary faunas dominated by C. carinata (#75%). This species dominates many faunal samples from a wide depth range (50–4000 m) around many parts of New Zealand, although mostly at the shallower end of this range (Hayward et al., 2013). Several studies have related abundant, epifaunal C. carinata to relatively high, sustained carbon flux (Mackensen et al., 1995; Hayward et al., 2010b), and their high dominance (BP 5 50–80%) in many
faunas may result from a short life-cycle and high productivity. Another cassidulinid, G. canalisuturata, is less common but occasionally reaches a similar level of dominance (70–75%) at upper mid-bathyal depths in the southern part of the region. Two other cassidulinids, C. reniforme and G. subglobosa, have rare modern and fossil occurrences, dominating near-monospecific (55–70%) faunas at middle-abyssal depths (3000–4000 m). Two cosmopolitan, epifaunal species (Alabaminella weddellensis, Epistominella exigua) that are opportunists flourishing during seasonally high phytodetrital fluxes (Gooday & Turley, 1990; Smart et al., 1994) are widespread in deeper water around New Zealand. They are occasionally recorded in near-monospecific numbers (#72%) in New Zealand modern and Miocene faunas. Trifarina angulosa occurs in near-monospecific numbers (61%) in an unusual submarine plateau-edge setting at lower-bathyal depths (1000–2000 m). This species seems best adapted to clean, current-swept, coarse-sediment settings, but usually at much shallower, shelf or upperbathyal depths (Echols, 1971; Harloff & Mackensen, 1997). ECOLOGICAL DISTRIBUTION OF FOSSIL ‘‘MONOSPECIFIC’’ FAUNAS Holocene sediment occurs beneath most salt marshes, estuaries, and harbours, and often preserves ‘‘monospecific’’ fossil assemblages dominated by the same species as in the modern. Pre-Holocene sedimentary rocks that were deposited in the above environments are uncommon around New Zealand, and if present, are usually so weathered that they have lost their foraminiferal faunas. Thus far, only one pre-Holocene example [Arenodosaria antipoda (Stache, 1864)] of a ‘‘monospecific’’ or nearmonospecific fauna inferred to have accumulated in sheltered brackish conditions has been recorded in New Zealand and that from the late Eocene in Northland (Hayward, 1985). All but one of the remaining fossil (early Miocene) examples of ‘‘monospecific’’ benthic foraminiferal faunas are from normal-marine salinity, inner-shelf paleoenvironments. Three are inferred to be current- or wave-concentrated, post-mortem accumulations of robust, larger foraminifera (A. aucklandica, L. orakiensis, M. intermedia) deposited in shallow water or on a beach. One ‘‘monospecific’’ fauna (E. crispum) occurs in an early Miocene intertidal to shallow-subtidal gravel beach deposit, where the dominant species lived but specimens may have been concentrated by wave-winnowing removal of smaller species. Another fossil ‘‘monospecific’’ assemblage (N. novozealandica) occurs in mudstone inferred to have accumulated in a sheltered, deep (50–100 m), quiet water, harbour or inlet. Possible dysoxic conditions may have influenced the lower diversity in this setting. The fossil A butonensis ‘‘monospecific’’ fauna is the only one to have lived at bathyal or abyssal depths, where it is inferred to have been endemic to the unusual conditions in and around a hydrocarbon seep.
