The human body is populated by a greater number of microbes than its own cells. These microbes survive using metabolic pathways that vary drastically from humans’.
Arpita Bose, PhD, of Washington University in St. Louis, is interested in understanding the metabolism of these ubiquitous microorganisms, and putting that knowledge to use to address the energy crisis and other applications.
One of the biggest research questions for her lab involves understanding photoferrotrophy, or using light and electrons from an external source for carbon fixation. Much of the source of energy humans consume comes from carbon fixation in phototrophic organisms like plants. Carbon fixation involves using energy from light to fuel the production of sugars that we then consume for energy.
Before Bose began her research, scientists had found that some microbes interact with electricity in their environments, even donating electrons to the environment. Bose hypothesized that the reverse could also be true and sought to show that some organisms can also accept electrons from metal oxides in their environments. Using a bacterial strain called Rhodopseudomonas palustris TIE-1 (TIE-1), Bose identified this process called extracellular electron uptake (EEU).
After showing that some microorganisms can take in electrons
from their surroundings and identifying a collection of genes that code for
this ability, Bose found that this ability was dependent on whether a light
source was also present. Without the presence of light, these organisms lost
70% of their ability to take in electrons.
Because the organisms Bose was studying can rely on light as a source of energy, Bose hypothesized that this dependence on light for electron uptake could signify a function of the electrons in photosynthesis. With subsequent studies, Bose’s team found that these electrons the microorganisms were taking were entering their photosystem.
To show that the electrons were playing a role in carbon
fixation, Bose and her team looked at the activity of an enzyme called RuBisCo,
which plays an integral role in converting carbon dioxide into sugars that can
be broken down for energy. They found that RuBisCo was most strongly expressed
and active when EEU was occurring, and that, without RuBisCo present, these organisms
lost their ability to take in electrons. This finding suggests that organisms
like TIE-1 are able to take in electrons from their environment and use them in
conjunction with light energy to synthesize molecules for energy sources.
In addition to broadening our understanding of the great diversity in metabolisms, Bose’s research has profound implications in sustainability. These microbes have the potential to play an integral role in clean energy generation.
The technical-sounding category of “light-driven
charge-transfer reactions,” becomes more familiar to non-physicists when you just
call it photosynthesis or solar electricity.
When a molecule (in a leaf or solar cell) is hit by an
energetic photon of light, it first absorbs the little meteor’s energy, generating
what chemists call an excited state. This excited state then almost immediately
(like trillionths of a second) shuttles an electron away to a charge acceptor
to lower its energy. That transference of charge is what drives plant life and
The energy of the excited state plays an important role in
determining solar energy conversion efficiency. That is, the more of that
photon’s energy that can be retained in the charge-separated state, the better.
For most solar-electric devices, the excited state rapidly loses energy,
resulting in less efficient devices.
But what if there were a way to create even more energetic
excited states from that incoming photon?
Using a very efficient photosynthesizing bacterium as their inspiration,
a team of Duke chemists that included graduate students Nick Polizzi and Ting
Jiang, and faculty members David Beratan and Michael Therien, synthesized a
“supermolecule” to help address this question.
“Nick and Ting discovered a really cool trick about electron
transfer that we might be able to adapt to improving solar cells,” said Michael
Therien, the William R. Kenan, Jr. Professor of Chemistry. “Biology figured
this out eons ago,” he said.
“When molecules absorb light, they have more energy,” Therien said. “One of the things that these molecular excited states do is that they move charge. Generally speaking, most solar energy conversion structures that chemists design feature molecules that push electron density in the direction they want charge to move when a photon is absorbed. The solar-fueled microbe, Rhodobacter sphaeroides, however, does the opposite. What Nick and Ting demonstrated is that this could also be a winning strategy for solar cells.”
The chemists devised a clever synthetic molecule that shows the advantages of an excited state that pushes electron density in the direction opposite to where charge flows. In effect, this allows more of the energy harvested from a photon to be used in a solar cell.
“Nick and Ting’s work shows that there are huge advantages
to pushing electron density in the exact opposite direction where you want
charge to flow,” Therien said in his top-floor office of the French Family
Science Center. “The biggest advantage of an excited state that pushes charge the
wrong way is it stops a really critical pathway for excited state relaxation.”
