Wai'opae pools among basalt bedrock and boulders. |
The Big Island has about 6 Marine Life Conservation
Districts, marine reserves established by the state of Hawaii that variously protect coastal marine
organisms from harvest. A short stretch of coastline containing the Wai’opae
pools is the only MLCD on the eastern end of the island. The site is southeast
of Hilo , near the town of Kapoho , tucked behind a few coastal
residences.
At Wai’opae the dark lava is spread in a wide flat bench
that creates a broad area of pools between emergent rocks. Some of the pools
are shallow and might be properly considered “tide pools”, but others are
deeper and create permanent subtidal habitat. Partly isolated from each other,
each pool is a small reef ecosystem.
Purple ember parrotfish, Scarus rubroviolaceus followed by an endemic saddle wrasse, Thalassoma duperrey among convict tangs. |
Closeup of coral polyps. |
Later I spent a little time in a round pool not wider than 5
or so few meters across, with black basalt enclosing a cozy aquarium. One side
of the pool was shallow, the other deep, but each with a number of brown plate
corals. The colonies of this species form rounded shelves against the rocks
like shelf fungi that grow on trees or fallen logs in a temperate forest.
The last pool I explored was the largest and had the most obvious
active connection to the ocean, indicated by a strong current present at the
southeastern end. I was already cold at this point in the afternoon, but I probably
ended up staying another hour in this pool. The axis of the pool was like a
shallow V-shaped valley, along which I swam back and forth several times. Fish
abundance in the pool was remarkable, and included wrasses, butterflyfish,
large purple and greenish parrotfish, and a dense school of striped convict
fish accompanied by several large black colored fish that swam with their
smaller associates. Blue needle fish were common in the surface water, creating
a ring around me, but keeping some distance.
Unidentified blenny perched in coral in a shallow pool. |
The pools I observed did not have continuous coral cover. In
fact, at some had just a few percent cover. Rather, corals appeared as discreet
colonies, with bedrock, volcanic rubble, or fuzzy algal turfs occupying the
rest of the space. They seemed absent from the shallowest areas, perhaps
because these are exposed a low tides. Lobe (Porites sp.), lace, and plate corals were common. In the pools I
found few species of larger macroalgae, but notable exceptions were a single
siphonous green alga (?Caulerpa sp.)
shaped not unlike an immature bunch of green grapes, and dichotomously branched
thin blades of an attractive red foliose alga. Larger invertebrates included
beautiful slate pencil urchins and two species of holothuroideans (sea
cucumbers).
A school of convict fish. |
Green siphonous macroalga, perhaps Caulerpa sp. |
Plate coral. |
Needlefishes swimming near the water surface. |
Hawaiian whitespotted toby, Canthigaster jactator. |
References
Hoover JP. 2014. Hawai’i ’s
Fishes. A Guide for Snorkelers and Divers. 2nd ed. Mutual
Publishing, Honolulu .
Krupp D. 2010. Hawaiian Coral Index Page: http://krupp.wcc.hawaii.edu/BIOL200/hawcoral/corindex.htm
Mahaney C, Witte A. 1993. Hawaiian Reef Fish. Blue Kirio
Publishing.
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