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Wetlands researchers publish findings on new cane invading the delta

Loyola press release - May 24, 2011

For almost a quarter century, Loyola University New Orleans biologists and ecologists Donald Hauber, Ph.D., Craig Hood, Ph.D, David White, Ph.D., and several undergraduate honors students, have studied the origination and effects of the common reed known locally as Rouseau Cane on the marshes and coastal wetlands of southeast Louisiana.

Their findings, which detail the spread of this plant and its role in coastal protection, is found in the recently published study, “Genetic Variation in the Common Reed, Phragmites australis, in the Mississippi River Delta Marshes: Evidence for Multiple Introductions.”

“Rouseau Cane has dramatically increased in the coastal wetlands along the Atlantic and Gulf Coasts during the past century,” White said. “The species’ spread is mainly due to the introduction of new gene types from Europe. These invasive types are becoming more common in the interior marshes of the Mississippi River Delta, land that is extremely rich in nutrients.”

The Mississippi River Delta covers an area roughly 521,000 acres, but during the last 40 years, it has been significantly reduced due to lack of river sediment coupled with high natural subsidence.

P. australis is the dominant emergent vegetation in the Delta’s outer two-thirds and is believed to play a major role in stabilizing these extensive marshes by breaking wave action and storm surges from the open Gulf while also capturing and retaining river sediment. “This stabilizing role protects the diverse interior marsh communities that provide food and breeding habitat for wildlife, particularly birds,” said White.

“In recent years however, the new European gene types of P. australis, have begun to expand into the interior marshes displacing food and habitat resources for wildlife,” said White. “This new invasion into these inner marshes will have negative impacts on sustaining the migratory and local wildlife.”

In the study, Hauber, Hood and White identified several new DNA types of P. australis which were likely brought here by migratory birds, river currents or ships. These European types are increasing the species’ footprint in the delta at an alarming rate, according to White.

In March, the three professors and university photographer Harold Baquet flew over the wetlands to study the impact from above. The flight was donated by LightHawk, a Wyoming based operation that partners with conservation groups by supplying planes and pilots at reduced costs helping worthy environmental causes around the U.S.

During the flight, White noted the massive impact of Hurricane Katrina on the wetlands. “Flying over the coast and the Mississippi Delta, it is a terrifying and powerful image because of what is no longer there and it proves to me that the city is more vulnerable to another significant storm surge than I previously imagined. If every citizen of Louisiana had this kind of flight opportunity, we’d be moving much quicker and with far more attention to protecting and restoring our coast.”

The flight also confirmed that the invasive types of P. australis were spreading throughout their research sites in the inner marshes of the delta. In a similar flight during the spring of 2006, White had observed small areas of the invasive P. australis that are now much larger and spreading to other areas even outside the delta. The recent flight also revealed effects of the Deepwater Horizon Oil Spill on the delta’s marshlands.

“Although the oil spill caused some coastal wetlands loss along the very margins of the delta’s shoreline, I would say, with some certainty, the total wetland loss in the delta is remarkably low as a result of the spill, though any loss is very troublesome,” White said. “The small amount of loss is partly due to the freshwater sheet flow that kept oil away from the delta freshwater wetlands, and partly because of the peripheral stands of the P. australis which became the frontline physical barrier to oil invasion inland.”

According to White, the oil-damaged P. australis on the outer most parts of the delta is, in some areas at least, already regenerating and resprouting stems. He is hopeful that by the end of summer 2011, much of the oiled cane will be back to full recovery. However, he added that some marginal wetlands will likely be completely lost.

White, Hood and Hauber will use the new photo images from the fly-over taken by Baquet to continue studying P. australis in their study areas. “The study of P. australis is central to the health and stability of the wetlands of the Mississippi River Delta,” said White.

For more information, contact Sean Snyder in Loyola’s Office of Public Affairs at smsnyder@loyno.edu or call 504-861-5882.

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