“So, in many ways it’s a Rube Goldberg Like conception,”
Therien said. “It is a design strategy that’s been maybe staring us in the face
for several years, but no one’s connected the dots like Nick and Ting have
In a July 2
commentary for the Proceedings of the National Academy of Sciences, Bowling
Green State University chemist and photoscientist Malcom D.E. Forbes calls this
work “a great leap forward,” and says it “should be regarded as one of the most
beautiful experiments in physical chemistry in the 21st century.”
CITATION: “Engineering Opposite Electronic Polarization of
Singlet and Triplet States Increases the Yield of High-Energy Photoproducts,”
Nicholas Polizzi, Ting Jiang, David Beratan, Michael Therien. Proceedings of
the National Academy of Sciences, June 10, 2019. DOI: 10.1073/pnas.1901752116
Have you ever questioned the quality of the water you drink every day? Or worried that cooking with tap water might be dangerous? For most of us, the answer to these questions is probably no. However, students from a Bass Connections team at Duke say we may want to think otherwise.
From bottle refilling
stations to the tap, drinking water is so habitual and commonplace that we often
take it for granted. Only in moments of crisis do we start worrying about what’s
in the water we drink daily. The reality is that safe drinking water isn’t accessible
for a lot of people.
Images like this hog farm motivated the Bass Connections project team DECIPHER to take a closer look at the quality of water in North Carolina. On April 16 they presented their concerning findings from three case studies looking at lead contamination, coal ash impoundments, and aging infrastructure at the Motorco Music Hall.
Nadratun Chowdhury, a Ph.D. student in Civil and Environmental Engineering, investigated lead contamination in water. Lead is an abundant and corrosion-resistant material, making it appealing for use in things like paint, batteries, faucets and pipes. While we’ve successfully removed lead from paint and gasoline, a lot of old water pipes in use today are still fashioned from lead. That’s not good – lead is very toxic and can leach into the water.
Just how toxic is it? Anything over a blood-lead level concentration of fifty parts per billion – fifty drops of water in a giant Olympic swimming pool – is considered dangerous. According to Duke graduate student Aaron Reuben, this much lead in one’s blood is correlated with downward social mobility, serious health concerns, diminished capacity to regulate thoughts and emotions, and hyperactivity. Lower income and minority areas are more at risk due to the higher likelihood of owning contaminated older homes.
Rupanjali Karthik, a Master of Laws student, conducted research on the intersection of water and aging infrastructure in Orange County. Breaks in water pipes are common and can result in serious consequences, like the loss of 9 million gallons of drinkable water. Sometimes it takes 8 or 9 months just to find the location of a broken pipe. In 2018, the UNC-Chapel Hill water main break caused a huge shortage on campus and at the medical center.
Excess fluoridation is also
an issue caused by aging infrastructure. In February 2017, a combination of
human and machine error caused an excessive fluoride concentration coming out
of an Orange County Water Treatment Plant. People were advised not to use their
water even to shower. A UNC basketball game had to move locations, and stores
were completely swept of bottled water.
Another issue is that arsenic, a known carcinogen, is often used as the fluoridation agent. We definitely don’t want that in our drinking water. Fluoridation isn’t even that necessary these days when we have toothpaste and mouthwash that supports our dental health.
Tommy Lin, an undergraduate
studying Chemistry and Computer Science, topped off the group’s presentation with
findings surrounding coal ash in Belmont, NC. Coal ash, the residue after coal
is burned in power plants, can pollute rivers and seep into ground water,
affecting domestic wells of neighboring communities. This creates a cocktail of
highly concentrated heavy metals and carcinogens. Drinking it can cause damage
to your nervous system, cancer, and birth defects, among other things. Not so great.
Forty-five plastic water bottles.
That’s how much water it takes Laura, a Belmont resident, to cook her middle-sized
family Thanksgiving. She knows that number because it’s been her family’s
tradition the past three years. The Allen Plant Steam Station is a big culprit
of polluting water with coal ash. Tons of homes nearby the station, like Laura’s,
are told not to use the tap water. You can find these homes excessively
stockpiled with cases on cases of plastic water bottles.
These issues aren’t that apparent to people unless they have been directly impacted. Lead, aging infrastructure, and coal ash all pose real threats but are also very invisible problems. Kathleen Burns, a Ph.D. student in English, notes that only in moments of crisis will people start to care, but by then it may be too late.
