What gas is in the bladders of bladder wrack? © Getty Images

What gas is in the bladders of bladder wrack?

Bladderwracks use gas-filled bladders to keep their fronds afloat and close to the sunlight, but what gas do they use?

Asked by: John Callister, by email

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Fucus vesiculosus (bladder wrack) and Ascophylum nodosum (egg wrack) are seaweeds that use gas-filled bladders to keep their fronds close to the water’s surface where the light is strongest. The gas contains the by-products of respiration and photosynthesis (O2, CO2 and CO), but the exact proportions vary because the bladders are in equilibrium with the surrounding air and water.


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