Navigating the Ropes of Tuna Wrangling

Alex Norton (black wetsuit, center) catches a live tuna in the Tuna Research and Conservation Center (TRCC) at Stanford's Hopkins Marine Station. Norton, the tuna husbandrist at the TRCC, is in charge of catching tunas in the TRCC tanks and keeping them calm for rapid sampling, before returning them to the tanks. The system shown above involves a blue mesh "crowder" that isolates a single tuna into a portion of the tank, where Norton can pick it up and transfer it to a sling for sampling (Photo courtesy of Alex Norton).

Alex Norton (black wetsuit, center) catches a live tuna in the Tuna Research and Conservation Center (TRCC) at Stanford’s Hopkins Marine Station. Norton, the tuna husbandrist at the TRCC, is in charge of catching tunas in the TRCC tanks and keeping them calm for rapid sampling, before returning them to the tanks. The system shown above involves a blue mesh “crowder” that isolates a single tuna into a portion of the tank, where Norton can pick it up and transfer it to a sling for sampling (Photo courtesy of Alex Norton).

Alex Norton never would have guessed that a conversation about a cool-looking squid shirt would lead to a job as a tuna husbandrist at Stanford’s Hopkins Marine Station. Or that the path to get there would involve milking deadly cone snails for their venom. But Norton’s lifelong love for closely observing animal behavior prepared him perfectly for both jobs.

Norton, the tuna husbandrist at Hopkins’ Tuna Research and Conservation Center (TRCC), grew up in a family of scientists – his grandmother was the first woman to receive a Ph.D. in marine biology from the University of Washington, and his father conducted graduate oceanography research at Stanford’s Hopkins Marine Station. Norton himself studied rockfish growth at UC Santa Barbara. So when Norton, who sold ornamental rocks for home decoration after college, saw Hopkins professor Bill Gilly walk into the rock yard one weekend wearing a Hawaiian-print shirt decorated with squids, sea urchins and kelp fronds, Norton finally had something to talk about besides which rocks to choose. Gilly realized the extent of Norton’s marine knowledge, and invited him to Hopkins to check out research going on.

Norton gently places a captured tuna into a sling for transfer to a tank. The key to successfully handling live fish, according to Norton, is to be calm, gentle and efficient, which helps calm both the fish and the researchers around him (Photo courtesy of Alex Norton).

Norton gently places a captured tuna into a sling for transfer to a tank. The key to successfully handling live fish, according to Norton, is to be calm, gentle and efficient, which helps calm both the fish and the researchers around him (Photo courtesy of Alex Norton).

Soon Norton was working part-time in Gilly’s lab isolating proteins in cone snail venom, to determine their effects on muscle seizures in prey. As Norton puts it, he became one of the few people “willing to milk a cone snail for its venom”. Cone snails – innocent-looking and often beautiful shells – pack a nasty punch with a small harpoon containing one of the most toxic venoms in the world. But Norton learned ways to handle them to safely extract their venom. He devised a technique of covering a plastic tube with a thick rubber layer and placing a piece of fish fin in front of the tube, then dangling it in front of the snail. The snail would sense the fish and fire its harpoon directly into the tube, releasing the venom as a sample that Norton could collect for his studies.

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Norton, who grew up surrounded by the wealth of nature in Pacific Grove and the Monterey Peninsula, remembers a childhood spent collecting and observing the animals around him. His parents would take him to snorkel in the Carmel River, so that he could watch trout swimming in the currents and lurking behind rocks. He kept terrariums in his backyard, with toads, newts, lizards and any other creatures he could find crawling around.

Norton talks of picking up bees and placing them on his arm, just to study them more closely. He quickly learned that if a bee arched its back, it was upset and he needed to flick it off to avoid being stung. If Norton was calm, however, the bee remained calm as well, and he could watch it indefinitely. These close observations of threat behavior paid off later, when Norton explored the nuances of cone snail behavior and attack warning signals while he extracted their venom.

Tuna tagging and live capture starts at sea on chartered fishing boats, where the TRCC catches wild yellowfin and Pacific bluefin tunas and holds them in large bait wells (tanks below the boat deck). Norton (center, black wetsuit), is responsible for climbing into the tanks and single-handedly placing each fish in a sling, so it can be transferred off the boat and transported to the TRCC. Here, Norton is passing a sling, with a tuna inside, up to handlers on deck (Photo Courtesy of Natalie Arnoldi).

Tuna tagging and live capture starts at sea on chartered fishing boats, where the TRCC catches wild yellowfin and Pacific bluefin tunas and holds them in large bait wells (tanks below the boat deck). Norton (center, black wetsuit), is responsible for climbing into the tanks and single-handedly placing each fish in a sling, so it can be transferred off the boat and transported to the TRCC. Here, Norton passes a sling with a tuna inside up to handlers on deck (Photo courtesy of Natalie Arnoldi, on-board F/V Shogun).

