Hawaii FEP - Western Pacific Fishery Council

Figure 4: Temperature and Salinity Profile of the OceanSources: http://www.windows.ucar.edu/tour/link=/earth/Water/temp.html&edu=high (accessed July 2005http://www.windows.ucar.edu/tour/link=/earth/Water/salinity_depth.html&edu=high (accessed July2005).3.2.5 Ocean ZonesThe ocean can be separated into the following five zones (see Figure 5) relative to the amount ofsunlight that penetrates through seawater: (a) epipelagic, (b) mesopelagic, (c) bathypelagic, (d)abyssopelagic, and (e) hadalpelagic. Sunlight is the principle factor of primary production(phytoplankton) in marine ecosystems, and because sunlight diminishes with ocean depth, theamount of sunlight penetrating seawater and its affect on the occurrence and distribution ofmarine organisms are important. The epipelagic zone extends to nearly 200 meters and is thenear extent of visible light in the ocean. The mesopelagic zone occurs between 200 meters and1,000 meters and is sometimes referred to as the “twilight zone.” Although the light thatpenetrates to the mesopelagic zone is extremely faint, this zone is home to wide variety ofmarine species. The bathypelagic zone occurs from 1,000 feet to 4,000 meters, and the onlyvisible light seen is the product of marine organisms producing their own light, which is called“bioluminescence.” The next zone is the abyssopelagic zone (4,000 m–6,000 m), where there isextreme pressure and the water temperature is near freezing. This zone does not provide habitatfor very many creatures except small invertebrates such as squid and basket stars. The last zoneis the hadalpelagic (6,000 m and below) and occurs in trenches and canyons. Surprisingly,marine life such as tubeworms and starfish are found is this zone, often near hydrothermal vents.39