An Empire of Crabs
by Carolyn Tepolt, PhD student
I’m in the basement of a 17th-century Portuguese fort, surrounded by massive, rough-hewn stone walls built to repel an assault from marauding Spaniards. I’m not too concerned about attack from sea today, though. The fort now houses a marine biology laboratory, and my focus is on getting a handful of small green crabs to hold still long enough for me to hook them up to tiny heart monitors. It’s fitting that I’m studying these particular crabs in the heart of Portugal, one of the world’s most expansive colonial empires. Green crabs are expansive colonizers too, hitching rides across the seas and putting down roots all over the globe. It’s this kind of behavior, along with a voracious and undiscriminating appetite, that have earned the species a spot on the World’s 100 Worst Invasive Species list.
What makes green crabs so successful? My five years of thesis research have been driven by that single, simple question. Green crabs thrive in Portugal, and in Norway, and on every continent except Antarctica. I want to know how they do it. Have sun-drenched Portuguese crabs adapted to deal with the heat better than crabs in chilly Norway? This is where the tiny heart monitors come in. I use them to look at how green crabs living in very different environments deal with extreme temperature. Studying heart function holds a certain personal appeal: I had open-heart surgery when I was 5.
In that fortress of science, I found that Portuguese crabs’ hearts can handle temperatures of nearly 100ºF. Farther north under a near-midnight sun, I found that Norwegian crabs hit their limits around 94ºF. But even the Norwegian crabs are impressive by comparison to their non-invasive neighbors: most other crabs and lobsters can barely manage 90ºF. These are the first pieces of the puzzle. All green crabs can handle a very wide range of temperatures. On top of that, specific populations have adapted over time, fine-tuning to match their local environments.
Back in the Palumbi Lab at Hopkins, I’ve turned to cutting-edge genetics to dig deep into the causes of these differences. Using this technology, I can examine many thousands of genes at the same time, reconstructing the ancestry and adaptation of green crabs as their empire expands. This summer, I’ll pick through the DNA to see where it specifically differs between populations, looking for genes that might help give Portuguese crabs their resilience to high heat.
Global temperatures are rising quickly. To understand how animals and ecosystems will change in the near and warming future, we need to know the details of how adaptation works. The expansion of the empire of crabs provides a template for successful adaptation, and can tell us how animals will cope with changing environments.
Squid Talk: When Looks Speak Volumes
by Hannah Rosen, PhD student
What if you could change your appearance in the blink of an eye? Imagine you could make your body white, then your arms red, and then turn your whole body into a moving strobe light in a matter of seconds, no wardrobe change necessary. For any humans reading this, such a feat would be completely and utterly impossible. But if you happen to be a Humboldt squid, these patterns are just part of your daily routine.
Scientists at Hopkins Marine Station are working hard to understand not only how, but also why these squid are able to transform themselves so quickly. Humboldt squid live from the coast of California all the way down to Chile, and they can get to be up to four feet long! They share their amazing ability of rapid color change with all other cephalopods. They create their patterns using little sacs of color that cover their entire bodies like tiny freckles. The sacs are usually too small to be seen, but the cephalopods use their muscles to pull on the sacs and show their colors, much like stretching out a deflated balloon.
But these color patterns aren’t just for looks; scientists believe the Humboldt squid are using this special ability to talk to each other. These squid live in schools, like fish, and even hunt together. When one squid approaches another they both flash from white to red very quickly, which creates an effect making them look like swimming strobe lights. What does the flashing mean? It doesn’t mean the squid are having a party. Most likely, this flashing is used with different body positions to say things like “hey, who are you?” or “you’re cute, let’s hang out!” or “this is my fish, go get your own!”
Dr. William Gilly’s lab at Hopkins is trying to figure out exactly what the squid are saying. They’re doing so by strapping special cameras to the squid and then releasing the animals back into the wild. After a certain period of time, the cameras release themselves from the squid and float to the surface. There the camera sends out a GPS signal so the scientists are able to recover it and the video it recorded. This squid’s-eye-view is giving them a never before seen look at the day in the life of a Humboldt squid. They’re hoping that with enough of these videos they can figure out what this fashionable marine animal is trying to say. Talk about making a statement!
