In Mexico, beaches are being replenished with new sand to help turtles survive
Restoring beaches with sand dredged during dredging operations can directly affect sea turtle reproduction. The reason is that the sex of future hatchlings depends not on chromosomes, but on the temperature of the sand during egg incubation.
After coming ashore, a female sea turtle finds a nesting site, digs a hole with her hind flippers, and lays her eggs. She then covers the nest with sand and returns to the sea.
After that, the female plays no further role in the development of her offspring. It is the conditions inside the nest that determine whether the eggs will hatch into males or females.
Sea turtles do not have sex chromosomes analogous to the human X and Y chromosomes. The sex of the embryos is determined by temperature, with the mid-incubation period being particularly important.
As a rule, cooler sand favors the development of males, while warmer sand favors females. A temperature difference of just a few degrees is enough to alter the sex ratio.
Therefore, even the depth of the nest, the color of the sand, its structure, and composition can affect the temperature inside the clutch.
During beach restoration, material extracted from the seabed is used. It is transported to shore by special dredgers, after which the sand is distributed along the coastline.
However, artificially added sand may differ from natural sand in grain size, shell content, and color. This affects how quickly it heats up and how deeply the heat penetrates.
That is why, during beach restoration, it is important to select material whose characteristics most closely match those of natural sand. The surface may also be loosened to make it more suitable for turtle nesting.
Large dredgers are used for large-scale beach restoration. They extract sand from the seabed along with water and pump it into a special hold.
One such dredger has a suction line with a diameter of about 86 centimeters. The vessel can continue moving while filling its hold.
After loading, it heads toward the shore, connects to a pipeline, and pumps the sand-water mixture onto land. The water drains away, and the sand remains on the beach.
The hold capacity of such a vessel is 15,150 cubic meters. For comparison, a typical private swimming pool holds about 72 cubic meters of water, meaning one load of the vessel is roughly equivalent to 160 such pools.
The dredger is approximately 128 meters long and 25 meters wide. Its power plant, with a capacity of about 25,000 horsepower, consists of three diesel-electric main engines.
The vessel was built at a shipyard in Brownsville, Texas. It was originally used for dredging federal navigation channels.
The vessel is owned by a Seattle-based company founded in 1905. The new dredger represents one of the largest single investments in the company’s history.
The chairman of the board of directors, after whom the vessel was named, remarked:
“This dredger is the culmination of many years of work by our dedicated team, and I am honored to have it bear my name.”
Despite their considerable size, such vessels have limitations. The main problem is a draft of about 8.5 meters. A fully loaded dredger cannot operate in shallow waters, where the most important sections of the coastline are often located.
Therefore, smaller dredgers capable of operating closer to shore are used for some of the work.
Furthermore, beach restoration is not a permanent solution to the problem of erosion. Over time, the sand is washed back into the sea, so such work effectively becomes a regular measure to maintain the shoreline.
Several species of sea turtles nest along the Gulf of Mexico coast. Among them are the loggerhead, the green turtle, and the Atlantic ridley, or Kemp’s ridley.
The latter is considered one of the rarest sea turtles in the world, and a significant portion of its nesting occurs specifically along the Gulf of Mexico coast.
Leatherback turtles, on the other hand, primarily lay their eggs on the Atlantic coast of the United States.
Therefore, beach restoration is important not only for protecting coastal infrastructure but also for preserving sea turtle nesting sites.
U.S. federal engineering agencies are working to increase the proportion of material recovered during dredging operations that can be reused, rather than simply being disposed of.
In this way, dredging can simultaneously ensure navigability and support beach restoration.
At the same time, the characteristics of the sand are of fundamental importance to the turtles. The material deposited on the shore affects the temperature of the nests and, consequently, the sex ratio of the future offspring.
Ultimately, beach restoration serves as an example of how engineering work can directly impact wildlife: a vessel dredges sand from the seabed, delivers it to the shore, and the properties of this material can determine how many hatchlings—and of which sex—will eventually return to the water.
This is reported by The Pulse.
As a reminder, in the Dnipropetrovsk region on the banks of the Samara River, people spotted a black swan—a bird that is not typical of Ukraine’s wildlife. The unusual appearance of the bird caught the attention of witnesses.
