North American researchers have demonstrated that DNA present in seawater can be used to measure the genetic diversity, population size, and health status of local dolphin populations, in an approach that could bolster marine conservation efforts.
The study, published in the scientific journal ‘Frontiers in Marine Science’, is based on the analysis of environmental DNA (eDNA) collected from seawater samples off the California coast.
The team followed 15 groups of dolphins near Santa Catalina Island, between October and December 2021, collecting seawater samples a few meters from the animals.
The researchers sequenced the mitochondrial DNA found in the water — released through skin, mucous membranes, feces, blood, or respiration — to assess the genetic diversity of the populations.
According to the lead author, Frederick Archer, genetic diversity is an important indicator of population size and the species’ capacity to adapt to environmental changes.
The analysis identified 836 genetic variants in 126 water samples, most of them originating from cetaceans. Among the species studied were the common dolphin
The researchers concluded that collecting as many samples as possible from different groups significantly improves the accuracy of genetic estimates.
In the case of the common dolphins — the species with the greatest genetic diversity in the area studied — between 60 and 72 liters of seawater would be needed to obtain reliable results.
The team considers that the method could be used in regular environmental monitoring programs, allowing the tracking of changes in species distribution and the assessment of impacts from factors such as pollution, climate change, or underwater noise.
According to the authors, the technique offers a less invasive and more economical alternative for studying marine mammals that are difficult to observe directly.
