A species of sponge in the Flower Garden Banks National Marine Sanctuary.
NOAA
A team of researchers including three oceanographers from Texas A&M University found that human pollution from floods in 2016 and Hurricane Harvey in 2017 made its way to the National Marine Sanctuary of the Flower Garden Banks, which is about 100 Located miles off the coast of Texas.
Kathryn Shamberger, Assistant Professor of Oceanography, and Texas A&M oceanographers Shawn Doyle and Jason Sylvan, and researchers from Rice University, the University of Houston-Clear Lake and Boston University have published their work in the current issue of Frontiers in Marine Science .
The team examined sponges in the Flower Garden Banks, a popular diving area known for its colorful coral reefs. It was designated a national marine reserve in 1992 and now has 17 different reef systems.
The researchers found bacteria from human wastewater, including E. coli, in sponges on the Flower Garden Banks after flooding events in 2016. Hurricane Harvey in 2017 also carried contaminated water from the Texas coast to the Flower Garden Banks. Researchers had previously believed the area was far enough on the Gulf that such pollution was not a problem.
Shamberger said the team was surprised to find bacteria that are typically associated with sewage in coral reef sponges far offshore.
“It has been known for decades that freshwater from land can reach these reefs and lower surface salinity, but changes in salinity so far offshore are small as freshwater mixes with seawater as it flows offshore,” she said. “In addition, the reefs of the Flower Garden Banks are approximately 60 feet deep and low-salinity water remains on the surface, so it was believed that these reefs are largely protected from land pollution.”
Doyle said the researchers used sponges that live on the reefs as hypersensitive monitoring tools for water quality.
“Because they filter and concentrate bacteria from hundreds of gallons of seawater a day, we were able to use the sponges’ microbiomes (a collection of microorganisms that live on or in an animal) to find signs of wastewater that was far too diluted to be treated recognize the water column, ”said Doyle. “Both flood periods examined in this study showed bacteria associated with sewage in the sponges. However, we do not know how often floods transport harmful bacteria to these coral reefs.”
Hurricane Harvey was the largest rainfall event in US history, dropping an estimated 13 trillion gallons of rain over southeast Texas in late August 2017.
Shamberger said Harvey’s floods were swept up the Texan coast with the currents when they reached the Gulf of Mexico, and only a small amount of runoff flowed offshore to the Flower Garden Banks.
It appears that marine life associated with Harvey’s polluted waters has low mortality rates, but she added that more work needs to be done to determine how flood-related bacteria affect the health of the Sponge and coral reef ecosystems in the region.
The big picture is that even coral reefs 100 miles offshore can be negatively impacted by pollution on land, Shamberger said.
“Intense storms with excessive rainfall that cause flooding in urban coastal areas will continue to increase with climate change and threaten these coral reefs,” she said. “Anything that can help reduce flooding will make coastal communities more resilient to future storms and protect offshore marine ecosystems that support coastal economies.”
The study was funded by the National Science Foundation, the golf research program of the National Academies of Science, and Rice University.
