Dive Pacific 175 Dec2020 Jan 2021

SOUNDINGS
LOCAL NEWS
Marine heatwave conditions forming: NIWA
NIWA forecasters say a marine
heatwave is forming around
parts of New Zealand after sea
surface temperatures (SSTs)
warmed considerably last month.
Meteorologist Ben Noll says the
warmest region is the north of
the North Island where ocean
temperatures are 1.6°C above
the November monthly average.
In this region, marine heatwave
conditions are affecting
Northland and northern
Auckland’s coastal waters and
extend west into the Tasman
Sea.
In other areas around the
country, sea surface temperatures
are between 0.7 to 1.1°C
above average.
“High pressure systems in
October led to warming of the
sea surface and prevented cooler
water underneath from mixing to
the top.
The east and west of the South
Island is 1.1˚C above average as
is the east of the North Island.
West of the North Island is +0.8˚C
above average, and north of the
South Island +0.7˚C.
New Zealand is now in a La Niña
climate regime which tends to
bring more northerly winds and
has historically been associated
with warm Tasman Sea temperatures.
NIWA subscribes to the definition
of a marine heatwave as
being an extended period of
extremely warm ocean temperatures
that can extend up to
thousands of kilometres. These
temperatures must be above
the 90th percentile – or the
value above which 90 per cent of
historical observations occur.
Chance leads to first look at coral larvae
Small orange flecks spotted
floating in a respiration
chamber at a NIWA laboratory
have led to a discovery about the
spawning habits of a deep-sea
stony coral in New Zealand
waters.
NIWA scientists collected
colonies of the deep-sea stony
coral, Goniocorella dumosa, from
the Chatham Rise in June to
help assess the resilience of
corals to sedimentation.
The small orange flecks turned
out to be larvae that had
been released from the
mature coral polyps. This
coral species is prevalent
throughout the southern
hemisphere but its larvae have
never been seen before. They
measure about 1.1mm x 0.8
mm and were covered in small
hair-like filaments called cilia.
Deep sea stony coral
months to reach this stage. It’s
fascinating to watch and record
their development as they form
feeding tentacles and a calcified
base.”
Coral lavae
NIWA scientist Dr Jenny
Beaumont says they settled
“within a few days, which is
a contrast to other deep-sea
corals, some of which can take
NIWA’s coral expert, Di Tracey,
says being able to observe the
larvae has changed the understanding
of the reproductive
process of this species.
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26 Dive New Zealand | Dive Pacific