Guam National Wildlife Refuge Comprehensive Conservation Plan

Analysis
Guam National Wildlife Refuge Comprehensive Conservation Plan
Goals and objectives were designed directly around the conservation targets. In developing
objectives, the team analyzed each conservation target to determine its key ecological attributesthose
aspects of the environment, such as ecological processes or patterns of biological structure
and composition-that are critical to sustain the long-term viability of the target. The team
developed “desired” conditions that were based partly on scientific literature review and partly on
team professional judgment. These desired condition levels for specific indicators were used to
help design objectives for each target, as presented in Chapter 2. The team listed and ranked
stresses and sources of stress (collectively “threats”) for most of the targets. A stress is the
impairment or degradation of a key ecological attribute for a conservation target.
5.3 Habitats, Plants, and Wildlife
The Ritidian Unit is made up of a diversity of different habitat types ranging from fringing reef
platforms, including marine species and coral, to beach strand, to coastal back strand, to limestone
forest, and caves.
Habitat Types, Plants, and Marine Wildlife
Submerged lands and waters comprise over 68 percent of the Ritidian Unit, stretching from the
coastline to the 100-foot depth offshore (Federal Register 2007a). This marine ecosystem includes
pelagic waters, fringing reefs, reef channels, seagrass beds, limestone intertidal benches, and
submarine cliffs (USFWS 1994c). Compared to the remainder of Guam, the marine resources and
coral reef habitats at the Refuge are relatively pristine (Donaldson and Rongo 2006). The Ritidian
Unit has a higher species diversity and coverage than much of Guam, as well as coral assemblages
of Acropora prolifera not found elsewhere on the island (Kurashina et al. 2000).
The condition of the marine resources may be attributed to the fewer number of people and lack of
rivers, as well as limited development and access in the northern region compared to the rest of
the island (WPRFMC 2005). The marine waters off northern Guam are exceptionally clean
because of minimal terrestrial sedimentation from the limestone plateau. Wave surge also
enhances water quality by flushing contaminants or debris and circulating nutrients. The
unpolluted water enhances the settlement and propagation of corals and algae
Coral Assemblages and Benthic Cover
The majority of the coral reef habitat is comprised of a 712 foot-wide fringing reef (Eldredge 1983,
Kurashina et al. 1990). Patches of aggregate reef occur in combination with coral, coralline algae,
or macroalgae. A spur and groove formation, which lies perpendicular to the shore, exists
seaward beyond the aggregate reef. An isolated, single coral patch reef can be found on the
north-west perimeter of the Refuge (Randall and Myers 1983, Burdick 2004).
The Ritidian Channel is the only cut through the reef for several miles in each direction. This
channel is located on the northern tip of Ritidian Point (Kurashina et al. 1990). Marine and coral
reef surveys conducted at the Ritidian Unit (e.g. Donaldson and Rongo 2006) have found a marked
distinction between habitat areas to the west of the Ritidian Channel (open to public use), an area
subject to greater wave energy, and areas east of the Ritidian Channel (closed to public use) which
Chapter 5. Refuge Biology and Habitat 5-3