post

Habitat and Ecosystem – US Pacific Remote Islands

Baker Island

Baker Island, which is part of the Phoenix Islands archipelago, is located 13 miles north of the equator at 0 degrees 13′ N and 176 degrees 38′ W and approximately 1,600 nm to the southwest of Honolulu (Figure 8). It is a coral-topped seamount surrounded by a narrow-fringing reef that drops steeply very close to the shore. The total amount of emergent land area of Baker Island is 1.4 square kilometers.

  • Coral Reefs
    Within the 10-fathom curve, the potential coral reef area of Baker Island is estimated at 5.2 km2. Surveys have found 82 species of stony corals, 13 genera of algae, and 247 species coral reef fishes at Baker Island. Although stressors such as climate change and coral bleaching, diseases, tropical storms, and marine debris remain, the coral reef ecosystem around Baker Island is healthy and productive. Reef fish populations are reported as being healthy and diverse.

  • Deep Reef Slope and other Pelagic Habitat
    Most of the submerged habitat is deep and relatively unexplored. Because of its position near the equator, Baker Island lies within the westward flowing South Equatorial Current. Baker Island also experiences an eastward flowing Equatorial Undercurrent that causes upwelling of nutrient and plankton rich waters on the west side of the island.


Howland Island

Howland Island, which is also part of Phoenix Islands archipelago, is located 48 miles north of the equator at 0 degree 48′ N and 176 degrees 38′ W, and 36 nm north of Baker Island. The island, which is the emergent top of a seamount, is fringed by a relatively flat coral reef that drops off sharply. Howland Island is approximately 1.5 miles long and 0.5 miles wide. The island is flat and supports some grasses and small shrubs. The total land area is 1.6 square kilometers.

  • Coral Reefs
    The potential coral reef area with the 10-fathom curve of Howland is estimated to be 3.0 square kilometers. At Howland Island, surveys found 91 species of corals, nine genera of algae, and 302 species coral reef fishes. Although stressors such as climate change, coral bleaching, diseases, tropical storms, and marine debris remain, the coral reef ecosystem around Howland Island appears healthy and productive.

  • Deep Reef Slope and other Pelagic Habitat
    Howland Island is a seamount surrounded by a narrow-fringing reef that drops steeply very close to the shore. To date, information about the habitat of Howland Island’s deep reef slope and the marine life it supports are unavailable. Because of its position slightly north of the equator, Howland Island lies within the margins of the eastward flowing North Equatorial Counter  Current and the margins of the westward flowing South Equatorial Current. Sea–surface temperatures of the EEZ around Howland Island are often near 30° C.

Jarvis Island

Jarvis Island, which is part of the Line Islands Archipelago, is located at 0 degrees 23′ S, 160 degrees 01′ W and approximately 1,300 miles south of Honolulu and 1,000 miles east of Baker Island (Figure 11). Jarvis Island is a relatively flat and low (15–20-ft beach rise) sandy coral island with a total land area of 4.5 square kilometers. It experiences a very dry climate.

  • Coral Reefs
    Jarvis Island is surrounded by a narrow-fringing reef, but a broad submerged reef terrace extends off the eastern shoreline, dominated by moosehorn and rose corals. Live corals cover about 50 percent of the reef terrace. The potential coral reef area with the 10-fathom curve is estimated at 3.0 square kilometers. At Jarvis Island, surveys reported 59 species of stony corals, 10 genera of algae, and 252 species of coral reef fishes. Despite stressors such as climate change, coral bleaching, diseases, tropical storms, and marine debris remain, the coral reef ecosystem around Jarvis Island appears healthy and productive.

  • Deep Reef Slope and Pelagic Habitat
    Jarvis Island is surrounded by a narrow-fringing reef that drops steeply very close to the shore. To date, detailed information about the habitat of Jarvis Island’s deep reef slope and the marine life it supports are unavailable. Due to its position below the equator, Jarvis Island lies within the South Equatorial Current, which runs in a westerly direction. Sea surface temperatures of the EEZ around Jarvis Island are often 28°– 30° C.19 Although depth of the mixed layer in the pelagic waters around Jarvis Island is seasonally variable, average mixed layer depth is around 80 meters.

Palymra Atoll

Palmyra Atoll is made up of approximately 26 islets surrounding three central lagoons. This low-lying coral atoll system is approximately 1,056 nm south of Honolulu and is located at 5 degrees 53′ N latitude and 162 degrees 05′ W longitude. Palmyra Atoll and Kingman Reef occur at the northern end of the Line Island archipelago,situated halfway between Hawaii and American Samoa. Palmyra Atoll is located in the Inter-tropical Convergence Zone (ITCZ), an area of high rainfall.

  • Coral Reefs
    Palmyra Atoll is surrounded by extensive reef flats on all sides. The potential coral reef area within the 10-fathom curve around Palmyra Atoll is estimated at 47.2 square kilometers. At Palmyra Atoll, the following numbers of coral reef associated organisms are reported to occur: 170 species of corals, 13 genera of algae, and 343 species of coral reef fishes. Palmyra Atoll is observed to have a higher diversity of corals, anemones, and fishes than other Pacific Remote Islands because it is located within the eastward flowing Equatorial Counter Current which flows from areas in the western Pacific with high levels of biodiversity.

  • Deep Reef Slope and Pelagic Habitat
    Information about the deep reef slope around Palmyra Atoll and the marine life it supports are unavailable. However, the area of deep reef slope is not believed to be extensive. Because of its relative proximity to the equator, Palmyra Atoll lies in the North Equatorial Counter Current, which flows in eastward direction. Sea–surface temperatures of the EEZ around Palmyra Atoll are often 27°–30° C.20 Although the depth of the mixed layer in the pelagic waters around Palmyra Atoll is seasonally variable, the average mixed layer depth is around 90 meters.