Climate Change Boot Camp – How Can Corals Get in Shape?
by Rachael A. Bay, PhD student
On the small island of Ofu in American Samoa, the coral reef and the island community are tightly connected. The reef provides food for the people and protects the villages from storms. From an early age, children learn that sea cucumbers can regenerate their bodies and that whistling makes hermit crabs come out of their shells. The marine environment is in all senses an essential part of day-to-day life. While warming ocean temperatures threaten coral reefs throughout the tropics, Ofu’s corals are special. They have proven to be more tolerant of high temperatures than other corals in the region. This offers hope that the reefs will continue to provide for this community into the future.
What makes corals on Ofu so strong? Why can they withstand temperatures that, in theory, should kill them? Researchers from Hopkins are discovering that corals can train to withstand high temperatures, much like a runner trains for a marathon. Few people can endure 26 miles the first time they lace up their running shoes, but with practice, some eventually make it.
Corals are known to be very sensitive to heat and just a few degrees can be the difference between life and death. But can they practice and eventually become accustomed to heat? To test this, researchers built an array of temperature-controlled tanks: a 24-hour fitness center for corals. Some corals were allowed to be lazy, never being subjected to hot temperatures. Others had regular workouts; they experienced hotter than normal temperatures every day. After a week, all corals underwent a fitness test: they were immersed in water hotter than they had ever seen. And the winners? The corals that had trained the hardest: those that were accustomed to dealing with hotter temperatures. It turns out practice pays off, even if you are a coral.
For corals, the ultimate challenge, the marathon, is climate change. Human activities are increasing carbon emissions and causing ocean temperatures to rise faster than they ever have before. Because of the changing climate, coral reefs around the globe are deteriorating. People in island communities like Ofu depend on coral reefs for their well-being and their way of life, but this relationship has an uncertain future if corals do not survive the changes that are occurring.
While it is encouraging that some corals might be able to get in shape for the race, it’s unlikely that they can withstand rising temperatures forever. With a good workout they can hit the ground running, but our actions – whether humans can lessen their impact on climate – determine whether the distance to the finish line is 5 miles or 500 miles.
Monitoring the Kelp Forests of Hopkins Marine Station
by Kerry Nickols, Postdoctoral Researcher
In the backyard of Stanford University’s Hopkins Marine Station is a lush forest reaching upwards of 15 meters (50 feet) high. It is home to a diverse community of species and one of California’s treasured protected areas. To visit this impressive forest, however, you will need at least a mask and a snorkel, and probably a thick wetsuit. Diving right in, researchers at Hopkins Marine Station are creating new ocean observing systems to connect scientists, teachers, students, Californians, and ocean enthusiasts to the underwater kelp forest environment.
The kelp forest at Hopkins shelters a myriad of amazing organisms, including giant kelp that grows up to 1 foot per day and rockfish that can live for decades. The history of this particular kelp forest makes studying it very valuable because this forest has been protected since 1931 and became a no-take marine reserve in 1985. In 2007, through the Marine Life Protection Act, a law mandating a network of marine protected areas within California, the reserve was expanded from Hopkins Marine Station to Lovers Point. The studies conducted here are isolated from fishing activities, allowing scientists to focus on how things other than fishing affect the kelp forest, such as climate change, ocean acidification, and low oxygen events. The data collected near Hopkins Marine Station will provide a baseline for healthy kelp forests and help us compare nearby fished areas and new reserves established by the Marine Life Protection Act.
Recently Hopkins started two programs, the Marine Life Observatory and the Kelp Forest Array, that both focus on long-term monitoring and question-driven research. Within the ocean science community, California is well known for its extensive network of ocean observing systems, but most of these ocean observing systems are focused on physical measurements of the ocean, such as temperature, salinity, and pH. These physical measurements can help scientists check the pulse of the ecosystem, but they may not be able to detect the response of the ecosystem to changes in the pulse. For example, we may see from an ocean observing system that the ocean is becoming more acidic, but we might not observe how giant kelp responds to acidic seawater. Researchers at Hopkins are working to solve this problem by combining physical measurements from the Kelp Forest Array with biological measurements from the Marine Life Observatory, a living observatory focused on the organisms and communities of the kelp forest. Together, these two programs will allow scientists to see how kelp forest inhabitants react to changes in the ocean. In addition, live data streams, web cams, historical data archives, and public programs will help connect people with the kelp forest like never before.
Currently, several researchers at Hopkins Marine Station are using the Marine Life Observatory and the Kelp Forest Array to study the kelp forest ecosystem. Dr. Jennifer O’Leary is studying the cues that baby abalone use to find a place to live and grow, as well as their response to ocean acidification. Dr. Kerry Nickols is quantifying how the structure of kelp forests changes water motion and influences the transport of young animals. Graduate student Paul Leary is measuring oxygen concentrations within the kelp forest and how fish react to low oxygen conditions. Together, these young scientists are answering challenging questions to gain a holistic understanding of how kelp forest ecosystems survive in coastal California, and what we can do to help them maintain their health in a changing ocean.