SUMMARY This review shows that ‘‘monospecific’’ and nearmonospecific foraminiferal faunas may result from taphonomic or ecological processes. Physical taphonomic processes include: waves or currents winnowing smaller tests, leaving behind high-dominance, large robust tests of one or a few species (e.g., P. radiata); tidal or bottom-current transport and sorting of large robust tests (e.g., Z. parri, E. crispum, extinct larger foraminifera); and current transport of small fragile tests in suspension to deposit them in huge numbers in quiet, sheltered embayments (e.g., C. carinata). Chemical taphonomic processes may produce highdominance agglutinated faunas (e.g., Amb. exiguus, M. fusca) by dissolution of calcareous tests in low pH, usually brackish settings. Preferential dissolution of the small and fragile calcareous tests close to the calcium calcite compensation depth can produce near-monospecific faunas of dense, robust calcareous species (e.g., O. umbonatus, N. umbonifera). Ecological causes of ‘‘monospecific’’ and near-monospecific foraminiferal faunas are less clear. By far, the majority of such faunas occur intertidally, where environmental drivers, such as exposure to the air, temperature, salinity, pH, or food supply, may be highly variable and in some instances extreme. It appears that only a few species have adapted to these extremes and thus, foraminiferal species diversity is already naturally low (a , 5; e.g., Murray, 1991; Hayward et al., 1999a). High-dominance (BP .50%) agglutinated faunas mostly live in organic-rich, low pH (,7.5) environments in salt marshes or lower-salinity parts of estuaries. It would appear that ‘‘monospecific’’ T. salsa faunas are the most tolerant of low salinity and desiccation, whereas E. macrescens, M. obliqua, and T. inflata-dominated faunas are most adapted to desiccation in higher salinity situations. It is not yet clear which factors determine dominance among the latter three species. High-dominance faunas from unvegetated, intertidal habitats are predominantly calcareous (e.g., Ammonia, Elphidium spp.), but the reasons for their predominance in one place or another are again unclear. Presumably, when the optimal combination of such factors as salinity, temperature, interstitial oxygen, and phytoplankton food source are present for an individual species, it is able to outcompete all others and develop a ‘‘monospecific’’ fauna. Most (75%) of the normal-marine-salinity subtidal faunas with BP .50% occur in higher latitudes around New Zealand, where species diversity is considerably lower than further north. This presumably makes it easier for near-monospecific faunas to develop. In some instances the abundance of tests of one species may result from their opportunistic nature (r-strategist) with short life cycles and greater productivity (e.g., A. weddellensis, C. carinata, E. exigua, N. flemingi), but this is not always the explanation. All modern ‘‘monospecific’’ (BP .80%) faunas occur at inner-shelf or intertidal depths, with just one fossil Miocene ‘‘monospecific’’ fauna (A. butonensis) inferred to have lived at greater depths (bathyal). The reason for this species’ high dominance was clearly its adaptive advantage to living in (and being endemic to) the chemically stressful environment
