There’s a vast ecosystem stretching far below the ocean’s surface — one where the light dims, the pressure mounts, and life takes on forms that can seem downright alien. But even there, a place that seems a world apart from human society, our plastic trash is building up.
In the deep sea, it’s a challenge to study where that plastic accumulates and how it affects animals. So scientists at the Monterey Bay Aquarium and our partners at the Monterey Bay Aquarium Research Institute (MBARI) launched an ambitious collaboration.
The resulting study, which examined microplastic in the waters of Monterey Bay, was published June 6 in the journal Scientific Reports.
“We designed this study to answer a fundamental gap in our knowledge of marine plastic once it reaches the ocean,” says lead author Anela Choy, a former MBARI researcher and now a professor at the Scripps Institution of Oceanography in San Diego.
The research team gathered data by using remotely operated vehicles (ROVs), robotic submarines designed by MBARI engineers, to collect water samples at depths from 200 to 600 meters (about 650 to 2,000 feet).
They also searched for plastic in animals with important roles in the marine food web: pelagic red crabs; and tadpole-like creatures called giant larvaceans, which surround themselves with clouds of mucus that capture food — and, as the researchers discovered, plastic.
As we celebrate World Oceans Day, it’s too easy to forget about the deep sea. It’s the largest habitat on the planet, and is increasingly threatened by human activities. Monterey Bay Aquarium scientists, and our colleagues at the Monterey Bay Aquarium Research Institute, are working to understand and protect the deep ocean. It’s a big job—and we’ll need your help.
To bring the message about the deep ocean to a wider public, Executive Director Julie Packard and MBARI President and CEO Chris Scholin shared their thoughts about safeguarding the deep sea in an op-ed column published in today’s New York Times.
“The oceans are the largest home for life on our planet and the blue heart of Earth’s climate system,” they write. “We must use them wisely. Otherwise, we risk using them up.”
Stretching more than two vertical miles from the seafloor to the ocean’s surface, the water column is Earth’s biggest habitat by volume. For researchers trying to untangle its complex, multi-tentacled food web—the way energy flows from one ocean denizen to the next—it’s a vast and challenging realm in which to accomplish this task.
Recent work by scientists at the Monterey Bay Aquarium Research Institute (MBARI) has revealed whole new layers of predator-prey interactions in the water column, particularly in the often overlooked roles played by jellies and other soft-bodied animals—many of which, researchers discovered, feed on their own kind.
This research is promising, says Anela Choy, the biological oceanographer who led the study, but much more remains to be discovered about deep-sea food webs.
“I wish I knew just how much there was that we didn’t know,” she says. “That’s what keeps us all going.”
New appreciation for jellies
Many feeding interactions in the deep sea are difficult to observe because they take place in total darkness, thousands of feet below the surface, in cold, crushing conditions that test even the capacities of MBARI’s advanced robots. Before the advent of robotic exploration technology, much of what scientists gleaned about food webs was gathered from animals hauled to the surface in nets—or discovered in a predator’s guts.
One problem with that approach, Anela says, is that squishy animals like jellyfish and other gelata, while among the most prevalent life forms in this ecosystem, almost never make it to the surface intact.
“They’re really hard to capture—that’s the traditional way of studying diet, is to capture those animals and look in their stomachs,” she says. “With a net, they often immediately break apart. “If they are the predator of interest, we cannot ascertain their gut contents this way because they are very damaged.”
Obstacles to overcome
There are other obstacles to understanding food webs. The traditional way of studying diet is to capture an animal and look into its stomach to see what prey have been eaten. Anela notes that gelata digest very quickly and thus are often missed with diet work.
The high-definition cameras on MBARI’s diving robots have recorded thousands of deep-sea animal observations since 1989. All of the video has been rigorously archived to reflect its subject, location, time, depth and even water temperature and other physical parameters. From this footage, Anela and her colleagues gleaned a wealth of information: 743 documented instances of undersea creatures eating, being eaten, or having just fed.
(Anela singled out two video technicians at MBARI, Susan von Thun and Kyra Schlining, who “watched every single hour of videotape from every midwater dive” to build an unprecedented underwater feeding dataset.)
Hundreds of feeding observations
From the video, the team tallied 242 unique kinds of predator-prey relationships. Many involved jellyfish and other soft-bodied animals, which don’t seem to particularly mind having a robot watch them eat, and which are often transparent, meaning the researchers could easily peer inside their bodies to view their most recent meal.
In their published study, they documented the complexity of predator-prey relationships they uncovered from this treasure trove of data.
