The Gulf Oil Spill and Sea Turtles

The green sea turtles (Chelonia mydas) that are found in San Diego Bay are of part of the Pacific population which is listed as endangered and is therefore protected and closely managed. Similarly, other species and populations of sea turtles found along U.S. coasts and in U.S. waters are protected and closely monitored; all five species of sea turtles found within U.S. waters are listed as either endangered or threatened. All five of these species are found within the Gulf of Mexico.

1. Green (Chelonia mydas) - Breeding populations in Florida & Mexico's Pacific coast (includes San Diego's turtles) = Endangered; all other populations, Hawaii, = Threatened
   
2. Loggerhead (Caretta caretta) - Threatened
   
3. Leatherback (Dermochelys coriacea) - Endangered
4. Kemp's ridley (Lepidochelys kempii) - Endangered
   
5. Hawksbill (Eretmochelys imbricata ) - Endangered
   

A sixth species, the Olive ridley (Lepidochelys olivacea) is found along the Pacific coast - usually Mexico and south. The seventh species of sea turtles, the Australian Flatback (Natador depressus), is only found in waters near Australia and Papua New Guinea. (photo by C Turner T, Green turtle near St. Thomas)

According to NOAA's Office of Response and Restoration, as of May 31st:

• 253
• total number of sea turtles verified from April 30 to May 31 within the designated spill area

• 228 or 90%
  
• total number of turtles stranded dead

• 15
• number of turtles stranded alive
  

• 3
• of those 15, the number that subsequently died
  

• 7
  
• number of turtles captured May 31 "alive and very oiled" (6 Kemp's ridleys, 1 green; all pelagic-stage juveniles) by a "directed search efforts from a search vessel that included NOAA, Florida Fish and Wildlife Commission staff and other partners"
  

• 40 mi
  
• distance offshore the NOAA+partners team was that captured the above mentioned 7 turtles

• 12 and 1
  
• of the 253 turtles verified within the spill area, the number of alive (12) and dead (1) turtles collected with "visible external evidence of oil. All others have not had visible evidence of external oil."

• 21
• turtles in rehabilitation

The summary report also states that, "turtle strandings during this time period have been higher in Louisiana, Mississippi and Alabama than in previous years for this same time period. This may be due in part to increased detection and reporting, but this does not fully account for the increase." Even without the oil spill, the turtles in the Gulf of Mexico, like all ocean waters, are subject to many threats which cause mortalities every year. These threats include entanglement (in active and abandoned fishing gear, as well as debris/pollution), fishery bycatch, natural predation (i.e. sharks) and poaching, cold-stun/hypothermia during cold snaps, diseases and parasite-related infections, and habitat loss (includes nesting beaches and foraging grounds such as seagrass beds and coral reefs).

My advisor from NOAA's Southwest Fisheries Science Center has even joined in the efforts to rescue some of these turtles, off the Louisiana coast, from some of the many oil driftlines.

Driftlines are usually made up of floating alga - usually Sargassum - and other floating debris that are brought together from currents and wind into these convergence zones. Juvenile turtles, especially, use these floating patches to rest in, feed in, and avoid predators. However, the oil which is being clumped together at the surface is also becoming collected in these driftlines. (photo: loggerhead hatchlings in Sargassum)

NOAA's Office of Response and Restoration's "Oil and Sea Turtles: Biology, Planning, and Response" guide describes oil-spill associated risks to turtles as follows:

• Although surprisingly robust when faced with physical damage (shark attacks, boatstrikes), sea turtles are highly sensitive to chemical insults such as oil.
• Areas of oil and gas exploration, transportation, and processing often overlap with important sea turtle habitats.
• Sea turtles are vulnerable to the effects of oil at all life stages—eggs, post-hatchlings, juveniles, and adults in nearshore waters.
• Several aspects of sea turtle biology and behavior place them at particular risk, including a lack of avoidance behavior, indiscriminate feeding in convergence zones, and large predive inhalations.
• Oil effects on turtles include increased egg mortality and developmental defects, direct mortality due to oiling in hatchlings, juveniles, and adults; and negative impacts to the skin, blood, digestive and immune systems, and salt glands.
  

(From page 35)

Clearly this blog is specifically focused on sea turtles, yet the reason I personally am dedicated to studying these long-lived, migratory, charismatic animals is because they are excellent sentinels to the overall ocean health. Through studying the well-being of turtles and their habitats, we also learn a great deal about several ocean ecosystems, marinelife, and even our own coastal safety, homes/businesses and economy.

These are just some initial details and information about the current disaster and its impact on marine turtles... more to come. Until then - here's to keeping our fingers crossed that the spewing stops soon; and here are many thanks to those folks who are out there helping to protect and rescue the marine and coastal resources that are oh-so-important and wonderful.