of the Corals
Posted by Mark Heckman, Educator, Waikiki Aquarium/ University
of Hawai'i - Manoa
Frigate Shoals is a unique site. All that is left of
the original volcanic island is a tiny spire of rock, La
Perouse Pinnacle. The rest of the volcanic island has sunk
beneath the sea or been eroded away over time. The pinnacle
stands as a last reminder of the toehold the scalding magma
left behind in this vast ocean.
it is not over yet, like all of the Hawaiian Islands, corals
and coralline alga grow here. Together with other types
of sea life that make shells or skeletons, they have created
a vast area of reef and islets that surround the pinnacle.
Miles of rich reef are here, filled with fish and invertebrates.
The reef is a strong matrix of coral skeletons and coralline
algae, with sands between. Life, that contrary effort to
entropy, forever building and organizing, has not yet given
in. French Frigate Shoals is much
older than the main Hawaiian Islands. This trend will
continue as we move up the chain. Creation, erosion, subsidence,
it is all just part of the history of these islands and
particular interest, are the extensive group of corals,
the Acropora (1). These are the corals
that people imagine when they think of coral reefs. Go to
Fiji, Australia, the Indian Ocean, Palau, New
Guinea, Paris (2), and you will find the
Acropora. They come in plate forms over 12 feet in diameter
and in branching forms like thickets, delicate as lace or
thick as antlers.
wait, what place did I miss in that list? Hawai`i, what
about Hawai`i? It's warm enough, the water is clear enough.
If Acropora is the main coral group in the rest of the world,
what happened to Hawai'i? Herein lies a mystery. There are
currently just a few Acropora coral heads in the entirety
of the main Hawaiian Islands. It seems like they should
be here. They are close, they have been in found in Hawai`i
in the past, but they just aren't abundant now.
ideas have been proposed as to why these corals are so numerous
at French Frigate Shoals. Certainly the easiest is one of
proximity. If you are near a friend, you are in close proximity.
If they have a cold, and they sneeze on you, that proximity
will transmit an organism or two. If the friend is across
the room, that same cold organism will probably not make
the case of Acropora, the closest source for Hawai`i is
(choose one): Okinawa (3), Bora Bora (4),
Los Angeles (5), or Johnston Island (6)?
Did you pick correctly? Currents must have a big impact
here. Somehow, whether through eddies (current swirls) or
larger sub-tropical counter currents, Acropora have made
it across to French Frigate Shoals. They may have come as
the planula larvae that corals release, or settled on objects
that floated across.
may work their way back down to the main Hawaiian Islands.
They were part of Hawai`i's geological past, fossil reefs
on O`ahu have Acroporid corals. Perhaps they died off due
to changes in sea level. In the past three ice ages, as
the water cooled and was tied up in ice sheets and glaciers
further north, coral reefs have been exposed as when sea
levels dropped more than 300 feet. This was probably a bit
much for relatively slow growing marine organisms that are
sensitive to temperature and do not do well out of water.
the reasons, Acroporids are abundant at French Frigate Shoals.
Diving is unlike anywhere else in the Hawaiian Archipelago.
Take a look at the pictures; it does not look like the underwater
environment in the main Hawaiian Islands for a variety of
fish, such as the Chevron butterflyfish, (Chaetodon trifacialis),
depend on Acropora for food, they will eat nothing else.
Lose the Acropora, lose the fish. Other fish and wildlife
depend on corals such as the Acropora as well. Seaweeds
grow underneath, urchins graze, and the labyrinth of spaces
provides night and day hiding spaces for a wide variety
of colorful reef fish. The beauty of an Acroporid reef is
clear to any beholder.
Veron, JEN (2000), Corals of the World, Melbourne, Australia,
and Expedition Research Scientists: Dr. Jim Maragos, US
Fish and Wildlife Coral Reef Biologist, Dr. Don Potts, University
of California, Santa Cruz.
You can say "a crop poor a" if you are from the
United States or "ackro pore a" if you are from
Australia. Scientists can be a stubborn lot and sometimes
don't agree on how to say the words they create. But it
is not their fault, scientific terms are based on Latin,
a language we know how to write, but no longer know how
to speak. This leads to some confusion.
Paris does not have any Acropora at present. It doesn't
even have an ocean. But if you get to Paris, while you are
sitting at a sidewalk café, consider that 40 million
years ago, it was an ocean and Acroporids put in one of
their first appearances there. They've 'been around.'
Sorry - although Okinawa definitely has Acroporid corals,
including all of the same species (and more) that are found
at French Frigate Shoals, there are many such places in
the Pacific. Distance is a big issue here, there are much
Bora Bora just has a great sound to it, doesn't it? Easy
to imagine relaxing on a Tahitian beach, snorkeling in the
beautiful waters with the beautiful branching corals. But,
sorry, it is not the right answer. There are much closer
sources. Try again.
Not even close - Los Angeles barely has corals at all, too
cold. Reef building corals do best in warmer waters.
YES! In all of the Hawaiian archipelago, French Frigate
Shoals is the closest to Johnston Atoll, a mere 450 miles
away. Johnston also has all of the species found at French
Frigate (and a few more). This is the closest source and
makes the best match. Other close sources include Kingman
Reef at 1,050 miles, Palmyra at 1,100 miles, and Wake Island
at 1,550 miles.