OXYGEN-UPTAKE AND NUTRIENT EXCHANGE OF SEDIMENTS MEASURED INSITU USING A FREE VEHICLE GRAB RESPIROMETER

A free vehicle grab respirometer is describe. It can measure oxygen uptake and nutrient exchange of deep-sea sediments and then return to the surface with four replicate box cores containing the undisturbed sediment and overlying water on which these measurements were made. Total oxygen uptake and nutrient exchange were measured in situ in the eastern North Pacific at two stations, one in the Dan Diego trough at a depth of 1193 m and one off the Patton Escarpment at 3815 m. Both stations underlie the eutrophic California Current system. There was no significant difference in total oxygen uptake between stations, but the values were significantly higher than previous measurements made at comparable depths. Ammonia, nitrite, and phosphate were evolved while nitrate was taken up at 1193 m. At the deeper station, all the nitrogenous compounds were evolved but phosphate was taken up. A delicate ammonia gradient seems to exist across the sediment-water interface. © 1979.