On the first anniversary of the Gulf oil spill, scientists are observing strange deaths and deformities in animals that could be related to the disaster, experts say.
In the past six months, the numbers of dolphin and sea turtle deaths in the Gulf of Mexico (map) have risen, and some fish that inhabit the Gulf's coral reefs have developed abnormalities. (Read more about the Gulf oil spill anniversary.)
Yet projects to document and measure the oil's effects on Gulf marine life are still in the very early stages, scientists caution. Preliminary results may not be available for months, and it may be several years before any kind of scientific consensus is reached.
Such uncertainty is not unusual for oil-spill studies, noted William Patterson, a marine biologist at the University of West Florida (UWF) in Pensacola.
"If you look at the literature surrounding the Exxon Valdez oil spill [in 1989], there are still some unknowns associated with that," Patterson said.
"What we know [in the case of Exxon Valdez] is that there was an insult to the system, that there were effects on the food web and ecosystem, and that some species have not recovered to the levels they were at before." (Related: "Exxon Valdez Anniversary: 20 Years Later, Oil Remains.")
Some of the Exxon Valdez oil's effects are circumstantial evidence, he added, "but it's pretty compelling evidence."
Mysterious Spike in Dolphin, Turtle Deaths
This winter, an alarmingly high number of bottlenose dolphins—113 at last count—washed up dead on U.S. shores, according to the National Oceanic and Atmospheric Administration (NOAA). The agency confirmed in early April that six of the bodies had Deepwater Horizon oil on them.
(Read more: "Dolphin-Baby Die-Off in Gulf Puzzles Scientists.")
"What's important to note, however, is that even though they have this oil on them, it may not be the cause of death," Blair Mase, NOAA's marine-mammal investigations coordinator, told reporters at a news briefing April 7.
"That's something the investigative team and our working groups are looking into."
So far this year scientists have also seen a rise in deaths of various species of Gulf sea turtle hatchlings. But NOAA researchers say the culprits may be contact with boats and fishing gear and possibly poisoning by toxins in algal blooms, which naturally appear in the Gulf each spring.
"The carcasses that we have looked at . . . had no visible oil on them," said Barbara Schroeder, national sea turtle coordinator for NOAA.
Fish Found With Deformed Ovaries, Missing Fins
UWF's Patterson has recently observed an increase in physical abnormalities consistent with oil exposure in red snappers that live in Gulf coral reefs.
"There are parasites showing up on the fish. They're always present, but this fall and winter we're seeing them in what appears to be higher abundances," Patterson said.
Some of the fish are suffering so severely from a disease called fin rot that entire fins are missing—something Patterson said he has never seen before. Some female red snappers also have been discovered with hardened or deformed ovaries.
Other red snappers have strange pigmentation issues, Patterson said. "We have some images of red snappers sent to us by commercial fishermen that have black bands across the sides of the fish that is discolored skin."
These symptoms are not unusual in themselves, Patterson said, but the fact that they're appearing at what looks to be increased rates at the same time concerns him.
"Some of these things that we're seeing are classic symptoms of hydrocarbon exposure that have been documented in lab studies."
For example, the odd pigmentation could be caused by the fish's kidney or bile duct being affected or clogged by oil components.
"So it does seem to be pointing in one direction, but we don't have anything definitive yet to tell the full story."
Chuck Jagoe, an environmental toxicologist at Florida A&M University in Tallahassee, is working with Patterson to test Gulf red snappers for telltale enzymes that are produced when the fish flush toxic oil components from their bodies.
"These enzymes are associated with the detoxification process," Jagoe said.
"They can give us an indication that the animal has not only been exposed to [oil] compounds, but that the compound is having some kind of biological effect."
Jagoe has just begun testing the fish, and the first results won't be available until at least early summer.
One Species Not Enough Evidence
UWF's Patterson said he also plans to investigate whether other Gulf species are exhibiting symptoms similar to those of the snappers.
Even nearly a year after the disaster, oil could still be lurking in the Gulf's waters, he added.
"Oil is not one thing," Patterson said. "It's thousands of organic compounds. Some of them are fairly [unstable] and microbes break them down very quickly, while others could persist for a long time."
Finding other affected species will be crucial to making a case that the oil spill is having a systemic effect on Gulf fish species, said Prosanta Chakrabarty, a fish biologist at Louisiana State University in Baton Rouge who was not involved in the snapper project.
"With one species, we can't really tell," Chakrabarty said.
He also noted that red snappers are already a vulnerable species due to overfishing, and that it's possible the symptoms that Patterson is seeing are due to inbreeding caused by a decreased population.
Whatever the cause of the deformities, though, "the oil spill didn't help any," he said.
Fish Populations Measured via GPS
Chakrabarty is involved in another project called Depthmap, which aims to use fish-population data collected using GPS technology before and after the spill to investigate the Gulf oil spill's impact on marine life. Museum records are also used to fill out pre-spill data.
"If, for example, 80 percent of Gulf pancake batfishes were found off the coast of Louisiana and they're not there anymore," then that could be an indication the spill negatively affected the species, he said.
And if this pattern is repeated for many fish species, it would indicate the spill has had a pervasive impact on Gulf marine life.
Chakrabarty's team hopes to gather pre- and post-spill population data for 600 fish species in the northern Gulf, but has only begun analysis for a fraction of that number due to limited funding.
His early results suggest that of the 53 species examined so far, 43 had major populations that lived in regions that were in the path of the spill.
Deep-Sea Effects Leave Scientists in the Dark
Even if Depthmap's goals were met, however, scientists would still know only about the impact the spill had on fish that live in relatively shallow water. But the spill's largest potential damage is to deep-sea creatures, Chakrabarty said. (See pictures of deep-sea animals.)
The broken wellhead blew at 5,000 feet (1,500 meters) underwater, and plumes of gushing oil floated nearly 1 mile (1.6 kilometers) up from the seafloor, polluting different layers of water as they rose.
"We knew that the oil wouldn't last at the surface for very long, but what happened at the deep sea?" Chakrabarty said.
Of particular concern, he added, are the effects of the oil dispersants piped into the waters near the wellhead in a desperate bid to break apart the oil before it reached the surface.
"The deep sea is such a stable environment. . . . It isn't used to perturbations like this influx of [dispersants]," Chakrabarty said.
"So what the impact [is] of having [dispersants] enter that area, even momentarily, is difficult to understand."
Despite his concerns about the deformed fish, UWF's Patterson added that it's important for scientists not to jump to conclusions.
"As scientists, we shouldn't be unwilling to say we're not quite sure," he said.
"Instead of going out on a limb and making grand announcements, I think it's a safer approach to say, Well, these are issues that we're seeing that we're not able to attribute to any one thing, but we're concerned about them.
"And that's where we are."
*The photographer, a commercial fisher in the Gulf, requested to remain anonymous.