Conversations with Pescadores in Baja California
by Laura Lilly, Earth Systems SES student
People often think of social science as a completely separate realm from the concrete facts of natural science, but Hopkins PhD student Elena Finkbeiner disagrees. She thinks that understanding the interactions between the two fields is crucial for developing successful sustainable fisheries programs, and that some of her most important – and toughest – work is gaining the trust of fishermen (pescadores), in order to learn their stories.
For the past several years, Finkbeiner has traveled to Bahia Magdalena, a highly productive, world-renowned bay along the Pacific coast of Baja California Sur, to observe the activities of regional small-scale fishermen. Finkbeiner, a student in Prof. Larry Crowder’s lab at Hopkins, first visited Baja California to study sea turtles, but realized that they are only one species impacted by poor fisheries management. Finkbeiner is interested in understanding how strategies that focus on fishing a broad range of species may help coastal communities and marine systems withstand sudden shocks. Finkbeiner’s work consists of interviewing fishermen in Bahia Magdalena, and studying the area’s interannual ocean cycles, fish catch compositions, and income variations over time.
Surprisingly, even though Bahia Magdalena is a world-famous natural region with a wealth of biological diversity, it has limited federal protection. Finkbeiner feels it is crucial to work with fishermen to understand the ways in which both natural processes and human use affect the region. She hopes that this more complete knowledge, combined with increased communication between local fishing needs and government legislation, will help develop better cooperative systems in which fishermen can fish as sustainably and sensibly as possible to maintain their livelihoods and the region’s unique biodiversity.
Corals Have a Story to Tell – Are We Going to Listen?
by Francois Seneca, Postdoctoral Researcher
Climate change is affecting virtually every living thing on earth and in turn creating problems for human populations globally. Coral reef ecosystems have been especially impacted and you may have heard the analogy that reef-building corals are the proverbial canary in the climate change coal mine. Now is time to listen carefully to those colorful canaries!
Among the many stressors affecting coral reefs, increasing sea surface temperature due toclimate change is the most pervasive and devastating, as it can even threaten pristine reefs far from direct human impacts. For this reason, coral scientists are looking for potential ways that corals can survive the changes that are already happening. The small island of Ofu, 70 miles East of the main island of Tutuila in American Samoa, has attracted the attention of some Hopkins scientists because a very special group of corals lives there. Ofu’s natural beauty is mesmerizing. Its lush, steep mountains slope down to a belt of turquoise lagoon waters, where we find unusually tough corals. Some of them can survive huge daily swings in temperature and pH levels, conditions which are likely to kill corals in other places. These corals represent a valuable opportunity to understand how keystone marine organisms – known to be sensitive to environmental change – can naturally tolerate seemingly adverse conditions, and provide clues as to how such tolerance might be enhanced as conditions get worse in the future.
At Ofu, the physical characteristics of the lagoon are such that a natural experiment is occurring. Imagine an area of the lagoon transformed into an aqua-gym for gaining the strength to face climate change! In the lagoonal pool, corals experience regular fluctuations in temperature and pH dictated by tidal and wave conditions. And, during summer, it’s boot camp! At low tide, shallow pools become so warm that you can’t feel the difference between the air and water temperatures when going for a dip. This kind of treatment should kill corals in most other places, but somehow these corals are thriving. We want to know: How did they become so strong? How fast can “aqua-gyms” produce stronger corals? Will these corals survive forthcoming even harsher conditions? Can this happen elsewhere? And, should we take extra care protecting these corals?
A team of young scientists lead by Professor Palumbi is currently investigating these questions. The HMS coral team looks at physiology, genetics, gene expression and immune responses in these stronger corals in order to understand the source of such improved fitness. So far, we have discovered that strong corals can cope with harsh conditions by constantly be prepared with certain genes. Incredibly, just a few months of training in the “aqua-gym” can bring newly transplanted corals to equivalent tolerance levels to those found in corals native to the stressful lagoonal habitat. Yet, the native corals are also genetically different from corals living in less harsh conditions. Our hope is that understanding what makes these corals more tolerant than others, and how those differences lead to such increased resilience, will allow us to identify similar qualities in other coral populations across the globe. Recognizing naturally resilient corals will be invaluable information for helping managers and policy makers to protect the reefs with the best potential for survival amid climate change.
