The Rena disaster on 5 October 2011 impacted the surrounding environment of the Bay of Plenty in New Zealand. The ship was carrying 1368 containers – eight of which contained hazardous materials – as well as 1700 tonnes of heavy fuel oil and 200 tonnes of marine diesel oil. Environment Minister Nick Smith declared that the spill was New Zealand’s worst maritime environmental disaster.

Oil

Over the following 6 months, 360 tonnes of heavy fuel oil poured into the sea from the Rena. Some of the oil dispersed or sank to the seabed, and some made its way to the shore. A thick, black tar-like substance covered a number of beaches and coastlines. Beaches were closed. Volunteers for the clean-up were warned that contact with spilled oil could lead to vomiting, nausea and rashes, and local residents were urged to close their windows to limit fumes. It was estimated that over a thousand tonnes of sand were removed to extract the oil from the sand.

Heavy fuel oil contains polycyclic aromatic hydrocarbons (PAHs) and heavy metalsPAHs and heavy metals are known to be cancer-causing and can cause sickness and defects in organisms. Benthic organisms can ingest small droplets of oil falling to the seabed. Heavy metals and PAHs then enter the food chain, causing a build-up of these contaminants in organisms higher up in the food web, such as fish and birds.

Toxic oil from the spill will have different levels of long-term and short-term effects on the environment. In the short-term, the oil caused the death of about 2000 seabirds. It is estimated that 20 000 seabirds were affected. Filter-feeding whales were at risk from sticky oil clinging to their baleen plates as they fed. It will take a number of years to determine the full effects of the oil spill on the ocean’s ecosystem, which contains large kelp forests and is the home of a large fishing industry.

Salvage efforts removed unspilled oil from the ship when the weather and rough seas permitted. Although further research needs to be carried out, scientists believe that the efforts made to salvage most of the oil before it spilled from the ship may have been enough to prevent any real long-term damage to marine ecosystems.

Containers and debris

Within the first week of the disaster, 88 of the 1368 containers from the ship had fallen into the ocean. As the ship broke up over the next 3 months, more containers fell into the sea. Transponders transmitting the location of containers were attached to some but not all, because they could not be accessed before they fell overboard. Some containers were never recovered – including some containing dangerous goods such as cryolite. Cryolite is a mineral that can be used as a pesticide or insecticide. Research is being carried out to determine the effects of cryolite on marine life.

Many containers broke up, spilling their contents, which washed up on beaches as far away as Whangapoua Harbour on the Coromandel Peninsula. Debris was even found at Medlands Beach on the far side of Great Barrier Island. These items included bags of milk powder sachets, timber, packets of noodles, paper, rope and plastics – including small plastic beads.

Volunteers and contractors helped to clean up the debris along the beaches and coastal areas. Debris was stockpiled and removed by helicopter. A large amount of debris on the rocky coastline north of Tairua couldn’t be accessed easily. It was difficult to retrieve debris entangled in seaweed. The small plastic beads were retrieved using portable vacuum equipment that picked up material that was then put into a tank. Sand and other heavy material would sink to the bottom, leaving the beads floating on the surface. The equipment was portable and could be used in small spaces.

Debris from the Rena posed a significant risk to shipping. It also polluted beaches and posed a threat to marine life – either from entanglement or by ingesting it as food.

Nature of science

Scientists are often called on when disasters strike. In this case, environmental scientists needed to consider the effects of different kinds of pollution on the environment and make decisions as to how to respond both in the short term (such as cleaning up the oil spill) and in the long term (such as research on the effects of marine organisms).

Useful links

The Maritime New Zealand website contains many articles and images about the Rena disaster.
www.maritimenz.govt.nz/Rena/

    Published 11 January 2012