Asked by: John Callister, by email
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.
Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.