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Vol. XXXIX: Supplement THE FESTIVUS Page 3
therefore, is the first land mass to be intermittently
exposed to the North Equatorial Countercurrent from
the west which brings source elements including
planktotrophic larvae across the Barrier. The nearest
atoll Pukapuka, in the Tuamotu Archipelago, is 4,280
km to the southwest and the closest island is Ua Huka of
the Marquesas and is at a distance of 3,965 km.
Secondly, low habitat diversity of the atoll, which is
mainly prolific coral cover, makes suitable habitats for
these planktonic links from the west. Those source
elements from the east on the North Equatorial Current
encounter a lack of the coarse intertidal and subtidal
environments of the coastal diversity. Clipperton lacks
the rocky shores, mud and sand bottoms, mangroves, and
such food sources as marine algae and other plants that
are necessary to establish a hold and maintain viable
populations for many west American mainland (TEP)
taxa.
Physical Environment
Île Clipperton located at the nexus of the Panamic
Province (10/18'N and 109/13'W), is somewhat
characteristic of Pacific atolls having volcanic
foundations. Where the top of the highest peak of the
submarine Clipperton Ridge, described by Menard &
Fisher (1958), reaches the surface of the sea, an eggshaped
coral reef supports a narrow, low, uninterrupted
land strip of limestone debris with a single cavernous
mass of altered trachyte rising to approximately 20 m
(Clipperton rock) on the southeastern border.
Clipperton is a “near atoll,” since a true atoll has no
volcanic outcroppings. The small ring is 11.8 km in
circumference, with only 1.7 square km of exposed land
encircled by a healthy fringing coral reef (Figure 1). The
lagoon, which makes up 85% of the atoll, is surrounded
by a ribbon of land variable in width from 25 m to 320
m (pers. comm., John Munch, 2007). Beyond the wavewashed
outer ring of the atoll are reef-flats lined by
coral-sand beaches or cobble strands. From there, white
ridges of unconsolidated limestone fragments (coral bits)
reach a maximum elevation of four meters from where
the land mass slopes down and encloses the sizeable (7.2
km square) central lagoon.
The lagoon has sediment of fine organic debris and
hordes of minute biting isopods (Cirolana sp.) Poupin,
pers. comm, 2007). Clipperton has a landing strip built
in 1944 on the northwest side of the widest part of the
atoll. The strip consists of coral pieces that are stained
dark gray or black by microscopic algae and is not
recommended for use today.
The following eight habitats are represented at
Clipperton and environs:
(1) large deposits of storm-generated coral, with one
extensive volcanic outcropping, bordering an intolerably
low salinity lagoon (Figure 3),
Figure 3. Aerial view taken from the south of Clipperton Rock located
on the edge of the lagoon, 2005. Photo: C. Fresser.
(2) a shallow, often tidally exposed reef front with low
coral cover and abundant crustose coralline algae (Figure
4),
Figure 4. Tidally exposed reef front on west side of Clipperton, 2005.
Photo: C. Fresser.