Tane 36: 197-223 (1997)
INTRODUCED M A R I N E ORGANISMS IN N E W Z E A L A N D
AND THEIR IMPACT IN T H E WAITEMATA HARBOUR, A U C K L A N D
Bruce W . Hayward
Auckland Museum, Private Bag 92018, Auckland
SUMMARY
Sixty-one exotic marine organisms are listed that appear to have arrived in
New Zealand with human assistance in the last 150 years and have become
established. Of these, four were deliberately introduced, 25 probably came in as
fouling on vessels, 10 possibly in ships' ballast water, three probably as deck
cargo and the remainder as either fouling or in ballast water. The majority have
come in from Europe (11), east Asia (10), eastern North America (6), Australia
(6) and western North America (5). At least 12 species are known to have been
exported from New Zealand and become established in other countries. These
numbers are conservative estimates of the real number of introductions.
It is not possible to assess the risk posed by any exotic marine organism prior
to its arrival and establishment in New Zealand. Two surveys of the fauna of the
Waitemata Harbour made sixty years apart, provide an insight into some of the
changes that have occurred as a result of the establishment of at least 39
introduced exotic species. Many live in relatively low numbers and seem to have
had little significant impact on the original ecosystems. The largest diversity of
introduced organisms (especially Bryozoa) are fouling species on hard substrates,
but the greatest environmental changes can be attributed to four bivalves
introduced in the last 30 years. The Pacific oyster, Crassostrea gigas, is having
a major impact on intertidal hard shore communities. Thickets of the small Asian
mussel, Musculista senhousia, accumulate mud which temporarily smothers
extensive areas of low tidal and shallow subtidal flats in the upper harbour. The
small, fragile bivalve Theora lubrica, lives in billions in shallow-water muddy
substrates around the harbour edges and is one of the few organisms that thrives
in highly disturbed and polluted environments under the wharves and marinas.
The file shell, Limaria orientalis, is now one of the dominant molluscs in the
muddy shell gravels of the main harbour channels (10-30m deep) and has become
a significant component of the diet of bottom-foraging fish, such as snapper.
Keywords: Introduced marine organisms; marine invaders; ballast water; fouling
organisms; New Zealand; Waitemata Harbour; Orakei Basin.
197
INTRODUCTION
New Zealanders are aware of the numerous exotic terrestrial plants and
animals that have been assisted immigrants to our country since the arrival of
humans less than 1000 years ago. Some, such as sheep, cattle, pine trees and
pasture grasses, are of great economic benefit to our country. Many others, such
as possums, goats, rabbits, Old Man's beard and Kahili ginger, are an economic
and environmental disaster.
The enormous impact of these introduced pests and weeds on New Zealand's
natural terrestrial and freshwater ecosystems is well documented. Many millions
of dollars of public funding are spent each year trying to control or eradicate
them.
New Zealanders are far more aware of these exotic plants and animals on land
and in our freshwater lakes and streams than they are about similar introductions
in the marine realm. This is quite natural, as on land we can readily observe the
arrival of strange organisms and monitor changes, but in the sea it is more
difficult to notice new arrivals until they have become well established and have
greatly multiplied in numbers. Thus it is particularly difficult to determine which
of the widespread cosmopolitan marine species living around New Zealand today
came here naturally and which were introduced with the assistance of human
activities, such as shipping and have subsequently become well established.
HOW FOREIGN MARINE ORGANISMS R E A C H N E W Z E A L A N D
Natural transport methods
1. Currents
In some years, the natural current patterns around northern New Zealand
become favourable to carry juveniles and larval stages of a number of shallow
warmer water fish, sea eggs, molluscs and other organisms from Norfolk or the
Kermadec Islands to New Zealand (e.g. Powell 1976). These are carried
southward along the east coast of northern New Zealand in the East Auckland
Current, with new arrivals settling into suitable habitats they encounter. These
are mostly around the offshore islands, such as the Poor Knights, Mokohinaus,
Aldermen and White islands. Eddies in the current sometimes touch the mainland
coast and warm water immigrants are known to have become established in
places such as Cape Karikari, Cape Brett and Parengarenga (e.g. Powell 1976).
Undoubtedly the vast majority of these warm water migrants do not survive
the journey or do not encounter suitable habitats in which to settle. Of those that
do find a suitable new homeland, a number, such as the swimming crab Scylla
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(Dell 1964), grow to maturity but find the conditions too cool to breed
here and disappear after a few years. Only a few of these natural immigrants
appear to find conditions suitable to establish viable breeding populations.
The New Zealand fossil record documents thousands of natural immigration
events of tropical and subtropical marine species reaching New Zealand and
becoming established during warm periods since we split from Gondwana, 80-55
million years ago. It also documents the extinction of many of these warm water
taxa during periods of cooler sea climate (Beu 1990).
In the ten thousand years since the Last Ice Age, several thousand species
may have been added to the modern New Zealand marine fauna by this method
of introduction. Most are still restricted in their distribution to the northeast coast
of the North Island. These range extensions and contractions occur continually
in the marine environment. If climate warming eventuates we can expect many
more species to naturally extend their ranges into northern New Zealand waters.
Current transport will successfully introduce only those taxa that can survive
the journey suspended in oceanic water for perhaps one to several weeks, ie.
organisms that have long-lived, planktonic larval stages such as many sea eggs,
crustaceans and some molluscs, or organisms that are free-swimming such as reef
fish.
serrata
2. Attached to logs or organisms
Barnacles, tube worms, algae and some nestling molluscs and crustaceans may
be attach to free-swimming organisms, such as turtles or whales, or more
frequently to floating logs which occasionally cross the oceans. Their chance of
survival and successful establishment in New Zealand would be similar to
organisms carried in by currents. Fossils document many successful introductions
in the distant past and undoubtedly there have been a number since the Last Ice
Age that are now part of our native marine biota.
