Saved by sponge

As oceans warm up, women in Zanzibar switch from seaweed to climate-resilient sponge farming to stay afloat

- KIZITO MAKOYE

AMID THE refreshing breeze caressing Zanzibar's Jambiani coast, Hindu Rajabu wades through knee-deep water to a lagoon. Wearing swimming goggles and a snorkel perched on her headscarf, the 31-year-old mother of two cautiously navigates the Indian Ocean to locate her floating sponge farm.

Rajabu is among a handful of women in Jambiani village who in 2020 started to cultivate natural sponges. These fascinating animals are made of loosely arranged cells that surround a skeleton of fibres. The specialised cells, nestled within thousands of tiny chambers, act as microscopic pumps, tirelessly drawing water into the sponge's body with their whip-like tails. This unique pumping mechanism, which helps sponges extract nutrition and oxygen, also purifies the ocean water by removing impurities, including sewage. These sponges are also used for bathing and general hygiene because they are naturally antibacterial and antifungal and can resist odours.

With the tide gently rising, Rajabu submerges herself to reach the buoys cradling the sponge farm. Carefully, she inspects the sponges, suspended from thick polyethylene ropes. Using a knife, she removes any fouling organisms, such as bacteria and fish, which have attached themselves to the ropes. This periodic cleaning is essential to prevent the sponges from being overwhelmed by these unwanted inhabitants. The sponge farms are made of multiple ropes that run parallel to each other. They have sponges at different development stages. "We usually harvest them once a week when we collect the sponges that are big enough to be sold in the market," says Rajabu. Women typically dive deep into the ocean to collect healthy wild sponges, which serve as the foundation for their farms that are set up close to the seashore where water is up to two metres deep. These sponge colonies are then carefully cultivated and fragmented to promote new growth.