FIG. 4.

(A) Vertical O₂ concentration profile along an infaunal burrow, measured in the aquarium with slits filled with agar plates in a sideboard. (B) Data points were obtained from the horizontal O₂ concentration profiles at different depths. The values indicate the average O₂ concentrations at the center of the burrow (i.e., 10 mm from agar surface). The error bars indicate the standard deviations of the measurements for 10 min at each position. (B) A typical horizontal O₂ concentration profile in an infaunal burrow. An O₂ microelectrode was inserted into the center of a burrow through the agar plate. Zero millimeters, 5 mm, and 10 mm on the horizontal axis correspond to the agar surface, the agar-burrow interface, and the center of the burrow, respectively.