Carbon Monoxide Production by a Bathypelagic Siphonophore

A physonectid siphonophore, Nanomia bijuga, associated with a verticallymigrating deep scattering layer, has been observed with a gasfilled float at depths in excess of 300 meters in the sea. This implies that gas is secreted and maintained in the pneumatophore against a diffusion gradient of 30 atmospheres or more. Analysis of the enclosed gases revealed concentrations of carbon monoxide exceeding 90 percent. Necessary voiding of this gas during a vertical ascent of 300 meters could give rise to a transient population of bubbles which would act as sound-reflecting targets.