Scientific Studies and History of the Ala Wai Canal, an Artificial Tropical Estuary in Honolulu

Fifteen studies of the Ala Wai Canal, O'ahu, Hawai'i, initially were spawned by two federally funded summer research programs designed to introduce high-school students from around the state of Hawai'i to the challenges, practicalities, and excitement of work in the natural sciences and engineering. This special issue reports on the end products of 10 of those studies. The canal is an artificial estuary created in the 1920s to drain coastal wetlands and borders the present tourist mecca of Waikiki. Today, it is polluted and hypereutrophic, and it receives high levels of nutrients that sustain levels of primary production that rival all but a few of the world's water bodies. Acting as a sediment trap for the combined drainage of the Manoa and Palolo Streams, the midportion of the canal contains two large sedimentary sills that restrict seawater exchange. This restricted flow and the high rain rate of organic matter result in severe oxygen depletion behind the sill. The canal's small reservoir size, variably oxygenated water column and sediments, single oceanic outlet, and receipt of natural freshwater drainage-within the confines of a rapidly developed major metropolitan area-combine to make it an excellent aquatic laboratory for the study of present and historical water exchange characteristics; phytoplankton, zooplankton, and benthic foraminifer behavior; biogeochemical responses of shallow, tropical water masses to hypereutrophication; and historical records of heavy metals, radionuclides, and other pollutants over the past 60 yr. We believe this special issue will attract the attention of a variety of scientists and academicians, as well as administrators and others interested in the environmental quality of Hawai'i