The ocean currents that could sweep Gulf of Mexico oil up the Atlantic coast mightalso become a contaminated highway for billions of young sea creatures, some of which will grow to maturity off the Carolinas.
Commercially valuable seafood species such as snappers and grouper sometimes spawn in the gulf, their larvae riding currents to settle onto North Carolina reefs. Coveted Atlantic bluefin tuna, which brought North Carolina fishermen $1.4 million last year, are spawning now within miles of the oil leak.
Rare turtles are also swimming onto beaches in the gulf and Carolinas to lay their eggs.
Scientists say oil could stunt the animals' growth, cause breathing problems or kill them outright. Fish larvae and eggs are especially sensitive to toxic substances.
The odds remain low that the spill will reach North Carolina beaches. But oil leaking from the Deepwater Horizon well has reached the gulf's Loop Current, which flows south around the tip of Florida and then northward up the Atlantic coast on the Gulf Stream.
"The Gulf Stream stitches us all together," said Duke University marine biologist Larry Crowder.
The key questions, he added, are how much oil the Gulf Stream will deliver, for how long and in what form.
Well owner BP also acknowledged Thursday that more oil is gushing from the well than it had estimated. Some scientists think the volume has already surpassed the 11 million gallons the Exxon Valdez spilled in Alaskan waters 21 years ago.
Loggerhead turtles now nesting on Carolina beaches could hit oil in the Gulf Stream well offshore. The turtles, a threatened species, have to surface periodically to breathe as they swim and could become coated. So would sea birds and mammals such as dolphins.
"The first thing loggerhead hatchlings do is swim off to the Gulf Stream to hide in algae and feed," said Crowder, who studies endangered sea turtles, sea birds and marine mammals. "Even if the oil doesn't come onto the beach, they would be swimming into an oiled habitat."
The effect is impossible to predict, he added, because it's unknown how diluted the oil might be.
Swimming through oil
About 90 percent of North Carolina's commercially valuable sea life, including shrimp, blue crabs and many fish species, spawn offshore in fall and winter. By now their young have been swept through inlets into the vast, protective Albemarle and Pamlico sounds.
But if oil is still flowing past the North Carolina coast late this year, Crowder said, the spawning fish could have to swim through it.
Scientists have also reported thick plumes of leaked oil below the ocean's surface. Trapped there by salinity and temperature differences, the oil can't evaporate toxic components into the air as it could on the surface.
This mid-water zone links the surface and bottom. The underwater plumes could endanger dense concentrations of small fish and crustaceans there that predators feed on from above and below.
"Getting toxicity into that part of the food chain is a real problem because of the system's value as prey for just about everything else," said Douglas Rader, the North Carolina-based chief oceans scientist for the Environmental Defense Fund.
"If preliminary reports of large lenses of oil at different depths are correct, then you've got a prescription for a much bigger and much less manageable impact."
UNC Wilmington's Steve Ross is among researchers who have studied a deep-sea coral reef, called the Viosca Knoll, that is near the gulf oil slick. Pristine, deep-water coral reefs also lie off the Atlantic coast from North Carolina to Florida.
A thick blanket of oil could smother the living coral, Ross said. Oil droplets that attach to debris sinking to the bottom could also rain onto sensitive bottom-dwelling creatures. Researchers aren't sure what to expect.
"We have serious concerns that are difficult to answer because the appropriate studies have not been funded," Ross said. "Both we and [government] agencies have been remiss" in not assessing such risks sooner.