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These days, Norton is the lead fish handler at the TRCC, the go-to man when researchers want to catch live tunas from the tanks, in order to sample them non-invasively or measure their swimming abilities. The TRCC has several large tanks, 6 feet deep and 15 feet across, that hold live yellowfin and Pacific bluefin tuna. The tuna range from 2 to 3 feet long and up to 20 kilograms (that’s almost 50 pounds, for those of you who are rusty on your conversions), occasionally tipping the scales at over 100 pounds. Many mornings, Norton gets into the tanks with the fish, and – with the help of any researchers willing to don wetsuits and get their hands wet – Norton scoops up individual fish using his bare arms, and places them into slings to be transferred to respirometry flumes or quickly sampled while live. Although the tank water level is lowered to waist-height during samplings, catching a squirming tuna sometimes entails accidental full submersion, and guarantees unexpected splashing (tunas are sometimes coined the “Ferraris of the Sea” for their speed, strength and precision of movement). One day, a tuna escaped from the grasp of Norton’s fellow handler in a TRCC tank, and hurtled straight toward Norton, ramming into his chest. Norton was mostly unharmed, but the fish created a wave of water that splashed up into the rafters, 10 feet above.

Some of the best aspects of Norton's job are the moments he spends surrounded by sun and sea, working with fish, and joking with researchers and friends (Photo courtesy of Alex Norton).

Some of the best aspects of Norton’s job are the moments he spends surrounded by sun and sea, working with fish, and joking with researchers and friends (Photo courtesy of Alex Norton).

Norton’s job requires a combination of strength, calm, and the ability to read fish movements and understand when they are upset and likely to injure themselves if handled. Norton credits Chuck Farwell, the lead tuna handler at the Monterey Bay Aquarium, with teaching Norton all of his tuna-handling skills, but Norton’s lifelong animal observations also paid off, giving him a strong “fish sense” that allows him to anticipate the animals’ movements. Norton has been key to the TRCC’s ability to sample live tunas in a non-stressful environment.

Norton probably couldn’t have predicted as a 10-year-old that his path would lead from observing the arched backs of bees to anticipating the warning protrusions of cone snail radulas, to wading through schools of wary tunas, but somehow it all fits together in retrospect. He loves the daily opportunities to learn new things from the researchers around him, and the ever-changing adventure that working in the tanks with tunas brings. Most of all, he enjoys the ultimate observational experience of being able to track the behaviors of animals he never could have reached with a mask and snorkel or backyard terrarium.

Cracking the shell of schistosomiasis

 – Re-introducing natural predators to control parasite infections in western Africa

A man carries freshwater prawns to the Senegal River as part of a re-implementation project by Hopkins post-doctoral scholar Susanne Sokolow to reduce schistosomiasis-hosting snails. The prawns have been wiped out of the Senegal River by habitat loss, but when present, they serve as a successful biological control mechanism (Photo credit - Susanne Sokolow).

A man carries freshwater prawns to the Senegal River as part of a re-implementation project by Hopkins post-doctoral scholar Susanne Sokolow to reduce schistosomiasis-hosting snails. The prawns have been wiped out of the Senegal River by habitat loss, but when present, they serve as a successful biological control mechanism (Photo credit – Susanne Sokolow).

Despite the miracles of modern medicine, nature sometimes still has the best answers to disease control. Schistosomiasis, a parasite-borne disease that affects people from sub-Saharan Africa to Southeast Asia and South America, is one of a slew of infections known by the World Health Organization as “Neglected Tropical Diseases”, so categorized because they are treatable and preventable, but still exist due to poverty and unsanitary living conditions. Susanne Sokolow, a postdoctoral scholar working with professor Giulio De Leo at Stanford’s Hopkins Marine Station, is taking a new, ecology-based approach to the problem of schistosomiasis prevalence in western Africa, by targeting and reducing the hosts that the parasites depend on.

Cleaning off -- Children carry dishes to the Senegal River for washing. Because people spend so much time on and around the river, they are exposed to Schistosoma parasites, which easily penetrate human skin. The parasites rely on human hosts to complete their lifecycle (Photo credit - Susanne Sokolow).

Washing Up — Children carry dishes to the Senegal River for washing. Because people spend so much time on and around the river, they are frequently exposed to Schistosoma parasites, which easily penetrate human skin. The parasites rely on human hosts to complete their lifecycle (Photo credit – Susanne Sokolow).

The group of Schistosoma species, which cause schistosomiasis, use several types of freshwater snails to host parasite reproduction. In their larval form, the parasites latch onto snail gonads, diverting snail energy reserves to parasite growth. Once the parasites have developed sufficiently, they release their hold on the now-castrated snails and cast off into the river, where they can penetrate the skin of humans wading in the water. Schistosoma parasites complete their lifecycle in the human body, and release their eggs into fecal matter and urine, which often ends up back in the river, placing parasite eggs within reach of their snail hosts and beginning the cycle anew. The parasites are not lethal to humans, but cause a range of debilitating symptoms, including chronic anemia, stunting, organ damage and cognitive impairment, all of which create a preventable reduction in health and quality of living.