So, what can people do? Not much, according to the Bass Connections team. They noted that providing clean water is very much a structural issue which will require some complex steps to be solved. So, for now, you may want to go buy a Brita.
“Gap maps” are the latest technology when it comes to organizing data. Although they aren’t like traditional maps, they can help people navigate through dense resources of information and show scientists the unexplored areas of research.
A ‘gap map’ comparing conservation interventions and outcomes in tropical mangrove habitats around the world turns out to be a beautiful thing.
At Duke’s 2019 Master’s Projects Spring Symposium, Willa Brooks, Amy Manz, and Colyer Woolston presented the results of their year-long Masters Project to create this map.
You’d never know by looking at the simple, polished grid of information that it took 29 Ph.D. students, master’s students and undergraduates nearly a full year to create it. As a member of the Bass Connections team that has been helping to support this research, I can testify that gap maps take a lot of time and effort — but they’re worth it.
When designing a research question, it’s important to recognize what is already known, so that you can clearly visualize and target the gaps in the knowledge.
But sifting through thousands of papers on tropical mangroves to find the one study you are looking for can be incredible overwhelming and time-intensive. This is purpose of a gap map: to neatly organize existing research into a comprehensive grid, effectively shining a light on the areas where research is lacking, and highlighting patterns in areas where the research exists.
In partnership with World Wildlife Fund, Willa, Amy, and Colyer’s team has been working under the direction of Nicholas School of the Environment professors Lisa Campbell and Brian Silliman to screen the abstracts of over 10,000 articles, 779 of which ended up being singled out for a second round of full-text screening. In the first round, we were looking for very specific inclusion criteria, and in the second, we were extracting data from each study to identify the outcomes of conservation interventions in tropical mangrove, seagrass, and coral reef habitats around the world.
While the overall project looked at all three habitats, Willa, Amy, and Colyer’s Master’s Project focused specifically on mangroves, which are salt-tolerant shrubs that grow along the coast in tropical and subtropical regions. These shrubs provide a rich nursery habitat to a diverse group of birds and aquatic species, and promote the stability of coastlines by trapping sediment runoff in their roots. However, mangrove forests are in dramatic decline.
According to World Wildlife Fund, 35 percent of mangrove ecosystems in the world are already gone. Those that remain are facing intense pressure from threats like forest clearing, overharvesting, overfishing, pollution, climate change, and human destruction of coral reefs. Now more than ever, it is so important to study the conservation of these habitats, and implement solutions that will save these coastal forests and all the life they support. The hope is that our gap map will help point future researchers towards these solutions, and aid in the fight to save the mangroves.
This year’s team built a gap map that successfully mapped linkages between interventions and outcomes, indicating which areas are lacking in research. However, the gap map is limited because it does not show the strength or nature of these relationships. Next year, another Bass Connections team will tackle this challenge of analyzing the results, and further explore the realm of tropical conservation research.
Roughly 400 miles separate Memphis and New Orleans. Interstate 55 connects the two cities, snaking south parallel to the Mississippi River. The drive is dull. There are few cars. The trees are endless.
South of the Louisiana border, the land turns flat, low, and wet. The air grows warmer, and heavy with moisture. I-55 cuts through the center of Maurepas Swamp, a 100,000-plus acre tract of protected wetlands. Groves of gumball and oak are rare here—instead, thin swamps of bald cypress and tupelo trees surround the highway on either side. At night, only their skeletal silhouettes are visible. They rise from the low water, briefly illuminated by passing headlights. Even in the dark, the trees are unmistakably dead.
* * *
Traditionally, Maurepas Swamp serves as a natural barrier against flooding that threatens New Orleans each year. Native flora soaks up the rainfall, spreading it across a network of cypress roots and cattail. But centuries of logging and canal construction have drastically altered the swamp’s ecological composition. The Mississippi levee system compounded the issue, isolating the swamp from vital sources of fresh water and nutrients. Flooded with saltwater, much of the existing cypress withered and died. Young trees, now, are few and scattered.
Maurepas Swamp highlights the danger of even the most well-intentioned changes to the environment. This problem is hardly unique to the wetlands. “Many of the issues that we are experiencing today were seen as solutions in the past,” says Nancy Grimm, a professor of ecology at Arizona State University. “What we want to do now is to think about the future, so that the solutions of today don’t become the problems of tomorrow.”
