In comparison to other oil spills in the Gulf of Mexico — especially BP’s Deepwater Horizon Disaster — the spill of 168,000 gallons into Galveston Bay, Texas on Saturday seemed relatively minor to many nearby residents.

Capt. David Harris, who runs a recreational fishing boat business in the bay, said he’s unconcerned about the environmental impact.

“We don’t see any oil,” he said. “It seems business as usual.”

But experts warn – given the uniquely sensitive features of Galveston Bay – that even as visual evidence of the spill dissipates, the environmental impacts could prove problematic down the line, and the full extent of the spill’s damages may not be known for a year or more.

“People have the tendency to focus on the horrible pictures of birds and turtles and all the animals that you’d like to hug covered in oil, but the real damage is done elsewhere,” said Doug Rader, the Environmental Defense Fund’s chief ocean scientist. “Around Galveston Bay, this stuff can last a very long time, and create a very long-term impact.”

The spill occurred Saturday when an oil barge collided with another vessel on a busy shipping route in the bay. The collision ruptured a tank containing an especially viscous form of crude oil, ultimately spilling about 168,000 gallons into the water. The spill caused officials to shut down ship traffic entering from the Gulf of Mexico for three days.

Calm weather allowed the surface oil to be cleaned up quickly, and local activists say they got lucky when winds carried much of the oil out of the bay and into the much larger, less sensitive gulf (they point out oil spilled anywhere isn’t good, but it’s less bad if it’s more spread out and not covering wetlands).

While the spill was much smaller than other more infamous spills like Deepwater Horizon or Exxon Valdez, some experts warn that it could have similar effects because of where it occurred, and the timing.

Galveston Bay is one of the largest estuaries in the United States. It is a breeding ground for many species of fish and other sea creatures, and is a major stopping point on migratory routes for birds.

Compounding the problem is the timing of the event: The first weeks of spring are when many marine species lay eggs, which can be especially vulnerable to the effects of spills. And birds are just now coming back from their winter migrations, often stopping at Galveston as they make their way over the Gulf of Mexico.

“Scientifically, we’re very concerned,” said Greg Stunz, the director of the Center for Sportfish Science and Conservation at the Texas A&M University-affiliated Harte Research Institute for Gulf of Mexico Studies.

“These are really key habitats,” he said. “Small crustaceans just hatched weeks or days ago. Those life phases are particularly susceptible to pollution ... and you won’t see the effects on them until a year later.”

Still, environmentalists and scientists think they may have dodged a bullet. So far, little oil has been spotted in the wetlands of the bay, and it seems as if workers were able to contain it quickly enough to prevent catastrophic damage.

But they say it will be a while, possibly years, before the full extent of the damage is known.

“This has the makings of a really bad oil spill, but it could’ve been a lot worse,” said Bob Stokes, president of the Galveston Bay Foundation. “I’m hopeful that the worst is behind us, but you never know.”