Marine Resources Assessment for the Marianas Operating ... - SPREP

AUGUST 2005 FINAL REPORT
seagrass cover decreased with increasing distance from shore. Meanwhile, the diversity of corals,
macroinvertebrates, and fish were directly related to the distance from shore. Corals found along the
inner reef flat include Porites australiensis, Porites lutea, and Leptastrea purpurea. The coral along the
outer reef flat is more diverse than the inner reef flat and includes the species Pocillopora damicornis,
Acropora valida, Acropora abrotanoides, Pavona venosa, and a new record for Guam, Pavona bipartita.
The reef flat between Neye Island and the main island is swept by strong currents and is less subject to
siltation. There is a high biodiversity of marine fauna at Neye Island with the coral cover and diversity high
on this particular reef flat. Coral cover is dominated by large Porites microatolls and eleven Acropora
species. There is low algal cover and high coralline algae cover, and 34 species of echinoderms have
been identified.
2.7.2.3 Coral Communities and Reefs of Tinian
Barrier reefs, fringing reefs, and a broad shelf area (1,000 m wide) are found off the Tinian Harbor
(Eldredge 1983; NCCOS/NOAA 2005; Figures 2-8a, 2-8b, and 2-8c). The largest amount of coral cover
is probably found along the outer edges of the reef (fore reef and terrace) (Starmer et al. 2002). Fringing
and fore reefs (less than 200 m wide) occur immediately next to the western shoreline of Tinian
(NCCOS/NOAA 2005). Corals are found on the fore reef and insular shelf seaward of the fore reef. On
the eastern side of the MRA study area, from Puntan Tahgong, the northeastern tip of the island, to north
of Unai Asiga, coralline algae populate the fringing and fore reefs, and the insular shelf seaward of the
fore reef. From Unai Asiga to south of Unai Masalok, coralline algae occupies the reef crest and corals
are found along the fore reef and a large portion of the seaward shelf.
From Unai Masalok to Puntan Masalok (the southern extremity of the study area on the eastern Tinian
coast), no fringing reefs are found and the shelf is composed of coralline algae. Furthermore, there are no
fringing reefs from Puntan Masalok to Puntan Carolinas (southernmost point of Tinian). Coralline algae
occupy the entire shelf from Puntan Masalok to an area north of Puntan Barangka where coral cover
begins to dominate (Figures 2-8a, 2-8b, and 2-8c). Fringing reefs reoccur past Puntan Carolinas
(NCCOS/NOAA 2005). An oval-shaped, offshore, submerged reef (3.5 km by 1 km) composed primarily
of coralline algae is located approximately 2.7 km southeast off the southern most point of Tinian
(NCCOS/NOAA 2005). NCCOS/NOAA (2005) determined that the overall coral cover around Tinian
ranged from 10 to 50%.
Coral cover ranges from 14 to 59% on coral reefs at Kammer Beach and Two Coral Head, respectively
(Quinn and Kojis 2003). Dominant coral species in terms of cover are Goniastrea retiformis at Kammer
Beach, and P. rus at Two Coral Head. Coral cover is much higher at Two Coral Head compared to
Kammer Beach due to fewer coral predator-resistant species (Quinn and Kojis 2003).
Unai Chulu, Unai Babui, and Unai Dangkolo are three beach areas and nearshore reefs within the MRA
study area that have been evaluated for amphibious training landing exercises (Marine Research
Consultants 1999). Unai Chulu and Unai Babui are located on the northwestern side of Tinian and Unai
Dangkolo on the east side of the island, north of Puntan Masalok. A narrow fringing reef composed of
coralline algae (50 to 90% cover) borders the carbonate sand beaches of Unai Chulu and Unai Babui
(NCCOS/NOAA 2005). Landward of the fringing reef is a reef flat in a water depth of 0.5 m (Marine
Research Consultants 1999). At Unai Chulu, within 20 m seaward of the shoreline, the reef flat substrate
includes sand, rubble, and outcrops of a fossil reef. Live cover in the inner reef flat is mostly composed of
turf algae. The few coral specimens of the genus Porites located in this area of the reef form circular, flattopped,
and lobate colonies. In the middle of the reef flat, echinoids have bioeroded the reef substrate,
and corals (small branching and encrusting colonies) are more abundant when compared to the inner reef
flat. The fringing reef is exposed to wave action, resulting in few coral colonies. Seaward of the fringing
reef, the reef front forms a spur-and-groove system (alternating channels and ridges that are
perpendicular to the fringing reef). Spurs are 1 to 2 m wide and the grooves are approximately 5 m wide.
Abundant coral cover was observed within the spurs. Seaward of the spur-and-groove system is a deep
reef front terrace (Marine Research Consultants 1999). The reef morphology off Unai Babui is similar to
that of Unai Chulu except that the spur-and-groove system was more developed at Unai Babui.
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