around a hydrocarbon seep, presumably feeding on the endemic chemosynthetic microbes (e.g., Sassen et al., 1993). ACKNOWLEDGMENTS I am grateful to many colleagues who, over the years, have contributed to the studies reviewed here, particularly Ashwaq Sabaa, Hugh Grenfell, and Brigida Figueira. I also thank NIWA, GNS Science, University of Auckland, and Auckland Museum for the loan of sediment or faunas that contributed to the studies covered by this review. SEM images were taken by Hugh Grenfell. I thank Marty Buzas, George Scott, Joachim Scho¨nfeld, and Elizabeth Alve for their helpful comments on the manuscript. REFERENCES Alve, E., and Murray, J. W., 1999, Marginal marine environments of the Skagerrak and Kattegat: a baseline study of living (stained) benthic foraminiferal ecology: Paleogeography, Paleoclimatology, Paleoecology, v. 146, p. 171–193. Ballance, P. F., and Gregory, M. R., 1991, Parnell Grits—large subaqueous volcaniclastic gravity flows with multiple particlesupport mechanisms: SEPM Special Publication 45, p. 189–200. Basson, P. W., and Murray, J. W., 1995, Temporal variations in four species of intertidal foraminifera, Bahrain, Arabian Gulf: Micropaleontology, v. 41, p. 69–76. Berger, W. H., and Parker, F. L., 1970, Diversity of planktonic foraminifera in deep-sea sediments: Science, v. 168, p. 1345–1347. Buzas, M. A., Hayek, L.-A. C., Reed, S. A., and Jett, J. A., 2002, Foraminiferal densities over five years in the Indian River Lagoon, Florida: a model of pulsating patches: Journal of Foraminiferal Research, v. 32, p. 68–92. Chaproniere, G. C. H., 1984, Oligocene and Miocene larger Foraminiferida from Australia and New Zealand: Bureau of Mineral Resources Bulletin 188, p. 1–98. Culver, S. D., Camp, R. L., Walsh, J. P., Hayward, B. W., Corbett, D. R., and Alexander, C. R., 2012, Distribution of foraminifera of the Poverty continental margin, New Zealand: implications for sediment transport: Journal of Foraminiferal Research, v. 42, p. 305–326. Cushman, J. A., Todd, R., and Post, R. J., 1954, Recent foraminifera of the Marshall Islands, Bikini and nearby atolls, part II. Oceanography (biologic): U.S. Geological Survey, Professional Paper 260H, p. 319–384. Eagle, M. K., Hayward, B. W., and Grant-Mackie, J. A., 1995, Early Miocene beach, rocky shore, and enclosed bay fossil communities, Waiheke Island: Records of Auckland Institute and Museum, v. 32, p. 17–44. Echols, R. J., 1971, Distribution of foraminifera in sediments of the Scotia Sea area, Antarctic waters: Antarctic Oceanography I, Antarctic Research Series, v. 15, p. 93–168. Figueira, B., 2012, Salt Marsh Foraminiferal Proxy Record of Late Holocene Sea-Level Rise, South Island, New Zealand: Ph.D. Thesis, University of Auckland, 205 p. Filipescu, S., and Kaminski, M. A., 2011, Re-discovering Entzia, an agglutinated foraminifer from the Transylvanian salt marshes, in Kaminski, M. A., and Filipescu, S. (eds.), Proceedings of the Eighth International Workshop on Agglutinated Foraminifera: Grzybowski Foundation Special Publication, v. 16, p. 29–35. Fisher, R. A., Corbet, A. S., and Williams, C. B., 1943, The relation between the number of species and the number of individuals in a random sample of an animal population: Journal of Animal Ecology, v. 12, p. 42–58. Foster, B. A., and Battaerd, W. R., 1985, Distribution of zooplankton in a coastal upwelling in New Zealand: New Zealand Journal of Marine and Freshwater Research, v. 19, p. 213–226. Goff, J. R., Rouse, H. L., Jones, S. L., Hayward, B. W., Cochran, U., Mclea, W. W., Dickinson, W. W., and Morley, M. S., 2000, Evidence for an earthquake and tsunami about 3100–3400 years
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Received 15 July 2013 Accepted 23 March 2014
APPENDIX 1 Sources of New Zealand ‘‘monospecific’’ and near-monospecific modern and fossil foraminiferal faunal data, arranged north to south. Localities shown in Figure 1. MODERN