Grasping for Solutions -- A man holds up a market-sized African prawn (species) of the type that Susanne Sokolow and collaborators are using to control schistosomiasis proliferation along the Senegal River Basin. The prawns consume freshwater snails, which serve as hosts for schistosoma parasites (Photo credit - Djibril Sarr Faye; courtesy of Susanne Sokolow).

Grasping for Solutions — A man holds up a market-sized African prawn (M. vollenhovenii) of the type that Susanne Sokolow and collaborators are using to control schistosomiasis proliferation along the Senegal River Basin. The prawns consume freshwater snails, which serve as hosts for Schistosoma parasites (Photo credit – Djibril Sarr Faye; courtesy of Susanne Sokolow).

The rate of schistosomiasis infections originally spiked after the Diama Dam was built on the Senegal River in the 1980s to prevent saltwater backwash into agricultural lands along the upper river. The dam had the unintended consequence, however, of preventing species of native African prawns (Machrobrachium vollenhovenii) from traveling between the upper freshwater regions of the river and the lower saline estuaries necessary for reproduction. African prawns feed on the snails that host schistosomiasis, so diminishing prawn numbers led to an increase in freshwater snails, and a corresponding drastic rise in schistosomiasis in people living along the Senegal River Basin.

Because the Diama Dam almost completely eliminated prawn populations along the Senegal River, Sokolow and collaborators are investigating ways to reintroduce these natural predators to the river, in order to reduce host snail numbers. The current project involves flying prawns in from Cameroon, and implementing them into the Senegal River by hand. The prawns are contained in large net enclosures near frequently-used riverbank sites so that they concentrate feeding on nearshore snail populations, and will be more easily accessible for people to harvest.

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A map of Western Africa, showing the Senegal River (blue) and the Diama Dam (red star) near the mouth of the river (Map courtesy of: http://www.toptenz.net/top-10-wars-of-the-future-that-will-be-fought-over-water.php).

A map of western Africa, showing the Senegal River (blue) and the Diama Dam (red star) near the mouth of the river (Map courtesy of: http://www.toptenz.net).

Sokolow originally began working on the project as a postdoctoral scholar at UC Santa Barbara with Professor Armand Kuris and Kevin Lafferty. Along with Kuris and Lafferty, Sokolow and De Leo’s current collaborators include Projet Crevette and the 20/20 Initiative, both of which focus on reintroducing prawns to African rivers to reduce schistosomiasis parasites, as well as a prawn aquaculture team from Kentucky State University, and Stanford Urology professor Michael Hsieh. The project was recently named one of seven Environmental Venture Projects by Stanford’s Woods Institute for the Environment.

Part of Sokolow’s work involves investigating just how hungry African prawns are for freshwater snails, and how effective the prawns will be as a snail removal tool if reintroduced into rivers. Interestingly, small-to-medium sized prawns consume the highest proportional snail biomass relative to their own biomass, making them the “most effective” prawn size class of snail removers. This finding is valuable because it means that by the time prawns reach their larger market size, they are no longer as effective at removing snails. Since prawns are an important protein source for people living along the river, and are considered a delicacy abroad, being able to harvest the prawns for food and money after they have consumed snails provides a win-win opportunity for local communities (fortunately, the prawns do not serve as a host for schistosomiasis parasites, so humans cannot contract the disease by eating prawns).

Free-crawling -- Men release freshwater African prawns near the shores of a populated area of the Senegal River. The prawn re-implementation project has focused on placing prawns in parts of the river that people use the most, so that prawns will target snail (and schistosomiasis) reductions in these areas, and so that people can more easily harvest the prawns (Photo credit - Susanne Sokolow).

Free-crawling — Men release freshwater African prawns near the shores of a populated bank of the Senegal River. The prawn re-implementation project has initially focused on placing prawns in netted-in areas of the river that people use often, so that prawns will target snails (and schistosomiasis parasites) in these areas, and so that people can more easily harvest the prawns (Photo credit – Susanne Sokolow).

The costs of transport from Cameroon, as well as the travel stress, which shortens prawn lifespan, have encouraged Sokolow and project partners to explore methods of prawn aquaculture farms along the Senegal River. Prawn farming within Senegal would reduce travel distance and costs for importing prawns, and create additional local jobs in aquaculture.

Even when drugs to cure a disease such as schistosomiasis can be cheaply administered, they do not prevent re-infection, which must be tackled by addressing the underlying sanitation problems that arise from the ways in which people use their surroundings. Sokolow’s work capitalizes on the multiple benefits that the naturally predatory African freshwater prawns present, to provide long-term biological control and to help re-implement an important harvestable and marketable resource.

Heads up! Searching for head-to-tail orientation in the radially symmetric starfish

A juvenile starfish that Levine has raised to track gene expression (Photo Courtesy of Judith Levine).

