Science and technology - Aquaculture: Seaweed at scaleFloating offshore farms should increase production of a useful crop, and might even help alleviate climate changeIN MANY PLACES where seaweed used to thrive, often growing in vast “forests”, it is disappearing.The cause is global warming, which, by heating the ocean’s upper layer, reduces its density through thermal expansion―thus making it more buoyant.That extra buoyancy means it is less likely to mix with cooler, denser and more nutrient-rich waters below.This is bad for the marine environment in general.More specifically, it is bad for commercial seaweed farming, a business with revenues of (depending on whom you ask) between $6bn and $40bn a year.The algae involved, particularly kelp, are popular in Asian cuisine.They are also used as fertiliser, and are processed into carrageenan, a natural binder and emulsifier employed in foods, cosmetics and drugs.Most are grown either on the seabed or on ropes attached to it. But some are cultivated on small floating platforms.To counter the effects of surface heating, which are particularly pronounced in the tropics, researchers are trying to improve the floating-platform approach by assisting the upwelling of cooler waters to stimulate algal growth on such platforms.
