Greenwash brings toxins back to European ports
Widely enforced bans on the underwater cleaning of ships with anti-fouling coatings, a major cause of both invasive marine species and toxic pollution around harbours, are being eroded in many European ports. The loosening of controls opens the door to severe ecological damage.
The ports of Southampton, Rotterdam, Antwerp and Algeciras are among the latest areas to decide to allow hull cleaning using remotely controlled or diver-operated carts, a practice previously banned for environmental and safety reasons. The cleaning carts reduce ship fuel bills by scrubbing off marine growth, but when used on anti-fouling coatings they deposit heavy concentrations of toxic anti-fouling chemicals that can devastate local ecology. The procedure also deposits invasive foreign organisms into local habitats.
Filtration systems attached to newer carts, claimed to avert pollution problems, are considered by industry experts to be little more than window-dressing.
The recent Port approvals have specified cleaning procedures using ‘reclaim’ systems – filters that are supposed to collect the dangerous debris removed from the ship bottoms. Analysis by industry experts however suggests that the reclaim systems are no more than greenwash, and that tons of toxic chemical compounds are dumped into sheltered areas of water each time a commercial ship is cleaned.
Underwater hull cleaning was largely banned during the 1990s for two reasons. To be effective at removing unwanted marine growth, the harsh cleaning method also scrubs off layers of anti-fouling – composed of toxic copper, tin and zinc compounds with herbicides and other biocides. Also, the marine growth removed from the hull tends to re-establish in a new habitat, overwhelming local species and sometimes growing hugely out of control. The Asian Green Mussel, now responsible for catastrophic damage along large areas of American coasts and deep into the Amazon, is a well-known example.
When removed during cleaning, anti-fouling paint is usually visible as dense semi-dissolved plumes, dispersed into the water by the action of the cart’s rotating brushes or high-pressure water jets. Marine growths can be seen as fragments of shell and clouds of tiny larvae-sized particles.
The ‘reclaim’ systems try to suck up this material as it is dislodged, carrying it to above-surface filtration units. But the mechanics involved have been compared to trying to capture the exhaust gases of a rocket at take-off using a vacuum cleaner.
While larger particles such as the shells of crustacea may be viably collected, larvae as small as 2 microns are known to be capable of growing, reproducing and establishing unwanted colonies. Biocides from anti-fouling paint meantime gradually sink into the sediment where they can be ingested by flora and rapidly pass up the food chain.
Cleaning dislodges NIS
Cleaning carts need to generate considerable force to dislodge marine growths. Usually this means rotating steel-tipped bristles, usually about 15” in diameter, which are pushed hard against the hull through suction and maneuvered along the surface by a diver, or remotely controlled. Some newer systems attempt to achieve similar cleaning power through rotating high-pressure water jets. In both cases the resulting water turbulence is extreme, and results in removal of layers of anti-fouling.
A New Zealand Ministry for Primary Industries review in 2015 noted that “biosecurity risks associated with the set up and deployment of brush carts include dislodgement of fouling, exfoliating paint and other material by the diver’s movement or equipment or the hydraulic or pneumatic hoses of the cleaning device, cleaning of niche areas and edges and containment, capture and extraction of waste material removed (where a capture system is fitted)”.
The efficiency of filtration of captured waste was also an area of concern: “Capture and removal or treatment of waste from in-water cleaning is critical because cleaning does not kill all the organisms removed. Fragmentation and dislodgement plays an important role in natural dispersal of some algae and clonal organisms. In experimental trials of diver-operated brushes, Hopkins et al. (2008) found that 8% of the material not collected by the suction system was viable. This material was in addition to that knocked off the hull by the divers’ fins and hoses and other gear dragged across the hull while using the brushes. Woods et al. (2007) reported that up to 70% of organisms removed by hand scrapers during in-water cleaning was viable.
“The propagules of algae and other fouling taxa can be as small as 2 μm (Clayton 1992), and the smallest practically-achievable filtration standard seems appropriate for in-water cleaning. Based on systems tested so far, 12.5 μm appears to be the smallest size of filtration currently achievable.”
It has been suggested that financial pressure on Ports has led them to overlook the twin risks of water contamination and obliteration of local species: ship operators may be more inclined to unload at docks that allow in-port cleaning.
The volume of copper entering coastal waters is already a general concern and in some areas a very acute problem.
A 2016 paper by VictoriaTornero and GeorgHanke in the Marine Pollution Bulletin points out: “Biocides such as copper(I) salts, mainly in the form of copper oxide (Cu2O) and copper thiocyanate (CuCHNS), have been the main alternatives to TBT in many antifouling coatings. Copper losses at sea from coatings of moving ships are considered as a significant and increasing anthropogenic source of copper to the aquatic environment (OSPAR, 2010a). Although much less toxic than TBT, copper may also negatively affect organisms at concentrations higher than physiologically necessary and its risks on the marine ecosystem should not be neglected (Karlsson et al., 2010; Ytreberg et al., 2010).”
Copper-based anti-fouling coatings are by design ablative, with top layers gradually leaching off to expose fresher, more potent material. A ship that is berthed in port has the same daily migration of copper oxide release. A port with 3000 ship calls per year will have an environmental impact of approximately 16 x tons of pure copper oxide released in the inner harbour.
Cleaning greatly increases this. Each underwater cleaning of a medium-sized ship is estimated to release up to 3 tns of anti-fouling paint, composed of 60 to 80 percent toxic biocides, into the water. The biocidal content is usually as high as the law will allow, with copper compounds being the norm.
Depending on their sailing patterns, some ships might undertake a cleaning operation between once and four times a year, leading to an estimation of more than 1 million tons of biocides entering the world’s oceans annually.
The effects of concentrations of copper discharge in enclosed bays (which applies in the case of most ports) is apparent in the case of the Marina del Ray bay in California. With levels of copper in the bay regularly exceeding limits, Los Angeles County has mandated to reduce copper loads by 85 percent by 2024 as part of a Total Maximum Daily Load restriction adopted by county officials in 2014. Urgent action is now under consideration.
Meantime the US Navy is being sued for the effects of cleaning the hull of decommissioned aircraft USS Independence in the waters of the Puget Sound. The Suquamish Tribe and two environmental groups estimate that between 49 to 73 dump truck loads of debris such as paint chips, copper, zinc and other metals from the ship went directly into Sinclair Inlet, a waterway already suffering from water quality problems. The case is also under investigation by the Environmental Protection Agency. Washington State requires ships with copper-based paint to be dry-docked before their hulls can be scraped, but the state does not have the authority to force the Navy to comply. The Navy, however, may be forced to conduct an expensive clean-up of the site.
Problems of Hull-borne NIS
Invasive marine species include tiny algae spores to larger organisms such as barnacles, tube worms and molluscs. Examples include the Northern Pacific seastar, a carnivorous starfish native to the Northwest Pacific and now established in the Northeast Pacific and Southern Australia. The fast-breeding organism has proven a pest to native species, including the endangered spotted handfish, as the seastar preys on their eggs.
The NOAA Fisheries Service estimates that in the US alone, the cost of managing both aquatic and terrestrial species is $137bn per year.