Australia is the most likely source of most successful immigrant species
introduced attached to logs because of the current and storm patterns, availability
of logs and similar climatic factors. Most tropical fouling species would find it
too cold to become established in New Zealand. Temperate northern hemisphere
fouling organisms are less likely to survive passage through the tropics during
their long journey to New Zealand.
3. On feet of migrating seabirds
Migrating seabirds are another mode of trans-oceanic transport that has
probably been responsible for the natural introduction of a number of terrestrial
and tidal flat animals and plants to New Zealand. This is particularly true for
many microscopic organisms that live in brackish intertidal mud flats. They could
199
easily be transported in mud attached to the feathers or feet of one of the millions
of wading birds that migrate to New Zealand along the east Asia flyway each
season.
This is the most plausible explanation for the observation that 19 of the 20
brackish species of foraminifera (Protozoa) living in New Zealand have a
cosmopolitan temperate-subtropical distribution and also occur along north
Atlantic coasts (Hayward & Hollis 1994).
Human-assisted transport methods
Despite the above-mentioned methods of natural transport and introduction of
marine organisms to New Zealand, there are vast numbers of shallow water
marine species living in other parts of the world that have not been able to cross
the oceanic and climatic barriers. Recognition of introductions of marine species
facilitated by some form of human assistance is often difficult. Strong suspicions
are raised when coastal species that come from temperate and subtropical seas in
the northern hemisphere are recorded suddenly appearing in New Zealand waters
or are found living here in limited areas around one or more ports.
There are several forms of deliberate and accidental human-assisted transport
methods.
1. Deliberate introductions
There have been numerous attempts to introduce foreign marine organisms to
New Zealand waters especially prior to the 1920s. These have included Atlantic,
sockeye and Quinnat salmon, European lobsters, Australian prawns, herrings,
turbot and edible crabs. Most have failed, except for the salmon which are
commercially farmed (Hine 1995).
Three species of the intertidal cord grass, Spartina,
were deliberately
introduced from the U K and U S A and planted here between 1913 and 1960
(Partridge 1987). They were introduced as a biological aid to reclamation of
sheltered tidal flats, which in those days were not valued as ecosystems and
important nurseries for marine life as they are today (Chapman & Ronaldson
1958). Spartina is now recognised as an environmental weed and thousands of
dollars are spent each year around the country trying to control and eradicate it.
2. Aquarium releases
Although freshwater is the preferred medium for aquaria, saltwater is
reasonably common especially for colourful, tropical coral reef community
imitations. A number of overseas marine organisms are imported live into New
Zealand specifically to supply this market. There is every possibility that one or
more of these species may be released by accident or on purpose into the New
200
Zealand marine environment. A green alga, Caulerpa taxifolia, alleged to have
escaped from a Monaco aquarium, is now a rampant marine weed in the western
Mediterranean (Nelson 1994).
3. Fouling on vessels
Accidental introductions of fouling organisms on commercial ships, fishing
and recreational boats and other mobile structures such as towed barges and
drilling rigs are believed to be common.
Fouling organisms on vessels have been moving across oceans for centuries
and are still doing so. Most fouling organisms are tubeworms, barnacles,
mussels, oysters, sea-squirts, hydroids, bryozoa, sponges, algae, wood-boring
and nestling bivalves and sea slaters (e.g. Chilton 1910, Foster & Willan 1979,
Skerman 1960a). Polynesian canoes bringing the first humans to this country,
may have introduced fouling organisms but coming from the tropics it is unlikely
that any survived to become established. Captain Cook's ship the Endeavour was
the first of thousands from the northern hemisphere to have its hull cleaned of
fouling organisms on a New Zealand shore. Since then billions of fouling
organisms from overseas would have arrived in New Zealand waters and we can
not be sure how many species have become established - probably in the
hundreds.
For every species that arrives and becomes established there must be
thousands of introductions that do not survive. For example a survey of the
Maui platform when it arrived in New Zealand from Asia in the 1970s showed
the presence of 12 species of encrusting barnacle - including 6 not currently
living in New Zealand. There were also two exotic algae, an exotic crab, a fish
and a hydroid (Foster & Willan 1979). None of these are known to have become
established here since then.
With the development of metal-hulled ships and antifouling paints the number
and diversity of fouling organisms now arriving in New Zealand may be
somewhat less than it was in the days of wooden ships. Now however, there are
far more vessels (commercial and recreational) coming to New Zealand
(Dromgoole & Foster 1983) and the flow of marine organisms arriving by this
method certainly has not stopped.
Gordon and Matawari (1992) document the fouling bryozoa (moss animals)
around New Zealand ports and conclude that a minimum of 18 species are exotic
introductions brought in by shipping. They conclude that 42% of the main
marine-fouling bryozoa of Europe are now also present in New Zealand ports and
harbours. The historical records show a procession of these bryozoa arriving in
New Zealand, starting last century and still continuing today. There appears to
have been an increase in arrivals of fouling bryozoa in the last 40 years (Gordon
201
& Matawari 1992), presumably coinciding with increased shipping and boating
movements.
4. In ballast water
Ballast water has been used in ships since late last century to lower their
centre of gravity in the water when they have little or no cargo in their holds,
and to make them safe for travelling (Hayden 1995). Sea water is usually taken
into the ship's ballast water tanks as it unloads in the shallows of a foreign port.
