Introduction to Environmental DNA (eDNA)
Marine biologists now have a powerful tool in their arsenal—environmental DNA (eDNA). This innovative technology allows scientists to identify marine life by analyzing DNA fragments in water samples. Integrating eDNA with autonomous underwater vehicles (AUVs) has streamlined the process, making it possible to conduct extensive marine studies without the need for traditional, labor-intensive methods.
How eDNA Works
Each seawater drop contains DNA from microorganisms, fish, and mammals. Scientists use robotic laboratories on underwater drones to filter and sequence this DNA, providing a comprehensive snapshot of the marine ecosystem. This method eliminates the need for large ships or lengthy expeditions, allowing for real-time data collection in various weather conditions and over extended periods.
Applications of eDNA
Tracking Marine Life: Robotic vehicles have traced great white sharks in the Pacific Ocean and tracked tropical fish along the Jersey Shore as they move northward due to climate change.
Detecting Invasive Species: In Santa Cruz County, California, eDNA sampling has helped monitor the spread of invasive species like striped bass and New Zealand mud snails in local streams.
Reef Ecosystem Studies: Researchers use eDNA to assess coral reef biodiversity by identifying species often overlooked in traditional surveys, providing a clearer picture of the reef’s health and diversity.
Advancements in Technology
The combination of Oxford Nanopore Minion sequencers and AUVs allows these devices to follow environmental signals, such as temperature and salinity, to locate marine life. These advancements have made eDNA sampling more portable and efficient.
Sampling remotely means that scientists might not have to go to sea in stormy weather to collect data, and can allow them to sample over a long period, instead of collecting information during a short cruise. It also doesn’t require them to harvest the fish. Robotic vehicles recently traced the DNA of great white sharks congregating in the middle of the Pacific Ocean, tracked tropical fish along the Jersey Shore as they headed north to escape climate change, and found farm-raised fish genes while screening samples from New York Harbor.
Challenges and Limitations
While promising, eDNA technology faces challenges. DNA degrades quickly in water, providing only a snapshot of recent marine activity. Additionally, human DNA contamination in coastal areas can complicate results. Despite these issues, eDNA sampling is poised to become a faster and cheaper method for monitoring marine ecosystems, especially as human activities in the ocean increase.
Stoeckle has been working with New Jersey state biologists to conduct DNA-based counts of commercial fish species by dropping one-liter bottles into the ocean at various depths and sampling the water inside. It’s part of a census of commercial species that has been ongoing since the 1960s, information that helps resource managers determine catch limits for local fishermen. But in addition to the target species, they are finding that some species of fish are moving north from their normal range along the coast of Florida and the Carolinas; they’re environmental refugees who are trying to escape increasing temperatures. The researchers found DNA from the gulf kingfish, which normally resides in the Chesapeake Bay and has never before been identified in New Jersey, as well as the Brazilian cownose ray, which is native to the Gulf of Mexico and has been unknown in northeastern waters.
Conclusion
Environmental DNA is transforming marine biology by offering a non-invasive, efficient way to study underwater life. As technology advances, eDNA will play a crucial role in understanding and preserving marine ecosystems. There’s a need to monitor the oceans more closely, because we are doing more in the ocean, such as building wind farms and pipelines and natural gas and oil extraction. These are all things that may be beneficial economically, but we want to know what we are doing to the environment.
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