1.9.1 The area contains several thousand square
miles of coral reefs made up of at least 57 species of hard coral
and 12 species of soft coral. Coral communities are fragile ecosystems.
They require a delicate balance across a range of environmental conditions
in order to be healthy and grow. The health of a coral ecosystem may
be threatened by changes to even one of those environmental conditions.
Corals derive a substantial portion of their nutrition from symbiotic
algae (called zooxanthellae) within their tissues. Because algae require
light for photosynthesis, clear and clean water conditions are necessary
for growth and well-being. The introduction of pollutants can be toxic
to the coral.
1.9.2 The physical structure of the reef is provided
by calcium carbonate, which forms the rock framework or reef “skeleton”.
This calcium carbonate is deposited at a rate of about one-centimetre
per year by the living coral animal (polyp). These polyps exist in
a thin layer at the surface of the reef rock. The coral reef system
of the NWHI has taken thousands of years to build and, if damaged,
regeneration of the reef may never occur. If optimal conditions for
regeneration exist, it would still take hundreds, and perhaps thousands
of years, for a damaged area of the reef to return to its previous
condition.
1.9.3 In the NWHI, transiting ships are a primary
anthropogenic threat to this fragile ecosystem because of ship groundings
and pollution from operational and accidental discharges. Secondary
and cumulative damage may occur when dislocated coral fragments caused
by groundings are tossed against healthy coral by wave action, currents,
and storms.
1.9.4 The isolation of the NWHI affords both protection
from and vulnerability to invasive species, which can be transferred
by ships. The islands’ ecosystems have evolved without the influence
of outside forces, demonstrated by the high level of native and endemic
species. To date, 11 non-native species have been identified in the
waters of the NWHI. Non-native species can displace native species
and seriously disrupt and imbalance the natural ecosystem.