What Does an Octopus See When It’s Looking Back at You?
by Judit Pungor, PhD student
“I’d like to be, under the sea, in an octopus’s garden…” We all know the familiar chorus of this classic song, but have you ever thought about what it would really be like to be in an octopus’s garden? And what it might look like, to the octopus?
Octopuses, and their cousins the squids and cuttlefishes, have eyes that can see nearly as well as, and in some ways even better, than our own can. They use visual information in all sorts of ways, from spotting predators and prey to aiding in their amazing abilities to camouflage and communicate. But it turns out there’s more there than meets our eye…
One of the most fascinating things that we are learning about octopus vision is that unlike us, they have the ability to see the polarization of light. Light is a wave that has different properties. The speed at which the wave vibrates, or its frequency, is what is read by our eyes as color; blue waves vibrate faster than yellow waves, which in turn vibrate faster than red waves. Some animals, like the octopus, can see not only the speed of vibration of the wave, but they can also see the orientation in which the wave is vibrating, known as its polarization. If a wave is traveling sideways, it looks different to them than a wave that is vibrating straight up and down.
Octopuses use polarization information to enhance their visual abilities. They can detect transparent prey because light is slightly reoriented, or polarized, when it passes through a transparent animal. Octopuses can even use polarization information to communicate with each other, by changing the polarization of the light that is reflected off their skin to send different signals to their fellow octopuses. Since most animals can’t see these polarization differences, their signals even remain hidden from everyone else!
We are studying how octopuses collect, interpret, and store polarization information in the parts of their brains that process visual signals. Octopus eyes evolved independently from our own; our last common ancestor had some light sensitive cells, but nothing nearly as complicated as an eye. Since octopus eyes evolved along a completely different pathway from our own, the way that they process visual information might have also evolved to be really different from how we do. Our lab uses electrophysiology, which records the tiny electrical signals sent along neurons in the brain, to see how they organize light information and how that might be similar or different to what we know about our own visual systems. We hope to learn more about what an octopus sees in its surroundings, so we can better understand the lives of these fascinating creatures.
So what does an octopus’s garden look like? It’s looking like it will probably be a lot stranger than we ever would have thought!
Feeding Frenzies – Understanding How Fish Feed, In Order to Maximize World Aquaculture Production While Reducing Environmental Impacts
by Laura Lilly, Earth Systems SES student
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, or the farming of aquatic organisms, and aquaculture has been lauded as the next food frontier. Many in the industry want to avoid the booms and busts and the negative environmental impacts that the agricultural revolution and the commercial fishing industry have experienced, though. 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.
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 both Stanford’s Center for Food Security and the Environment (CFSE) and the Tuna Research and Conservation Center (TRCC) at 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 for helping to 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. His 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.
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 also 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.
Squid in Swimsuits – Tracking Humboldt Squid off the California Coast
by Laura Lilly, Earth Systems SES student
Squid have long been portrayed in books and myths as the infamous adversary of mariners –mysterious creatures who only emerge from the ocean depths to harass hapless sailors. But Stanford Professor William Gilly of the Hopkins Marine Station has set out to track and understand the real-life movements of a squid species that has started to appear more frequently off the California coast. Dosidicus gigas, known as the Humboldt squid, and 6 feet long in a good year, made headlines last December because of its massive strandings around Monterey Bay. But Gilly believes that this behavior may simply be part of a larger trend in the species’ expansion into temperate waters.
Gilly’s lab has begun to attach satellite pop-up tags and video cameras to Humboldt squid, which is quite a feat considering that a squid’s body is designed to be as slippery, streamlined and flexible as possible to glide through the water. The research team had to invent a method which involved slipping a child’s bathing suit around the squid’s body, and attaching tags or cameras to that, but it’s been worth the hassle. Video footage directly from a squid’s view gives Gilly’s lab unique perspective on social behaviors from “inside the pack”, and offers glimpses into the secrets of their lives. Squid have been seen meeting in large congregations and remaining in a certain area for several hours – whether for mating, hunting or another form of socializing, researchers don’t yet know.
