Kelp (brown algae seaweed) possess gas-filled floats known as pneumatocysts that enable fronds to float on the water surface, maximizing exposure to sunlight and enhancing photosynthesis. The gas content of the pneumatocysts can vary, but are usually filled with a combination of oxygen, nitrogen, and carbon dioxide. Depending on the species, the kelp may contain one large pneumatocyst or several smaller pneumatocysts distributed throughout the kelp.Edit Summary
“…gas-filled floats keep [kelp] fronds at or near the sea surface…” (Koehl and Wainwright 1977:1067)
Mechanical adaptations of a giant kelpLimnology and Oceanography, 22(6): 1067–1071November 1, 1977
“[The floats] contain a mixture of oxygen, nitrogen, and carbon dioxide in varying relative proportions depending on the physiological status of the plant and the partial pressure of the particular gas in the surrounding medium. These gas-filled pneumatocysts provide buoyancy and let entire plants float to the sea surface” (Thiel et al. 2005:186).