Conservation & Science

Voyage to the White Shark Café

For nearly 20 years, researchers from Monterey Bay Aquarium and Stanford University have fitted electronic tracking tags on adult white sharks each fall and winter along the California coast around San Francisco Bay. Each year, the tags documented a consistent migration by the sharks to a region more than 1,200 miles offshore—halfway to Hawaii—that’s been considered an oceanic desert. They dubbed it the White Shark Café, guessing that opportunities to feed and to mate might be the draw.

Now a team of scientists will spend a month at the Café in a month-long expedition to learn why the sharks make an epic annual migration to such a distant and seemingly uninviting location. The multi-disciplinary team is bringing an impressive complement of sophisticated oceanographic equipment, from undersea robots and submersibles to windsurfing drones that will search signs of sharks and their possible prey.

Funded by the Schmidt Ocean institute (SOI), the team is led by Stanford University Professor Barbara Block and includes marine biologists and oceanographers from Stanford University, Monterey Bay Aquarium, Monterey Bay Aquarium Research Institute (MBARI), the University of Delaware, and NOAA’s Office of Ocean Exploration and Research.  They are traveling aboard the SOI research vessel Falkor and set sail from Honolulu on April 20. They will return to port in San Diego on May 19.

Unraveling a mystery

We’ve studied these sharks for nearly 20 years, and they’ve told us consistently that the White Shark Café is a really important place in the ocean—but we’ve never known why,” said Dr. Salvador Jorgensen, a senior research scientist and shark research lead at Monterey Bay Aquarium.

Sophisticated oceanographic monitoring tools like these Saildrones will collect data to document the presence of white sharks and their prey species in the cafe. Photo courtesy Schmidt Ocean Institute.

By documenting the biology, chemistry and physical conditions in the region—a swath of the Pacific Ocean the size of Colorado—the researchers hope to understand what makes the Café an annual offshore hot spot for one of the ocean’s most charismatic predators. Read more…

Untangling the mysteries of deep-sea food webs

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.

A gonatid squid eats a deep-sea fish. These types of predator-prey relationships were easier to document, leading marine biologists to undervalue the “who eats who” complexity of predation by more delicate gelatinous animals. Photo © MBARI

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.

High-definition video cameras captured this image of a helmet jelly eating two types of prey: a small squid and (on its bell) another species of jelly. Photo © MBARI

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.

MBARI’s remotely operated vehicles, like the Doc Ricketts, have recorded video documenting hundreds of feeding interactions in the deep sea. Photo © MBARI

So Anela and her MBARI co-authors, Steve Haddock and Bruce Robison, tried a different approach.

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.

This complex food web shows groups of animals (indicated by different colored circles and lines) that were observed eating each other during MBARI remotely operated vehicle dives. Thicker lines indicate more commonly observed predator/prey interactions. Illustration © 2017 MBARI

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.

The transparent bodies of animals like this medusa jelly let researchers peek into their guts and discover what they’ve been eating — in this case, a red mysid shrimp. Photo © MBARI

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.

Jellies often eat other jellies, as is the case with this red medusa preying on a siphonophore. Researchers documented some animals that fed on 20 or more prey species. Photo © MBARI

(That’s the approach used in a recent study by Aquarium researchers to document changes in North Pacific seabird diets over the past 130 years.)

“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.

—Daniel Potter

Choy, C.A., Haddock, S.H.D., Robison, B.H. (2017). Deep pelagic food web structure as revealed by in situ feeding observationsProceedings of the Royal Society B. 284: 20172116, doi: 

Fish carbon-era: How our fossil fuel habit is changing the future of seafood

Jim Barry and deep-sea urchin
MBARI researcher Jim Barry handles a sea urchin in his lab. Photo © 2009 MBARI / Todd Walsh

In the early days of ocean acidification research, experiments were simple, says benthic ecologist Jim Barry. Some involved plopping fish into containers of high-carbon seawater. This sort of lab test allowed researchers to observe animals’ physiological responses to our ocean’s changing chemistry.

