Mumby, P. J., Edwards, A. J., Arias-Gonzalez, J. E., Lindeman,
K. C., Blackwell, P. G., et al., 2004. Mangroves enhance the biomass of coral reef fish communities in the Caribbean. Nature,
427, 533–536.
Robertson, A. I., Alongi, D. M., and Boto, K. G., 1992. Food chains
and carbon fluxes, pp. 293–326. In Robertson, A.I., and Alongi,
D. M. (eds.), Tropical Mangrove Ecosystems, Washington, DC:
Coastal and Estuarine Studies Series, American Geophysical
Union, 329 pp.
Saenger, P., 2002. Mangrove Ecology, Silviculture and Conservation. Dordrecht: Kluwer Academic Publishers, 360 pp.
Spalding, M. D., Blasco, F., and Field, C. D. (eds.), 1997. World
Mangrove Atlas. Okinawa, Japan: International Society for Mangrove Ecosystems, 178 pp.
Tomlinson, P. B., 1986. The Botany of Mangroves. Cambridge:
Cambridge University Press, 413 pp.
Cross-references
Coral Cay Classification and Evolution
Low Wooded Islands
Mangroves
MARIANA ISLANDS, CORAL REEF GEOLOGY
Bernhard Riegl
Nova Southeastern University, Dania, FL, USA
Definition
The Mariana Islands are an arch of volcanic islands
stretching $500 miles from Guam to Uracas. Coral reefs
occur only in the volcanically inactive southern part
(Figure 1). Most of the human population lives on Guam
and Saipan and the political organization is split into the
U.S. Territory of Guam and the Commonwealth of the
Northern Mariana Islands.
The Marianas are part of the Izu-Bonin-Mariana (IBM)
arc system, stretching $2,800 km from Japan to south of
Guam. Modern reef building occurs exclusively in the
southern Marianas from Guam to Farallon de Medinilla
(Figure 1). Corals also occur in the northern arc but no
extensive framework production is reported, likely due
to a combination of high latitude and relative tectonic
instability. In the southern Marianas, temperatures are
tropical and ideal for reef-building organisms. Mean
annual air temperatures in Guam are 27
C, with $6
C variations between daily maxima and minima (Figure 2).
Relative humidity ranges 65–80% by day and 85–100%
by night (Mink and Vacher, 1997). Long-term annual
SST means vary between 28
C and 29
C. Tinian has
a mean tidal range of 45 cm and a spring tide range of
65 cm (Doan et al., 1960). Rainfall averages at Guam
85–115 in./year (Gingerich, 2003), at Tinian 43–97
in./year (Gingerich, 2002), and at Saipan 34–145 in./year
(Carruth, 2003). Wet and dry seasons are well developed
with $70% of total annual rainfall from July–December.
Seasonally pulsed rainfall in combination with steep
slopes, lateritic soils and deforestation led to runoff and
sedimentation problems on coral reefs (Wolanski et al.,
2003, 2004). The Marianas are influenced by the ENSO,
and coral records indicate an $0.75
C warming over the
past two centuries (Asami et al., 2005).
Holocene coral reefs in the southern Marianas
Two major Holocene reef-building episodes are known in
the southern Marianas. An early Holocene episode is
found in the Merizo (Guam), Milencatan (Rota) and
Tanapag (Saipan) Limestones, and the modern reef
(Siegrist et al., 1984b). Present-day coral frameworks are
mostly narrow and of the fringing type, their morphology
often clearly influenced by underlying morphology. In
Guam, many small bays are reef-fringed with rivers entering. In such cases, reefs are discontinuous at the
rivermouths and increase in thickness and coral cover away
from the rivers (Wolanski et al., 2003, 2004). Two notable
exemptions to the general pattern of narrow fringing reefs
hugging the islands’ shorelines exist in Cocos Lagoon
(Guam) and Tanapag Lagoon (Saipan), where barrier reefs
occur. Development of these lagoons is structurally controlled. Additionally, fringing reefs are developed along
the shorelines inside the lagoons (Emery, 1962; Randall,
1979). Also Tinian had a small section of barrier reef that
was filled and dredged into a port during World War II.
Four distinct coral habitats (Figure 3), of which only
one involves an actively growing reef, occur in the
Marianas (Randall, 1985):
– Habitat I consists of in situ reef frameworks, with welldeveloped buttress and channel system (Pagan,
Anatahan, Saipan, Aguijan, Rota, Guam).
– Habitat II occurs among volcanic boulders, in situ
frameworks are absent or only thin veneers (Pagan,
Guguan, Anatahan).
– Habitat III exists primarily between old limestone
rocks and boulders, in situ frameworks are absent
(Aguijan).
– Habitat IV occurs along limestone slopes with few boulders, in situ frameworks are absent (Saipan, Rota, Guam).
Underlying, and determining the position of late Holocene
reef growth are the early Holocene Merizo Limestone
(also called “2 m limestone”) on Guam, the Milencatan
Limestone on Rota, and the Tanapag Limestone on
Saipan. These limestones represent the first phase of reef
building in the early Holocene from the post-Wisconsin
transgression through the mid-Holocene highstand at
$4,000 year B.P. (before present). They contain beautifully preserved, emergent reef facies in the low supratidal
to shallow subtidal and are exposed to about 2–4 m.
The emergence of these early Holocene reefs is likely
due to tectonic factors (Kayanne et al., 1993; Siegrist
and Randall, 1992). Thickness on Guam varies between
5 and 1 m (Siegrist and Randall, 1992). The limestones
are coral-dominated and contain virtually all genera that
are found in the modern reefs. Growth history on Rota is
as follows (Bell and Siegrist, 1988): at 5,500 year B.P.
sea level flooded an older, bioclastic facies of the already
MARIANA ISLANDS, CORAL REEF GEOLOGY
663
K. C., Blackwell, P. G., et al., 2004. Mangroves enhance the biomass of coral reef fish communities in the Caribbean. Nature,
427, 533–536.
