Surveying Life Above Davidson Seamount in Monterey Bay National Marine Sanctuary

July 25, 2025

Sanctuary staff are aboard the NOAA Ship Rueben Lasker conducting visual surveys of marine mammals, and using cutting-edge technology to collect environmental DNA (eDNA) samples from the water column. These efforts aim to better understand how the seamount influences biodiversity in the waters above and around it.

woman wearing a hard hat collects water from oceanographic sampling equipment — Sea Grant Fellow Melissa Ashley collects water samples from Niskin bottles to be analyzed for eDNA. Photo: Amity Wood/NOAA

Located 75 miles off the coast of San Simeon, California, the 26-mile-long Davidson Seamount is one of the largest known undersea mountains in U.S. waters. Rising 7,480 feet from the seafloor, its summit still lies 4,101 feet beneath the ocean’s surface. Past deep-sea explorations to the seamount’s crests, ridges, and flanks have revealed deep-sea coral forests, vast sponge fields, and expansive octopus nurseries, but less is known about life in the waters above.

As Davidson Seamount rises high in the water column from the seafloor, it may create complex current patterns that influence nutrient delivery to the surrounding areas–fueling a hotspot for productivity. This food source attracts larger animals, including fin, blue, and beaked whales, and offshore seabirds such as albatrosses, petrels, and shearwaters. Sanctuary staff aim to better understand the connection between this phenomenon and the food web above and around the seamount, as the upper surface layers are typically regarded as having a greater abundance and diversity of marine mammals and seabirds than areas further away from the seamount.

Staff are also utilizing eDNA sampling. eDNA is the genetic material shed by organisms in the water column (like exfoliated skin cells in humans) which is adding to our knowledge of the importance of seamount communities. By identifying who left DNA in the water, scientists can tell which species were there recently, even if the animals were never seen by people.

Using Niskin bottles attached to a conductivity, temperature, and depth (CTD) rosette, we collect and analyze water samples at various times, depths, and locations to study eDNA and detect organisms–without having to collect living animals. Each eDNA sample collected is filtered through a cellulose membrane to separate the DNA from the water. The DNA is then preserved in a solution that prevents it from breaking down and allows for long-term storage. Scientists use short DNA sequences called primers to target specific regions of genetic code, which are then amplified to make them easier to read. These sequences are then compared to reference databases to identify the organisms present—often down to their family, genus, or even species level.

man preparing supplies in a laboratory for filtering water samples — Research ecologist Chad King prepares the extraction equipment to filter eDNA from water samples collected at depth. Photo: Amity Wood/NOAA

water sample pump with extraction tubes — eDNA samples are collected by pumping water samples with a controlled flow rate through cellulose filter. Photo: Amity Wood/NOAA

eDNA can be a helpful tool not only to inform us about what kind of species may be present in the water column, but also an estimate for the abundance of a species in a particular location. This information can be used to assess species movements, monitor changes over time, and characterize their role in the area’s food web and ecosystem. eDNA can be linked to other ocean properties, such as water temperature, conductivity, and oxygen levels, providing a deeper understanding of species distribution and how seamounts may be influencing the ocean’s biodiversity.

This work is conducted under the authority of the National Marine Sanctuaries Act (16 U.S.C. § 1431 et seq.), specifically under Section 309 (16 U.S.C. § 1440), which authorizes NOAA to support and coordinate scientific research and long‑term monitoring of sanctuary resources.