Kingman Reef

Kingman Reef, is located 33 nm northwest of Palmyra Atoll at 6 degrees 23′ N and 162 degrees 24′ W. It is comprised of a fringing reef opening onto a lagoon. Kingman Reef does not have any permanent emergent islets that support vegetation.

  • Coral Reefs
    The potential coral reef area within the 10 fm curved Kingman Reef is estimated at 20.9 km². At Kingman Reef, 181 species of hard corals, 15 genera of algae, and 225 species of reef fishes are reported to occur (Brainard et al. 2005, USFWS 2012). These reefs support spectacular coral diversity an abundance of mushroom corals and anemones on lagoon reefs, and many varieties of table and staghorn corals flourishing on ocean-facing reefs. Kingman Reef also supports among the highest density of giant clams in the Pacific, including the northern range extension of one particularly rare species Tridacna squamosa. Giant clams continue to decline throughout their entire range due to overharvesting and several species are listed by IUCN as depleted or endangered; Kingman Reef serves as a critically important refuge for the continued existence of these clams. More than 225 fish species have been recorded, including sharks, rays, eels, groupers, jacks, goatfishes, butterflyfishes, damselfishes, mullets, wrasses, parrotfishes, surgeonfishes, and tuna.

  • Deep Reef Slope and Pelagic Habitat
    Information about the deep reef slope around Kingman Reef and the marine life it supports are unavailable. However, the area of deep reef slope is not believed to be extensive. Because of its relative proximity to the equator, Kingman Reef lies in the North Equatorial Countercurrent, which flows in a west to east direction. Sea–surface temperatures of the EEZ around Palmyra Atoll and Kingman Reef are often 27°–30° C.21. Although the depth of the mixed layer in the pelagic waters around Kingman Reef is seasonally variable, average mixed layer depth is around 80 meters.

Wake Island

Wake Island is an atoll located at 19° 18′ N latitude and 166° 35′ E longitude, and is the northernmost atoll of the Marshall Islands archipelago, located approximately 2,100 miles west of Hawaii. Boundaries of the Monument are shown in Figure 16. The atoll has a total land area of 6.5 square kilometers and is made up of three islets: Wake, Peale, and Wilkes. The islets support a rare grass species, Lepturus gasparricensis, in addition to widespread Pacific insular plants, and were home to the endemic Wake rail until it went extinct during World War II.

  • Coral Reefs
    The potential coral reef area within the 10-fathom depth around Wake atoll is estimated to cover 22.9 square kilometers. Sharks, particularly the gray reef, are reportedly abundant. The giant clam (T. maxima) is reported to be abundant in the lagoon. According to the USFWS (2010), approximately 100 species of corals have been reported at Wake Atoll, a number somewhat lower than found at larger and less isolated neighboring atolls to the south. Fish populations are abundant with at least 323 species recorded, including large populations of the Napoleon wrasse, sharks of several species, and large schools of the bumphead parrotfish, all of which are globally depleted.

  • Deep Reef Slope and Pelagic Habitats
    Information about the deep reef slope around Wake Atoll and the marine life it supports are unavailable. However, the area of deep reef slope is not believed to be extensive because the outer reef slope descends sharply to great depth. Sea–surface temperatures of the EEZ around Wake Atoll are often between 27°–30° C.22 The depth of the mixed layer in the pelagic waters around Wake Atoll is seasonally variable, with the average mixed layer depth at around 80 meters.

Johnston Atoll

Johnston Island is located at 16° 44′ N latitude and 169° 31′ W longitude and is approximately 720 nm southwest of Honolulu. French Frigate Shoals in the NWHI is the nearest land mass (~ 450 nm to the northwest). Boundaries of the Monument are shown in Figure 18. Due to its proximity to the Hawaiian Islands, there is believed to be genetic and larval connectivity between the marine flora and fauna of Johnston Atoll and the Hawaiian Islands. Johnston Atoll is an egg-shaped coral reef and lagoon complex situated on a relatively flat, shallow platform approximately 21 miles in circumference (205 square kilometers). The atoll includes four small emergent islands totaling 2.8 square kilometers. Johnston Atoll, the largest and main island, is natural in origin, but has been enlarged by dredge and fill operations. Sand Island is a naturally formed island (eastern portion) connected by a narrow, man-made causeway to a dredged coral island on its western portion. The remaining two islands, North Island and East Island, are completely man-made from dredged coral.

  • Coral Reefs
    The potential coral reef area within the 10-fathom curve of Johnston Atoll is estimated at 150 square kilometers. Johnston Atoll, which has 45 Scleractinian and hydrozoan corals present, has fewer coral species than are found in the Hawaiian Islands. The reef is composed of alternating sand/loose coral and live coral, with the most dominant coral species present being table coral (Acropora). The coral Montipora is also widely found. Approximately 300 species of fish have been recorded in the nearshore waters and reefs of Johnston Atoll. This number is smaller than that of other islands in the Central Pacific, and is likely due to Johnston Atoll’s small size and remote location. One species of angelfish, Centropyge nahackyi, is endemic.

  • Deep Reef Slope and Pelagic Habitats
    Information on the deep reef slope around Johnston Atoll and the marine life it supports limited. However, the area of deep reef slope is not believed to be extensive. Sea surface temperatures of the EEZ around Johnston Atoll are often 27°–30° C.23. Although the depth of the mixed layer in the pelagic waters around Johnston Atoll is seasonally variable, average mixed layer depth is around 80 meters.