Knowledge of ocean parameters from our digital ocean systems, distributed through the Copernicus Marine Service*, helps us to understand the behaviour of juvenile sea turtles in order to better protect them.
A study published this week in Frontiers in Marine Science, that included a co-author from Mercator Ocean International, used Copernicus Marine data to show that the food-rich waters of the Bay of Biscay may be a deadly temptation for small turtles during wintertime.
The Aquarium La Rochelle has been rescuing and rehabilitating sea turtles for decades. To make sure that the turtles have the best chance of survival after being reintroduced to the wild, the aquarium recently set out to understand where they travelled to after their release.
The study used satellite tracking and sighting data to investigate whether the Bay of Biscay is an ecological trap or a favourable habitat for young sea turtles. It found that whilst larger (and therefore likely older) turtles swim towards their birth homes in Africa or the US after release, smaller (and likely younger) turtles may be getting trapped in colder waters for the winter.
Caption: Turtle being released by Aquarium La Rochelle.
Credit : Oceane Cottier and Arthur Paré/Aquarium La Rochelle
“Copernicus Marine data were used to obtain information on the ocean currents, water temperature and prey abundance along the turtles’ trajectories. This enabled us to link turtle movement patterns to these oceanic factors, as well as the size and mass of the turtles,” explains study co-author Philippe Gaspar, senior scientist at Mercator Ocean International.
When ready to reproduce, older turtles return to their own place of birth. For younger turtles, their priority is to grow and develop. This might explain why the smaller turtles tend to remain in the food-rich Bay of Biscay after they are released.
“Joint analysis of the ocean currents and turtle trajectories show that small turtles do not passively follow the currents but actively swim to remain in this favourable habitat,” says Philippine Chambault, the first author of the paper from the Aquarium La Rochelle.
“The Bay of Biscay waters are especially cold during wintertime, less than 10°C, and so this area is assumed to be outside the geographical range for turtles. Our observations suggest that while the turtles could be visiting this area to forage for food, it may be an ecological trap for very small turtles that may suffer from hypothermia in the cold months,” said Philippe Gaspar. “A turtle’s body temperature is largely controlled by the temperature of the environment, and temperatures below 10°C are often lethal.”
CURRENT/TRAJECTORY INTERCOMPARISON
The results of the study confirm the crucial role of rehabilitation centres and the need to prioritise turtle conservation.
“These findings have important turtle conservation implications,” added Florence Dell’Amico, co-author of the study, who cares for the sea turtles at the Aquarium La Rochelle. “Maps of their ecological range need to be updated, and these study findings can help to plan effective rehabilitation and release strategies for turtles rescued from this area.”
Philippe, Philippine, Florence and colleagues are now using Copernicus Marine data to optimise the process of releasing turtles. In particular, they are investigating whether the survival rate of the released turtles could be improved by changing the time or location at which they are released.
Caption: Mapped Copernicus Marine data showing the biomass of epipelagic micronekton, small sea creatures that turtles like to eat. Micronekton was one of the factors included in this study. Credit: Copernicus Marine Service/Mercator Ocean International.
Philippe concludes: “Such work could not be carried out without the Copernicus Marine data. If you want to know about the ocean, anywhere and anytime, it’s the best place to go.”
* Link to the Copernicus Marine catalogue.