Flooding: Bad for Oysters, Great for Oysters

Some Houston-area oyster reefs have been shut down by the state health department as a result of this week's major rain storm, which washed a potentially unsafe amount of bacteria into the region's bays. In the short term, the closures are bad for commercial harvesters and oyster-loving foodies. But according to the Texas Parks & Wildlife Department, it's actually pretty beneficial to everyone — oysters included — in the long run.

In a phone interview, Lance Robinson, deputy director of the department's Coastal Fisheries Division, said that the sudden influx of freshwater could possibly be tainted, temporarily, with "fecal coliform" from animal livestock or flooded wastewater plants, forcing the Health Department to shut down particularly troublesome areas, as it did in a few parts of Galveston Bay yesterday. Interestingly, Robinson also said that industrial pollution typically isn't much of a post-flood problem, because facilities are heavily regulated and monitored to prevent a "catastrophic secondary impact" from occurring. But the bacteria is bad enough, and could make raw oysters unsafe for eating.

The influx of freshwater alone is enough to ruin an active oyster crop. Robinson said oysters are "resilient" and "adaptable," having survived in this environment for "millennia," but they can't really move to evade floodwaters. Mortality is inevitable. 

"There's not much you can do about that," Robinson said. "It's just Mother Nature taking its toll. But there can be, and there usually is, a silver lining."

According to Robinson, the freshwater flooding "wipes the slate clean" in the ecosystem, similar to the way a controlled burn rids a forest of dead plants and brush. The result, he said, is a "recharge" that usually leads to an oyster bumper crop a few years down the road.

Robinson said the Texas estuary, a place where freshwater and saltwater mixes, has struggled to find enough freshwater as the state's booming human population demands more and more for itself. When rainfall and flooding pump freshwater into the bays, it "jumpstarts productivity" by clearing out dead organic material and depositing it as a nitrogen source for microscopic organisms that feed the rest of the food chain. 

Even though oysters may die at first, flooding will also kill a lot of the other organisms that attach themselves to oyster shells, like sponges or mussels, clearing more room for juvenile oysters to attach themselves to the (probably lifeless) shell and grow. If a flooding event coincides with spawning season, which peaks in May and lasts through the summer before peaking again in the fall, then, Robinson said, we should expect a bigger crop of oysters a few years after the fact.

"Although it is certainly disruptive when it's occurring, and we don't want to see people lose property and lives, to the ecosystem it can be a benefit to marine estuarine resources," Robinson said.

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