PATTERNS OF REEF DEVELOPMENT
One-half
the shoreline of Guam is bordered by various types of fringing
reefs and reef-like platforms, one-fourth by erosional supratidal
bench platforms along limestone coasts (Fig.
1), and one-fourth by sea cliffs, mangrove swamps, and truncated
volcanic rock platforms. A triangular-shaped barrier reef
encloses the shallow Cocos Lagoon at the southwest tip of the
island (Fig. 4). A raised
barrier reef (Cabras Island) and a much modified and disturbed
barrier reef (Luminao Reef) and a coral bank (Calalan Bank) enclose
the deep lagoon of Apra Harbor. A large patch reef associated
with Anae Island lies offshore along the southwest coast and a
smaller one called Pugua Patch Reef (popularly, but incorrectly
called a double reef) lies offshore along the northwest coast.
The distribution of reef platforms around the island
is shown in Figure 488 on the
inside back cover.
One of
the most conspicuous aspects of the reefs around Guam, and of
coral reefs in general, is the presence of distinct physiographic
and biologic zones. Patterns of zonation arise and are maintained
primarily by the interaction of physical, chemical, and biological
processes—mainly those of accretion of reef deposits by corals,
calcareous algae, and other calcium carbonate metabolizers; erosion;
and sedimentation. Reef zones are most distinct in parallel
bands that follow the long axis of a fringing or barrier reef
platform (Text Fig. D). If
you were to swim from the shoreline of the wide fringing reef
at Tumon Bay in a seaward direction the zones most likely encountered
would be: 1) a narrow intertidal zone, 2) a reef flat divided
into an inner sub zone that retains a moat of water during low
spring tides and an outer subzone that exposes during such times,
3) a narrow wave-washed reef margin, 4) an irregular reef front
slope with channels and ridge-like buttresses (Figs.
2 and 3) that grades into
a flattened submarine terrace, and 5) a steeply dipping seaward
slope that extends downward past the lower limit of reef-building
corals (Text Figs. B and D).
Other reef zonation patterns are shown in vertical profiles
of the wide Achang Reef along the southern coast (Text
Fig. E and Fig. 2), a narrow
fringing reef along the southwest coast near Umatac Bay (Text
Fig. F), the Cocos barrier reef and lagoon system at the southwest
tip of the island (Text Fig. G
and Fig. 4), an embayment reef
at Fouha Bay (Text Fig. H),
the deep Manell Channel at the western end of Achang Reef (Text
Fig. I), the deep river channel that bisects the wide Ipan
Reef along the southeast coast (Text
Fig. J and Fig. 3), a truncated
basaltic platform at Facpi Point (Text
Fig. K), and a supratidal erosional bench cut into raised
limestone at Pati Point (Text Fig.
L and Fig. 1). Regardless
of the type of reef, limestone bench, volcanic platform, or sea
cliff present, most of their subtidal regions have a variety of
corals, algae, and other reef-associated organisms growing on
their surface.
CONSERVATION AND MANAGEMENT OF
CORAL REEF RESOURCES
Although
corals themselves are not directly consumed as food by humans,
their value as a natural resource is in no way reduced. Corals
provide a great variety of habitats, food, and breeding and spawning
grounds for a multitude of other reef-associated organisms, many
of which are directly or indirectly used for human consumption.
Traditionally the reefs of Guam have always been important
in providing food, especially protein, for its residents, and
to the present time continues to do so. As mentioned in
the introduction, coral reefs attract many tourists to Guam and
provide a wide variety of recreational activities to the young
and old alike. Even the white beach sands found along most
of the coastal areas of Guam are of reef origin. Fossil
coral reefs provide an abundant source of aggregates for construction
and cement products used by the building industry. Coral
reefs are of interest to science because of their high diversity
and productivity. Coral reefs also function as our island's
first line of protection against typhoon and tsunami waves.