A juvenile starfish that Levine has raised to track gene expression (Photo Courtesy of Judith Levine).

Starfish share their unique pentaradial symmetry with such diverse-looking creatures as spiky sea urchins, crunchy sand dollars, and sluggish sea cucumbers, all of which belong to the group of marine creatures known as echinoderms. Yet for all the bicycle wheel appearances, echinoderms come directly from a bilateral ancestor (an organism with a left-and-right, mirror image body plan, like most animals on the planet). This means that for some reason echinoderms evolved from a successful bilateral body into the only group of animals with a five-point layout.

The beginning stages of starfish larval development. Levine is targeting the expression of specific genes as the bat star develops (Photo courtesy Judith Levine).

Universal beginnings — The early stages of starfish larval development. Levine is targeting the expression of specific genes as bat stars develops (Photo courtesy of Judith Levine).

In the world of evolutionary biology, body plans are a big deal. Most large-scale animal body evolution occurred during the Cambrian Era (a whopping 500 million years ago), when resources and open ecological niches were still widely available for anything that could survive well enough to carve out a place for itself. Radical overall shape changes haven’t really occurred since. Because the majority of animals on the planet have a head-to-tail bilateral body plan, the unique radial evolution of echinoderms raises questions about how and why they were able to accomplish this drastic change surrounded by so many close relatives who are solidly bilateral organisms.

To get to the heart (or perhaps head) of how radially symmetric echinoderms came from a bilateral ancestry, Judith Levine, a Ph.D. student in Professor Chris Lowe’s lab at Stanford’s Hopkins Marine Station, is teasing apart which end of the starfish constitutes a head. Knowing which parts of the starfish link genetically to the head, middle and tail of a bilateral organism allows scientists to make regional comparisons between the bodies of echinoderms and other animals. From this, they can delve further into the evolution of which bilateral ancestral structures gave rise to various parts of echinoderm body plans. The head-to-tail axis is one of the most ubiquitous, and therefore most evolutionarily popular, body traits of all animals, and some people theorize that it’s a reason that bilateral animals evolved so successfully and dominantly across the globe. But if echinoderms also have that head-to-tail axis in some form, then the genetic code behind the bilateral axis is not necessarily the only thing that dictates animal body shape, since radial body plans have also come out of those genes. In that case, scientists will have to analyze other aspects of animal body shapes to determine which axes code uniquely for bilateral body shapes.

An adult bat star spawns (orange egg masses underneath) in the lab. Levine collects adult bat stars and sea cucumbers from the kelp forest off Hopkins, and induces spawning to produce the eggs she uses for her morphological studies (Photo courtesy of Judith Levine).

The birth of a new star — An adult bat star spawns in the lab (orange egg masses underneath). Levine collects adult bat stars and sea cucumbers from the kelp forest off Hopkins, and induces spawning to produce the eggs she uses for her morphological studies (Photo courtesy of Judith Levine).

To further complicate matters, starfish and sea cucumbers don’t spend their whole lives mimicking constellations. Echinoderms produce distinctly bilateral larvae, which undergo metamorphosis during development to take on the radial adult form. All of which makes it very difficult, when you pick up a fully-grown starfish from a tide pool off Monterey’s rocky shores, to determine which end might correspond mostly closely to a head.

Levine works with larvae from bat stars and warty sea cucumbers, both local and abundant species in the kelp forest off Hopkins, as models for cluing into gene expression. Using a process known as in situ hybridization, Levine tracks how and where in their bodies developing larvae express certain genes corresponding to the head-to-tail sequence. She has so far been able to identify and piece apart several genes in the bat star that play important roles in normal bilateral head-to-tail axis development, but she’s waiting to draw conclusions until she has analyzed more genes. She’s confident, though, that what she finds will fill in an interesting and so-far-unknown aspect of how the various creatures on the planet ended up looking like they do. Teasing out how different shapes developed can lead to better understanding of our planet’s history, and potential life finds on other planets. Levine’s project is partly funded by NASA’s Astrobiology program, which studies how life begins and how it evolves. Understanding the unique evolution and developmental transitions of echinoderms helps fill in our knowledge of how life forms diversify into their numerous shapes and successes.

Levine analyzes bat star larvae at her lab bench. She has enjoyed the opportunity to watch echinoderm larvae metamorphose into their adult shapes (Photo courtesy of Judith Levine).

Scoping out change — Levine analyzes bat star larvae at her lab bench. She has enjoyed the opportunity to watch echinoderm larvae metamorphose into their adult shapes (Photo courtesy of Judith Levine).

For Levine, though, part of the reward of the project comes from raising and working daily with the animals from the very beginnings of their larval stages. Her care and attention makes her a somewhat unique “starfish parent” and allows her to learn the nuances of each organism’s individual development. Levine, who has a background in morphology research, finds something almost magical in watching echinoderms transform. The bat star, which can reach the width of a human hand as an adult, is barely the size of the period at the end of this sentence when it metamorphoses into the miniature star shape that will grow into the iconic five-armed orange animal creeping slowing over the rocks off Hopkins.

