Tagged white shark, photographed at the Farallon Islands off Northern California and tagged with an acoustic tag (front) and a pop-up satellite tag (rear) as part of the TOPP research program.
Pacific bluefin tuna are the super-athletes of the ocean. TOPP researchers followed several of them to migrate all the way across the Pacific basin, from California to Japan and back in a matter of months. Credit: TOPP. Copyright Randy Wilder, Monterey Bay Aquarium.
California sea lions tagged as part of the TOPP project. Credit: Dan Costa, UC Santa Cruz.
Unlike human habitat, temperatures in the marine environment cannot be controlled by a thermostat. So what do marine animals do when the heat cranks up? NOAA Fisheries scientist Elliott Hazen led a research team with 11 U.S. and Canadian scientists to find out exactly how climate change impacts apex predators—animals at the top of the food chain. The results of their work are now published in Nature Climate Change in this paper.
Based out of the Southwest Fisheries Science Center in Pacific Grove, California, Dr. Hazen combined information from the 4,300 apex predators tagged through the Tagging of Pacific Predators (TOPP) Programand climate change scenarios based on predictions by the Intergovernmental Panel on Climate Change. By the year 2100, Hazen and his colleagues found some predators could be facing up to a 35 percent loss of habitat as the ocean water with their preferred temperature moves northward.
Dr. Hazen predicted different responses from different predator “guilds” like seabirds, sharks, tunas, turtles, whales, seals, and sea lions. Those that have a very specialized diet and limited range of temperatures they can tolerate, such as salmon sharks, blue sharks, and mako sharks face the biggest challenges. Others, like seabirds and tunas, might actually see their habitat grow.
Two of the most important habitats in the Pacific Ocean are known as the North Pacific Transition Zone and the California Current and they fared very differently. Migratory species that head to the North Pacific Transition Zone for the cooler temperatures might find their route a bit longer as the zone moves as much as 600 miles northward. Those who stay within the California Current—right along the coast of California—may do better, as the massive upwelling of nutrients helps protect the zone from major changes even as the temperature warms.
Dr. Hazen chose to study apex predators because they help control and structure food webs in the ocean. His study is the first to use not only sea surface temperature predictions, but also models of chlorophyll-a, the green pigment found in phytoplankton, the microscopic plant-like plankton that are at the bottom of the food web. Where phytoplankton are abundant, zooplankton, small fish, larger fish, and apex predators are sure to follow.
This study leverages the resources of NOAA, NASA, National Science Foundation, and a number of international partners engaged in characterizing the marine environment by using direct and remotely-sensed measurements and integrating numerical simulations.
Dr. Hazen hopes his findings can identify which species are the most vulnerable to new threats so we can focus conservation efforts on those who need it most. Read Dr. Hazen's 6-page paper here.