A key illustration from the study draws lines showing predator-prey interactions between 20 different functional groups seen feeding on each other in the footage, from fish to crustaceans to jellies to cephalopods like squid. Fittingly, the resulting tangle of colorful who-eats-whom lines resembles a jellyfish.
“Jellyfish get kind of a bad rap,” Anela says, noting that some biologists cast them as nuisances—trophic dead ends that don’t feed back into the food web.
“This shows something totally different,” she says.” It shows they’re central parts of deep sea ecosystems, with really diverse diets and serving as both predators and prey.”
One species of jellyfish was observed eating 22 different kinds of prey.
(In the figure, many of predator-prey nodes loop back on themselves. “That,” says Anela, “is cannibalism—species within those broad animal groups feeding on one another.”)
There’s more to come
“Our method gives you a totally different view of the interactions going on in the food web,” Steve Haddock says.
It’s a bit like going from a map with only train tracks to one that includes highways, he says: “You feel like things are connected in only a certain way, but suddenly you see these other connections. This study really complements and expands our view of what’s going on in the ocean.”
Still, Steve says there’s much left to learn.
“Even though this method has revealed a large diversity of interactions, there’s still a whole other universe of interactions we haven’t discovered,” he says.
The next layer of discovery may not come from video observations. Steve sees great promise in techniques like analyzing predators’ gut DNA for hints about their recent meals. Another avenue that is already widely utilized is compound-specific stable isotope analysis, which looks for chemical signatures that might accumulate in a creature’s tissue from eating certain prey.
“There will continue to be a lot more revelations about food web connections,” Steve says.
Anela agrees: “You hear that the deep sea is like outer space—it’s so poorly known and so poorly explored, every time we go down there we learn new things. All of that is true. But really, understanding that food webs tie everything in the ocean together is the reason I study them.”
Our ever-growing understanding of those connections, she says, will be critical to stewarding the ocean in the future.
Today’s guest post on the importance of ocean science comes from Nancy Barr of the Monterey Bay Aquarium Research Institute (MBARI), our partner institution.
The casual observer of the ocean might notice day-to-day changes in the waves and currents, or in the water’s color or smell. But how do we know what is going on far below the surface, if we are not there to observe it?
One key focus of MBARI technology development is to create a “persistent presence”—being where changes are taking place, as they happen. It means placing instrumentation in the deep ocean for extended periods of time, instead of relying on the occasional research cruise to make observations and collect data.
Tracking seafloor movement
Sediment moves from the continents into the deep sea both gradually, and in large bursts. This movement plays an important role in providing nutrition to deep-sea organisms. But it can also harm seafloor infrastructure, like underwater Internet cables—and it could possibly trigger geohazards like tsunamis.
MBARI engineers and scientists devised several instruments to record sediment-moving events as they happen. For the past two years, MBARI scientist Charlie Paull and an international research team have been monitoring movement in Monterey Canyon with a suite of instruments and sensors. The effort proved its worth in 2016, when the instruments detected a movement so strong, it swept a large volume of sediment down the canyon—carrying a one-ton steel tripod more than 3 miles down the canyon and burying it deep in the mud.
Through September 2, Monterey Bay Aquarium and Monterey Bay National Marine Sanctuary host Big Blue Live – an unprecedented series of live natural history broadcasts from PBS and the BBC. Big Blue Live highlights the remarkable marine life that gathers in Monterey Bay each summer, and celebrates an ocean conservation success story of global significance. We’re publishing guest commentaries about conservation efforts that contribute to the health of the bay and our ocean planet. This comes from Kim Fulton-Bennett, who coordinates external communications for the Monterey Bay Aquarium Research Institute.
Lunging humpbacks and frolicking otters are potent symbols of the abundance of marine life in Monterey Bay. But the vast majority of animals in the bay, and in the ocean as a whole, live below the surface. To fully appreciate and protect the wonders of the bay, we need to find ways to map, explore and understand this invisible world.
For almost 30 years, researchers at the Monterey Bay Aquarium Research Institute (MBARI) have explored the depths of the bay using high-tech tools such as robotic submersibles equipped with high-definition video cameras. Over the years we’ve progressed from simply looking around in awe to amassing vast databases of marine observations, conducting complex underwater experiments and documenting threats to deep-sea life.
MBARI’s research has revealed many previously unknown hot spots of biodiversity in the deep sea. In 2002, MBARI’s robotic vehicle Tiburon first explored the crest of Davidson Seamount, an underwater mountain range about 60 miles off the Big Sur coast. Flying over the rocky seafloor, 4,000 feet below the surface, Tiburon’s video cameras captured stunning images of massive corals growing over nine feet tall.
