SOLOMONS, MD (October 13, 2023) — A decades-long Arctic biological data set, meticulously maintained by University of Maryland Center for Environmental Science (UMCES) professor Jacqueline Grebemier, has played a pivotal role in solving the mystery behind the recurring die-offs of eastern Pacific gray whales. A recent study published in the prestigious journal Science has shed light on the cause of three significant die-offs in the eastern North Pacific gray whale population since the 1980s, implicating fluctuations in stocks of a shrimp-like creature residing in the Bering and Chukchi seas.
These die-offs, one of which began in 2019 and continues, have resulted in a reduction of up to 25% in the gray whale population within just a few years. The study’s findings emphasize the importance of collecting consistent Arctic data over the years to comprehend the impact of climate change on the ecological system.
University of Maryland Center for Environmental Science Professor Jacqueline Grebmeier underscored the significance of their research, stating, “This study shows the value of collecting data year after year in the Arctic to address the question of how climate change is impacting the ecological system. Physical changes such as the retreat of sea ice are well-documented, but it is much more challenging to understand how these changes affect the biological system.”
The study relied on a long-term biological data set pertaining to gray whale prey in the Bering Strait region. This data set, initiated by Grebmeier in the 1980s, has been incorporated into an Arctic monitoring network known as the Distributed Biological Observatory (DBO). Lee Cooper, another UMCES faculty member, significantly contributed to the development of this invaluable dataset.
The eastern Pacific gray whales are a remarkable example of a large whale population that has recovered to pre-commercial whaling numbers. Currently, there are approximately 14,500 of these small baleen whales, which embark on lengthy migrations each year, traversing the Pacific Coast of North America. They travel from lagoons in Baja California, Mexico, to the productive Arctic waters, where they feed on amphipods living in the sediments. Their diet mainly consists of these tiny creatures, with tens of thousands of amphipods inhabiting each square meter.
As the gray whale population rebounds from the historical whaling era and approaches levels close to what their Arctic feeding grounds can support, lead author Joshua Stewart, an assistant professor with Oregon State University’s Marine Mammal Institute, noted that “they have likely become more sensitive to environmental conditions due to competition for limited resources.”
Dave Weller, co-author and director of NOAA’s Southwest Fisheries Science Center’s Marine Mammal and Turtle Division, highlighted the value of long-term data, stating, “When we began collecting data on gray whales in 1967, little did we realize the important role they would play in understanding the effects of climate change on an iconic sentinel species in the Pacific. This research would not have been possible without our reliable long-term record.”
The study has revealed that benthic amphipods, the calorie-rich prey preferred by gray whales, are highly sensitive to changes in sea ice cover. Underneath the sea ice, algae grow and sink to the seafloor, enriching the amphipod population. With less ice, there is a reduced amount of algae reaching the seafloor, resulting in warmer water that favors smaller benthic crustaceans and faster currents, which diminish the habitat for gray whales’ preferred prey.
While the study doesn’t suggest an imminent risk of losing gray whales due to climate change, Joshua Stewart cautioned, “But we need to think critically about what these changes might mean in the future. An Arctic Ocean that has warmed significantly may not be able to support 25,000 gray whales like it has in recent past.”
The research involved a team of dedicated scientists and collaborators, including Trevor W. Joyce of Ocean Associates, John Durban of the Marine Mammal Institute and Sealife Response, Rehabilitation, and Research, John Calambokidis of Cascadia Research Collective, Deborah Fauquier of the NOAA Fisheries Office of Protected Resources, Holly Fearnbach of SR3, Morgan Lynn, Wayne Perriman of the Southwest Fisheries Science Center, NOAA Fisheries, Manfredi Manizza of the Scripps Institution of Oceanography, University of California, San Diego, and Tim Tinker of Nhydra Consulting and University of California, Santa Cruz.
