Corps says disease, not dredging, hurt PortMiami coral

Sediment forms a white plume trailing a barge hauling mud dredge from Government Cut to an offshore disposal site.
Sediment forms a white plume trailing a barge hauling mud dredge from Government Cut to an offshore disposal site.

A “catastrophic” outbreak of disease, not mud churned up by the $205 million “Deep Dredge” at PortMiami, killed coral in Government Cut, according to a report issued by the U.S. Army Corps of Engineers.

The two-year-long dredging raised concerns after biologists and environmentalists began documenting damage to coral and seagrass struggling in cloudy water as 5 million cubic yards of mud was barged to an offshore dumping site. Dredgers deepened the channel by more than 50 feet to make way for massive new ships sailing through an expanded Panama Canal. In September, federal wildlife managers with the National Marine Fisheries Service warned the Corps damage covered four times the area allowed under its permit.

Corps officials now say coral planted on a 12-acre artificial reef and newly planted seagrass in a 17-acre underwater meadow are thriving.

“We are pleased at the success of the mitigation features,” Col. Jason A. Kirk, the Corps’ Jacksonville District Commanders, said in a December statement when the agency formally announced completion of the work.

Completed about three months after work ceased, a survey concluded that most coral died after an outbreak of white plague disease, a virus researchers believe is spread when coral already under stress begin to bleach. Corps scientists examined about 252 acres of sea bottom and middle and outer reefs in the channel. Where there was dead coral, about 85 percent appeared to be caused by the disease, they said, which first appeared in the region in 2014.

But environmentalists, who won a legal fight to get the Corps to clean up work and do a better job of monitoring plumes of mud, say the agency is not accurately assessing the affect of the disease. The September marine fisheries letter pointed out that 94 percent of coral near the dredge were covered with sediment, which could have fueled the spread of disease, compared to 7 percent far from the work.

"The Corps' report misleadingly and conveniently blames the disease and warm temperatures for the destruction of our corals, but all of the available evidence, including evidence from every other federal, state, and local government agency involved, shows that the Corps' dredging that was smothering the reefs long before the disease even began," said Miami Waterkeeper executive director Rachel Silverstein.

The Corps is required to monitor the area for at least another year to determine whether permanent damage occurred that would need to be addressed.

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