Grimm is the co-director of the UREx Sustainability Research Network. UREx aims to climate-proof urban municipalities without sacrificing environmental stability. To do so, UREx has partnered with several cities across the United States and Latin America. Each city hosts a workshop geared towards municipal decision makers, such as government officials, environmental NGOS, and more. Together, these participants design different “futures” addressing their cities’ most pressing concerns.
Phoenix, Arizona is one of the nine initial cities partnering with UREx. One of the hottest cities in the United States, Phoenix is already plagued with extreme heat and drought. By 2060, Phoenix is projected to have 132 days above 100°F—a 44 percent increase from data collected in 2010.
UREx doesn’t dwell too much on these statistics. “We’re bombarded constantly by dystopian narratives of tomorrow,” says Grimm, with a slight smile. “Instead, what we want to think about are ways we can envision a more positive future.”
The Phoenix workshop produced five distinct visions of what the city could look like in sixty years. Some scenarios are more ambitious than others—“The Right Kind of Green,” for example, imagines a vastly transformed city defined by urban gardens and lush vegetation. But each vision of Phoenix contains a common goal: a greener, cooler city that retains its soul.
A visualization accompanies each scenario. In one, a family walks about a small orchard. The sky is blue, and the sun is out. But no one seems bothered by the heat. The oranges are vibrant; the trees thick, and full. It’s an idyllic future. But it’s one within grasp.
There are many things in life that are a little easier if one recruits the help of friends. As it turns out, this is also the case with scientific research.
Lilly Chiou, a senior majoring in biology, and
Daniele Armaleo, a professor in the Biology Department had a problem. Lilly
needed more funding before graduation to initiate a new direction for her
project, but traditional funding can sometimes take a year or more.
Chiou and Armaleo are interested in lichens,
low-profile organisms that you may have seen but not really noticed. Often looking
like crusty leaves stuck to rocks or to the bark of trees, they — like most
other living beings — need water to grow. But, while a rock and its resident
lichens might get wet after it rains, it’s bound to dry up.
This is where the power of lichens comes
in: they are able to dry to a crisp but still remain in a suspended state of
living, so that when water becomes available again, they resume life as usual. Few
organisms are able to accomplish such a feat, termed desiccation
Chiou and Armaleo are trying to understand how
lichens manage to survive getting dried and come out the other end with minimal
scars. Knowing this could have important implications for our food crops, which
cannot survive becoming completely parched. This knowledge is ever more
important as climate becomes warmer and more unpredictable in the future. Some farmers
may no longer be able to rely on regular seasonal rainfall.
They are using genetic tools to figure out the mechanisms behind the lichen’s desiccation tolerance[. Their first breakthrough came when they discovered that extra DNA sequences present in lichen ribosomal DNA may allow cells to survive extreme desiccation. Now they want to know how this works. They hope that by comparing RNA expression between desiccation tolerant and non-tolerant cells they can identify genes that protect against desiccation damage.
As with most things, you need money to
carry out your plans. Traditionally, scientists obtain money from federal agencies
such as the National Science Foundation or the National Institutes of Health,
or sometimes from large organizations such as the National Geographic Society,
to fund their work. But applying for money involves a heavy layer of
bureaucracy and long wait times while the grant is being reviewed (often, grants
are only reviewed once a year). But Chiou is in her last semester, so they resorted
This is not the first instance of
crowdfunded science in the Biology Department at Duke. In 2014, Fay-Wei Li and
Kathleen Pryer crowdfunded the sequencing of the
first fern genome, that of tiny Azolla.
In fact, it was Pryer who suggested crowdfunding to Armaleo.
Chiou was skeptical that this approach would work. Why would somebody spend their hard-earned money on research entirely unrelated to them? To make their sales pitch, Chiou and Armaleo had to consider the wider impact of the project, rather than the approach taken in traditional grants where the focus is on the ways in which a narrow field is being advanced.
What they were not expecting was that
fostering relationships would be important too; they were surprised to find
that the biggest source of funding was their friends. Armaleo commented on how
“having a long life of relationships with people” really shone through in this
time of need — contributions to the fund, however small, “highlight people’s
connection with you.” That network of connections paid off: with 18 days left
in the allotted time, they had reached their goal.
