By Theresa Pinto M.S., Contributing Reporter

MIAMI BEACH, FLORIDA – A new report shows that nitrogen-loading from fertilizer is destroying Florida’s Looe Key Reef, faster than damage from warmer waters and climate change. However it is the heavier rains caused by global warming that is increasing the run-off of sewage, fertilizers, and topsoil, bringing nitrogen along with them.

Florida's Looe Key Coral Reef is Being Destroyed by Fertilizer and Runoff, Miami Beach, Miami, Florida, News
The researchers collected data on nutrients and algal concentrations for thirty years and their analysis showed that the reactive nitrogen levels near Florida’s Looe Key Reef were elevated above levels known to cause coral die-off, photo courtesy of Florida Atlantic University Harbor Branch Oceanographic Institute.

Florida Atlantic University conducted the longest study to date on coral death, centered on Florida’s Looe Key Reef. The report, published online July 15th and using thirty years of data, shows that nitrogen-loading is the main culprit of coral bleaching in the area.

Sometimes referred to solely as Looe Key, it is a coral reef located inside the Florida Keys National Marine Sanctuary, in the lower part of the island chain south of Big Pine Key. It is named after the HMS Looe, which ran aground and sank there in 1744.

The researchers collaborated with the University of Georgia and the University of South Florida to collect seawater and seaweed tissue samples for the analysis.

For thirty years, the researchers collected the tissue samples to measure nutrients and algal concentrations. Their data showed that the reactive nitrogen levels near Florida’s Looe Key Reef were elevated above levels known to cause coral die-off.

The excess nitrogen depletes phosphorus levels in the area which in turn causes metabolic stress to the corals, reducing the temperature threshold at which corals are susceptible to coral bleaching.

In their analysis of the results, they conclude that because high levels of nitrogen were detected during coral bleaching events but prior to warmer oceans, the ‘primary driver’ of coral bleaching was the nutrient imbalance and not climate change.

“Our results provide compelling evidence that nitrogen loading from the Florida Keys and greater Everglades ecosystem caused by humans, rather than warming temperatures, is the primary driver of coral reef degradation [sic],” said Brian Lapointe, the study’s primary investigator.

However, the nitrogen mostly comes from coastal runoff of improperly treated sewage, fertilizers, and topsoil. And, according to FAU, nitrogen runoff is predicted to increase by nineteen percent globally simply as a result of changes in rainfall due to climate change.

Florida's Looe Key Reef is named after the HMS Looe, Miami Beach, Miami, Florida, News
Florida’s Looe Key Reef is named after the HMS Looe, which ran aground and sank there in 1744, photo courtesy of National Oceanic and Atmospheric Administration.

In the meantime, controlling runoff contamination and waste handling on land could help alleviate some of the harmful runoff.

The Miami Waterkeeper is currently working on a countywide fertilizer ordinance. According to Miami Waterkeeper, 85 municipalities and 32 counties in Florida have passed similar laws since 2007.

A different study published earlier this year showed that, ‘although residential lawn fertilization is estimated to be the 2nd largest source of household nitrogen in the U.S.’, fertilizer ordinance education helped reduce nitrogen pollution in Tampa Bay.

Coral reefs in general provide ecosystem services worth $375 billion annually.

The National Oceanic and Atmospheric Administration assessed Florida’s coral reefs as an asset valued at $8.5 billion, generating $4.4 billion in local sales and $2 billion in local income, including 70,400 full and part-time jobs.

The recent report by the U.S. Geological Survey on corals evaluated their flood risk reduction value at $1.8 billion.

Additionally, nearly half of all federally managed fisheries depend on coral reefs for income and NOAA’s National Marine Fisheries Service estimates the annual commercial value of them to be over $100 million.


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