North Island Northland, Cavalli Islands (Hayward, 1982) Northland, Bay of Islands, Urupukapuka Island (Hayward, 1981) Northland, Helena Bay (Hayward, 1993) Northland, Whananaki Estuary (author’s unpublished data) Northland, Waimamaku Estuary (Hollis et al., 1995) Auckland, Great Barrier Island (Hayward & Grenfell, 1994) Auckland, Mahurangi Harbour (Grenfell et al., 2007; Hayward et al., 2008) Auckland, Kaipara Harbour (Hayward et al., 1999b; Hayward et al., 2008) Auckland, Waitemata Harbour (Hayward et al., 1997) Auckland, Manukau Harbour, Puhinui (Grenfell et al., 2012) Waikato, Tairua Harbour (author’s unpublished data) Waikato, Firth of Thames (Hayward et al., 1999b, 2008; author’s unpublished data) Waikato, Raglan Harbour (Hayward et al., 2008) Bay of Plenty, Ohiwa Harbour (Hayward et al., 2004a)
‘‘MONOSPECIFIC’’ FORAMINIFERAL FAUNAS
Hawkes Bay, Ahuriri Inlet (Hayward et al., 2006a) Wellington, Kapiti Island, Okupe Lagoon (Goff et al., 2000) Wellington, Pauatahanui Inlet (Hayward & Triggs, 1994) Wairarapa, Lake Onoke (Hayward et al., 2011b) South Island Marlborough Sounds, Anakoha Bay (Hayward et al., 2010d) Marlborough Sounds, outer Queen Charlotte Sound (Hayward et al., 1997) Marlborough Sounds, Shakespeare Bay (Hayward et al., 2010c) Marlborough, Big Lagoon (Hayward et al., 2010a) Nelson, Nelson Haven (author’s unpublished data) Nelson, Wanganui Inlet (Figueira, 2012) West Coast, Oparara Inlet (Hayward & Hollis, 1994) Canterbury, Avon Estuary (author’s unpublished data) Canterbury, Banks Peninsula, Okains Bay (author’s unpublished data) Canterbury, Akaroa Harbour, Takamatua Bay (Figueira, 2012) Otago, Shag River Estuary (Hayward et al., 2012) Otago, Purakanui Bay (Hayward et al., 1996) Otago, Akatore Estuary (Hayward et al., 2007a) Otago, Pounawea (Southall et al., 2006; Hayward et al., 2007a) Otago, Catlins Lake (Hayward et al., 2007a) Southland, Waikawa Harbour (Figueira, 2012) Southland, Mokomoko Inlet (author’s unpublished data) Stewart Island, Port Pegasus (Hayward et al., 1994) Chatham Islands, Te Whanga Lagoon (Hayward & Grenfell, 1999) Auckland Islands (Hayward et al., 2007b) Campbell Island, Port Perseverance (Hayward et al., 2007b) Offshore North Cape, offshore, middle bathyal (Hayward et al., 2006b) Poverty Bay, mid-outer shelf (Culver et al., 2012; Hayward et al., 2013) Cook Strait, mid-shelf (Hayward et al., 2007c) Chatham Rise, upper bathyal (Hayward et al., 2001) Fiordland offshore, middle abyssal (Hayward et al., 2013) Campbell and Bounty Plateaux, mid-shelf–lower bathyal (Hayward et al., 2007c) Solander Trough, middle bathyal–middle abyssal (Hayward et al., 2007c) Macquarie Ridge, middle bathyal (Hayward et al., 2013) Fossil faunas Northland, Hokianga Harbour, Otaua Group, Orbitolite bed, early Miocene, O06/f9569 (Chaproniere, 1984) Northland, Kaipara Harbour, Pakauranga Point, Waitakere Group, Pakauranga Miogypsina Sandstone, early Miocene, Q08/f9631 (Jones, 1969, 1972) Auckland, Pakiri River, Kawau Subgroup, early Miocene, R09/f58 (Hayward, 2004) Auckland, Mathesons Bay, Waitemata Group, early Miocene, R09/f84, f85, f86 (Hayward et al., 2011a) Auckland, Waiheke Island, Fossil Bay, Kawau Subgroup, early Miocene, R11/f8, f23 (Hayward & Brook, 1994; Hayward, 2004) Auckland, Waiheke Island, Double U Bay, Kawau Subgroup, early Miocene, R10/f12, f79, f81 (Hayward & Brook, 1994) Waikato, Coromandel Peninsula, Cape Colville, Kawau Subgroup, early Miocene, S09/f4 (Hayward, 2004)
APPENDIX 2 Relative abundance of foraminiferal species in Recent ‘‘monospecific’’ faunas from New Zealand. This appendix can be found on the Cushman Foundation website in the JFR Article Data Repository (http://www.cushmanfoundation.org/jfr/index.html) as item number JFR-DR2014006.