Diving into History at Cannery Row

Exploring altered marine communities in the shadow of Steinbeck’s famous Monterey scene

A bird’s-eye view of Cannery Row (horizontal road along middle of picture) and the offshore waters in 1932. The canning factories are visible extending downward (into the water) from Cannery Row. Red circles indicate locations of some of the main cannery pipes that Stanford student Andrew Miller plans to compare for sessile marine species compositions. (Photo courtesy of Monterey Public Library, California History Room; edited by Andrew Miller)

Pipe-works — A bird’s-eye view of Cannery Row and the offshore waters of Monterey, CA in 1932. The canning factories are visible extending downward (into the water) from Cannery Row. Red circles indicate locations of the cannery pipes that Stanford student Andrew Miller plans to compare for sessile marine species compositions. (Photo courtesy of Monterey Public Library, California History Room; edited by Andrew Miller)

Cannery Row – it’s a short and bustling bayside street renowned for its colorful history, and, for a time, lucrative sardine processing factories. Made famous by its portrayal in John Steinbeck’s lively novella, Cannery Row above the waterline has been turned into a must-see tourist destination and the home of the world-famous Monterey Bay Aquarium (itself the old Hovden Cannery). But canning history lingers beneath the waves as well, in the form of old steel cannery pumping pipes in varying states of decay. Stanford student Andrew Miller plans to spend his summer diving off Cannery Row to explore the differences in species habitation between the old cannery pipes and the surrounding rocky bottom.

Miller, a junior majoring in Stanford’s Earth Systems program, became interested in the effects of invasive substrates on sessile marine communities (non-moving critters such as barnacles, mussels, limpets and algae) when he explored the idea of researching artificial reefs and shipwrecks off the Florida coast. Numerous wrecks have been purposefully sunk off Florida to encourage marine community growth, increasing tourist diving in the region. However, no one has compared the marine community make-up of the artificially-placed structures to the species compositions on the surrounding natural reefs and seafloor.

Time-hopping. An old sardine hopper rests out of the water at Stanford’s Hopkins Marine Station. Wooden sardine hoppers used to float in the waters off Cannery Row, connected to the canneries via the underwater pipes that Miller plans to study. Fishermen would dump their catches into the hoppers, which would suck the fish through the pipes and into the canneries (Photo courtesy of Andrew Miller).

Time-hopping – An old sardine hopper rests out of the water at Stanford’s Hopkins Marine Station. Wooden sardine hoppers used to float in the waters off Cannery Row, connected to the canneries via the underwater pipes that Miller plans to study. Fishermen would dump their catches into the hoppers, which sucked the fish through the pipes and into the canneries. (Photo courtesy of Andrew Miller)

When opportunities to study the Florida wrecks didn’t pan out, Miller turned instead to the old cannery pipes off Cannery Row – themselves a form of invasive substrate, though with a lengthy history. Canneries began appearing along the shores of Monterey around the end of World War I, and the canning industry boomed in the 1920s. The pipes were originally connected to fish hoppers, giant wooden boxes that floated in the water offshore of the canneries. Fishermen dumped their catches of sardines and anchovies into the hoppers, and powerful pumps sucked the fish through the pipes to the canneries for processing. Today, the pipes remain beneath the waves, forming an alternative substrate to Monterey’s native rocky bottom.

Miller, who started diving just a year ago, is interested in looking at whether these human-placed substrates lend themselves to different compositions of sessile species than the surrounding rocky seafloor.

Diving deeper. Miller has been diving off Hopkins Marine Station for just over a year, and looks forward to rigorously identifying and quantifying the various species that inhabit the cannery pipes and surrounding rocky bottom (Photo courtesy of Andrew Miller).

Diving deeper – Miller has been diving off Hopkins Marine Station for just over a year, and looks forward to rigorously identifying and quantifying the various species that inhabit the cannery pipes and surrounding rocky bottom. (Photo courtesy of Andrew Miller)

The non-native substrates of the cannery pipes may allow different organisms, or even invasive species, to settle and propagate with greater success than they might have along Monterey’s native intertidal rocks and sand.

Miller, who will be working on the project this summer with Hopkins professor Jim Watanabe, will be conducting diving surveys and species counts to identify and quantify the sessile organisms, and their locations along and around the cannery pipes. Miller is excited to see how marine communities have responded to the continued presence of the cannery pipes, and whether these lingering bits of history have been absorbed into daily life beneath the sea, or whether they still stick out as an oddity befitting the bizarre inhabitants of Steinbeck’s historical streetside creation.

