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Home , Kure Atoll, Montipora dilatata

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0 100 200 400 km 24. Hawaiian Archipelago

Level II seafloor geomorphological regions include: 24.1 Main Hawaiian , Reefs and Banks 24.2 Northwestern , Banks and 24.3 Hawaiian Islands Abyssal Plain

Level III coastal regions include: 24.1.1 Main Hawaiian Islands Coastal 24.2.1 Northwestern Hawaiian Coastal

Regional Overview and water quality in most areas is good (Friedlander et al. 2005). The Hawaiian Archipelago, one of the most geographically isolated The Hawaiian Archipelago stretches 2,450 km from the Big island systems in the world, is composed of eight main volcanic of northwest to Kure . oceanic islands, 124 smaller islands, , banks, and numerous seamounts. Due to this isolation, the reef fauna of the Archipelago Physical and Oceanographic Setting are less diverse than other reefs, especially those elsewhere in the The Hawaiian Archipelago consists of a string of volcanic Indo-West Pacific Ocean. This relatively low faunal diversity, how- islands formed by the northwest movement of the Pacific tec- ever, contrasts with unusually high endemism among the reef tonic plate over the stationary Hawaiian “hot-spot.” The eight species. In addition, the uninhabited Northwest Hawaiian Islands Main Hawaiian Islands in the southwest range in age from one are some of the most pristine reef systems worldwide. They to seven million years and are characterized by high volcanic are home to the endangered , some of the mountains and narrow fringing reefs. The older Northwestern largest and most important colonies in the world, and Hawaiian Islands have undergone submergence with only North America’s largest nesting ground for the green sea turtle. Necker, and still containing exposed The region is also a major breeding, calving and nursery area for volcanic material. The rest of the chain is composed of coral the . On the inhabited Main Hawaiian Islands, atolls, small sand islands and submerged banks. The chain many watersheds and nearshore areas have been significantly continues as the submerged Emperor Seamounts northwest of modified. Their nearshore fish stocks are thought to have declined Kure Atoll, the northernmost atoll in the world. The northern 80 percent in the last century, and because of their high ende- extent of the North Equatorial Current is the major oceanic mism, invasive species are of particular concern. Despite impacts current affecting the islands, branching along the Hawaiian from ocean outfalls, urban growth and coastal development, coral ridge into a North Hawaiian Ridge Current and gyres in the lee ecosystems in these islands range from fair to excellent condition of the islands.

