Groundwater pollution – threatening coral reefs and the costal zone

Coastal protection, food security and tourism are the important eco-system services that coral reefs provide communities on Mexico's Yucatan Peninsula, leading scientists and natural resource managers at the 5th GEF International Waters Conference heard today at Cairns, Australia.

"If we lose this service, we lose a very large part of the economy," the Chair of the CRTR Program's Mesoamerican Centre of Excellence, Roberto Iglesias-Prieto, said during a morning session entitled The importance of land-sea interactions for coastal receiving waters, on Day 2 of the pre-conference technical workshops.

Yet, these services are under threat Professor Iglesias-Prieto said in his presentation, Groundwater pollution and the importance of coral reefs in the protection of the coastal zone.

 In one example, at Puerto Morelos, south of Cancun, a major threat is the pollution of the ocean caused by contaminated groundwater reaching the sea. The contaminants in this groundwater, including untreated waste leaching from a pig farm closed 10 years ago, is reducing the optical properties of the ocean water.

Corals are very sensitive to pollution. Sediment covers reefs. High nutrient levels cause higher algal growth which can out-compete the corals. Nutrients and other particles preventing light reaching the corals mean that the algae within them cannot photosynthesise. This stops the coral from calcifying. Compounding all these effects, rising seawater temperatures are also impact the health of corals.

In order for a reef to be sustainable, calcification must outstrip the constant erosion. In the Yucatan, this is not happening so all the services provided to the region by coral reefs are under threat. 

Coastal protection is one of the vital services at stake: In 2005 Hurricane Wilma struck the Yucatan Peninsula. It’s category 4 impact was felt for 60 hours. Outside the reef the wave heights reached 11 metres inside the reef waves were only 2.5 metres demonstrating that coral reefs absorbed 90% of the wave energy, protecting the coastal zone from tremendous damage.

Fisheries and tourism are further services based on a healthy marine environment. These underpin the Mexican economy

"If we lose the ecosystem services provided by coral reefs, we lose a very large part of the economy," Professor Iglesias-Prieto said.

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