These days, many studies attempt to address the more difficult question of how acidification and ocean warming might affect interconnected marine species. “What you can’t learn from tests of fish in a jar,” Barry says, “is how climate change affects the way energy moves through a food web.”

That line of inquiry may start in the pages of scientific journals, but it leads somewhere more intimate: our dinner plates.

Read more…

Pinpointing plastic’s path to the deep sea

Until now, little has been known about how microplastics move in the ocean. A new paper by our colleagues at the Monterey Bay Aquarium Research Institute (MBARI), just published in the journal Science Advances, shows that filter-feeding animals called giant larvaceans collect and consume microplastic particles in the deep sea.

Larvaceans are transparent tunicates that live in the open sea and capture food in sticky mucus filters. Plastic particles accumulate in the cast-off mucus feeding filters and are passed into the animals’ fecal pellets, which sink rapidly through the water, potentially carrying microplastics to the deep seafloor.

Researchers at MBARI documented that tadpole-like giant larvaceans consume microplastic beaads. Photo courtesy MBARI.

The new findings contribute to an emerging picture about the ubiquitous nature of ocean plastic pollution. Over the last decade, scientists have discovered tiny pieces of plastic in all parts of the ocean—including deep-sea mud. One recent study documented microplastic fibers in deep-sea sediments at levels four times greater than an earlier study had found in surface waters. Plastic has also been discovered in the tissues of animals at the base of the ocean food web. Another just-published study found that fish confuse plastic particles with real food items because it smells just like organic matter in the ocean.

Despite their name, giant larvaceans are less than 10 millimeters (4 inches) long, and look somewhat like transparent tadpoles. Their mucus filters—called “houses” because the larvaceans live inside them—can be more than 1 meter (3 feet) across. These filters trap tiny particles of drifting debris, which the larvacean eats. When a larvacean’s house becomes clogged with debris, the animal abandons the structure and it sinks toward the seafloor.

Principal Engineer Kakani Katija studies giant larvaceans during field expeditions in Monterey Bay. Photo courtesy MBARI.

In early 2016, MBARI Principal Engineer Kakani Katija was planning an experiment using the DeepPIV system to figure out how quickly giant larvaceans could filter seawater, and what size particles they could capture in their filters. Other researchers have tried to answer these questions in the laboratory by placing tiny plastic beads into tanks with smaller larvaceans. Because giant larvacean houses are too big to study in the lab, Kakani decided to perform similar experiments in the open ocean, using MBARI’s remotely operated vehicles (ROVs).

When she discussed this experiment with Postdoctoral Fellow Anela Choy—who studies the movement of plastic through the ocean—they realized that in-situ feeding experiments using plastic beads could also shine light on the fate of microplastics in the deep sea. Read more…

How do you tag a jellyfish?  

They’re so soft—so squishy! Where to put a tag—and why bother? Questions like these moved scientists from the Monterey Bay Aquarium, the Monterey Bay Aquarium Research Institute (MBARI), Hopkins Marine Station and other institutions around the world to publish the first comprehensive how-to tagging paper for jellyfish researchers everywhere. This missing manual was long in the making

A wild sea nettle swims off Point Lobos near Carmel. Photo ©Bill Morgan

Tommy Knowles, a senior aquarist at Monterey Bay Aquarium, explains why.  Historically, ocean researchers demonized jellies as “blobs of goo that hurt you,” and that interfered with scientific gear. That changed in the  latter part of the 20th century as scientists grew keen to understand entire ecosystems, not just individual plants and animals. Knowing who eats what, how, where and when, they learned, is critical for conservation.

Jellyfish, however, remained a very under-appreciated member of the ecosystem for years, largely because so little was known about them.

Senior Aquarist Tommy Knowles and his colleagues work in the lab and in the filed to advance jellyfish science. Photo by Monterey Bay Aquarium/Tyson Rininger

“People didn’t know how to keep them alive in the lab or even on the boat,” says Knowles. Today, the field is coming into its own at a time when climate change has added urgency to the need to understand ecosystems in order to preserve ocean health.