Tagging data also reveals that the Humboldt squid may be able to swim and feed in low-oxygen layers in the ocean, where most fish cannot. Squid are known for their propulsive water jets, which help them burst upward, then gently glide down, tracing vertical zigzags to conserve energy instead of swimming constantly. But in low-oxygen waters, they appear to lose their quick speed bursts. To test squid oxygen limits, Gilly’s lab created the equivalent of a human treadmill, where they place squid in tanks and stimulate them to swim rapidly, mimicking the speed of their jet bursts. The researchers then decrease oxygen levels and test whether squid continue their fast movements. Gilly has found that at low oxygen levels, squid simply cannot keep swimming fast, and begin to show a body stress response. So as low-oxygen layers expand with increasing ocean temperatures, Humboldt squid will probably be able to expand their habitat ranges and continue to capitalize on prey availability – but they won’t always be able to perform at their highest level.
And the squid strandings of last winter? In contrast to the media hype, Gilly believes it’s a typical behavior when squid move into a new area. They are simply “testing the waters”, some of which – like sandy beaches above the surfline – don’t work out to colonize. And as waters warm and low-oxygen areas expand northward along the California Current, the Humboldt squid may be here to stay as the newest, and most successful, marine predator off our coast.
The Whys and Hows of Intertidal Survival
by Megan M. Jensen, PhD student
Let’s take a moment, and pretend to go tidepooling in Monterey Bay. Conveniently, the tide is low enough for us to get a really good look at the array of plants and animals that call the rocky intertidal zone home: seaweeds of many shapes, sizes and colors, barnacles, sea stars, mussels, snails, and hermit crabs, just to name a few.
On some level, it’s surprising that the intertidal zone supports such a diverse array of life — after all, the environment that these organisms call home is an incredibly stressful one. Due to the rise and fall of the tides, intertidal organisms go from terrestrial to marine conditions (and back again) twice a day. Exposure at low tide presents two primary challenges: first, in order to survive being out of water frequently, organisms must have evolved ways of preventing fatal water loss. Second, these plants and animals can experience large and rapid changes in temperature as they go from air to seawater, especially on hot days.
During high tide, organisms are exposed to tremendous hydrodynamic stresses. Approximately every ten seconds, waves break and crash on the shore, imposing astounding forces on the organisms living there. Further compounding the harshness of their environment, many organisms calling the rocky intertidal zone home are very slow-moving or don’t move at all — they cannot escape from high temperatures or large waves.
But despite the intense physical stresses of the intertidal zone, it is one of the most diverse and productive ecosystems on the planet. Considering the unique combination of stresses imposed on intertidal plants and animals raises the question: why does anything live here? More importantly, how does anything live here?
Does continual battering by waves limit the size of intertidal seaweeds and animals? What strategies allow organisms to avoid overheating? These are the kinds of questions we ask in Mark Denny’s biomechanics lab at Hopkins Marine Station. Using ideas and concepts from physics and engineering, we ask questions about how organisms are able to survive and thrive in the intertidal zone.
Many areas of engineering have helped inform what we do in the Denny Lab. Solid mechanics — how materials behave — helps us explain how seaweeds break under repeated wave forces. Thermodynamics — the study of how heat relates to energy — helps us predict the body temperature of snails under any weather conditions. These powerful models give us the ability to predict organism survival under future climate scenarios — a particularly important tool as our planet warms due to anthropogenic climate change. The principles of fluid mechanics help us describe how waves affect intertidal organisms, and allow us to answer questions about the largest hydrodynamic forces that organisms see.
The tenacious plants and animals living in the rocky intertidal zone have evolved to cope with one of the harshest ecosystems imaginable. By combining principles from different disciplines, we try to unravel the secrets behind organism survival in this dynamic and fascinating environment.
Forests Without Oxygen – Tracking Hypoxia Pulses and Fish Responses in California’s Kelp Forest
by Laura Lilly, Earth Systems SES student
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 have teamed up to explore how these low-oxygen events impact Monterey’s kelp forests and intertidal zones, and how the numerous fish species living in the kelp survive and respond.
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.
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.
Who is where?
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 several age-classes of juvenile rockfish. Beers and Litvin will be using the Kelp Forest Array, a monitoring system set up last year in the kelp forest off Hopkins, to track fish movements within the kelp forest. Using the KFA’s acoustics sonar imaging system, they will be able to image and identify individual animals and their movements as low-oxygen waves hit. This information will help them answer the questions “Who is where?” when these events are happening.
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.
by Nikki Traylor-Knowles, Postdoctoral Researcher
Stepping off the plane, as I arrive on the island of Ofu, American Samoa, I am overcome by the sweltering heat and sounds of the waves crashing against the landing strip. Also, the brightness: six months of sitting at my office desk, in Pacific Grove, scouring over spreadsheets has left me pasty and pale. My backpack is full of fieldwork essentials: sunscreen, Benadryl, band-aids, antibiotic cream, granola bars, mask and snorkel, bathing suit, shorts, and a lab notebook. I am greeted by our hosts, and their pack of dogs, and shown to my room. I change into my bathing suit, put on my sunglasses, and walk down the path to the National Park laboratory. It’s time to heat up some coral!
