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A diver brushes sediment off coral in the Port of Florida.

A diver brushes sediment off coral in the Port of Florida. Image: Screenshot


The Inertia

Researchers at the University of Miami looking into a dredging project have discovered that over 500,000 corals are dead. The project, which took place between 2013 and 2015, took place in the Port of Miami’s shipping channel which bisects the Florida Reef Tract.

A study published in Marine Pollution Bulletin in August entitled “Extensive coral mortality and critical habitat loss following dredging and their association with remotely-sensed sediment plumes” says that “560,000 corals within 0.5 km of the channel were lost due to dredging.”

The researchers at the University analyzed independent data from satellites and underwater surveys. The initial findings of the study said that a form of coral disease happened to strike the area at the same time as the dredging project but, after analyzing the data again when scientists controlled for bleaching and disease loss, it was found that corals near the dredge site were more likely to die than those further away.

As one would expect, the regions closer to the dredging project were impacted by much more sediment coverage. “Dredging poses a potential threat to coral reefs, yet quantifying impacts is often difficult due to the large spatial footprint of potential effects and co-occurrence of other disturbances,” wrote the authors of the study. “To control for contemporaneous bleaching and disease, we analyzed the spatial distribution of impacts in relation to the dredged channel. Areas closer to dredging experienced higher sediment trap accumulation, benthic sediment cover, coral burial, and coral mortality, and our spatial analyses indicate that >560,000 corals were killed within 0.5 kilometers, with impacts likely extending over 5–10 kilometers.”

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In less complicated terms, the corals were buried in sediment, which makes it nearly impossible for them to feed and reproduce, among other things.

Researchers also found that sediment plumes, which are areas where the sediment remains suspended, were bad news for corals, as well. According to the report, they can be closely tied to negative impacts on the seafloor.

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“This connection allowed us to predict impacts beyond where ship-based monitoring was taking place and showed that dredging likely damaged this reef several kilometers away,” said study co-author Brian Barnes in a statement. “While this same relationship may not apply in all projects, this is a remarkable finding that further establishes Earth-observing satellites as independent monitoring tools to fill in gaps where data are otherwise not available.”

The area where the dredging took place is smack in the middle of areas that are critical habitat for a variety of endangered corals.

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