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Study: Mud stirred up during PortMiami dredge killed coral

Posted November 22

— Dredging at PortMiami killed far more coral than the U.S. Army Corp of Engineers predicted, scientists from the National Marine Fisheries Service and the University of Miami have concluded in a new study.

Researchers set out to determine what killed coral near the $205 million dredge work at the port, which was done to make way for the larger ships sailing through an expanded Panama Canal to bring cargo to South Florida. Their study, published this month in the online journal PeerJ, compared work done in the channel to nearby coral. It puts at odds two governmental agencies that clashed over the dredge. Environmentalists had long worried that that $205 million dredging would damage the coral.

The Miami Herald (http://hrld.us/2gFJYNi ) reports the Corps contended a disease outbreak was responsible. State environmental regulators argued that mud stirred up by the dredge or leaked by a barge as it ferried sediment offshore smothered coral.

The research team studied pictures taken before, during and after the dredge and said sediment spread across an area about 14 times bigger than the Corps permit allowed for. The study found that warm temperatures in the summer of 2014 triggered widespread bleaching and disease and the coral — stressed by the sediment — died in larger numbers than nearby coral.

The project deepened the port's channel by 6 feet, making it 52-feet deep. It completes a $1 billion makeover that includes a new tunnel at the port.

"We now know the Corps dramatically underestimated both the severity and the geographic extent of the sediment impacts on the reef," said Miami Waterkeeper Rachel Silverstein, whose group joined other conservationists in a legal fight to clean up the dredge. "The monitoring and the protocols that were supposed to protect this reef during the dredge clearly failed and this study is providing peer-reviewed, statistically valid evidence showing that impacts from the dredging resulted in widespread impacts."

Beginning in the summer of 2015, the fisheries service repeatedly warned the Corps that damage appeared to be more widespread and the agency was in danger of violating its permit. The Herald reports that the Corps also failed to provide updated surveys of the work, which prompted the fisheries service to issue a sharp letter accusing the agency of selectively choosing "certain results to downplay the permanent effects" of the dredge.

Corps officials said the study used limited data and failed to distinguish between the types of sediment that buried coral during the dredge.

"Drawing broad scale conclusions based on limited data is very misleading and not good science," Corps spokeswoman Susan Jackson told the Herald via email. She said the agency is "committed to understanding potential impacts" and has expanded monitoring efforts, which include cameras on the ocean floor to record conditions.

The researchers conclude that the study highlights the need to be more careful when dredging near sensitive reefs and should serve as a warning for the upcoming $374 million expansion at Port Everglades in Fort Lauderdale.

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