Global climate change models predict that if carbon dioxide emissions continue at the current rate, the Pacific Ocean sea surface temperature will increase by approximately 2.8 degrees Celsius. For coral reefs, heat stress often causes bleaching, the release of the symbotic algae Symbiodinium, which can lead to death. But different corals can have different thresholds for bleaching. If these organisms are able to acclimate in the short term and adapt over generations then perhaps some survival will be possible.
Due to the well-documented temperature changes on the reefs in Ofu, it has become a natural laboratory for conducting studies on the thermal tolerance of corals. The corals in Ofu are living in water that can get extremely hot, with highs in the 90 degree Fahrenheit range. These temperature exceed the average temperatures in which corals should be able to survive.
In Ofu, we use special portable heat stress tanks to test the tolerance of the local corals to changes in temperature. We use these tanks to examine the temperature limits of the corals, much like the physical fitness test measures physical endurance, but instead of measuring the time in which a mile is completed, we measure the temperature at which the coral bleaches. This indicates how resilient they are to heat stress. We can then identify individual corals that may have the genetic propensity to survive in heat stress. Ultimately we want to understand what it is that makes these corals “super survivors” and able to withstand these drastic environmental changes.
Coral reefs are one of the most diverse, productive, and economically important ecosystems on the earth. Approximately 27 million people live within 30 km of a coral reef that is considered important to their local economy. Coral reefs act as a natural barrier protection from wave action and provide nutrition for many coastal communities. Despite this importance, coral reefs are increasingly in trouble due to rising-ocean temperatures caused by human activities. By understanding how corals can survive changes in their environment, we will be able to better direct our protection efforts. This will help not only coral reefs, but also the millions of people who are dependent on these reefs for their existence.
The Science of Searching
by Diana LaScala-Gruenewald, PhD student
A plane crashes in the middle of the desert. The sole survivor stands feet from the wreck. Her mouth is gritty and dry, and she is surrounded by glittering drifts of sand and hard, red cliffs. Her chances of survival rest on the odds of finding a nearby oasis.
Oases are few and far between. And in this desert, the nearest one may be obscured by the mountainous terrain. What strategy should she use to improve her chances of finding water?
Unless the survivor is very lucky, walking in a straight line will not bring her to a water source. A purely random search is also unlikely to work. She needs a strategy that combines some randomness with “directional persistence” – the tendency to continue traveling in a single direction. A “Lévy walk” is a search strategy which incorporates an optimal mix of these two components.
Fortunately the survivor is likely to choose a Lévy walk search strategy as she looks for water: People tend to search one location thoroughly, and then relocate before searching again. And within the animal kingdom, we are not alone. Animals as diverse as deer, monkeys, and sharks use Lévy walks, too.
Although examples of Lévy walks are numerous, scientists still do not fully understand how and why they arise. Do animals use different search strategies when the landscape is flat as opposed to mountainous? When is a particular strategy most useful? Did we all evolve to Lévy walk, or is it a behavior that arises in response to complex environments? These questions are fundamental to foraging theory, which explores how animals search for food. But the answers may also help explain how animals distribute themselves, which is crucial to making informed conservation decisions.
In my research I use a small, marine system to explore these questions. My study organisms, limpets, are snails that eat microscopic algae and live in the rocky intertidal zone – the region of the ocean exposed by low tide. Like a woman searching for water in a mountainous desert, limpets must navigate the bumps and cracks of the rock on which they live as they search for food. I map the topography and chemical composition of the rock, and compare it to the locations of microscopic algae. Then, I use a waterproof camera to track limpets as they search for food. Later, I can describe the motion mathematically. I try to determine how topography, rock composition, and food distribution influence limpet search strategies.
My research is a small piece of a larger picture. From a scientific perspective, limpet search strategies may shed light on those used by other animals. But search strategies are also used in human pursuits: They inform the way we look for enemy submarines, obscure data, and missing people.
When a plane crashes in a desert, the survivor is likely to Lévy walk, thereby increasing her chances of finding water. If the rescue team that comes to look for her understands the way animals – and people – navigate complex environments, they will be able to guess how far she is from the crash site. With luck and a little bit of science, they’ll find her.