Every couple of years a liberal coat of toxic anti foul paint is needed on a boat's hull to stop the colonisation of barnacles, weed and other organisms on the hull. Is there an alternative to poisoning our sea?

Anti foul paints work like this: you slap them on, and put the boat back in the water. From that day forth, the bottom of your boat is protected by the mechanism of the slow leaching of toxins from the paint which kill any organism foolish enough to think that the bottom of your boat might make a nice new home. The result? A spotless hull, good boat speed, and fuel efficiency; a badly fouled boat may use up to 40% more fuel.

The anti fouling business is big. In New Zealand, we have over 60,000 moored (always in the water) launches and yachts, many of which sit in marinas. Westhaven, the country's largest marina, houses some 2000 boats.

Prices differ for boat size, but as a guide it costs around $4500 to have a 50ft yacht lifted out of the water, cleaned and brushed with a fresh coat of anti foul paint by a contractor.
Drop it back into the water, and over the course of that anti foul paint's useful, 18-month-to-two-year life it will have leached about 3kg of copper back into the water.

Copper is the active ingredient (among other 'biocides') common to almost all anti fouling paints used in New Zealand, and around the world. A 2011 NIWA study concluded that anti foul was the main source of copper found in marinas, and that samples showed that levels "were above the guidelines for protection of marine aquatic life."

Advertisement

At the time Auckland Council's Stormwater Contaminant Scientist, Marcus Cameron said: "The results were quite surprising - the modelling indicated that copper levels could be quite elevated in marina waters and the sampling broadly confirmed that. On top of this the estimates of copper being exported from marinas were also significant, with as much copper exported from the four marinas in the Waitemata Harbour as from inputs of stormwater for the whole Waitemata Harbour catchment."

The principal scientist on the study, Dr Chris Hickey, says that copper concentrations "are not at levels that you'd cause large fish kills, but it's certainly at levels that would modify the environment, particularly those sensitive species."

Panuku Development Auckland (formerly Waterfront Auckland) has recently re-started monitoring water quality in Westhaven and the other Council-owned inner city marinas it manages.

As part of the monitoring, identification of substances in the water are measured against Australian and New Zealand Guidelines for Fresh and Marine Water Quality (known in New Zealand as the ANZECC guidelines).

The latest results received for Westhaven are from November last year and show elevated levels of copper in three test locations from the eight locations tested. These elevated levels did not exceed the ANZECC guidelines, but came close.

Said Panuku Development Auckland spokesperson Luke Henshall: "This isn't surprising given the marina is over 60 years old and the historic cleaning practices in the marina during that time would likely have led to increased levels of copper in the sediment in the sea floor. Dredging programmes as part of future infrastructure developments planned for the marina will likely address this."

New Zealand's own Environmental Protection Agency (EPA), which commissioned the NIWA study, completed a reassessment of copper-based anti fouling paints in 2013. The findings prompted the response to tighten regulations around the cleaning of hulls and the application of anti foul paint.

EPA senior communications officer Jo Watt commented to Element: "In making its decision on the anti-fouling paints the EPA's decision-making committee determined that the benefits associated with copper as an anti fouling biocide sufficiently outweigh the risks to human health and the environment presented by copper-based anti fouling paints.

It appears that other governments around the world do not concur with ours. Copper-based anti foul paint is already banned in Sweden, Denmark and Holland, it is also banned in some states of the United States. It is under review in many more jurisdictions around the globe.

Dr Hickey says the while we don't have the volume of recreational boats as in Europe, we may be approaching the same scenario of unacceptably high copper levels. "Certainly the work we've done suggests we are getting close to that. It's [the copper] focused on harbours and marinas - whereas in Europe it's not just where they [boats] live, it's where they move to - although one could argue that parts of the Hauraki Gulf are under pressure. It's a hard call."

The ban in Sweden has seen entrepreneurs developing alternatives, and recently Björn Alven, the co-owner of boatwash company Rentunder, was here in New Zealand talking to the industry. His product is a drive in, in-water boatwash which scrubs the fouling off yachts and power launches with a series of brushes, all the while containing in a pen the debris which comes off in the process.

"Our system actually means that boat owners don't ever have to use anti foul paint again," says Alven. "Sure, they have to wash the boat more often, but it takes 15 minutes, it's inexpensive by comparison, it doesn't have to be taken out of the water, it maintains perfect boat performance and cuts carbon emissions by improving fuel efficiency. It also means their boat isn't leaching copper into the ocean for the rest of its life."

Alven says having in-water boat washing facilities in a marina means that as more and more vessels use them, fewer and fewer boats are applying regular coats of anti-foul paint and the health of the sea bed in the marina constantly improves.

Rentunder looks poised for rapid expansion, having just raised capital for the purpose.

Other innovations to tackle the problem include the attempt to build boat hulls from materials which imitate shark skin - as sharks do not suffer from marine growth the way whales do, and ultrasonic systems, which uses multiple bursts of ultrasonic energy to resonate through the hull, killing single cell organisms such as algae.

The ultrasonic system is advanced, but uptake of the system is minimal.

Anti foul paints containing other active ingredients other than copper are also available, but generally accepted to be more expensive and not as effective as copper-based paints.

Our toxic past
60 years ago the tin-based anti foul paint known as Tributylin was being touted as the miracle paint. It killed a wide range of marine life fouling, but also killed a bunch of things not stuck on the boat. So toxic was it that it was banned in Europe in 1987, and in many other countries, including New Zealand, soon after.

It also gave rise to the renaissance of copper-based paints. Copper had been used much earlier, having been tacked to wood hulls by the British Navy in 1761. When Lord Nelson took to the water in the Battle of Trafalgar in 1805, it was a brand new copper-bottom fleet, which was credited with giving his ships a 20% speed advantage.