pneumatocyst

{{about|algae|lung and other pneumatocysts|pneumatocele|the similarly pronounced stinging cells|nematocyst}}

File:Giantkelp2 300.jpg) with many pneumatocysts]]

In phycology, a pneumatocyst is a floating structure that contains gas found on brown seaweed. A seaweed's thallus may have more than one. They provide buoyancy to lift the blades toward the surface, allowing them to receive more sunlight for photosynthesis.

The proportion of gases in the pneumatocysts varies depending on the physiological status of the alga and the partial pressure of gases in the surrounding air or water.{{cite journal|last=Thiel|first=M.|author2=L. Gutow|year=2005|title=The Ecology of rafting in the marine environment|journal=Oceanography and Marine Biology: An Annual Review|publisher=The Floating Substrata|volume=42|pages=181–264}} The pneumatocyst can hold O₂, CO₂, N₂, and CO.{{cite journal|last1=Foreman|first1=Ronald E.|title=Physiological aspects of carbon monoxide production by the brown alga Nereocystis luetkeana|journal=Botany|volume=54|issue=3–4|year=1976|pages=352–360|issn=1916-2804|doi=10.1139/b76-032}}

File:Algae bladder 4290.jpg]]