To measure the buoyancy forces generated by the gas-filled medulla of D. antarctica, 10 individuals were haphazardly collected from Brighton Beach on July 23, 2002. All measurements were carried out at the beach so that all replicates were fresh and weight reduction due to desiccation effects could be ruled out. To test the forces exerted by the buoyancy of the blades, thalli cut at the stipe were submerged by placing a neutrally buoyant plastic mesh container upside down over the kelp in a seawater-filled barrel. The force necessary to keep the container with the kelp at water level was measured with a spring scale attached to a metal rod, which was used to push the container with the kelp down, and taken as the buoyancy of the tested individual. To analyze the correlation of exerted buoyancy forces with mor-phometrical parameters, the overall length, planform area, and fresh weight of the tested kelp were also determined.
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