Artifical Upwelling Aquaculture in Southeast Alaska

Abstract

Coastal oceanic upwelling of deep, nutrient-rich waters to the surface has long been recognized as a natural phenomenon associated with levels of biological production which are orders of magnitude higher than values for the open ocean. Some current research suggests that by artificially upwelling seawater, these same high levels of biological production are possible. In 1973 the concept of artificial upwelling was applied to a small bay in southeastern Alaska, and rough biological and engineering estimates were made which revealed the possibility that this aquaculture scheme might be economically feasible. On this basis, the Institute of Marine Science at the University of Alaska developed a research program to evaluate artificial upwelling on a small scale prototype system in Seward, Alaska. Deep water and surface water were pumped into separate earthen ponds where phytoplankton abundance, diversity and productivity were measured. Concomitant with these studies, oceanographic surveys were made of nine candidate upwelling sites in southeastern Alaska. In January of 1975 a study was conducted to assess the economic feasibility of conducting artificial upwelling aquaculture using tidal energy at one of these nine selected sites. The study began with development of primary and secondary biological production estimates based on available seawater nutrients. Twelve candidate aquaculture species were evaluated and four selected for more detailed study. Pink salmon (Onchorhynchus gorbuscha) was chosen as the best species for culture using both biological and economic criteria. Production estimates were made based on an optimum cost/benefit relationship between pipe costs to deliver seawater of varying quantity and nutrient quality, and the resultant biological productivity. An economic evaluation of this system is presented. Alternate schemes were also investigated for adding nutrients to an embayment (fish-processing wastes), and for generating power (wind energy) to create the upwelling.