November 21, 2016
Mud from PortMiami dredge spurred coral die-off, study finds
A new study has confirmed what federal wildlife officials long suspected: dredging at PortMiami to make way for massive new ships killed far more coral than the U.S. Army Corps of Engineers predicted.
The study, published this month in the online journal PeerJ, sought to set the record straight on what exactly killed coral around the $205 million dredge and come up with more realistic expectations from such work. The Corps had contended a disease-outbreak was largely responsible, while state environmental regulators and conservationists argued that mud stirred up by the dredge or leaked from a barge as it ferried sediment offshore smothered coral and clouded water.
Using evidence gathered by the Corps, including photographs taken before, during and after, researchers said sediment spread across an area about 14 times bigger than what was allowed under a Corps permit, causing coral to die. After warm temperatures in the summer of 2014 triggered widespread bleaching and disease, coral stressed by the sediment died in larger numbers than nearby coral, the study found.
Deepening the port channel by about six feet to 52-feet deep will allow new larger ships sailing through an expanded Panama Canal to bring cargo to Miami and completes a $1 billion makeover, including a new tunnel. Environmentalists had worried that digging up more than 5 million cubic yards of bottom would cause damage to threatened coral, which help provide a first line of defense against storm surge from hurricanes.
“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.”
But Corps officials argued the study, authored by a team of scientists from the National Marine Fisheries Service and the University of Miami who compared work done in the channel to coral in a nearby reef, used limited data and failed to distinguish between the types of sediment that buried coral
“Drawing broad scale conclusions based on limited data is very misleading and not good science,” Corps spokeswoman Susan Jackson said in an email.
The study again puts at odds two government agencies that have repeatedly clashed over how the dredge has been carried out. Over the summer of 2015, the fisheries service repeatedly warned the Corps that damage appeared to be more widespread and that the Corps was in danger of violating its permit. The Corps also failed to provide updated surveys of the work, prompting the fisheries service to issue a sharp letter accusing the Corps of “selectively [choosing] certain results to downplay the permanent effects” of the dredge.
The authors say the new study shows the need to be more careful when dredging near sensitive reefs and should serve as a warning for the $374 million Port Everglades expansion.
That expansion, which environmentalists have challenged in court and which still needs Congressional authorization, would widen parts of the port channel to 300 feet and deepen it by up to six feet. The Corps has agreed to repeat an environmental assessment, but the study warned that a baseline assessment of coral done after a regional bleaching event may not be providing a true picture of coral in the area. Environmentalists fear the new survey may not take into account findings from the PeerJ study, which recommends stopping work when coral are stressed or spawning.
Jackson said the Corps is “committed to understanding potential impacts,” and has expanded monitoring efforts including cameras installed on the ocean floor to record conditions. The agency, she said, also plans to post “real-time monitoring” during construction on its website.