Leatherback turtles and sea level, new study

This video is called HD Leatherback Turtle footage (Dermochelys coriacea).

From Wildlife Extra:

Researchers find the wetter the nests, the fewer sea turtles are hatched

Leatherback turtles are vulnerable to rising sea levels

Sea level rise has been studied in terms of its impacts on coastal ecosystems and habitats; but few studies have looked at its effects on mobile marine species, or their use of coastal habitats.

Many ecosystems that are threatened by sea level rise are home to sea turtle nesting sites. There are seven species of sea turtles in the world, four listed as endangered and two listed as vulnerable.

Conservation and research groups are working to preserve and protect the turtle nesting habitats from human encroachment but, a new study says, their efforts are fighting an uphill battle as oceans continue to rise.

While it’s true that sea turtle nesting habitat could disappear in the future, there is a more imminent threat resulting from sea level rise: environmental changes to turtle nests.

The environment of nests has a number of known impacts on reptile eggs and embryo development. Studies have shown that nest temperature influences the sex ratios in new born turtles and high humidity leads to longer incubation times in loggerhead turtles.

But this new study has shown that the sand water content (or moisture) of nests also seems to influence embryonic development. Rising seas, erosion, and an increase in storms are all likely to change the sand water content of nesting sites.

In their study, researchers focused on one species of sea turtle, the leatherback. Compared to other sea turtle species, leatherbacks have lower reproductive success, with successful hatchings averaging only 40 to 50 per cent of the original clutch.

Researchers worked on the Caribbean coast of Colombia where sand samples were taken from two depths at three nesting zones to determine water content.

Turtle hatchings were monitored and recorded, with each hatching representing a successful emergence. Once hatchings stopped, nests were excavated and the remaining eggs were removed. The stage of death of the embryos was determined for each egg.

Overall, the researchers found strong correlations between sand water content and hatching success – increases in moisture led to decreases in hatching. Nests with greater water content yielded fewer turtles.

This could be a major problem for leatherbacks as sea levels continue to rise, especially where nesting sites are also threatened by coastal development. Currently, our oceans are rising about 3.2mm per year, and we are seeing an increase in major storm frequency resulting in coastal erosion.

Suitable habitat is decreasing for many species and if the water content of their nests plays that large a role in the viability of offspring, then turtles are likely to be impacted by this long before their habitat disappears.

However, the researchers feel it is important to keep in mind that animals have the ability to adapt. Turtles may be able to change the structure or permeability of their eggs in order to get around this problem.

The greatest danger is if the environment changes too quickly, they may not have time to adapt.

Debris from logging in tropical forests is threatening the survival of hatchling leatherback turtles and the success of mothers at one of the world’s most important nesting sites in Colombia, report investigators: here.

A two-metre-long turtle has reportedly washed onto a beach in Calella, near Barcelona on the northeast coast of Spain. The apparently dead leatherback turtle, which reportedly weighs 700kg, was filmed being removed from the beach with a crane: here.