Sugars Formed from Untreated Sewage Have a Role in Destroying Coral Reefs

Add sugar or organic carbon compounds to the list! 

Scientists have identified phosphates, nitrates, and ammonia as the most likely culprits in causing a 80% reduction in coral cover in the Carribean.  These pollutants help algae grow, which compete with coral for space. However, new research by David Kline of the Smithsonian Tropical Research Institute in Panama suggests that carbon-induced bacterial growth may be a major problem for coral reefs.

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Kline exposed corals to solutions of basic chemicals found in sewage and agricultural runoff and found that 35% of corals exposed to sugar compounds died compared to about 7% of those given nitrate or phosphate. Sugars led to an explosive growth of coral-associated bacteria not caused by other chemicals. These lab experiments suggest that corals already under stress from warmer water temperatures and the loss of fish and urchins that eat algae may succumb directly to the rapid growth of the normally symbiotic bacteria.  The policy implications of this research are substantial -- sewage discharged into coastal areas should treated to reduce organic carbon levels and organic carbon levels need to be monitored along with those of other pollutants.  This will be a real policy challenge because 90% of sewage dumped in the Caribbean is untreated.
Science report on coral reef research