 

Forests without Oxygen

Tracking hypoxic pulses and fish responses in California’s kelp forest

Sensors that detect turbulent water mixing have been placed in the kelp forest off Stanford's Hopkins Marine Station, so that researchers can understand the fine-scale movements of low-oxygen waves through the kelp forest. Divers must monitor and clean the equipment every few days to ensure that the sensors are still functioning properly. (Photo courtesy of Ryan Walter, Stanford Environmental Fluid Mechanics Laboratory)

Sensors that detect turbulent water mixing have been placed off Stanford’s Hopkins Marine Station, so that researchers can understand the fine-scale movements of low-oxygen waves through the kelp forest. Divers must monitor and clean the equipment every few days to ensure that the sensors are still functioning properly. (Photo courtesy of Ryan Walter, Stanford Environmental Fluid Mechanics Laboratory)

It turns out that if you live in a kelp forest, you can’t always take oxygen for granted. And the waves breaking against the rocky shore overhead aren’t the only ones you feel.

Monterey Bay, the backyard of Stanford’s Hopkins Marine Station, is world-renowned for its famous giant kelp (Macrocystis pyrifera), which can grow to over 100 feet. But the California coast also experiences a strong annual spring upwelling season, which brings low-oxygen waters up from the ocean depths and toward shore. Internal bores – water waves below the ocean’s surface – push these low-oxygen waters up Monterey Bay’s submarine canyon and toward the coast. So from March to June every spring, the kelp forests, and the animals living in them, are subjected to intermittent low-oxygen pulses that can drop to barely tolerable levels, and can last 8 to 12 hours at a time. Several Hopkins researchers are exploring how these low-oxygen events impact Monterey’s kelp forests and intertidal zones, and how the organisms living around the kelp survive and respond.

In situ measurements of oxygen and temperature at two smooth ocean floors (top and middle graphs) in comparison to the kelp forest floor (bottom graph) off Hopkins Marine Station. The top two graphs indicate a low-oxygen event from Aug. 9-12, but the kelp forest bed shows a modified signal due to its more complex topography. (Image courtesy of Paul Leary)

In situ measurements of oxygen and temperature at two smooth ocean floors (top and middle graphs) in comparison to the kelp forest floor (bottom graph) off Hopkins Marine Station. The top two graphs indicate a low-oxygen event from Aug. 9-12, but the kelp forest bed shows a modified signal due to its more complex topography. (Image courtesy of Paul Leary)

The details of oxygen distribution

Paul Leary, a Ph.D. student in Professor Fiorenza Micheli’s lab at Hopkins, is looking at how low-oxygen waves interact with the kelp forest on both a larger and smaller scale, and what the avoidance patterns of fish are. Leary has deployed several mooring buoy systems in the kelp forest off Hopkins, to monitor temperature, oxygen and other water properties. When low-oxygen events occur, Leary will be able to track their movements through the kelp forest. Unlike in an open-water coastal environment, internal wave energy through a kelp forest is diminished by the kelp, reducing the turbulence that helps mix water from the surface to the seafloor. So after low-oxygen waves move through the kelp forest, they may leave pockets of hypoxic water along the bottom, altering and compressing fish habitats.

Who is where?

Leary also plans to look at the responses of fish living in the kelp forest to these recurring low-oxygen waves. He will compare surveys of fish movements during hypoxic events with surveys from before and after the events, to help determine the oxygen “avoidance thresholds,” beyond which fish won’t venture into hypoxic waters. This information will help him answer the question “Who is where?” when these events are happening.

In conjunction, Jody Beers, a postdoctoral researcher in George Somero’s lab at Hopkins, and Steve Litvin, a postdoctoral researcher in Micheli’s lab, will be tackling the physiological aspects of kelp forest fish, by comparing oxygen tolerances in age-classes of juvenile rockfish.

Sensors give a real-time reads of low-oxygen events, which can be correlated with fish movements to determine how organisms respond to hypoxic pulses. (Photo courtesy of Ryan Walter, Stanford Environmental Fluid Mechanics Laboratory)

Sensors give a real-time reads of low-oxygen events, which can be correlated with fish movements to determine how organisms respond to hypoxic pulses. (Photo courtesy of Ryan Walter, Stanford Environmental Fluid Mechanics Laboratory)

In particular, Beers is interested in whether different age-classes experience varying vulnerability to hypoxia. If a juvenile rockfish survives a spring season of upwelling, for example, does that give it an increased low-oxygen tolerance in its second upwelling season, compared to a newly recruited larval rockfish? Beers plans to test animal respiration and metabolism in the lab, as well as analyze cell viability and oxidative stress under varying oxygen conditions, to gain a comprehensive picture of adaptations to low-oxygen events.

The rockfish family is the dominant fish family in the kelp forests off California, and has immense value in the ecosystems along our rocky shores, in addition to commercial and recreational fishing value. As low-oxygen zones in oceans around the world expand with warming water temperatures, understanding how fish tolerate the regular hypoxia cycles along coastal California will give us insight into the survival mechanisms that they and other species draw upon in the face of low-oxygen waves.