The ballast water may contain numerous shallow water pelagic organisms or
larvae as well as benthic organisms that have been sucked in from the shallow
water under the ship (Nelson 1994).
Ballast water introductions are a concern, because they are a relatively recent
method of human-assisted transport in which larval and non-fouling organisms
may be involved. Ballast water provides a mechanism by which organisms
previously unable to cross oceanic and climatic barriers may now be introduced
to New Zealand. The speed of modern shipping greatly improves the chances of
ballast water organisms surviving the trip across the oceans.
Studies overseas of the content of ballast water and associated sediment in the
bottom of ballast water tanks, have shown that a number of organisms are being
transported and surviving trans- oceanic crossings in this medium (Hallegraeff &
Bolch 1992, Kelly 1993).
It is difficult to prove beyond doubt that any particular organism has definitely
been introduced to New Zealand in ballast water. However, the weight of
circumstantial evidence suggests that several that are unlikely to have been
transported as fouling organisms, have been brought in this way. These
organisms include some algae, molluscs, crustaceans and microscopic organisms.
These days it is very popular to blame ballast for all new arrivals and marine
diseases, but such accusations often do not stand up to scrutiny. For example,
ballast water has been ruled out as the vector for introducing or translocating the
dinoflagellates that caused the 1993 toxic blooms around New Zealand (Jones &
Edwards 1995). Mackenzie (1995) found that the resting cysts of the toxic
dinoflagellate Alexandrium ostenfeldii were well distributed all around New
Zealand, and not just around the ports, well before the 1993 event. Unusual
marine climate conditions are accepted as the main cause of these blooms
(J asperse 1993).
Although ballast water can be ruled out as causing the 1993 events in New
Zealand, it has been shown that live toxic dinoflagellate cysts are present in some
ship's ballast water entering Australia (Hallegraeff & Bolch 1992). Thus it is
highly probable that toxic dinoflagellates have in the past been introduced to New
Zealand in ballast water. Whether they have survived, or whether any of those
202
involved in the 1993 event were originally ballast water introductions may never
be know.
One of the best documented candidates for ballast water introduction into New
Zealand is the east Asian brown kelp, Undaria pinnatifida. It is believed to have
arrived in Wellington Harbour in 1987 in ballast water as the more resilient,
microscopic gametophyte stage (Hay & Luckens 1987, Nelson 1994). Since its
arrival and establishment here, the more temperature sensitive macroscopic
sporophyte stage has been spread as fouling on domestic ships' hulls to many
other New Zealand ports (Hay 1990, Nelson 1995).
5. Transfer with aquaculture organisms
The introduction of associated species and diseases when importing live
organisms to establish aquaculture ventures is well-documented around the world,
especially with oysters (Elston 1993, Hine 1995). The importation of adults poses
greater risks than the translocation of gametes, larvae or juveniles (Hine 1995).
INTRODUCED MARINE ORGANISMS ESTABLISHED IN
NEW Z E A L A N D
Sixty-one exotic marine immigrants that have successfully established
themselves around New Zealand and are currently recognised as having arrived
here with human-assistance, are listed in Appendix 1. They include a protist
foraminifer, a sea anenome, 2 corals, three tube worms, 2 sea slugs, 2 sea snails,
4 bivalves, a crab, a barnacle, a sea slater, 18 bryozoa, a sea squirt, a fish, 20
seaweeds and 3 sea grasses. There are likely to be many more.
Analysis of these organisms' mode of life and life histories suggests that 4
were deliberately introduced, 26 probably came in as fouling, 10 probably came
in ballast water, three as deck cargo and the remainder either as fouling or in
ballast. These are similar to figures derived several years ago for exotic marine
immigrants to Australia (Pollard & Hutchings 1990).
The largest number (11 species) of organisms introduced to New Zealand
appear to have come from Europe, followed by eastern Asia (e.g. Japan, Korea,
etc.), both coasts of North America and Australia (Table 1). Eighteen species
have been spread around much of the world and it is impossible to be sure of the
source of those that reached New Zealand.
IMPACTS OF INTRODUCED MARINE ORGANISMS
Human-aided introductions are relatively new phenomena which are bringing
in vast numbers of organisms previously unable to get to New Zealand by natural
203
Table 1.
Zealand
Identified regions of origin for human-assisted exotic marine immigrants to New
Europe
East Asia (NW Pacific)
eastern Nth America
Australia
western Nth America
Sth America
Tropical Pacific
not determined
11
10
6
6
5
3
2
18
spp
spp
spp
spp
spp
spp
spp
spp
Total
55
spp
processes despite millions of years of opportunity. Around the world these
human-assisted migrations are leading towards an homogenised world biota, in
which there will be the same marine fauna and flora in similar climate zones.
Potentially positive impacts
Some introduced marine organisms are currently of economic benefit to New
Zealand. For example, Quinnat salmon is the basis for marine ranching
operations and the introduced Pacific oyster, Crassostrea gigas, much faster
growing than the native New Zealand rock oyster, Saccostrea cucullata, is the
basis of the New Zealand oyster farming industry.
The small bivalve, Limaria orientalis, that arrived in New Zealand in the
1970s and now lives in billions on the floor of the Waitemata Harbour and inner
Hauraki Gulf, could be regarded as beneficial as they are now a significant food
source for bottom-foraging fish, such as snapper (Dromgoole & Foster 1983).
