Exploring the Mysterious World of the White Shark
In the heart of what was once deemed an oceanic "desert," the researchers discovered that the Pacific's high seas teem with abundant and unusual life forms, organisms that researchers suspect play a critical role in explaining the fascinating behaviors of white sharks in the open ocean.
The team embarked from Honolulu aboard the Schmidt Ocean Institute's R/V Falkor and headed east to an expanse of the Pacific dubbed the White Shark Café, halfway between Hawaii and Mexico. Led by principal scientist Barbara Block of Stanford University, the team aboard the Falkor included marine biologists, engineers and oceanographers from Monterey Bay Aquarium, Stanford, Monterey Bay Aquarium Research Institute (MBARI), University of Delaware, NOAA, Montana State University and ocean technology innovator, Saildrone.
While no one on the team knew what they'd find, everyone hoped to gather insights about what might be driving the behaviors of white sharks, and what role this offshore habitat plays in the lives of these apex ocean predators.
Location Services for White Sharks
In preparation for the expedition, the team deployed 34 tags on adult white sharks off the coast of California in the fall of 2017, knowing that a few months later those same sharks would swim toward the middle of the Pacific Ocean.
The tags were programmed for release during the month the Falkor was in the Café, delivering their stored data to orbiting satellites. Following the blips emitted from the tags as they popped to the surface, the Falkor made its way into the heart of the Café, sampling marine life and ocean conditions in waters where the tags surfaced.
Over the course of the month, the team recovered 10 of those unbelievably small pop-up satellite tags from the open ocean.
"Tracking and then recovering released tags from white sharks across a 160-mile swath of open ocean required incredible precision and patience from the team," explains Monterey Bay Aquarium research fellow Paul Kanive, a member of the expedition team. But the effort was worth it.
"In one month at the Café, we doubled the amount of tagging data in our collection," says Aquarium research scientist Sal Jorgensen. "The trip was hugely successful in that regard."
A drone collected data to document the presence of white sharks and their prey species in the White Shark Café.
Deep Data Discoveries
The pop-up tags provided locations for the team to collect a wide variety of samples and data that will eventually help create 3D diagrams of the Café's living, underwater structure. As an example, they gathered eDNA—water samples taken from different depths providing microscopic traces of skin, feces and mucus from all the different organisms that live in the Café. Sequencing and identifying the genetic codes from this "DNA soup" will help show which animals gather and move throughout the waters, and where they occur.
The researchers also towed midwater (1,500 feet deep) net trawls to gather species that form the lower rungs in the food ladder, such as lightfish and lanternfish—creatures that represent the largest biomass of vertebrates on the planet.
These small, shimmering myctophids, whose light-producing organs help them hunt and evade predators, each day take part in the world's largest collective migration.
"It's a massive daily commute from the deep sea, to the warmer surface waters under the cover of darkness, and then back down again by dawn," explains Sal. "These midwater species including shrimp, squid, jellies, tunas and sharks, together form a massive living blanket, and the whole soupy layer travels up and down together."
Each member of the team brought different skills and had different opportunities to collect samples to help quantify the enormous movement of life up and down the water column in the Café.
Pioneering deep-sea biologist Bruce Robison of MBARI drove the remotely operated vehicle (ROV) SuBastian, illuminated elusive life forms in the deep ocean and recorded them on film and video to share with the world.
Paired with data from drones that sail on the ocean's surface, the researchers were able to match the movements of white sharks to this daily commute of lower-trophic level animals throughout the Café.
As Barbara of Stanford University explains: "We found a high diversity of deep sea fish and squids (over 100 species), which in combination with observations made by the ROV and DNA sequencing, demonstrate a viable trophic pathway to support large pelagic organisms such as sharks and tunas."
"The Café is far from the desert it was thought to be," says Sal. "It's home to an abundance of life that satellite imaging is not detecting. It only appears to be a desert on the surface because in the Café the base of the food ladder, the plankton that harvest energy from the sun, is concentrated at depths beyond the reach of satellites. In fact, for white sharks, it is more of an oasis."
Sal Jorgensen and Barbara Block with the small pop-up satellite tags recovered from the open ocean.
A Legacy of White Shark Research
The expedition to the White Shark Café follows over 20 years dedicated to white shark research by the Aquarium, Stanford and other partners around the world. The white shark has long captured public interest, evoking awe and imparting a sense of prehistoric wildness that is larger than us.
"It's been fascinating to learn more about their activities, and through the tagging that the Aquarium sponsored, the white sharks led us to one of the most overlooked and under-studied places in the ocean," says Sal.
"After years of seeing the tagging data, we began to notice incredible diving behavior and came to realize that they spend most of their life here, in the middle of the ocean and at depths where sunlight ceases to reach, a place called the 'twilight zone.' This trip was about following the sharks out there to see and describe this ecosystem."
Prior to the trip, multiple teams of scientists spent weeks at sea tagging and tracking white sharks, dedicated months to analyzing data, and committed years to illustrating the complexities of white shark behavior such as breeding and migrating.
"These white sharks are showing us that there is something truly important about the open ocean," says Sal. "They've heralded the need to ask new and better questions about how apex ocean predators thrive in their underwater world."
Answering those questions inevitably requires that we consider how best to protect the places essential to maintaining healthy populations of not only ocean predators, but all marine life that call home to the world's largest habitat.
This valuable expedition is made possible in part with support from Aquarium members and donors. Thank you!