Page 224 - French Polynesia

tanding in the middle of one of the 241 islets that make up This loss of zooplankton biomass enriches the surrounding ocean
S Rangiroa, one can look to one side and see the vast expanse of
the Pacific Ocean, then turn to face the other direction and look
upon the lagoon whose area is nearly three hundred times that of
the total land mass. The lagoon is so large you cannot see across it surgeonfishes, jacks, butterfly fishes, parrotfishes, squirrelfishes,
to the islets on the far side.
T he atoll of Rangiroa is composed of a ring of 241 small islets,
or motu, separated by 150 hoa, which are channels of varying
width and depth that connect the lagoon to the sea. The windward
rim of the atoll is composed of relatively narrow (350-600 m wide)
motu. These are Rangiroa’s largest motu and house the main resi-
dential and commercial locations, the towns of Avatoru and Tiputa.
The southern rim is widest (800-1200 m) with smaller motus sepa-
rated by multiple hoa. The western leeward rim is similar to the
northern rim with an average width of 500 m and slightly smaller
motu with a higher degree of separation. The western rim is also
most exposed to tropical storms and cyclones.
R angiroa’s lagoon is continually flushed by the tides allowing
for a large exchange of water each day. Since there is so much
exchange with the ocean, there is an estimated loss of 4.3 tons
of biomass per tide (about ten tons per day for the two passes).
waters and contributes to high fish population in the passes. The
lagoon can be divided into three separate sections: the northern
fringe, the southern fringe, and the western fringe, in addition
to the lagoon floor. Coral pinnacles can be found throughout the
lagoon. The biology is abundant and diverse. Common fish include
and wrasses. The lagoon floor around the pinnacles is normally at
a depth of 20-25m and is very uniform.
T he flora and fauna inside the lagoon is generally very diversi-
fied. There are 90 families (about 800 species) of fish and 33
families of molluscs. The fish community of the coral reef contains
migrant species as well as species that live on the reef after their
post-larval stage of life. Inside the lagoon, fish aggregate around
the corals and the inner slope of the lagoon. There is a different
dynamic at the inner reef flat, where it connects with the hoa. This
area is a nursery for many fishes, but mainly damselfish, surgeon-
fish, and parrotfish. Within the pass, there is a community of reef
fish composed of damselfish, butterflyfish, wrasses, surgeonfishes,
and lemon sharks and grey reef sharks and also many migrant spe-
cies of fish.