Impacts of High-Density Suspended Aquaculture on Water Currents: Observation and Modeling

Abstract

Large-scale aquaculture activities in China have been rapidly developing in coastal waters, and they inevitably affect hydrodynamic structures and, hence, substance transportation. Predicting the effects is critical for understanding the environmental ecology and biochemical processes in these waters. To realize the solution, we conducted a field observation in Sungo Bay, which is an important aquaculture bay in China, and we developed a three-dimensional numerical model by arranging so-called porous structures, representing the aquaculture facilities, on grids of the culture layers. The energy-loss coefficients were specified to determine the momentum loss by the friction of the structures. We determined the appropriate coefficients for the oyster, scallop, and kelp cultures by using numerical simulation. According to the observation and model results, the aquaculture substantially weakened the current velocities in the culture layers and altered the vertical structures of the water currents. For this high-density and large-scale culture bay, the decrease rates of the current velocities in the culture layer were up to ~68%, ~65% and ~60% in the culture zones of oysters, scallops, and kelps, respectively. Bivalve cultures and kelp and bivalve cultures reduced the water-exchange ability of the bay by 33% and 50%, respectively. The method and results of this study provide a reference for studies on other aquaculture bays.