139 Biological Setting Fact Sheet The isolation of the Hawaiian Islands has resulted in unusually high Rationale: isolated oceanic island archipelago in the North-Central Pacific with a high degree of endemism endemism among the reef fauna. Over 25 percent of Hawaiian reef Surface: 2,479,560 km2 are endemic to the region. In addition, although the clear Sea surface temperature: 24°C (winter), 23°C (summer) and 27°C () oceanic waters are low in primary productivity, they do provide Major currents and gyres: North Equatorial Current, Kuroshiro Current the environmental conditions needed for rather rich nearshore Depth: Main Hawaiian Islands shelf (roughly 0–200 m): 2%; Northwestern Hawaiian Islands, ecosystems. There are approximately 60 species of stony Banks and Seamounts (roughly 0–200 m): 4%; slope and abyssal plain (roughly 200+ m): 94% , more than 100 sponge species, 1071 marine mollusks species, Substrate type: volcanic basalt rock with carbonate reefs 884 crustacean species, and 557 species of reef and shore fishes Major community types and subtypes: fringing coral reefs, atolls, coral banks, seamounts, in the Archipelago. The Hawaiian Islands Region is also a major and open-ocean pelagic systems breeding, calving and nursery area for the humpback whale. Productivity: Low (<150 g C/m2/yr). Endemics: Levels of endemism in the coral reef fish, invertebrate and algal biota in Hawaii are among the highest in the Pacific. Around 25 percent of nearshore fishes and stony corals are endemic. The uninhabited Northwestern Hawaiian Islands include habitats Hawaiian monk seal is the only endemic marine mammal. and species absent in the Main Hawaiian Islands. Because of Species at risk: Hawaiian monk seal; Hawaiian dark-rumped petrel; band-rumped storm-petrel; Newell’s their isolation and the limited fishing effort upon them, average shearwater; short-tailed albatross; green, hawksbill and leatherback sea turtles; humpback whale; fish biomass is more than 260 percent greater than in the Main Hawaiian goby; the inarticulated brachiopod and a rare endemic Hawaiian rice coral, dilatata Hawaiian Islands (Friedlander and DeMartini 2002). Apex preda- Important invasive and introduced species: Numerous nonindigenous marine invasive species have tors such as jacks and sharks predominate—composing 54 per- been identified in the Hawaiian Islands, including 287 invertebrates, 20 algae, and 20 fishes. Invasive cent of biomass in the Northwest compared to only 3 percent in marine algae (Gracilaria salicornia, Hypnea musciformis) are causing significant economic damage, and the snowflake coral is threatening black corals harvested for jewelry. Mangroves do not occur naturally the Main Hawaiian Islands. Over 90 percent of the threatened in Hawaii but introduced species, the red and oriental mangroves, have become invasive. Several green sea turtles in Hawaii were born at , introduced marine fish species have become established. found in the Northwestern Hawaiian Islands. These islands are Key habitat: coral reefs also home to the major remaining breeding populations of the Human activities and impacts: tourism, coastal development, coastal recreation, recreational and endangered Hawaiian monk seal. The deepwater Southeast Han- commercial fisheries, shipping and military operations cock had a unique and productive fish fauna that was overfished in the early 1970s and has yet to recover.

Mother humpback whale escorting her calf in the Pacific Ocean. Photo: Doug Perrine/DRK PHOTO

140photo creditMarine Ecoregions of North America The Hawaiian monk seal keeps cool on hot, windless days by lying on damp sand. Photo: Frans Lanting/Minden Pictures

Human Activities and Impacts 2005). Because of the high endemism of the islands, there are The Main Hawaiian Islands support a population of 1.2 million special concerns about the introduction of invasive alien species. people, over 70 percent of which reside on the island of Oahu. The unique patch reef habitats of the Archipelago’s largest pro- Hawaii’s nearshore reefs annually contribute nearly $1 billion in tected embayment, Kaneohe Bay, have been overgrown by two gross revenues to the state’s economy. In addition to the resident introduced marine algae species. Moreover, the region’s near- population, nearly seven million tourists visit the islands each shore fishery stocks are thought to have declined 80 percent in year, making tourism the largest industry, much of it dependent the 1900s. The commercially most important fishery species upon the marine ecosystems. Anthropogenic stresses of greatest are pelagic tunas, but the reefs provide diverse, culturally and concern on the region’s reefs are coastal development and runoff, recreationally important fisheries. The Northwestern Hawaiian pollution, recreational overuse, damage from ship groundings, Islands are mostly uninhabited and fishing and other resource alien species, overfishing, damaging fishing practices, and over- extraction is currently limited to a small bottomfish fishery. Here, harvesting of ornamental reef species. Many watersheds and the greatest anthropogenic impact is from derelict fishing gear, nearshore areas in the Main Hawaiian Islands have been signifi- mostly discarded trawl nets. These islands, atolls and banks are cantly modified. Approximately 57 percent of Hawaii’s estuarine protected in the Northwestern Hawaiian Islands Coral Reef Eco- area is impaired by some form of pollution or habitat degradation, system Reserve, the Hawaiian and Pacific Isles Wildlife Refuge as whereas only 2 percent of its coastal shoreline is impaired (EPA well as in the National Wildlife Refuge.

Hawaiian Archipelago 141 Greater amberjack corral a school of bigeye scad. Photo: Doug Perrine/DRK Photo

142 Marine Ecoregions of North America Region Title 143