Potentially negative impacts
1. Ecological
Some introduced marine species may become rampant pests or weeds in their
adopted home by displacing existing species from the niches they have occupied
for millions of years, such as the Pacific oyster has done in New Zealand and
worldwide (e.g. Dromgoole & Foster 1983). Introduced species that are
voracious predators could have enormous impacts on existing biota, such as the
Pacific seastar (Asterias amurensis) has had in Tasmania (Barker 1994).
2. Disease introduction
Introduced species, whether new to New Zealand or not, have the potential
to introduce new diseases to our marine biota. This is more likely with fouling
organisms or aquaculture organisms than ballast water introductions, as they are
204
usually introduced as adults that may carry the diseases. It is less likely with
ballast water introductions, many of which are of larval or juvenile stages that
are less likely to be diseased (Hine 1995).
3. Environmental alterations
Introduced marine species may alter the environment in which they establish,
causing major changes to the existing ecosystem. For example, the introduced
Asian mussel, Musculista senhousia, settles in large numbers on the sandy sea
floor. Within a year they grow into a turf-like mat and their byssal threads
accumulate mud (Creese & Hooker 1996) up to 20cm deep (Fig. 1). The mud
kills off the original sand-dwelling organisms and provides a completely new
environment for a different biota (e.g. Theora lubrica, pers. obs.). Fortunately,
the Asian mussels usually die after two years and the mud thickets break down
and are washed away (Creese & Hooker 1996), allowing the original sanddwelling organisms to return.
4. Human health risks
The introduction of cholera or further toxic phytoplankton species that we
currently do not have could pose a serious threat to consumers of fish and
Fig. 1. A thick layer of mud accumulates around the beds of Asian mussels {Musculista
senhousia) and smothers the pre-existing sandy shore ecosystem. Heme Bay, Waitemata
Harbour, 1996.
205
shellfish in this country (Jones 1991).
5. Economic
Introduced marine organisms may impact on the economics of marine
aquaculture, or commercial fisheries, through the introduction of diseases, toxic
phytoplankton or of voracious predators of the farmed species (Jones & Edwards
1995).
New arrivals of fouling organisms could have major economic impacts. For
example, the introduced tube worm, Ficopomatus enigmaticus (Fig. 2), first
noticed in the Whangarei and Waitemata Harbours in 1967, grows profusely in
estuaries on submerged artificial structures such as piles, pontoons and pleasure
craft (Read & Gordon 1991). In 1980 massive growths of F. enigmaticus fouled
cooling water intake pipes for the Otara power station in the Tamaki Estuary,
Auckland (Fig. 3). Its regular and luxuriant growth in the pipes was a major
contributing factor towards the station's switch to the use of freshwater (Read &
Gordon 1991).
6. Tourism and recreation
Exotic marine immigrants may also impact on the recreational and aesthetic
values of the coast and sea. For example, the rocky shores and pebbly beaches
Fig. 2. The introduced tube worm, Ficopomatus enigmaticus, growing in profusion on the sides
of rocks near the Otara power station, Tamaki Estuary, Auckland.
206
Pacific oyster
Crassostrea gigas
widespread
abundant
' 1
Theora lubrica
m
^
POLLEN•
ISLAND
Asian mussel
Musculista I |
senhousia LTH
Barnacle
Balanus amphitrite
OTARA
Pyromaia tuberculata
widespread
few
Bryozoa
Watersipora
subtorquata
INTRODUCED ORGANISMS IN
THE WAITEMATA HARBOUR
Fig. 3. Examples of the variety of introduced marine organisms that are now established in
Auckland's Waitemata Harbour and their 1990s distribution within the harbour.
of parts of the Waitemata and particularly the Manukau Harbour have been
transformed by the prolific growth of the introduced Pacific oyster in the last two
decades. The beaches used to be pleasant, sheltered recreational areas where
locals could walk and swim in bare feet. Now they are rather unpleasant muddy
207
and shelly areas spiked with a multitude of dangerously sharp oyster shells (Fig.
4).
It is virtually impossible to predict prior to their arrival and establishment
here, what impact, if any, each introduced exotic marine organism might have.
The majority may have little perceptible impact, but there will always be a few
that relish the conditions in their new home, possibly even more than in their
native country and may become a pest or weed along New Zealand's coast.
INTRODUCED M A R I N E ORGANISMS IN T H E
W A I T E M A T A H A R B O U R (Fig. 3)
There is limited information on the present status and particularly the past
condition of our coastal marine ecosystems. This makes it very difficult to
determine what impact any introduced exotic marine organism may be having.
Auckland's Waitemata Harbour provides an excellent opportunity to document
new arrivals and their impact on the biota and environment. The Waitemata
Harbour has been New Zealand's busiest international port for at least the last
100 years and has warmer water than most of our other major ports. It is thus
the prime candidate to show the most impact from human-assisted immigrants.
It is also fortunate that in the 1930s the Waitemata Harbour was the site of
the first major study of seafloor communities in New Zealand (Powell 1937).
This provides a useful baseline against which results of a repeat survey of the
seafloor biota in the 1990s have been assessed (Hayward et al. in press).
Since the 1930s, there have been a number of environmental changes that
have potentially impacted on the sea floor biota (Dromgoole & Foster 1983). For
example most of the sewerage discharges have stopped, subdivision has increased
siltation in the upper harbour, and T B T (tributyl tin in antifouling paint)
poisoning has devastated some of our common harbour neogastropods - such as
the oyster borer, Lepsiella scobina, and the olive shells (Stewart et al. 1992).
The most dramatic changes to the harbour's biota in the past 60 years however,
can be attributed to human-assisted exotic marine immigrants.