Crabs and Climate Change – How marine invasive species can serve as models of thermal adaptation

Hanging out -- Several European green crabs (Carcinus maenas) dangle from non-invasive heart rate monitors that Stanford Ph.D. student Carolyn Tepolt designed to study their cardiac responses to heat stress. Tepolt is interested in how the crabs – a worldwide invasive species – respond to 5oC versus 25oC acclimation.

Hanging out — Several European green crabs (Carcinus maenas) dangle from non-invasive heart rate monitors that Stanford Ph.D. student Carolyn Tepolt designed to study their cardiac responses to heat stress. .

Invasive species are typically viewed as all-encompassingly bad. And often they do wreak havoc on the ecosystems they invade. But Carolyn Tepolt, a Ph.D. student in Professor Steve Palumbi’s lab at Stanford’s Hopkins Marine Station, sees the European green crab (Carcinus maenas) – a worldwide invasive species – as an opportunity. In light of growing concerns about how species will fare in warming oceans, Tepolt is using these invasive crabs to look at the analogue of climate change: what happens when a marine species moves into new and changing environments. This information may provide clues about how European green crabs respond to changing temperatures, and how they may fare in the different environments they invade, which can both help manage future population invasions, and tell us more generally how marine species may handle changing temperatures.

The European green crab originates along the coast of Europe, with populations ranging from Iceland to Morocco and covering a range of water temperatures. But over the last several hundred years, with the advent of global marine travel and ballast water, European green crabs have invaded the coastlines of every continent except Antarctica. This geographic dispersal created a natural experiment in adaptation to different water temperatures and other potential population distinctions.

Tepolt is interested in both genetic and physiological changes in European green crabs that have moved to new environments. Her work has involved traveling to seven European green crab population sites: two in its native range (Norway and Portugal), and five in habitats that the species invaded anywhere from 200 to 20 years ago (three along the East Coast of the U.S. and two along the West Coast). To ensure consistent acclimation methods in all of the locations she studied, Tepolt designed a portable system to test the physiological limits of cardiac function under varying temperatures. She created a series of standard  Igloo coolers to maintain crabs at either 5oC or 25oC for three weeks, before hooking them up to a miniature “crab EKG” to measure their heartbeats at high or low temperatures. The crab EKG is a specially-designed monitor that sends infrared signals through a crab’s carapace to track heartbeat. The infrared light that bounces back from the heart creates a voltage signal indicating the expansion and contraction of the heart with each beat, and produces a non-invasive running heart rate signal, analogous to that of a human hospital patient.

A typical EKG of a crab heart rate.

Tracking the beat — A monitoring record of heart rates of two European green crabs (each line represents a separate crab’s heart rate).

When crabs were acclimated to 25oC for three weeks before heart rate sampling, Tepolt found that they were more heat-tolerant – they could survive at higher temperatures than non-heat-acclimated crabs. The reverse is true, too: when crabs have been acclimated to cold temperatures, they can tolerate lower thermal limits.

What this means for European green crabs around the world is that the populations that evolved in Norway can tolerate lower extreme temperatures at the cold end of the temperature spectrum, while those from Portugal can survive at higher temperatures on the warm side (up to 36oC). The crab populations that have invaded the East and West Coasts of the United States also appear to have different temperature tolerances, but Tepolt theorizes that this is more a result of the original point of European origin.

The European green crab (C. maenas) is a small-bodied but adaptable species. The average crab grows to a carapace length of 5 cm, but populations have adapted to live on every continent except Antarctica, and range from British Columbia and California to Newfoundland to Morocco.

On the Move — The European green crab (C. maenas) is a small-bodied but adaptable species. Average European green crab carapace lengths range from 4-8 cm, but populations have adapted to live on every continent except Antarctica, and range from British Columbia and California to Newfoundland to Morocco.

Typical of invasive species, the European green crab seems to do quite well when it moves into new environments, perhaps in part because individuals tend to be less aggressive toward each other than do other crab species, allowing the species to reach higher densities. European green crabs also eat anything smaller than they are, including baby shellfish that develop in the same embayments. Green crabs have already wiped out some local populations of baby shellfish along the East Coast, reducing availability of the delicacies that humans enjoy. And despite often prolific population numbers, European green crabs haven’t yet reached the same level of cuisinal demand that other U.S. crab species have – in part because they are relatively small, and take more effort to shell than their meat is worth. But as the oceans warm and humans continue to link the globe with ship travel and species export, this thermally-flexible species is likely to keep invading new areas, and adapting to the varying temperatures that accompany the move.

Feeding Frenzies

Understanding how fish feed, in order to maximize world aquaculture production

   Offshore aquaculture, like this Pacific bluefin tuna farm in Mexico, has grown rapidly in the past few years. In order to avoid the same crashes and environmental degradation that the fishing industry has faced, Stanford Ph.D. student Dane Klinger is tracking the physiological needs and efficiency of fish species, to determine which ones can be farmed best in different areas of the ocean (Image courtesy of Stanford Tuna Research and Conservation Center).


