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Response team aboard USM’s Point Sur leads research effort after Bonnet Carré Spillway opening

Read prepares to release a tagged cobia.
Launching of Naval Research Laboratory glider (left) by Chief Scientist Adam Boyette and crewman Eric. (photo credit: Alison Deary)

In response to the earliest opening of the Bonnet Carré Spillway, in its 85-year history on January 9, researchers with the CONsortium for oil spill exposure pathway in Coastal River-Dominated Ecosystems (CONCORDE) led a three-day research effort aboard The University of Southern Mississippi’s R/V Point Sur to address key ecological questions regarding the impact of a large freshwater plume within Mississippi coastal waters.

Under normal flow conditions, the Mississippi River empties into the northern Gulf of Mexico through the Birdfoot Delta and the Atchafalaya River. Mild wintertime temperatures and heavy rainfall in the Midwest led to elevated Mississippi River levels and significant flooding of its tributaries, which prompted the Army Corps of Engineers to open the Bonnet Carré Spillway to relieve pressure on the levees. 

“The motivation for this study was to characterize a large plume of Mississippi River freshwater entering Mississippi’s coastal waters via Lake Pontchartrain,” said Adam Boyette, chief scientist of the research cruise. “Our aim was to examine the biological, chemical and physical composition of Mississippi’s river-laden coastal waters most impacted by the opening.”

The event marked the 11th time the Bonnet Carré Spillway has been opened since 1931.

Boyette said the large pulses of freshwater to coastal waters change the hydrologic regime and alter the concentrations of nutrients and organic matter, which can significantly impact coastal ecosystems of the Bonnet Carré Spillway.

“We collected hundreds of data points at surface, mid-depth and bottom water stations located in the Mississippi Bight between Feb. 9 and Feb. 11,” Boyette said. “We are still in the analyzing process and will know more about the influence of this large volume of freshwater once all the data is analyzed.”

CONCORDE worked jointly with four other GOMRI-funded research consortia, which include Ecosystem Impacts of Oil & Gas Inputs to the Gulf, Deep-Pelagic Nekton Dynamics of the Gulf of Mexico, Alabama Center for Ecological Resilience, and Consortium for Advanced Research on Transport of Hydrocarbons in the Environment.

Boyette said results from the research cruise are expected to be fully analyzed by May 2016.