Robertson, A. I., Alongi, D. M., and Boto, K. G., 1992. Food chains
and carbon fluxes, pp. 293–326. In Robertson, A.I., and Alongi,
D. M. (eds.), Tropical Mangrove Ecosystems, Washington, DC:
Coastal and Estuarine Studies Series, American Geophysical
Union, 329 pp.
Saenger, P., 2002. Mangrove Ecology, Silviculture and Conservation. Dordrecht: Kluwer Academic Publishers, 360 pp.
Spalding, M. D., Blasco, F., and Field, C. D. (eds.), 1997. World
Mangrove Atlas. Okinawa, Japan: International Society for Mangrove Ecosystems, 178 pp.
Tomlinson, P. B., 1986. The Botany of Mangroves. Cambridge:
Cambridge University Press, 413 pp.
Cross-references
Coral Cay Classification and Evolution
Low Wooded Islands
Mangroves
MARIANA ISLANDS, CORAL REEF GEOLOGY
Bernhard Riegl
Nova Southeastern University, Dania, FL, USA
Definition
The Mariana Islands are an arch of volcanic islands
stretching $500 miles from Guam to Uracas. Coral reefs
occur only in the volcanically inactive southern part
(Figure 1). Most of the human population lives on Guam
and Saipan and the political organization is split into the
U.S. Territory of Guam and the Commonwealth of the
Northern Mariana Islands.
The Marianas are part of the Izu-Bonin-Mariana (IBM)
arc system, stretching $2,800 km from Japan to south of
Guam. Modern reef building occurs exclusively in the
southern Marianas from Guam to Farallon de Medinilla
(Figure 1). Corals also occur in the northern arc but no
extensive framework production is reported, likely due
to a combination of high latitude and relative tectonic
instability. In the southern Marianas, temperatures are
tropical and ideal for reef-building organisms. Mean
annual air temperatures in Guam are 27
C, with $6
C variations between daily maxima and minima (Figure 2).
Relative humidity ranges 65–80% by day and 85–100%
by night (Mink and Vacher, 1997). Long-term annual
SST means vary between 28
C and 29
C. Tinian has
a mean tidal range of 45 cm and a spring tide range of
65 cm (Doan et al., 1960). Rainfall averages at Guam
85–115 in./year (Gingerich, 2003), at Tinian 43–97
in./year (Gingerich, 2002), and at Saipan 34–145 in./year
(Carruth, 2003). Wet and dry seasons are well developed
with $70% of total annual rainfall from July–December.
Seasonally pulsed rainfall in combination with steep
slopes, lateritic soils and deforestation led to runoff and
sedimentation problems on coral reefs (Wolanski et al.,
2003, 2004). The Marianas are influenced by the ENSO,
and coral records indicate an $0.75
C warming over the
past two centuries (Asami et al., 2005).
Holocene coral reefs in the southern Marianas
Two major Holocene reef-building episodes are known in
the southern Marianas. An early Holocene episode is
found in the Merizo (Guam), Milencatan (Rota) and
Tanapag (Saipan) Limestones, and the modern reef
(Siegrist et al., 1984b). Present-day coral frameworks are
mostly narrow and of the fringing type, their morphology
often clearly influenced by underlying morphology. In
Guam, many small bays are reef-fringed with rivers entering. In such cases, reefs are discontinuous at the
rivermouths and increase in thickness and coral cover away
from the rivers (Wolanski et al., 2003, 2004). Two notable
exemptions to the general pattern of narrow fringing reefs
hugging the islands’ shorelines exist in Cocos Lagoon
(Guam) and Tanapag Lagoon (Saipan), where barrier reefs
occur. Development of these lagoons is structurally controlled. Additionally, fringing reefs are developed along
the shorelines inside the lagoons (Emery, 1962; Randall,
1979). Also Tinian had a small section of barrier reef that
was filled and dredged into a port during World War II.
Four distinct coral habitats (Figure 3), of which only
one involves an actively growing reef, occur in the
Marianas (Randall, 1985):
– Habitat I consists of in situ reef frameworks, with welldeveloped buttress and channel system (Pagan,
Anatahan, Saipan, Aguijan, Rota, Guam).
– Habitat II occurs among volcanic boulders, in situ
frameworks are absent or only thin veneers (Pagan,
Guguan, Anatahan).
– Habitat III exists primarily between old limestone
rocks and boulders, in situ frameworks are absent
(Aguijan).
– Habitat IV occurs along limestone slopes with few boulders, in situ frameworks are absent (Saipan, Rota, Guam).
Underlying, and determining the position of late Holocene
reef growth are the early Holocene Merizo Limestone
(also called “2 m limestone”) on Guam, the Milencatan
Limestone on Rota, and the Tanapag Limestone on
Saipan. These limestones represent the first phase of reef
building in the early Holocene from the post-Wisconsin
transgression through the mid-Holocene highstand at
$4,000 year B.P. (before present). They contain beautifully preserved, emergent reef facies in the low supratidal
to shallow subtidal and are exposed to about 2–4 m.
The emergence of these early Holocene reefs is likely
due to tectonic factors (Kayanne et al., 1993; Siegrist
and Randall, 1992). Thickness on Guam varies between
5 and 1 m (Siegrist and Randall, 1992). The limestones
are coral-dominated and contain virtually all genera that
are found in the modern reefs. Growth history on Rota is
as follows (Bell and Siegrist, 1988): at 5,500 year B.P.
sea level flooded an older, bioclastic facies of the already
MARIANA ISLANDS, CORAL REEF GEOLOGY
663