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: 

Safeguarding seamounts: the hidden Yosemites of the deep

At the bottom of the ocean, amid vast, pitch-dark expanses of mud, there are a few exceptional, rocky places: undersea mountains. Here, the muddy seafloor and burrowing worms give way to bedrock and beautiful gardens of corals and sponges.

Seamounts are islands of biological diversity in the deep sea, home to rich marine communities of often long-lived animals. Photo courtesy MBARI/NOAA

Seamounts, as these peaks are known, “are the Yosemites of the deep sea that nobody sees,” says Dr. Jim Barry, a marine ecologist at MBARI—the Monterey Bay Aquarium Research Institute. “Under the surface, right off the horizon, is this wonderful world that’s been developing, slowly but surely, like a sequoia forest.”

Some seamounts are covered with ancient corals and deep-sea sponges that stand a meter tall and resemble oak trees. They’re also home to anemones, clams, small crustaceans and all manner of fishes. Many of these creatures rely on smell instead of vision to find food in these inky waters, at least half a mile deep.

Life on seamounts is of interest to marine scientists and to biotech researchers who hope to develop new pharmaceutical products based on properties in sponges, mussels and microbes. Photo courtesy MBARI

Seamounts are a frontier for scientific discovery, both for basic research, designed to fill knowledge gaps, and for applied research aiming to solve practical problems. Biotech companies, for instance, are interested in unique chemicals produced by deep-sea microbes, sponges, and mussels, which hint at pharmaceutical applications from antibiotics to fighting cancer.

Only a few seamounts are legally protected, like national parks are on land. One of those is Davidson Seamount, 80 miles southwest of Monterey and part of Monterey Bay National Marine Sanctuary. But the Trump administration is in the process of reviewing Davidson Seamount’s designation, with an eye for potentially stripping its protection and opening it up for new offshore oil and gas drilling. Read more…

Raising the “beautiful sea goddess”

Unearthly, transparent and beautiful—and also exceedingly delicate. The spotted comb jelly is so fragile a creature, just waving your hand through the water could destroy it. Now, for the first time anywhere, animal care staff at the Monterey Bay Aquarium have managed to culture these fragile, scintillating creatures.

Young spotted comb jellies were raised behind the scenes at the Monterey Bay Aquarium, and are now on exhibit.

Several of the newly hatched jellies are now on public display. It’s the latest advance in comb jelly science from the Aquarium team.

The species, known scientifically as Leucothea pulchra—Latin for “beautiful sea goddess”is “a clear football-shaped gelatinous animal” says Wyatt Patry, a senior aquarist who’s worked at the Aquarium for 11 years, and who led the culturing effort this winter.

“They’re ctenophores, not true jellyfish,” Wyatt notes. “Instead of stinging cells they have sticky cells called colloblasts.”

The spotted comb jelly’s common name refers to orange “knobs” or spots along its body.

“We don’t know what those do but we suspect they aid in prey capture,” Wyatt says. Two sticky tentacles trail behind it, acting like fishing lines.

“They also have cool whips called ‘auricles’ that they wave around—undulate—in this really cool slow wave motion, probably driving food into their mouths,” he says.

Read more…

Science on the front lines of ocean acidification

Life seems easy for the little red tuna crabs delighting Monterey Bay Aquarium visitors. The temperature and water chemistry in their exhibit are carefully controlled and stable. In the wild, it’s a different story. Conditions are changing—fast. Crabs and other critters are in a race with time, as record levels of atmospheric carbon dioxide (CO2) warm the planet and change ocean chemistry.

Our colleagues at the Monterey Bay Aquarium Research Institute (MBARI) are on the front line, documenting the impacts and identifying potential solutions for this serious threat to ocean health.

CO2 bubbled up slowly

For more than a century, scientists have known that burning fossil fuels warms our planet. They’ve also long been aware of another impact—this one affecting ocean chemistry.

In 1909, a brewery chemist discovered that CO2 both creates bubbles when it’s dissolved in liquid, and makes it more acidic.

In 1909, a chemist at the Carlsberg Brewery Laboratory discovered that CO2 dissolved in water not only creates tiny bubbles (like in beer). It also makes liquid more acidic. In other words, our burning of fossil fuels is changing the chemistry of the ocean, a process called ocean acidification.

The impact of rising atmospheric CO2 developed slowly and subtly. By the 1960s, however, climatologists began raising alarms. Decades later, Al Gore’s landmark book and movie, An Inconvenient Truth, framed climate change as an urgent threat to human survival. As the scientific community worked to build accurate models of climate dynamics and explore ways to deal with rampant carbon, some eyed the ocean—which absorbs 25 percent to 30 percent of the excess CO2 in the atmosphere—as a solution. Could we stash even more atmospheric carbon in the sea, sparing the planet the worst impacts of global warming? 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…

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