Offshore aquaculture, like this Pacific bluefin tuna farm in Mexico, has grown rapidly in the past few years. In order to avoid the same crashes and environmental degradation that the fishing industry has faced, Stanford Ph.D. student Dane Klinger is tracking the physiological needs and efficiency of fish species, to determine which ones can be farmed best in different areas of the ocean (Image courtesy of Stanford’s Tuna Research and Conservation Center).

Fish have been a crucial part of the human diet for thousands of years, but fishing alone can no longer sustain our growing population’s demand for seafood, so the world is turning more and more to aquaculture to feed hungry mouths. Fifty percent of seafood  consumed by humans currently comes from aquaculture – the farming of aquatic organisms – and aquaculture has been lauded as the next food frontier, but many in the industry want to focus on avoiding the booms and busts and negative environmental impacts that the agricultural revolution and the commercial fishing industry have experienced. Available freshwater- and land-based aquaculture space is limited, so people are turning to the relatively new field of offshore aquaculture. As aquaculture moves further and further out to sea, Stanford Ph.D. student Dane Klinger feels that it is crucial to understand the physiological mechanisms of how well fish feed and grow under different ocean conditions, in order to establish best methods to increase production and reduce environmental degradation.

  View from above of Pacific bluefin tuna schooling in an aquaculture pen off Baja California. In offshore aquaculture, fish are kept in large nets and cannot migrate to avoid unfavorable environmental conditions (e.g. strong currents or cold water), so matching the right fish species with the best areas of the ocean for aquaculture is essential to maintain growth efficiency (Image courtesy of Stanford Tuna Research and Conservation Center).


View from above of Pacific bluefin tuna schooling in an aquaculture pen off Baja California. In offshore aquaculture, fish are kept in large nets and cannot migrate to avoid unfavorable environmental conditions (e.g. strong currents or cold water), so matching the right fish species with the best areas of the ocean for aquaculture is essential to maintain growth efficiency (Image courtesy of Stanford’s Tuna Research and Conservation Center).

Klinger is working to learn as much as possible about both trends in aquaculture and the details of fish physiology. Klinger, a graduate student in Stanford’s Emmett Interdisciplinary Program in Environment and Resources (E-IPER), works in conjunction with Stanford’s Center for Food Security and the Environment (CFSE) and the Tuna Research and Conservation Center (TRCC) at Stanford’s Hopkins Marine Station. His multi-disciplinary approach allows him to understand both the economics of aquaculture production and the biology behind fish growth, which is essential to help improve aspects of offshore aquaculture practices.

One of Klinger’s goals is to create maps combining potential offshore aquaculture sites and species that will grow best in them, to recommend to the industry and help inform management efforts. Part of Klinger’s work involves traveling to fish farms in Japan, the Mediterranean and Mexico – areas that already have offshore aquaculture sites – to establish relationships with fish farmers, and learn about their current farming practices. Not everyone is willing to talk openly about their trade secrets, but the meetings can help build trust on the aquaculturists’ end, making them more likely to consider the recommendations that Klinger and others make for future fish aquaculture sites. Klinger combines the knowledge he gains from talking to farmers with physiological data for farmed species and maps of global sea surface temperatures. Together, this information can help pinpoint potential ocean areas for fish farms, and the best species to grow in each area.

A yellowfin tuna (Thunnus albacares) swims in the respirometer at the Tuna Research and Conservation Center at Stanford’s Hopkins Marine Station. Measuring respiration allows researchers to determine how efficient fish are at digesting different types of food – an important factor when considering which species to raise to maximize fish production and economic efficiency (Image courtesy of Dane Klinger).

A yellowfin tuna swims in the respirometer in the Tuna Research and Conservation Center at Stanford’s Hopkins Marine Station. Measuring respiration allows researchers to determine how efficiently fish are digesting different types of food – an important factor when considering which species to raise to maximize fish production and economic efficiency (Image courtesy of Dane Klinger).

Closer to home, Klinger is running experiments on bluefin tuna, yellowfin tuna, and Pacific mackerel at the Tuna Research and Conservation Center. Klinger measures digestion efficiency by feeding a fish and then placing it in a respirometer – a “tuna treadmill” tank with a constant water flow. The respirometer allows Klinger to measure changes in tuna metabolic rates with variables such as meal size, diet, and water temperature acclimation, giving him useful numbers on how these valuable species vary in their feeding efficiency and overall aquaculture potential.

As a student of an interdisciplinary program, Klinger can establish working ties across multiple departments and collaborators. He speaks of the dual value of enjoying the rigors and data that come from conducting respiration experiments with pelagic species, and at the same time looking at larger-scale aquaculture trends and determining areas of the ocean available for future aquaculture sites. For Klinger, it’s important that the data he collects goes toward change – in this case, helping to more efficiently feed the world’s growing population by applying new innovations to the same resources we’ve relied on for centuries.