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

AUGUST 2005 FINAL REPORT
massive corals are largely of Porites. Coral cover on this reef front exceeds 80% consisting of faviid,
mussid, and poritid species (Leptoia phrygia, Goniastrea spp., Platygyra spp., Favia stelligera,
Lobophyllia hemprichii, and Porites spp.). Since this area contains slow growing coral heads that are
healthy and large, Amesbury et al. (2001) believe that this site withstood the pressures of predation by A.
planci and physical damage by storms. Crevices and caverns within the reef front create a favorable
habitat for sponges.
On the deep fore reef (9 to 18 m depth range), Amesbury et al. (2001) found 52 species of corals, a
species richness comparable to that found on the shallow fore reef. The coral community on the deep
fore reef is healthy and Porites-dominated. Two faviids rare on Guam, Favia helianthoides and Favia
maritima, are common along the deep fore reef. The soft corals Sinularia leptoclados, S. racemosa,
Lobophytum batarum, and Sarcophyton trocheliophorum are also common on the reef slope.
The back reef to the east and south of Double Reef supports branching, platy, and massive corals
including Acropora palifera, Acropora acuminata, P. rus, and Porites spp. (>2 m diameter). The soft coral
Asterospicularia randalli is common and very abundant in this region of the reef. Dead coral skeleton is
evidence of recent coral mortality having affected the back reef (Amesbury et al. 2001).
Ritidian Area—The MRA study area on the northern shore of Guam found between Tarague Cave and
the Tarague Channel (Ritidian area) is bordered by a nearshore narrow fringing reef made of coralline
algae (NCCOS/NOAA 2005; Figures 2-7a, 2-7b, and 2-7c). Landward of the fringing reef is a reef flat
primarily populated by macroalgae and an intertidal area colonized by seagrass. Seaward of the fringing
reef is a fore reef colonized by corals (10 to 50% cover) (NCCOS/NOAA 2005).
Orote Peninsula ERA—The Orote Peninsula ERA is located at the eastern end of Guam (Figures 1-1, 2-
7a, 2-7b, and 2-7c). As per Paulay et al. (2001), the following is a description of the coral and reef
communities found within the Orote peninsula. The Orote peninsula ERA is characterized by steep karstic
cliffs plunging abruptly onto a steep fore reef macrohabitat. Erosional processes and seismic events
caused large boulders to become detached from the karstic cliffs and land on the fore reef pavement.
There are strong currents along this area of the Guam coastline. Paulay et al. (2001) identified four
macrohabitats in this area: the Orote Point fringing reef, the Orote cliff reef, the Orote reef slope, and the
Orote dropoff.
The Orote Point fringing reef is located between the tip of the Orote peninsula and Orote Island. There
are two fringing reefs, one facing the southwestern tip of Apra Harbor and the other facing the southern
coast of the Orote peninsula. Corals that populate these fringing reefs are more Apra Harbor-like to the
north end of the reef and more Orote-like toward the southern end. The northern and middle parts of the
reef support high coral cover composed mainly of P. rus and P. cylindrica. Corals on the southern end
consist of Acropora valida, A. digitifera, and Galaxea fascicularis.
The Orote cliff reef was surveyed on the southern face of Orote peninsula. The fore reef slope of the cliff
reef is the continuation of the cliff face. At sea level, wave action has undercut notches and caverns into
the cliff, and at the base, there are accumulations of large boulders originating from the cliff. The cliff reef
substrate is highly bioeroded by boring echinoids (Echinometra), and there is a low diversity of corals in
this macrohabitat comprised primarily of Montipora, Pocillopora, and Millepora platyphylla. The sessile
benthos here is primarily composed of sponges. The abundance of sponges at this location is
substantially higher than many other places on Guam (Paulay personal communication).
The Orote Point reef slope (from Spanish Steps to western tip of Orote Island) is characterized by higher
coral diversity and higher fish biomass and diversity compared to most locations of Guam. For the
majority, the western tip of Orote Island can be considered a high energy environment. The eastern end
of the Orote Point reef slope abuts the Apra Harbor southern reef slope. West of the P. rus dominated
Apra Harbor, the Orote Point reef slope is more diverse and includes 19 species of corals. The reef slope
is heavily bioeroded (“deeply honeycombed”) and supports a diverse cryptofauna (including shrimp,
lobster, and crab) and abundant crinoids. Sharks, tuna, groupers, snappers, parrotfish, and emperors are
abundant at this location. In total, 53 species of fishes were recorded on the Orote Point reef slope. This
2-35