A growing subject of interest

Understanding jellies is a concern for fisheries managers, too, since some jellyfish species prey upon the young and compete for food with the adults of commercially important fish. Other jellies impact tourism when blooms of stinging species foul beaches.

It’s not all negatives. We know that jellyfish play important roles in healthy marine ecosystems, by sheltering juvenile fish and crabs under their swimming bells, and nourishing hundreds of ocean predators. Jellies are a significant food source for ocean sunfish (the largest bony fish on the planet) and the endangered Pacific leatherback sea turtle, California’s state marine reptile.

A barrel jellyfish (Rhizostoma octopus) is tagged by a diver with an accelerometer using the “cable tie” method. Courtesy Sabrina Fossette/NOAA

As with other marine species that live and travel underwater—out of sight of human researchers—electronic data tags are useful tools for tracking jellies’ movements. Which gets back to the question: Just how do you tag a jellyfish? Read more…

Using science to save ocean wildlife

The Monterey Bay Aquarium is a science-driven organization, and rigorous science underpins all of our public policy, research and education programs. Much of our research centers on marine life that visitors can also see in our exhibits – from sea otters to sharks and tunas, even our giant kelp forest. Here’s some of what we’ve learned over the past 30-plus years that is contributing to conservation of key ocean species and ecosystems.

A sea otter works to crack a mussel shell open on a rock off the coast of Moss Landing, California. Photo by Jessica Fujii

Sea otters crack open tool-use secrets

Revolutionary female scientist Jane Goodall was the first person to discover that chimps use tools and live within complex social systems. Our team of female researchers are walking in Jane’s footsteps with their recent studies on use of tools by another mammal: the sea otter. When observing sea otters along the Monterey Peninsula, sometimes we can hear a “crack, crack, crack!” above the roar of the tide. That sound comes from sea otters using rocks and other tools to open prey items, such as crabs or bivalves, as they float on their backs. Sea otters are avid tool users, but until recently not much was known about how sea otters choose their tools, what aspects of their environments influence tool use, or whether they teach tool use to other otters. The Aquarium’s decades of research into sea otter behavior provided years of observations of sea otter foraging and tool-use behavior, including sea otter pups pounding empty fists against their chests. Could such activity be instinctual? Research Biologist Jessica Fujii has devoted much of her young career to studying the frequency and types of tools used and whether tool use can be coded in sea otter genes. Jessica is looking ahead to see how sea otters learn, teach, and eventually master tool use in the wild.

A sea otter rests in an eelgrass bed in Elkhorn Slough National
Estuarine Research Reserve. Sea otters contribute to the recovery of eelgrass and ecosystem health in this vital wetland on Monterey Bay. Photo by Ron Eby.

Sea otter surrogacy helps restore Elkhorn Slough

With 15 years of experience rescuing, rehabilitating, and then releasing surrogate-reared sea otters into Elkhorn Slough, an estuary near Moss Landing, California, the sea otter research team at the Aquarium began to wonder how and if their work was affecting the otter population there. Does releasing a few animals into the slough each year really make any difference? After crunching some serious numbers from the surrogacy program and the U.S. Geological Survey’s (USGS) annual sea otter census, the researchers discovered that it did. Nearly 60 percent of the 140 or so sea otters living in Elkhorn Slough today are there as a result of the Aquarium’s surrogacy program. While we’d known that sea otters served as ecosystem engineers for the giant kelp forests in Monterey Bay, we have now documented that sea otters in Elkhorn Slough are restoring the health and biodiversity of the estuary. This gives us further insights into how sea otters may contribute to coastal ecosystem resilience. Read more…

For deep-ocean science, nothing beats being there

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.

deep-sea
Creatures of the deep sea. Photo © MBARI

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

frame-recover-ondeck
First Mate Paul Ban assists with the recovery of a tripod frame onto the R/V Rachel Carson, Photo by Roberto Gwiazda © MBARI 2017

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.

Read more…

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