Over the next 10 years, MBARI conducted additional expeditions to Davidson Seamount in collaboration with the Monterey Bay National Marine Sanctuary. Video and data from these expeditions eventually convinced federal government officials that Davidson Seamount held unique animals and habitats that deserved protection. In 2009, the Sanctuary was expanded to include Davidson Seamount.
After almost 20,000 hours of deep-sea dives, MBARI researchers have compiled a unique database documenting not only deep-sea biodiversity, but also physical conditions in the ocean. By “mining” this database, researchers have made many discoveries, including the fact that oxygen concentrations deep in the bay have been gradually declining over the past 25 years. Scientists are still trying to figure out what this means for animals in the bay. It’s possible that some deep-sea animals could be forced to live closer to the surface, leaving certain depths more sparsely populated.
Tracking deep sea trash
This same database contains records of every piece of human debris and trash that MBARI researchers observed on the seafloor. In a 2013 paper, MBARI researchers used this unique data set to show for the first time where and how much trash was collecting in the depths of Monterey Canyon. This information has helped environmental organizations convince decision-makers and the public to reduce the amount trash that ends up in the ocean.
One of the biggest pieces of debris that MBARI discovered on the seafloor was a shipping container that was lost from a cargo vessel during a storm in February 2004. Using MBARI video, staff from the Sanctuary traced the origin of this container. Fines paid by the shipping company supported additional dives and research that showed how the container is affecting deep-sea animals—the first study of its kind in the world.
A more acidic ocean
MBARI researchers have also been at the forefront of research on ocean acidification, which poses a threat not just to marine animals in Monterey Bay, but around the world. Many researchers have tested the effects of acidified seawater on animals in the laboratory. MBARI’s efforts have focused on the more challenging task of measuring and studying the biological effects of pH shifts on animals in their natural habitat.
In the early 1980s, MBARI marine chemist Peter Brewer was one of the first researchers to suggest that carbon dioxide from human activities was dissolving into the ocean, making it more acidic. Brewer has spent the last 10 years working on automated systems for creating slight changes in the pH of seawater over a small patch of seafloor, superimposed on the natural daily and seasonal pH fluctuations in the surrounding seawater. Experiments based on MBARI’s system have been carried out in the Mediterranean, on the Great Barrier Reef, in Antarctica, and in the deep waters of Monterey Bay.
Because deep-sea animals are seldom seen, it’s easy to think of them as being relatively immune to effects of human activities. In his 2010 paper, Robison noted that overfishing, ocean acidification, and expanding low-oxygen zones in the ocean could potentially wipe out key organisms and cause irreversible changes in deep-sea food webs. Such shifts in deep-sea biodiversity could directly impact marine mammals, human fisheries, or even Earth’s climate. By keeping an eye on the invisible world below the surface, MBARI researchers are providing essential information about the health of Monterey Bay and of the world ocean.
Thousands of feet below the ocean’s surface lies a hidden world of undiscovered species, ancient animals and unique seabed habitats—as well as a vast untapped store of natural resources including valuable metals and rare-earth minerals. There’s growing demand globally to tap these minerals, which are key components in everything from cars to computers, skyscrapers and smartphones. And there are proposals around the world to begin mining the seafloor: in the Indian Ocean, off Papua New Guinea, and in the Red Sea.
Deep sea mining will have impacts on ecosystems that are lightly mapped and poorly understood. So, researchers from the Center for Ocean Solutions in Monterey and co-authors from leading institutions around the world propose a strategy for balancing commercial extraction of deep-sea resources with protection of diverse seabed habitats. Their approach, published this week in the journal Science, is intended to inform upcoming discussions by the International Seabed Authority (ISA) that will lay the groundwork for future deep-sea environmental protection and mining regulations.
“Our purpose is to point out that the ISA has an important opportunity to create networks of no-mining marine protected areas (MPAs) as part of the regulatory framework they are considering at their July meeting,” says lead author Lisa Wedding, an early career science fellow at the Center for Ocean Solutions. “The establishment of regional MPA networks in the deep sea could potentially benefit both mining and biodiversity interests by providing more economic certainty and ecosystem protection.”
Adds co-author Sarah Reiter, an ocean policy research analyst at the Monterey Bay Aquarium: “We’re advancing an approach that’s grounded in the best available science, consistent with international law, and feasible given political will.”
The Center for Ocean Solutions is a collaboration among Stanford University, Monterey Bay Aquarium and the Monterey Bay Aquarium Research Institute (MBARI). It works to solve the major problems facing the ocean and prepares leaders to take on these challenges.