The international trade of coal is highly dependent on transportation by sea, and researcher in Australia are warning that a major shipping disaster could have a devastating impact on coral reefs. A new study, publish in Nature Scientific Reports reveals that coal dust in seawater can kill corals and slow down the growth rate of seagrasses and fish.
“Corals exposed to the highest concentrations of coal dust died within two weeks,” says author Kathryn Berry, who led the experimental research. “Corals exposed to lower concentrations of coal lasted longer, but most of them also died after 4 weeks of exposure.
Corals need light to survive, and any form of suspended particles in the water column reduces the amount of light penetrating the water. Berry found that similar pathways for harm are likely from coal contamination in the ocean, including suspended particles and sedimentation resulting in reduced photosynthesis and coral feeding.
In addition, coal may also contain contaminants such as polycyclic aromatic hydrocarbons (PAHs) and trace metals, and a fraction of these contaminants can be released from coal dust into the surrounding seawater. Metals can be toxic to marine species by disrupting enzyme activity and membrane structure, but the effects of metals are highly dependent on speciation and bioavailability.
“Risks to the Great Barrier Reef posed by large coal spills depend on the probability of an accident and the potential impacts to marine life,” says author Dr. Andrew Negri. In 2013, the bulk carrier, MV Smart, broke apart in South Africa while carrying over 140,000 tonnes of coal. In Australia, over 60,000 tonnes of coal remained on board the Shen Neng 1 when it ran aground on the Great Barrier Reef off Gladstone in 2010.
Author Dr. Mia Hoogenboom hopes the results will inform management of coal shipping activities in Australia and around the world. “This research will allow decision makers to understand the risks to marine life to identify the species that are most vulnerable.” [ARC Centre of Excellence for Coral Reef Studies]
Title Image Caption: The different stages of coral health degradation after 14 days exposure to (a) 0mg per litre coal (b) 73mg per litre coal (c) 275 mg per litre coal. Photo credit: Kathryn Berry