A Simple Apparatus for Maintaining Gas-Supersaturated Seawater in the Laboratory for Experimental Purposes

Abstract

Gas bubble disease caused by supersaturated conditions is generally well understood for commercially important freshwater species, such as salmon and trout, but very little is known about impacts to marine finfish culture. We developed a relatively simple, low-cost apparatus to expose juvenile white seabass Atractoscion nobilis and striped bass Morone saxatilis to multiple gas saturation levels simultaneously. We found that the system was capable of operating under different temperatures and accommodating a range of juvenile fish sizes. Gas saturation treatments were maintained by mixing a supersaturated seawater source with a saturated one. The supersaturated seawater source was created by reducing pressure of an air- or oxygen-equilibrated water source maintained at a pressure of 623.2 mm Hg. The saturated seawater source was achieved by degassing seawater using a packed column. By mixing these two water sources manually by use of needle valves, differential gas pressures (ΔP) ranging from 0.0 to 167.2 mm Hg were maintained. The control treatment level ranged from −35.7 to 0 mm Hg and was maintained using a vacuum degasser. Oxygen-nitrogen (O₂:N₂) ratios ranged from 0.83 to 1.41. Temperature within the experiment was computer controlled. The supersaturation apparatus operated very effectively and delivered treatment levels that were stable and significantly different from one another throughout all trials.