Hundreds of sea turtles, more than sixty porpoises and a sperm whale have been found dead in the Gulf of Mexico region since the BP oil disaster began. As of mid-July, an area of almost 84,000 square miles, over one-third of the Gulf of Mexico, was closed to fishing.

While the impacts of the spill are most visible and devastating in the immediate area, the highly fluid nature of the ocean environment and highly migratory nature of some birds and marine species could transport effects of the oil over large distances.

Oil affects animals in several ways. The most obvious are the immediate, direct physical smothering and coating that impedes movement, vision and temperature control, and poisoning from ingestion of oil. Slower, less obvious. but no less harmful effects result from contamination of the environment, otherwise known as food and habitat. Less food is available as smaller prey organisms die, or else food is polluted. Oil on beaches, marshes, and flats poses a threat to eggs and juveniles. As eggs are contaminated, breeding success rates-which for protected species have been the subject of decades of time, money, and effort-decline.

Will oil from the Gulf of Mexico travel to the Gulf of Maine?

Susan Lozier, an oceanographer at Duke University and an expert on circulation in the North Atlantic Ocean, said it is not likely that substantial amounts of oil will reach Cape Cod, Georges Bank or the Gulf of Maine. She noted that initial reports that highlighted the potential for oil to move through the Florida Straits, along the Atlantic seaboard and across the North Atlantic in the Gulf Stream were based on the physics of how ocean currents would carry something that didn’t move or change over time.

Once the effects of oil evaporation, stirring, mixing and degradation are included, the projected concentrations of oil at significant distances from the source drop dramatically. Lozier predicts “oil will likely be seen only in trace quantities in the area north of Cape Hatteras, with a highly patchy distribution.”

Aside from breakdown of the oil en route, the Gulf Stream itself poses a major barrier to northward transport. Amy Bower, a physical oceanographer at Woods Hole Oceanographic Institution emphasized that surface water in the Gulf Stream moves northeastward and eastward so rapidly that cross-stream movement is difficult. According to Bower, “long, thin filaments of water can be pinched off from Gulf Stream meanders or rings”, which do deliver warm, southern water onto the New England shelf. However, Bower echoed Lozier’s assessment that any oil in Gulf Stream filaments is likely to be highly diluted.

What will be the impacts on animals that move between the two Gulfs?

The most prominent animal that spends time in both the Gulf of Mexico and the Gulf of Maine is the bluefin tuna. This species, which fuels a highly valued recreational and commercial fishery in New England, spawns in the Gulf of Mexico from April to June and then migrates north for the summer, mixing with eastern Atlantic and Mediterranean stocks.

NOAA Fisheries has intensified their regular larval surveys and satellite tracking in the Gulf of Mexico to monitor the impact on bluefin. “We are very concerned,” said Guillermo Diaz, a research fisheries biologist with the NOAA Fisheries in Silver Spring, Maryland, “We are not taking this lightly. It’s a dynamic situation changing on a daily basis.”

Molly Lutcavage, an expert on bluefin tuna who runs the Large Pelagics Research Laboratory, formerly of University of New Hampshire and now of University of Massachusetts, said that only two bluefin spawning areas have been documented in the western Atlantic ocean. Both are in the Gulf of Mexico and one is directly in line with the oil spill impact zone. “If bluefin eggs and larvae come in direct contact with surface oil, it will kill them,” according to Lutcavage, “while slightly older larvae and juvenile tuna could die from indirect effects through ingesting copepods or other prey.” Diaz confirms the potential for damage, “It is very difficult to predict the impact on bluefin tuna at this point, but it could be significant.” Lutcavage does emphasize that over half of the bluefin tagged in the Gulf of Maine and Atlantic Canada each summer don’t visit the Gulf of Mexico in their annual migrations, which may provide an “√∑escape hatch’ for the species to survive the spill.

Other species, including sharks, rays, swordfish, molas, black sea bass, tilefish, triggerfish, sea turtles and whales occasionally visit both gulfs. Researchers have been working for years to understand the annual migrations of right whales, humpback whales, sperm whales, leatherback turtles, loggerhead turtles and Kemp’s ridley turtles that are seasonal Gulf of Maine residents, but at this point the extent of migration to the Gulf of Mexico remains uncertain for all of these highly protected species.

Gordon Waring, of NOAA Fisheries Protected Species Branch in Woods Hole, Mass., notes that “Right whales migrate between winter calving grounds off the Florida and Georgia coasts and the greater Gulf of Maine. They are infrequently sighted in the Gulf of Mexico, and it is possible that those animals are among the group that feeds in the greater Gulf of Maine region in spring and summer”.

As with right whales, south-migrating humpback whales have been recorded in the Gulf of Mexico occassionally, said Keith Mullin from NOAA’s Southeast Fishery Science Center. Mullin also noted that male sperm whales leave the Gulf of Mexico and travel to northern latitudes and are occasionally seen in the Gulf of Maine region.

Sea turtles, including leatherback, loggerhead, and Kemp’s Ridley spend summer months in the Gulf of Maine feasting on jellyfish and salps. Tagging studies and DNA typing continue to shed light on whether these seasonal visitors spend their winters in the Gulf of Mexico, or in other nesting areas along the southeast U.S. and throughout the Carribean, but at this point the answer is not well known. Lutcavage, from UMass, notes that unlike bluefin tuna, which are highly attuned to chemical signals in the water, turtles may be less able to sense and avoid oiled areas, and may thus be more heavily impacted. In what’s being called an “unprecedented intervention,” the US Fish & Wildlife service and state wildlife officials are moving sea turtle eggs from Gulf of Mexico beaches to the Atlantic side of the Florida coast.

Above the sea, many Gulf of Maine birds are migratory, stopping on their seasonal migrations between nesting grounds in Boreal and Arctic Canada and the Southeastern US, Central and South America.

“This spill happened in one of the worst places possible from a bird-centric view,” said Jeff Wells of the Boreal Songbird Initiative. In a blog post in June, Wells outlined the impacts of the oil on bird species.

Wells anticipates that as summer progresses into fall, birds migrating south will intersect with the oil slick. Species that breed in the Northern Forest but migrate to the Gulf of Mexico for the winter, including mallard, Northern pintail, green-winged teal, American wigeon, ring-necked duck and greater and lesser scaup, face a “ticking time bomb,” according to Wells.

Wells said shorebirds that pepper Maine’s beaches in spring and fall, such as black-bellied and semipalmated plover, yellowlegs, solitary and least sandpipers, dunlin, short-billed dowitcher and Wilson’s snipe, will stop in the Gulf of Mexico to rest and feed before continuing down to their winter homes in the Caribbean and South America

While the transport of oil to Maine shores appears unlikely, the effects of the oil on species that spend time in the Gulf of Maine may be substantial.

This article is made possible, in part, by funds from Maine Sea Grant and the Oak Foundation. Heather Deese holds a doctorate in oceanography and is the Island Institute’s director of marine programs. Catherine Schmitt is communications coordinator for Maine Sea Grant.