Golden Bay Cement, a company with a proven commitment to the environment, is pleased to have its products used for marine restoration and enhancement in New Zealand; namely an artificial reef component called a ReefBall.

Innovation

The use of artificial reefs is hardly a new one. For decades people have been creating reefs from tyres, sunken ships, old cars, concrete culverts and assorted rubble. These, however, can often do more harm than good - leaching harmful chemicals into the ocean or damaging natural reefs when currents dislodge them and toss them around the sea floor. ReefBalls on the other hand, have been designed to emulate natural reef formations and, as most of the weight is concentrated in their flat bases, will sit on the sea floor without moving, even in turbulent seas.

The idea for ReefBalls originated with Florida diver Todd Barber. His company, the ReefBall Development Group, has placed over 100,000 around the globe in the last eight years.

Dave Head of Napier and a group of friends brought ReefBalls to New Zealand, setting up the company ReefBall NZ Limited and the NZ ReefBallTrust, which has already been offered substantial financial help from a large New Zealand charitable organisation. In April 2000, under the guidance of Todd Barber, trial production began at Firth's Awatoto Readymix Plant in preparation for a proposed artificial reef at Westshore and Bayview off Napier's northernmost coastline. Golden Bay Cement's GP was used along with supplementary cementitious material Microsilica 600, supplied by GBC subsidiary Microsilica New Zealand Ltd.

GBC's Microsilica 600 is an important supplementary cementitious material for the blend due to its durability enhancing qualities and high level of resistance to sulphide and chloride attacks. With Microsilica 600 used in the concrete, the Reef Balls will have an expected life of 500 years or more. By then, the build-up of coral or other marine life attached to the Reef Balls will be substantial, making the need for the artificial supports redundant.

ReefBall Construction

ReefBalls are made by pouring concrete into a fibreglass mould containing a central Polyform buoy surrounded by various sized inflatable balls to make holes. There are six mould sizes to tailor the units to the size requirements and purpose of the reef. The hole size is chosen to attract the type of marine life likely to thrive in the area, be they crayfish, moray eels or a small species of fish.

Before the concrete is poured, the inside of the mould is sprayed with a sugar solution. This acts as a mould release agent and allows for a roughened texture by preventing an outer film of concrete from setting. Hosing down the ReefBall after the mould casing is removed strips off the unset film of concrete leaving behind a rough stony texture to which organisms can attach more easily. Rough, individualised ReefBalls are preferred over the smooth, homogenous items normally produced from moulds, in order to more effectively emulate natural reef formations.

Polythene or similar covers are wrapped around the balls for up to two weeks to allow for a slow curing time. This prevents early cracking. The extremely durable polyform bladder used in the mould can be left in the unit to provide flotation, allowing the ReefBall to be towed behind anyboat. Once at the desired site, the bladder is deflated and removed. When divers are used to control the descent, units can be placed precisely on the sea floor so as not to endanger existing natural reefs that are being extended or repaired.

New Zealand Projects

Project Kaimoana, at Opotiki, has already gained initial approval from local government bodies and iwi. The artificial reef, aimed to bring marine diversity back to the area, is being wholly created by local community education centre Whakatohea Training Unit. Led by Aquaculture and Fishing Course Tutor Lloyd Hoskins, the project has already begun trial constructionof ReefBalls and is finalising the choice of aggregate and supplementary cementitious materials for strength and performance in a marine environment before beginning the reef construction.

A surf reef at Opunake, aimed at producing bigger waves, is another ReefBall project in the pipeline. This is being headed by Shaw Mead of ASR Limited. Funding for this is expected to come through before the end of 2001.

Proven Results Overseas

Among the many sites where ReefBalls have been put in place overseas is Australia's Great Barrier Reef. To protect the area's fragile coral reefs, which grow at the rate of one inch every 15 years, ReefBalls were used to create artificial snorkelling trails for tourists. The rapid development of marine life on and around ReefBalls makes them ideal for this purpose and proves them to be an ecologically advantageous option for artificial reefs.

Research Backing ReefBalls

According to Shaw Mead, Director of the New Zealand branch of international artificial reef producers ASR Limited: "Although a biological investigation is needed for each individual case, past studies have shown that stable, complex structures such as artificial reefs have higher bio-diversity and species abundance than mobile, abrasive substrates (e.g. sand). Artificial reefs can actually enhance the ecology of an area. In most situations, a reef is likely to have no significant effect on the ecology of the region."

Mead points out that a large amount of marine research into the ecological effects of artificial reefs shows that species abundance and diversity is enhanced when: