Oil Spill Impacts on Sea Turtles
The five species of sea turtles that exist in the Gulf were put greatly at risk by the Gulf oil disaster, which threatened every stage of their life cycle, from egg to adulthood. Scientists will be watching the impacts for years to come.
Already, data from the Sea Turtle Stranding and Salvage Network indicates a five-fold increase in sea turtle strandings in the aftermath of the Gulf oil disaster. Between 1986 and 2009, an average of nearly 100 sea turtles were found stranded annually in the oil spill area. Since the spill, roughly 500 sea turtles have been found stranded each year, most of which were the Kemp’s ridleys.
How Many Sea Turtles Were Immediately Affected by the Gulf Oil Disaster?
During the six months following the start of the Gulf oil disaster, 1,066 sea turtles were collected in the spill area. Of those, more than 450 showed clear signs of oiling.
The following map animation shows when and where injured and dead sea turtles were picked up in the months following the start of the oil spill.
Where Did These Numbers Come From?
This map is based on the consolidated numbers of sea turtles that were reported by the National Oceanic and Atmospheric Administration (NOAA). These records were used to map the animals collected each day. There are minor variations from official government records in the total number of animals shown, for several reasons. The date marked on each map is the date the data were posted online by the government. Since then, a few additional animals have been collected. Furthermore, due to the time needed to process and verify data, animals collected just a week to 10 days prior to the date of data release may have not yet been recorded.
Was the Oil Spill the Cause of All These Deaths and Injuries?
These numbers include all sea turtles collected in the oil spill area. While the actual cause of death has yet to be determined for most of the animals, it is clear that a large proportion of the deaths and injuries were related to the oil spill, as the number of animals collected--especially the birds and sea turtles--was far beyond what is usually found in that area.
Will the Total Number of Sea Turtles Affected Ever Be Known?
No. Although the sea turtles tallied in these maps may include some that were injured or died of causes unrelated to the spill, given the vastness of the Gulf others surely disappeared without being observed or collected by authorities. Scientists are also concerned about other impacts on sea turtles that can be even more difficult to discern, ranging from the sublethal effects of oil exposure on reproduction and other physiological functions, to the loss of important foraging or nesting habitat.
What is the Most Concerning Thing About These Numbers?
Unfortunately, the sea turtle species that was hardest hit by the spill was the Kemp's Ridley, the most endangered sea turtle in the world, and one that can least afford to suffer such losses. Of the more than 600 dead sea turtles, nearly 500 were Kemp's Ridley sea turtles.
How Did Sea Turtle Strandings Differ From Previous Years?
In the months after the explosion of the Deepwater Horizon, sea turtle strandings increased to more than six times the average strandings during those same months in the last two decades.
The above chart (put together by National Wildlife Federation senior scientist Doug Inkley
using Sea Turtle Stranding and Salvage Network data) shows monthly averages for 22 years of strandings, compared to the corresponding months in 2010, when the Gulf oil disaster occurred.
How Does Oil Impact Sea Turtles?
Studies have noted that sea turtles do not instinctively avoid oil slicks, putting them at greater risk for exposure when they surface for air. Juveniles and adults also sometimes mistake tar balls for food and will directly ingest the oil.
- Burning in mucous membranes of the eyes and mouth
- Irritation or inflammation of the skin
- Gastrointestinal inflammation, ulcers, bleeding, poor digestion
- Respiratory irritation, inflammation, pneumonia, emphysema
- Organ damage, suppression of the immune system, reproductive failure
Dispersants and "Burn Boxes"
Not only are scientists concerned by the impact of oil on sea turtles, the tactics used to get rid of oil also put turtles at risk.
After the explosion, BP pumped hundreds of gallons of chemical dispersants into the Gulf to break up the oil. We are still watching for what impacts that "toxic sludge" could have on the water column and Gulf ecosystems.
Another tactic used by BP to get rid of the oil was to burn the oil from the water's surface. In July, reports surfaced that these BP "burn boxes" were also unintentionally torching sea turtles and other wildlife.
How Does Oil Threaten Hatchlings?
Sea turtle hatchlings undergo an intense struggle that begins with forcing their way through the leathery eggshell, making their way to the surface, crawling across the wide expanse of the sand to the ocean - -and that's only the start of their journey. Few hatchlings make it to adulthood in prime conditions. Add oil and dispersants to the mix, and the results could be devastating.
If the hatchlings emerge on oiled beaches, they can suffer surface exposure to oil as they make the trek toward the water.
Once in the ocean, young turtles spend much of their time on the surface where they are more likely to run into an oil slick.
Sea turtle hatchlings rely on floating vegetation for places to seek cover from predators and to rest. Sargassum, a type of seaweed, is common habitat for young turtles, but was suffocated by oil, depriving the seaweed of vital sunlight. Without sargassum, many sea turtle hatchlings (and the array of other marine species that use sargassum for feeding, breeding or nurseries) have no refuge in the open ocean.
What Was Done to Help Sea Turtle Hatchlings Survive?
The Sea Turtle Conservancy, with support from the National Wildlife Federation, helped state and federal agencies execute a plan to relocate sea turtle hatchlings in the vicinity of the Gulf oil disaster to the east coast of Florida.
Trained personnel carefully dug up nests by hand in the late stage of incubation, and transported the eggs to a secure facility, where they were held until the eggs hatched. The turtles were then released on beaches along the Atlantic.
The relocation was done with full knowledge that some of the eggs might not survive. However, biologists predicted that if nothing was done and hatchlings were allowed to enter the Gulf, they would be put at high risk for encountering oil and the exposure would likely be fatal.
Over 14,000 sea turtle hatchlings were safely released into the Atlantic.
Watch this video about the sea turtle nest relocation efforts:
Sea Turtle Species of the Gulf of Mexico
Green Sea Turtles
Green sea turtles are the only marine turtle species that are dedicated herbivores as adults, subsisting primarily on sea grasses and algae. Post-hatchlings swim to open water to feed on vegetation and small marine animals near the water's surface. Juveniles and adults like to feed closer to shore. In the southeastern U.S., green turtles' peak nesting is from June to July. More about green sea turtles >>
Loggerhead Sea Turtles
Loggerheads' large skull and powerful jaws allow them to eat hard-shelled prey like whelks and conchs. Females have a relatively long nesting period, laying eggs between April and September. Hatchlings start emerging around late June and continue to hatch through mid-November in the southeastern U.S. and head out to open water where they reside in floating vegetation, including Sargassum algae. More about loggerhead sea turtles >>
Leatherback Sea Turtles
As their name implies, leatherbacks lack the hard shell that other sea turtles have. They are also the largest sea turtle, reaching lengths over six feet and weighing as much as 2,000 pounds. Within U.S. waters, leatherbacks nest most actively along Florida's Atlantic coast, Puerto Rico, and the U.S. Virgin Islands.
Hawksbill Sea Turtles
Though hawksbill nesting on Gulf shores is relatively minimal, they are a common sight along Texas and Florida coasts. Hawksbills prefer reef habitats but have also been known to inhabit estuaries and bays with mangrove trees. More about hawksbill sea turtles >>
Kemp's Ridley Sea Turtles
Kemp’s ridley sea turtles are one of the smaller marine turtle species, weighing around 100 pounds on average. They nest primarily on the coast of Mexico but nests have been found on the coasts of Texas and Florida as well. Hatchlings swim out to open water quickly to avoid predators close to shore, and ride currents within the Gulf of Mexico or have been known to follow the Gulf Stream current that takes them around Florida to the Atlantic Coast. More about Kemps Ridley sea turtles >>