Too many tourists make corals sick

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Coral reefs are literally sick of ecotourists, according to a study published in the most recent issue of the journal Conservation Biology.

The authors compared prevalence of brown band disease, white syndromes, black band disease, skeletal eroding band, and growth anomalies among reefs with and without permanent tourism platforms within the Great Barrier Reef Marine Park. Basing their study on eight reef sites (four with platforms and four without), the authors visually surveyed the corals for signs of disease using belt transects.

When their results were analysed, the authors found that coral diseases were 15 times more prevalent at reefs with offshore tourism platforms than at nearby reefs without platforms.

A greater diversity of corals was also found to suffer at sites with platforms: diseases affected 10 coral genera from 7 families at reefs with platforms and 4 coral genera from 3 families at reefs without platforms.

Human activity on coral reefs stresses the ecosystem and reduces coral health at reefs in close proximity to offshore tourism platforms. Near these platforms, several activities may increase nutrient levels:

  • seabird guano that accumulates and is washed onto the reef by rain or by cleaning of the platform;
  • visitors and tourism operators feeding fish;
  • from tourists entering the water.

Tourists also introduce pollutants, such as sunscreen and may physically damage the coral while snorkelling and diving. Corals may also be physically damaged by the platform infrastructure itself.

The authors suggest that measuring and monitoring coral disease near popular tourism destinations is necessary to inform strategies for controlling visitor use.  They advocate dispersing visitors and creating low-use sites without permanent platforms to benefit coral health.

For more information, see the paper: Lamb, JB and BL Willis (2011) Using coral disease prevalence to assess the effects of concentrating tourism activities on offshore reefs in a tropical marine park. Conservation Biology, 25, pp. 1044–1052.

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