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Population Genetics Brings New Insight into Marine Mammal Diversity

There are roughly 20,000 eastern gray whales plying the north Pacific seas. The tiny population of western gray whales, by contrast, may consist of just 150 individuals. While they are all part of the same species, one population is listed as of “least concern” for conservation purposes, and the other is considered “critically endangered.” 

The dramatic difference in population size and protected status between the two populations highlights an important point: conservation efforts are now targeted not just at the species level but at specific populations within that species. As genomic research gives us more insight into marine mammal populations, it will become increasingly important for offshore oil & gas developers to understand the population dynamics of the species they coexist with.

Battelle researchers have been studying population genetics of marine mammals—including bowhead whales, gray whales, beluga whales, Steller sea lions and sea otters—for more than 10 years. Recent studies of bowhead whales off of the north coast of Alaska have helped to define distinct populations using genetics and genomics, better understand their migratory routes, and estimate the population sizes. These data have been used to both guide oil & gas development plans and to set hunt limits for indigenous populations that still depend on the whale for subsistence and ceremonial purposes.

A similar study of gray whales is underway currently. The study seeks to better understand the population size and migratory patterns of the endangered western gray whales and to define the genetic markers that distinguish them from eastern gray whales. This will help developers operating near Sakhalin Island, an important feeding area for the western population, make better conservation decisions. Using genomic data, researchers will be able to monitor population size and movements and determine whether whales found in proposed development areas are part of the western population or are far-ranging members of the eastern population.

Genomic research into marine mammal populations has gotten easier due to changes in technology over the last decade. Next-Generation Sequencing (NGS) methods have made it dramatically faster, easier and cheaper to sequence DNA, making it possible to monitor marine mammals at both the population and individual level by their genomes. Traditionally, monitoring individuals might require matching biopsies taken from a particular whale at different times. However, researchers have discovered that DNA can be sequenced from shed cells and excretions left behind by animals as they move through the environment. Environmental DNA, or eDNA, allows researchers to monitor the movement of individuals and populations using seawater samples. This drastically decreases the costs and risks of biodiversity monitoring because researchers no longer have to biopsy or collect live animals.

The data gathered through these methods is critically important to understanding biodiversity at the population level in addition to the species level. Protecting endangered populations is essential to maintaining the genetic diversity of a species. Different populations may have different genes for disease resistance, for example, or may be better adapted to different environmental conditions. That’s why conservation efforts, including national laws and international treaties, seek to protect endangered populations even when the species as a whole is not endangered. For example, out of the 14 distinct populations of humpback whale that have been recognized, four have been proposed to be listed as endangered. Developers working in areas with humpback whales need to be aware of the specific populations that the whales belong to and target conservation efforts accordingly.

Battelle is pioneering new methods of collecting and analyzing DNA to make biodiversity and population studies faster and more economical for oil & gas developers and governing bodies. Battelle researchers also provide education and advice grounded in solid science to companies seeking to make conservation and development decisions. They are currently looking at eDNA methods to estimate population sizes and monitor individuals for land animals, such as polar bears, that may coexist in development areas.