Of the 61 marine species that are believed to be human-assisted introductions
to New Zealand (Appendix 1), 39 species (70%) are currently living in the
Waitemata Harbour. Fourteen of these have not spread beyond the Waitemata and
208
Fig. 4. Large, erect shells of the introduced Pacific oyster, Crassostrea gigas, stick up from the
muddy floor of Orakei Basin, Waitemata Harbour, 1996.
inner Hauraki Gulf. Many of the 39 introduced organisms appear to play only
minor roles in the ecology of the Waitemata Harbour but several bivalves have
had a major impact. Some examples are:
Foraminifera
One unicellular foraminifer, Siphogenerina raphanus, which is common in
other parts of the world, was probably introduced in ballast water. It is now
common throughout the subtidal sediments of the Waitemata Harbour (Hayward
et al. in press), but not common elsewhere in New Zealand.
Sea anenome
The anenome, Sagartia luciae, which occurs intertidally in muddy, slightly
brackish parts of the harbour, is believed to have arrived as fouling on ships
from its native home in the North-west Pacific and has not spread beyond the
Waitemata (Dromgoole & Foster 1983).
Bryozoa
The bryozoa are our best studied and documented fouling organisms with at
least 15 introduced exotic species occurring around the wharf areas (Fig. 5) in
209
Fig. 5. Auckland's commercial wharf area in the Waitemata Harbour is inhabited by a number
of introduced fouling organisms.
the Waitemata Harbour (Gordon & Matawari 1992). The prominent dark
bryozoan, Watersipora arcuata, appears to have been introduced in 1957
(Skerman 1960b). It had an initial period of luxuriant growth around low tidal
rocky areas in the 1970s, but appears to be nowhere near as common today (J.E.
Morton, pers. comm.).
Sea slater
The cosmopolitan, wood-inhabiting, intertidal isopod, Limnoria tripunctata,
is known only in New Zealand around the Waitemata Harbour. It was probably
introduced in wooden cargo many years ago (Cookson 1991, A . B . Stephenson
pers. comm.).
Barnacle
The widely-distributed barnacle, Balanus amphitrite, well-known for fouling
ships' hulls (Foster 1978), is presumed to have been introduced to New Zealand
last century on a hull. Its introduction is supported by its lack of a fossil record
in New Zealand (Buckeridge 1983). Balanus amphitrite is found here only in
several intertidal locations around the Waitemata Harbour (Foster 1978).
210
Crab
Shallow subtidal sediments in the Waitemata and inner Hauraki Gulf are the
home to low numbers of a small Californian masking crab, Pyromaia
tuberculata, which first appeared here in 1978. It possibly came in ballast water
from Japan, where it had previously been introduced (Webber & Wear 1981).
Sea-squirt
The elongate sea-squirt, Ciona intestinalis, lives around the Auckland wharves
and other rocky low tidal Waitemata Harbour shores. It appears to have arrived
here in the 1950s (Morton & Miller 1968, Dromgoole and Foster 1983).
Algae
A common sight around the sheltered shallows of the Waitemata harbour is
the Japanese green alga, Codium fragile ssp. tomentosoides. It was first
discovered on the eastern wall of the container terminal in 1973 (Dromgoole
1975). Today it lives attached to cockle shells and pebbles on the muddy and
sandy harbour floor and is often washed up on harbour beaches as drift (pers.
obs.). It has been introduced to many northern hemisphere areas and has caused
major devastation to the oyster fishery in Chesapeake Bay (Nelson 1994).
Fortunately it has not become such a worrisome weed in New Zealand.
A n attractive perforated brown alga, Hydroclathrus clathratus, occurs
infrequently on rocks around sheltered low tidal parts of the harbour (Dromgoole
& Foster 1983). It was first recorded from northern New Zealand in the 1970s
and was possibly introduced from warmer regions by shipping.
Sea grasses
Two small patches of deliberately introduced cord grass are known along the
shore of the Waitemata Harbour - one on the end of Te Atatu Peninsula (Spartina
x townsendii) and the other beside the boat launching ramp at Orakei Basin
{Spartina alterniflora, Fig. 6). Because they have not spread their impact in the
Waitemata is very minimal compared with some other New Zealand harbours.
Gastropods
The colourful nudibranch, Thecacera pennigera, was first noticed in New
Zealand in the early 1970s. In New Zealand it has been recorded only on fouling
bryozoan and sponges in the Waitemata Harbour (Willan 1976). The introduced
lilac and reddish-brown spotted nudibranch, Okenia plana, also occurs in the
Waitemata Harbour where it feeds on bryozoa on wharf piles (Morton & Miller
1968, Willan & Morton 1984).
A small ellobiid snail, Microtralia occidentalis, lives among the high tidal
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Fig. 6. A patch of the introduced cord grass, Spartina x townsendi, grows near the boat ramp,
Orakei Basin, Waitemata Harbour, 1996.
rocks of Rangitoto Island. Formerly thought to be an endemic species restricted
to the island (called Rangitotoa
insularis),
it is now believed to have been
introduced from the West Indies, probably as eggs attached to wooden deck cargo
on ships last century (Climo 1982).
Bivalves
Numerically and ecologically the largest changes in the seafloor biota of the
Waitemata Harbour that have occurred between Powell's 1930s surveys and our
repeat surveys in the 1990s, are those brought about by four exotic immigrant
bivalves (Hayward et al. in press).
