Artificial Reefs in the spotlight

TOILETS, shopping carts, washing machines and other assorted junk have been dumped into the sea to create habitats for marine organisms and the fish that feed upon them. But making reefs from refuse is now frowned upon. Alabama, for example, banned fishermen from sinking vehicles in the Gulf of Mexico in 1996, even when drained of potentially harmful fluids. Now more bespoke artificial reefs are taking shape. 

Reefs improvised from junk often do not work well. Corals struggle to colonise some metals, and cars and domestic appliances mostly disintegrate in less than a decade. Some organisms do not take to paints, enamels, plastics or rubber. Precious little sea life has attached itself to the 2m or so tyres sunk in the early 1970s to create a reef off Fort Lauderdale, Florida. Tyres occasionally break free, smash into coral on natural reefs and wash ashore.

Yet building artificial reefs that are attractive to marine life can pay dividends. Some of the reefs built in Japanese waters support a biomass of fish that is 20 times greater than similarly sized natural reefs, says Shinya Otake, a marine biologist at Fukui Prefectural University. He expects further gains from a decision by the Japanese government to build new reefs in deep water where they will be bathed in nutrients carried in plankton-rich seawater welling up from below.

The potential bounty was confirmed in a recent study by Occidental College in Los Angeles. Over five to 15 years researchers surveyed marine life in the vicinity of 16 oil and gas rigs off the Californian coast. These were compared with seven natural rocky reefs. The researchers found that the weight of fish supported by each square metre of sea floor was 27 times higher for the rigs. Although much of this increase comes from the rigs providing fish with the equivalent of skyscraper-style living, it suggests that leaving some rigs in place when production ceases might benefit the environment.

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