Why do some Seaweeds have Air Bladders?
Why do some seaweeds have air bladders?
(Photo: Paul Tyler)
Plants on the middle shore, bladder wrack and knotted wrack, have numerous air bladders along their length. When you see them on a low tide they lie in a big jumbled heap, but when the tide's in the bladders float and lift the weeds into an upright position. This ensures that the plants are nearer the sunlight and that all sides of the plant are exposed to the sun.
You can tell the age of a knotted wrack plant by counting the number of air bladders along the main stem. One bladder is produced each year, so a plant with 6 bladders in a row along the main stem will be 6 years old!
(Photo: Sue Scott)