Profuse growths of the introduced Pacific oysters,
(Dinamani 1971, Dromgoole & Foster 1983), are taking over
many of the intertidal rocky shores around New Zealand's northern harbours,
including the Waitemata. Additionally it is beginning to form intertidal banks of
live Pacific oysters by colonising cockle shell accumulations in the upper part of
the Waitemata Harbour off Te Atatu and in Pollen Island Marine Reserve. Dead
oyster shells are beginning to accumulate in intertidal drifts and their sharp shells
are converting high tide beaches into unpleasant substrates. Wherever the oysters
Crassostrea
Crassostrea
gigas:
gigas
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grow in profusion around the more sheltered shores of the Waitemata Harbour
they are accumulating mud around them and are thus contributing to further
environmental changes.
Musculista senhousia: The introduced small Asian mussel, Musculista
senhousia (Willan 1985) lives in patches (5m - lOha) which accumulate thick
mud drifts over the shallow subtidal and low tidal seafloor in many parts of the
Waitemata Harbour. These thickets continually die off, with new patches being
established each year (Creese & Hooker 1996). Subtidal and intertidal surveys
of the Waitemata Harbour in the 1990s (Hayward et al. in press) show that the
largest area of infestation is between mean low water and 2m depth in the
extensive low tide and shallow subtidal flats above the harbour bridge (Fig. 3),
which is where the mussel was first discovered about 1978 (J.E. Morton pers.
comm.). Within a decade it had spread north to Parengarenga and south to East
Cape but does not appear to have extended its range since then (Willan 1985,
1987, Morley 1988).
2
Limaria orientalis: Another bivalve immigrant that is now a prominent
member of the Waitemata Harbour seafloor communities is Limaria orientalis.
It was first noticed around the Waitemata Harbour and Hauraki Gulf in 1972,
when it appeared in large numbers in coarse sediment around low tide mark
(Grange 1974, Dromgoole & Foster 1983). After a few years it disappeared
almost entirely from intertidal areas but is now one of the three dominant
molluscs living in the muddy shell gravels of the Rangitoto and Waitemata
Harbour channels (Fig. 7). It lives in densities of between 5 and 100 per square
metre (Hayward et al. in press).
Theora lubrica: A small, thin-shelled, infaunal bivalve, Theora lubrica, has
in recent decades become the dominant mollusc living in mud and muddy sand
in the extensive low tidal and shallow subtidal flats throughout most of the
Waitemata Harbour (Fig. 8). Theora lubrica arrived in the northern harbours
about 1972, probably in ballast water from its home in Japan (Climo 1976,
Dromgoole & Foster 1983). It has since spread to most other ports in the country
and has recently been reported for the first time in harbours on the west coast
(Morley 1995, Morley et al. this issue). It is a short-lived species that can rapidly
colonise disturbed and muddy habitats and is perhaps the most pollution-tolerant
mollusc in the harbour, living in the contaminated sediments of the Westhaven
marina, beneath the Auckland wharves and in the Tamaki Estuary ( M . Morley
pers. comm.).
213
recreational amenities. The railway embankment and a set of control gates
created a permanent salt water lagoon that currently is flushed on average once
a month during spring tides. Since it was enclosed run-off from the surrounding
suburbs and accumulation of rotting algae have deposited a 10 to 30cm deep
layer of mud over the floor of most of the basin.
One of the two most abundant algae in the Basin that seasonally cover the
extensive shallow muddy floor is an unidentified, exotic, red, filamentous alga,
known from nowhere else in New Zealand and thought to have been recently
introduced from South-east Asia (Nelson 1994).
Growing in thick patches among and beneath these algae are millions of the
introduced Asian mussels. The mussels are present throughout the mud on the
floor of the basin in densities ranging between 5 and 2000 per m . A 2 to 20m
wide band around the margin of the basin is studded with the sharp, erect shells
of Pacific oysters which stick up from the soft muddy substrate (Fig. 4). Many
of these oysters have grown to unusually large sizes with 20-cm-long shells not
uncommon.
Basalt rocks around the edge of the Basin support the introduced seaanenome, Sagartia luciae, and the highest densities of the introduced barnacle,
Balanus amphitrite, to be found in the harbour.
2
NEW Z E A L A N D MARINE ORGANISMS INTRODUCED T O
OTHER COUNTRIES
There are documented cases of at least 12 New Zealand marine organisms
having been assisted to emigrate by humans and successfully established in
overseas countries. One is our small marine acorn barnacle, Elminius modestus,
which was introduced to South Africa and Europe on ships in the 1940s and is
now widespread there (Buckeridge 1982).
The export of live Bluff oysters to Tasmania a few decades ago, resulted in
the largest number of recorded introductions to any foreign land. Accidentally
introduced to Tasmanian waters when the shells were discarded were one chiton,
two snails, three bivalves, two crabs, a lamp shell and a star fish (Appendix I,
Hine 1995) - some of which are now major members of the Tasmanian marine
fauna (e.g. Maoricolpus roseus).
DISCUSSION
There is now documented evidence of the establishment of 61 exotic marine
species in New Zealand that have probably arrived with human assistance in the
last 150 years. We know of at least 12 that have been exported to other
215
countries. These numbers are conservative minimums. This paper provides a
glimpse of the changes brought about by these marine invaders to the ecosystems
in the Waitemata Harbour. It may be the most impacted area of New Zealand
coast, but similar changes are likely to be occurring throughout the country.
It is not possible to accurately assess the risk posed by any introduced exotic
organism prior to its arrival and establishment in New Zealand. The only way to
remove the risk is to eventually eliminate any possibility of human-assisted
introductions of exotic marine organisms arriving in New Zealand, whether
deliberate, in ballast water or as fouling.
