June 28, 2018

Environmental DNA (eDNA) is Promising New Tool for Marine Ecosystem Monitoring

Submitted by Zack Gold, Reef Check California Volunteer Diver

Monitoring marine biodiversity is critical for understanding the health of marine ecosystems. Current monitoring relies heavily on visual SCUBA surveys like the wonderful work done by Reef Check California every year. Unfortunately, traditional visual SCUBA surveys are expensive, logistically challenging and limited by taxonomic expertise and the amount of time divers can spend in the water. Any Reef Check volunteer knows this well, and that is why the work of Reef Check volunteers plays such a vital role in providing desperately needed data to keep track of our local marine ecosystems and the health of our Marine Protected Areas. Unfortunately, these limitations make it difficult to survey all marine ecosystems frequently enough to provide the best information on ecosystem health and impact of management policies.

Novel molecular techniques offer promising tools to monitoring marine ecosystems in real time. These techniques rely on the fact that all organisms leave trace amounts of their DNA in the environment. Just like we all leave traces of ourselves behind wherever we go—strands of hair or fingerprints, for example, fish, sharks, and invertebrates leave little pieces of themselves behind, too—things like scales and feces, which are filled with their DNA. Recent technological advances allow us to isolate and sequence this environmental DNA (eDNA) from just a liter of seawater, enabling rapid and accurate identification of organisms present in a community. As such, eDNA approaches are ideally suited to intensive marine biodiversity monitoring programs like Reef Check’s.

In order to investigate the applicability of eDNA for monitoring Southern California’s marine ecosystems, Zack Gold, a Ph.D. candidate in Professor Paul Barber’s lab at UCLA, is comparing eDNA methods to Reef Check SCUBA surveys. Last summer, Zack collected eDNA samples at 50 sites around Southern California while joining Reef Check’s summer surveys. By simultaneously collecting eDNA and traditional SCUBA survey data, Zack hopes to determine the advantages and limitations of each monitoring method. By demonstrating the effectiveness of eDNA in assessing marine ecosystem health inexpensively across broad spatial scales, his research has the capacity to revolutionize marine biodiversity monitoring, providing critical insights into the variables shaping marine protected area effectiveness in urban coastal environments.

So far, Zack has been able to detect over 400 species of fish and invertebrates from blue whales to giant black sea bass to thick-horned nudibranchs to purple urchins! The eDNA results were also able to tease apart unique marine communities seen at different sites, which is critical for being able to compare communities inside and outside MPAs. Although the first round of results are promising, more work needs to be done to complete reference sequences for all of the species of Southern California and to finish all the lab work from the 400 samples collected last summer. Zack is looking forward to sharing more of his results with Reef Check and coastal marine managers as the science is completed. Ultimately, Zack is planning to provide the results of the eDNA study to a wide array of marine managers and policy makers to demonstrate the effectiveness of eDNA in quantifying marine ecosystem health and the capacity of eDNA to provide cost added benefits to current ecosystem assessment.

Given how easy it is to collect and filter seawater samples, Zack believes it will be easy to imagine a future where eDNA samples are collected up and down the California coast to keep better track of our vital marine ecosystems- all with just a scoop of water. With the combination of Reef Check’s ongoing monitoring and eDNA tools being developed by Zack, more information can be gained to help assess and protect our reefs for generations to come.