an environmental model for aquaculture in the deep ocean - Estimating the Fate of Waste Nutrients and Particulates  

The deep-sea is the largest habitat on earth. Over 60% of the planet is covered by water more than a mile deep and as such the open ocean has become a new frontier for aquaculture expansion. As the aquaculture industry looks to expand seaward to exposed open-ocean sites, there is a significant need to understand the potential for aquaculture waste products to disperse through and affect the water column and benthic communities. Few studies have evaluated the impacts of offshore aquaculture on the ocean floor within deep-sea ecosystems. To help coastal managers and stakeholders prepare for siting farms in the open ocean, scientists with the NOAA National Ocean Service's Coastal Aquaculture Planning and Environmental Sustainably (CAPES) program used AquaModel software to forecast environmental interactions associated with a novel net-pen operation deployed in waters over 1,800-m deep. Working within a GIS platform, AquaModel provides a real-time, three-dimensional simulation of environmental effects related to waste dispersion from net-pen operations. The underlying model is based upon a suite of variables that represent nutrient flux within the net pen, in the open water, and in the sediment. AquaModel is the only comprehensive model currently available that provides both water column and benthic dynamic simulations. We modeled a pilot-scale project deployed 10 km off the southwest coast of Hawaii. At production capacity (26,572 kg), the model predicts insignificant dissolved nutrient impacts to the water column undetectable below 30 m in the immediate area of the net pen. Because of the great depth, strong currents (>20 cm/sec), and physical oceanographic nature of the site, dissolved wastes were widely dispersed and likely would be assimilated rapidly by the planktonic community in the oligotrophic receiving waters. Further, the model predicted that sedimentation and accumulation of particulate wastes would not be detectable through measurement of organic carbon or infaunal community biodiversity given the extensive dispersion field. The results support the notion that the deep sea is a promising frontier for marine seafood production where organic discharge from farms is effectively dispersed by natural oceanographic processes and assimilated into nutrient-limited food webs.