Are antifouling paints harming our sealife?
NIWA has recently completed a national project for modelling the leaching of copper from antifouling paints on vessels' hulls.
NIWA's modelling suggests that in many New Zealand marinas, copper concentrations could be above the guidelines for protection of marine aquatic life.
The port areas predicted to be at greatest risk are Nelson and the designated port area of Milford Sound in Fiordland, a world heritage area with high ecological value.
This modelling work was conducted for New Zealand's Environmental Protection Authority (EPA), which assesses the risk of hazardous substances to the environment.
Antifouling paints are used to protect our environment by preventing unwanted organisms attaching themselves to the hulls of boats.
Copper is used in almost all antifouling paints on boats in New Zealand. These paints are designed to leach copper into the water column while vessels are in the water.
Copper leaching from moored vessels represents a potentially significant source of copper in the marine environment. Dissolved copper, the most harmful form to organisms, is measurable in water samples from marinas and ports around New Zealand. Significant copper inputs also come from stormwater discharges, with high concentrations often measured in harbour sediments.
An existing OECD model, the Marine Antifoulant Model to Predict Environmental Concentrations (MAM-PEC), was used by NIWA scientists to predict concentrations of antifouling compounds at 11 ports and 13 marinas around New Zealand.
A study to test the predictions for the Auckland area was undertaken by Auckland Council's Stormwater Contaminant Scientist, Marcus Cameron, in collaboration with NIWA's Dr Jennifer Gadd and principal scientist Dr Chris Hickey. The study measured copper in the water column of Auckland marinas.
Dr Hickey says, "When the measured copper concentrations were compared to the predicted concentrations there was generally overlap between the modelled and measured results.
"We have provided a robust modelling tool configured for New Zealand ports and marinas, which the EPA can confidently use for their antifouling assessment procedure."
It will also assist the EPA in assessing the various antifouling paints approved for use in New Zealand waters.
"Based on the results from this study, and information compiled from previous studies, leaching of antifouling paints from vessel hulls appears to be the major source of copper in marina waters," says Hickey.
In Auckland, where the validation study was done, the highest concentrations were measured at Westpark and Milford marinas, which are both also influenced by urban stormwater and marina hard-stand activities such as boat-washing, scraping and repainting.
Marcus Cameron says,"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 lowest concentrations were measured at Bayswater Marina. Bayswater has floating walls, while the other marinas primarily use solid walls and have small entrances which restrict tidal flows.
"Even though these results were surprising, they are still comparable to results from studies overseas where in some cases leaching from antifouling paints on vessel hulls has been found to be the dominant source of copper in the marine environment," says Cameron.
The EPA is currently carrying out a reassessment of antifouling paints approved for use in New Zealand.