ACKNOWLEDGMENTS
This paper was prepared as a talk for a public forum on Marine Invaders organised by the
Auckland Conservation Board in 1996. The talk and paper draw heavily on material gathered together
by speakers for a National Symposium on Ballast Water held in Wellington in 1995 and organised
and published by the Royal Society of New Zealand. I am grateful to Margaret Morley, Jenny Riley,
Brett Stephenson and Hugh Grenfell for their advice and assistance with the Waitemata Harbour data
summarised here from our 1990s resurvey of the harbour's biota. Jenny Riley is thanked for her
drafting of Figures 3, 7, 8. The manuscript has benefitted from the critical reading and suggestions
of Margaret Morley, Brett Stephenson and Barbara Hayden.
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219
APPENDIX I. Preliminary list of exotic marine species that appear to have been introduced into New Zealand with human assistance and have
become established here. Also listed are New Zealand species that appear to have been exported to other countries by the same means.
Date of
intro.
How
introduced
Present NZ
distribution'
Native
to
2
introduced
also to
2
Wait
Hbr
References
INTRODUCED MARINE TAXA
Kingdom Protista: Phylum Sarcodina: Foraminifera
Siphogenerina raphanus
pre 1960 ?ballast
Hayward et al in press
Wait
Kingdom Animalia: Phylum Coelenterata: Order Actinaria (sea-anenomes)
1977
?fouling
Wait
Sagartia luciae
NW Pac
NAm,SAm,Eur
Dromgoole & Foster 1983
Order Scleractinia (corals)
(J
O
?ballast/fouling
?ballast/fouling
Tethocyathus cylindraceus
Hoplangia durotrix
Cairns 1995
Cairns 1995
W Atl
NE Atl
Phylum Annelida (worms)
Ficopomatus enigmaticus
Hydroides norvegicus
Polydora cornuta
1967
fouling
pre 1950 fouling
1967
fouling
Wait,Whang,HkBay
NI.SI
?N Pac
Aust
Wait, Whang
Eur,Aust
World-wide
Read & Gordon 1991
Dromgoole & Foster 1983
Read & Gordon 1991
Phylum Mollusca: Class Gastropoda (snails and slugs)
Microtralia occidentalis
Okenia plana
19th C
?cargo
?ballast
Wait
neNI
WIndies
Jap
Pac Is
Aust
Phytia myosotis
Thecacera pennigera
19th C
1973
?cargo
?fouling
Otag
Wait
e Atl
?SAm
Aust,NAm
Aust,Eur,Jap
1964
1972
1978
1972
?deliberate
?ballast
?ballast
?ballast
NI,SI
neNI
neNI
NI,SI
N Pac
Jap
E Asia
E Asia
World-wide
Climo 1982
Willan & Morton 1984, Hine
1995
Climo 1982
Willan 1976, Dromgoole &
Foster 1983
Class Bivalvia (bivalves)
Crassostrea gigas
Limaria orientalis
Musculista senhousia
Theora lubrica
WAust,wNAm
wNAm
Dinamani 1971
Dromgoole & Foster 1983
Willan 1985
Dromgoole & Foster 1983
Phylum Crustacea: Subclass Decapoda (crabs)
Pyromaia tuberculata
Subclass Cirripedia (barnacles)
Balanus amphitrite
Order Isopoda (sea slaters)
Limnoria tripunctata
1978
?ballast
Wait.HGulf
fouling
Wait
cargo
Wait
Wait,Nels
Wait
Phylum Bryozoa
?fouling
Anguinella palmata
1950s
Aeverrillia armata
pre 1960s ?fouling
(=Buskia, Morton & Miller 1978)
pre 1960s ?fouling
Amathia distans
Bowerbankia gracilis
pre 1960s ?fouling
Bowerbankia imbricata
prel967 ?fouling
?fouling
Bugula flabellata
1949
1949
Bugula neritina
?fouling
Bugula simplex
1988
?fouling
Bugula stolonifera
1962
?fouling
Buskia socialis
1977
?fouling
1963
?fouling
Conopeum seurati
1890s
?fouling
Cryptosula pallasiana
1977
plastic drift
Electra tenella
Schizoporella errata
pre 1960s ?fouling
Tricellaria occidentalis
?fouling
1950s
?fouling
1957
Watersipora arcuata
Watersipora subtorquata
1982
?fouling
Zoobotryon verticillatum
pre 1960s ?fouling
Phylum Chordata: Order Ascidiacea (sea squirts)
?fouling
Ciona intestinalis
1950s
Teleostei (fish)
deliberate
Oncorhynchus tshawytscha
1870s
Wait
Wait,Oneh,Nap,Nels
Wait,Nels
NI.SI ports
NI.SI ports
Lytl
NI.SI ports
HGulf
Nl.nSI
NI.SI
HGulf
Wait,Opua
Nl.nSI ports
NI,Nels ports
NI.SI ports
Wait,Oneh
Calif
wNAm
y
Dromgoole & Foster 1983
World-wide
y
Foster 1978
World-wide
World-wide
y
Cookson 1991
World-wide
eNAm,eSAm
NSW
y
y
Gordon & Matawari 1992
Gordon & Matawari 1992
