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Kermadec Ridge
Map ID number:
1
Location: Ridge extends north
from New Zealand’s North
Island
Approximate area: 197,998km 2
Description of area:
The Kermadec Ridge is
composed of a string of
volcanoes and vents, with
associated bacteria and
other components. Some
of the volcanoes breach
the summit to form four
island groups, the Kermadec
Islands. The area is
flanked by the Kermadec
Trench to the east (10km
deep) and the South Fiji
Basin to the west (4 km
deep).
Plate coral
Biological attributes:
The Kermadec Ridge is New Zealand’s window
into the marine fauna of the Indo-Pacific
in that it is the southernmost limit for many
taxa. Marine invertebrates found on the ridge
include brachiopods, corals, and sponges.
The rocky reef fauna and macroalgal flora of
the Kermadecs are distinct from that of the
rest of New Zealand.
Criteria applied:
Species diversity; species richness; endemism;
representation; extremities of range
(southern limit of some tropical taxa); meeting
ground; links to global patterns.
Status and management:
In 1990 a marine reserve was established
around the Kermadec Islands, extending
12 nautical miles (22km) from each island
group. Benthic fisheries are severely constrained
in some parts of this area by nominal
catch limits and special permit access
provisions.
State of information:
Information for the Kermadecs is patchy.
Some major taxa have been thoroughly studied;
others have been little studied or not all.
There is no information on bottom habitats
beyond those at shallow diveable depths.
Some bottom photographs exist for deeper
habitats.
References and further reading:
Brook (1999), Cole et al. (1992), Gordon
(1984), Nelson and Adams (1984), Schiel
et al. (1986).
©2004 DOC, Te Papa Atawhai/Rodger Grace
Trench (hadal)
environments
Map ID number:
2
Location: Two trenches are
located in the New Zealand
region: the Kermadec and
Puysegur, which lie to the
northeast and southwest of
the New Zealand landmass
respectively
Approximate area: 381,424km 2
Description of area:
Trenches are massive linear depressions
found throughout the world’s oceans. They
are formed at subduction zones, regions
where one tectonic plate slides beneath
another and is recycled into the earth’s
interior. Bottom sediments in trenches are
dominated by muds and fine sands of mixed
pelagic/terrestrial origin. The “hadal” zone is
defined operationally by biologists as depths
exceeding 6,000m; only trenches contain
ocean this deep.
The Kermadec Trench trends northeast from
East Cape. It is approximately 2,000km
long, with a maximum depth exceeding
10km in places. The Kermadec Trench is
narrow and steep in comparison with other
trenches, being about 40km wide on average,
with a wall gradient of about 1:6. The Puysegur
Trench originates off southern Fiordland
and trends southwest. The hadal portion of
this feature is not as deep or as extensive as
that of the Kermadec Trench.
Biological attributes:
Trench faunas, in general, exhibit a high
degree of regional endemism, possess
specialised ecological and physiological
adaptations, and exist within a community
structure that differs from adjacent areas of
abyssal sea floor.
Trenches are widely separated from each
other, and in geological terms are long-lived
features. These characteristics have significant
evolutionary and biogeographical
implications for trench faunas, including
the generation and maintenance of species
endemic to a single trench. It is reasonable
to expect trench endemism to be high among
hadal benthic taxa. On this basis, New Zealand’s
trench habitats probably contain many
species found nowhere else in the region.
Levenstein (1991) reviewed the world’s
known hadal polychaete fauna (120 species)
and found that about 30% of species
recorded from trenches were restricted to
hadal environments (the rest co-occur in the
BIODIVERSITY – NEW ZEALAND’S MARINE ECOREGION ■ 49