Scientists work to revitalize Alabama's Gulf coast oyster beds
For some people, oysters are something you serve up on the half shell. But, the mollusks also play a major role in the environment and economy of Alabama. On a Saturday morning, a pair of small boats ease up to a cove at Lightning Point near Bayou La Batre. On board are a handful of students, marine scientist, and volunteers. The passenger list also includes about sixteen 16 million baby oysters. Mobile Bay residents enjoyed oysters long before the first Europeans arrived. Today, the shellfish population is a fraction of what it was a few decades ago. The loss is more than an issue for fans of seafood.
“I can't remember the exact amount, but it's something like two acres of oysters is like having a sewage treatment plant with how much nitrogen they remove. They filter a bunch of water,” said Lee Smee. He chairs university programs at the Dauphin Island Sea Lab. He’s also a professor of marine and environmental sciences at the University of South Alabama. He points to the limestone breakwater he’s sitting on at the water’s edge.
“I was talking to some people that grew up here and they told me that this whole shoreline, you had the marsh, but you had this fringing oyster reefs,” Smee recalled. “So, you didn't need these rocks. It was just lined with oysters and so, hopefully, over time, we'll restore oysters here and they'll be covering these rocks and you'll have these really nice, natural fringing oyster reef that not only will protect the shoreline, but it's going to clean the water. It's going to spawn out here and boost the fishery. So, there's a million reasons why we want to have good healthy oyster populations out here to both protect the marsh, provide good habitat for other things and clean the water and do all these other benefits for us.”
Students and staffers at the Sea Lab stand in knee-deep water as bag after bag after bag of oyster shells is passed down from the boats.
“Our spat are these little guys. They almost look like a little fingernail,” said Christa Russell, a Ph.D. student working on the project. She sounds like a teacher proud of her students as she points out the tiny baby oysters attached to each shell.
“See that one has a little black stripe?” said Russell “That's a special breed that Auburn loves. They like to get that stripe on them.”
Spat is the term for baby oysters once they attach to a surface and start to grow. That’s after they swim around for the first week or two of their lives. Then the little oysters look for a place to settle down, permanently. Fowler says that’s when they become known as a spat.
“They fuse in the water column and grow a little plankton, so he's free swimming in the water,” Russell observed. “When they're about seven to 14 days old, they start looking for a place to settle. So, they actually settle down, grow a foot and from that point on, they're benthic and they stuck where they sit, so they have to pick a good spot.”
These oysters have another advantage. Many of them were raised in tanks with blue crabs nearby. Smee says the presence of a predator causes the oysters to grow heavier shells, giving them a better chance against threats.
“So, we've had these in the lab for a month growing with blue crabs because this makes the shells tougher and stronger. Half of them have not,” said Smee. “And so, we're going to build a reef today and then come back and it several times a month over the next year and kind of see if the predator exposure will help us be more successful with oyster reef restoration.”
That advantage comes at a frightening price if you’re a baby oyster. The ones with tough shells make the grade. The remainder are on the menu for the blue crab. Smee explains there’s more going on than who get’s eaten and who doesn’t. He says the oysters see what’s going on around them.
“There's mesh cage and we just keep a live blue crab in there and we feed it an oyster three times a week. The oysters are not only getting the cue of the crab, they're getting the cue of their friend getting eaten by the crab. So, it's extra scary,” said Smee.
“There have been some past studies that show that populations, we're at 80 percent less than historic populations have been in Mobile Bay, Mississippi Sound,” said Judy Haney, marine program director with the Nature Conservancy. All this work comes as the oyster population is one fifth. Haner says that decline can be traced to a lot of things that need to be fixed.
“And part of that was, we didn't have rocks like this, materials to construct roadbeds with. So a lot of these three-dimensional oyster reefs that we used to have along Mississippi Sound and Mobile Bay were actually harvested to use as road bases. The road that goes to New Orleans is paved with Mobile Bay oysters because that's the material that they had at the time to work with. Now we know better,” she observed.
The oyster reef is part of a bigger project to build up the coastline on Mobile Bay and restore the environment. Haner says the Lightning Point project has been going on for two years and has survived six named storms.
“It's really an interesting project here at Lightning Point,” she said. “We started working with the community several years ago to acquire property in the area and listen to their concerns, which one of the big concerns was erosion along the shoreline and, so we hired some engineers, secured some funds and basically have built back about forty two acres of marsh with some upland ridges in it, a mile and a half of breakwaters and jetties, two hundred and fifty six thousand cubic yards dredge material really to serve as protection for the community, but also habitat for fish, for birds, for shellfish.”
Those shellfish, particularly oysters, are also part of the culture of communities like Bayou La Batre going back centuries.
“They are, I think, the second largest commercial fishery in the Gulf and not only are they important as a fishery, but the culture of so many of these communities are tied to the oyster harvest and oyster festivals and these kinds of things that having healthy oyster populations is economically and ecologically very, very important,” said Lee Smee of the Dauphin Island Sea Lab.
Smee says the project shows how research is a benefit to not only science, but the environment and the community. If there are fewer oysters, there’s less money to be made by Alabama fishermen.
“Sometimes when we do science, it's not always clear to nonscientists why it's important,” Smee points out. “I think this is a really good example of a very practical application. We're interested in the mechanism behind how oysters harden their shell and we're working to identify those molecules and how that builds into the food web. We have all these questions that scientists are interested in, but for all the reasons I stated before, oysters are really important. If we can build them better, we can do something practical and everybody can get behind it.”