World-wide
World-wide
World-wide
World-wide
World-wide
SAust
World-wide
SAm
eNAm
World-wide
Jap
World-wide
Aust,Eur
Aust
Aust
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Gordon & Matawari
Skerman 1960b
Gordon & Matawari
Gordon & Matawari
y
Dromgoole & Foster 1983
Eur,eNAm
Eur
Eur
eNAm,eSAm
N Pac
wUSA
wNAm,wSAm
tropics
Wait,Lytl
SI
wUSA
1992
1992
1992
1992
1992
1992
1992
1992
1992
1992
1992
1992
1992
1983
1992
Hine 1995
Kingdom Plantae: Algae: Chlorophyceae (green seaweeds)
Codium fragile tomentosoides
1973
?fouling/ballast
Wait,HGulf
Jap
eNAm,Eur
y
Dromgoole & Foster 1983
Phaeophyceae (brown seaweeds)
Asperococcus bullosus
1950s
?fouling/ballast
StI,Marlb,Rangaunu
Eur
SAust
Jap,wNAm
Chnoospora minima
Colpomenia durvilleae
(=C. bullosa)
Cutleria multifida
Hydroclathrus clathratus
Punctaria latifolia
Sargassum verruculosum
Striaria attenuata
Undaria pinnatifida
:4830s
1980
'.'fouling
^ballast
Port Underwood
NI
tropics
SAm
c.1870
1970s
1940s
1840s
1950s
1987
'.'fouling/ballast
?ballast
''ballast
fouling
?fouling/ballast
ballast
Wait,Wgtn,SI
neNI
Wgtn,SI,StI
SI,StI
Wgtn-StI
sNZ ports
World-wide
World-wide
Eur
Aust
Eur
eAsia
World-wide
trop/subtrop
SAust
Rhodophyceae (red seaweeds)
Antithamnionella ternifolia
Champia affinis
Chondria harveyana
Griffithsia crassiuscula
Polysiphonia brodiae
Polysiphonia constricta
Polysiphonia sertularioides
Polysiphonia subtilissima
Polysiphonia senticulosa
1900s
19th C
19th C
1950s
1930s
1970
1930s
1970s
1980s
Fouling/ballast
fouling/ballast
?fouling
?fouling/ballast
?fouling^allast
?fouling/ballast
?fouling/ballast
?fouling/ballast
?fouling/ballast
Wgtn .Tim aru
Otag.SI
Porirua
Marlb.Otag.StI
Wgtn.SI
Otago Hbr
neNI.SI
neNI,Wgtn,Marlb
Wgtn,Marl b
SAm
SAust
Tasm
SAust
Eur
SAust
Eur
SAm
NAm
Aust
Solieriaceae indet.
1980s
?fouling/ballast
Wait
1953
1924
1913
deliberate
deliberate
deliberate
neNI
NLSI
Auck,BoP,Sthd
9
Adams 1983, Nelson & Knight
1995
Nelson & Duffy 1991
Parsons 1982, Nelson 1994
y
y
Aust,SAm,Jap
Tasm,Eur
NAmJap.Aust
Aust,NPac
y
Adams 1983
Johnson & Dromgoole 1977
Adams 1983
Adams 1983
Nelson 1994
Hay&Luckes 1987, Nelson
1995
Nelson & Maggs 1996
Adams 1983
Adams 1983, Nelson 1994
Adams 1983
Adams 1991
Adams 1991
Adams 1991
Adams 1991
Nelson 1994, Nelson & Maggs
1996
Nelson 1994
Angiospermae
Spartina alterniflora
Spartina anglica
Spartina x townsendii
eUSA
UK
UK
y
y
Partridge 1987
Partridge 1987
Partridge 1987
EXPORTED MARINE TAXA
Phyllum Mollusca: Class Polyplacophora (chitons)
Chiton glaucus
oyster exports
NZ
Tasm
Hine 1995
Class Gastropoda (snails)
Maoricolpus roseus
Zeacumantus subcarinatus
oyster exports
NZ
Tasm
NSW
Hine 1995
Powell 1975
oyster
oyster
oyster
oyster
exports
exports
exports
exports
NZ
NZ
NZ
NZ
Tasm
Tasm
Tasm
Wales
Hine 1995
Hine 1995
Hine 1995
Walne 1974
oyster exports
oyster exports
NZ
NZ
Tasm
Tasm
Hine 1995
Hine 1995
Elminius modestus
fouling
NZ
Eur,SAfr
Foster 1978, Buckeridge 1982
Phylum Brachiopoda (lamp shells)
Calloria inconspicua
oyster exports
NZ
Tasm
Hine 1995
NZ
Tasm
Hine 1995
Class Bivalvia (bivalves)
Neilo australis
Perna canaliculus
Ruditapes largillierti
Tiostrea chilensis
1960s
Phylum Crustacea: Order Decapoda (crabs)
Cancer novaezealandiae
Halicarcinus innominatus
Order Cirripedia (barnacles)
Phylum Echinodermata: Class Asteroidea (starfish)
Patiriella regularis
oyster exports
Akar = Akaroa Harbour; BoP = Bay of Plenty; Fiord = Fiordland; HGulf = Hauraki Gulf; HkBay = Hawkes Bay; Lytl = Lyttleton Harbour; Marlb = Marlborough; Nap
= Port Napier; Nels = Nelson; NI = North Island; Oneh = Onehunga; Otag = Otago Harbour; SI = South Island; Sthd = Southland; StI = Stewart Island; Wait = Waitemata
Harbour; Wgtn = Wellington Harbour; Whang = Whangaroa Harbour.
Aust = Australia; Calif = California; Eur = Europe; Jap = Japan; NAm = North America; NSW = New South Wales; Pac = Pacific; SAfr = South Africa; SAm = South
America; Tasm = Tasmania
Living in the Waitemata Harbour or not.
1
2
3