Could Oil Exposure Make Marsh Grass More Vulnerable to Fungus?

All of the affected areas were on or near the Mississippi Sound where oiling had occurred; in contrast, areas north of the sound, saw no infection.

12-27-2010 // Craig Guillot

As a widespread fungus outbreak affects a key marsh grass species in Alabama, some are questioning if the Gulf oil disaster has played a role. The fungus has the potential to halt reproduction of much of this year’s crop of Spartina alterniflora, a grass that is key in holding the fragile wetlands together.

The fungus, Claviceps purpurea, is naturally occurring and has been documented on the Gulf Coast since the late 1800s. While the fungus will not kill adult plants, it can produce shafts that protrude from plant seeds and essentially make them sterile. Spartina alterniflora is critically important to marshes on the Gulf coast, helping hold the delicate land in place and preventing erosion. In parts of Louisiana, oil and dispersants have severely impacted coastal marshes.

Bill Finch, executive director of the Mobile Botanical Gardens, originally made the discovery. Finch noticed something was wrong when he ventured out into the marsh in early December to collect seeds for restoration work.

"The population I looked at was pretty well infected with this fungus. There are many stress factors this year but I'm surprised at the extent of the outbreak," said Finch.

The Mobile Press-Register broke the story in early December, and after surveying 20 miles of shoreline, the newspaper documented the presence of the fungus in marshes along West Fowl River, Portersville Bay, Heron Bay, Raccoon Island and portions of the lower Mobile Bay. All of the affected areas were on or near the Mississippi Sound where oiling had occurred; in contrast, areas north of the sound, saw no infection.

Bruce Stein

Bruce Stein Ph.D., a conservation scientist with National Wildlife Federation, said that any kind of stress has the ability to make plants and species more vulnerable to diseases and fungi. He points to the Southwest, where drought has made pine forests more susceptible to pine beetles; and to the Chesapeake Bay, where oysters have become weakened through degraded water quality. While there is not yet any evidence to support that the oil is a factor in the Alabama marsh’s fungal outbreak, Stein said it is not out of the question to think that oiling could have stressed the plants.

“The susceptibility of different plants to diseases or fungal infections can be related to stress. When the plants are stressed, they are sometimes more vulnerable to infection. I don’t know if that is what is going on but it certainly can take place,” said Stein.

Finch said that the fungus has complex life cycles but it has been proven that hydrocarbons are a potent source of energy.

“What happens if you add more hydrocarbons to the soil and there is a higher dosage? Could that increase the abundance of fungi? These are the kinds of questions we need to be asking,” said Finch.

Judy Stout, Ph.D., a biologist and former professor at the University of South Alabama Department of Biological Sciences, has seen these fungi infections in the marshes of Alabama since the 1970s. She said that there are various conditions that can cause marsh grasses to become more susceptible to such fungi. A 1974 survey in the area showed that plants in one site that was disturbed by dredging had a higher infection rate than other marsh areas. Yet Stout remains skeptical that the oil is a contributing factor and said more research needs to be done on the matter.

"I am very cautious and concerned about it. In my gut I don't think there is a relationship but I have no evidence. If there is anything to be brought to the table by this is to say we don't understand it, to fund some studies and go find out,” said Stout.

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