Most studies that assess the seismic impacts on fauna refer to marine mammals and there is a notable lack of information about marine turtles. This is rather surprising, as turtles have to be considered in seismic surveys in almost 50 countries around the world.
For nearly five years, the Brazilian Institute of Environment and Renewable Natural Resources IBAMA has requested the implementation of complementary monitoring programs for marine turtles, especially when the seismic surveys are carried out near recognized sites of occurrence and reproduction of marine turtles.
In Brazil, the main breeding and feeding areas of marine turtles have been monitored and managed by Tamar since the 1980s. Despite these efforts, little is known about the sea and migration routes of several indigenous and visiting species. Recently, a new collaboration has begun involving several different research initiatives.
Satellite telemetry is a technique that allows monitoring of marine turtles over a wide geographical area, with identification of displacement routes and special areas of use. This provides information that is relevant both for understanding the ecology and also for impact assessment and definition of protection measures.
A PGS-backed research project is the first in Brazil to integrate the collection of seismic data with information about sea turtle displacements. It targets the Sergipe/Alagoas (SEAL) sedimentary basin, block SEAL-4-10-11.
Five years ago, from January 2014 to January 2015, around 30 turtles from two different species prevalent in the area were fitted with transmitters: 24 were placed on olive ridley sea turtles (
Lepidochelys olivacea) and six on loggerhead sea turtle ( Caretta caretta). Tracking results can now chart the migration of these animals from their breeding area in Sergipe, Brazil along coastal waters and farther out into oceanic areas. This data shows extensive use of the Brazilian continental shelf, from the south coast (Santa Catarina) and southeast coast of Brazil to French Guiana, as well as displacements across the Atlantic Ocean to the feeding areas in the equatorial portion of northwestern Africa (Cape Verde Region and Guinea Bissau).
These satellite telemetry results have corroborated historical information, greatly extending the body of knowledge regarding migration and areas of use for both species. A collection of data on the diving behavior of the animals is still under analysis.
Brazil. This PGS-backed research project is the first in Brazil to integrate the collection of seismic data with information about sea turtle displacements. Brazil's IBAMA institute requires environmental monitoring for permitting of seismic surveys offshore
New Monitoring Initiatives
Following the results of the first studies, a new monitoring initiative was proposed in 2018, targeting Rio Grande do Norte and Potiguar Basin. This research project is also supported by PGS. First, 42 transmitters were installed on hawksbill sea turtles (
Eretmochelys imbricata). Then, in a second initiative, a further 20 turtles in the Sergipe/Alagoas sedimentary basin were also fitted with tracking units. These studies have increased the number of hawksbill sea turtles and olive ridley sea turtles monitored by satellite telemetry by around 280% and 400%, respectively.
Integrated action between seismic companies and research groups in Brazil is significantly increasing the effectiveness of research efforts, boosting monitoring routines and capacity for analysis. The continuity of the research will serve to increase our knowledge about these endangered species. The project aims to establish and maintain a robust database that the project partners can use to guide spatial evaluations regarding overlapping areas of use of turtles and seismic surveys.
In the future, research on spatial ecology should be integrated with other techniques, such as genetics, stable isotopes and habitat modeling, thus expanding the possibilities for interpretation and use of information, and reducing the knowledge gap regarding the marine life-phase of these turtles.
Using satellite telemetry olive ridley, loggerhead and hawksbill turtles are being tracked from nesting areas in Brazil across a wide oceanic area.
Sea Turtle Facts
Some background on the types of sea turtles observed during the Tamaro project:
Hawksbill sea turtle is a critically endangered sea turtle belonging to the family Cheloniidae. This the only extant species in the genus Eretmochelys. They spend their time in coral reefs, rocky areas, lagoons, mangroves, oceanic islands, and shallow coastal areas. Named for its narrow head and sharp, bird-like beak, hawksbills can reach into cracks and crevices of coral reefs looking for food. Their diet is very specialized, feeding almost exclusively on sponges. The species weighs ca 40-68 kg, and grow to ca. 0.8 m long.
The olive ridley sea turtle is named for its pale green carapace and is the smallest and most abundant of all sea turtles. Olive ridley turtles are found in warm and tropical waters, primarily in the Pacific and Indian Oceans. They weigh ca. 34 - 45 kg and reach roughly 0.6 m in length.
Loggerhead sea turtle is the world's largest hard-shelled turtle. It has a cosmopolitan distribution, nesting over the broadest geographical range of any sea turtle, and inhabits the Atlantic, Indian, and Pacific Oceans and the Mediterranean Sea. This marine reptile is around 0.9 m long commonly weighs around 135 kg, belonging to the family Cheloniidae. Loggerheads are considered a vulnerable species by the International Union for the Conservation of Nature.