After their experience, they would
recommend crowdfunding as an option for other scientists. Having to create
widely understood, engaging explanations of their work, and earning the support
and encouragement of friends was a very positive experience.
“It beats writing a grant!” Armaleo said.
Guest Post by Karla Sosa, Biology graduate
Traveling through war-torn areas at risk of encountering landmines, militia, and difficult terrain, Alex Dehgan was protected only by a borrowed Toyota Corolla. Dehgan, the Chanler Innovator in Residence at Duke, has spent much of his life overseas addressing conflict in Afghanistan through promoting wildlife conservation.
As a result, Dehgan has served in multiple positions within the U.S. Department of State, including the office of the secretary, and the bureau of Near Eastern affairs. There, he aided in addressing foreign policy issues in Iran, Iraq, and Egypt and contributed to the improvement of science diplomacy. Recently, he founded the Office of Science and Technology as the Chief Scientist at the U.S. Agency for International Development.
Dehgan recently gave a talk at Duke on the snow leopard project, an effort he spearheaded focusing on snow leopard (Panthera uncia) and other wildlife conservation in Afghanistan. Because of the conflict, most people are not aware of the incredible wildlife and natural beauty within the country’s borders.
In his conservation efforts, Dehgan visited the Pamir, Karakoram, Hindu Kush, and Tien Shian mountain ranges hoping to learn more about the wildlife that lived there and the best way to promote their conservation. He used camera traps and collected scat to figure out species were in the area.
He began by talking about the Pamir mountains. Despite the fact that this is a very dangerous region to be, Dehgan ventured in ready to work with locals and discover the wildlife there. Once, a member of his team asked if they could forgo checking the camera traps for the day because they were being bombed by the U.S. Army. However, it was worth it because Dehgan had the opportunity to work with locals and collect images as well as data on several unique species.
This included the Marco Polo sheep (Ovis ammon polii), enormous sheep that live in single-sex groups for most of the year. They only come together to mate and when they do, the males clash heads with one another for the ability to procreate. He was also able to find a markhor (Capra falconeri), which he prefers to call a “Twin-horn unicorn.” Markhor means snake eater, but the animal does not actually eat snakes. These animals are so valuable that a hunter once paid $110,000 to shoot one. Dehgan and his team were able to collect hair and genetic samples of musk deer (Moschus), which can be found in very steep areas of the Pamir mountains. These animals derive their name from the musk they produce which is often used in perfumes.
The area is known as Nuristan, the land of the enlightened, and is unique in that each valley has its own tradition, crafts, and even dialect. Dehgan and his team worked with people from the region and trained them to look for the specific animals
One of the most remarkable places Dehgan visited was Band-e Amir, which he described as looking like the grand canyon. The most unique natural aspect is a system of six lakes formed by the same process that creates stalactites and stalagmites. Above the lakes is an incredible mountain range and on top of the mountains are marine fossils because it used to be at the bottom of the sea. Here, Dehgan was able to use camera traps to collect images of ibexes (Capra ibex), Persian leopards (Panthera pardus saxicolor), and poachers. Poaching would eventually become one of Dehgan’s key focuses. Dehgan and his team also discovered Asiatic wild asses and assumed the presence of Asiatic leopards after finding their skins in the nearby villages.
Dehgan discovered that there was a massive trade in wildlife driven by the U.S. military. Skins of snow leopards and Persian leopards could be found all over Afghanistan as a part of illegal wildlife trade and other wildlife like Saker Falcons could be sold for up to $1 million.
As a result, Dehgan started a program around wildlife trafficking. A major part of his effort took place on Chicken Street, a busy shopping area where illegal animal skins could frequently be found. Dehgan worked closely with U.S. Military police, training them on how to identify furs.
Dehgan also worked with Afghani airport employees on how to inspect baggage for illegal furs. This resulted in the shut down of nearly all illegal fur trade, which Dehgan said was one of his biggest successes. In fact, one day while in Afghanistan, Dehgan received word that a fur trader wished to speak with him. Assuming they were angry at him for reducing their business Dehgan said that he actually feared for his life. However, it turned out that the fur trader simply wanted to be trained to identify illegal furs because they too wanted to protect Afghanistan’s wildlife.
Dehgan explained that Afghanistan was one of the easiest places he ever did conservation. This is because 80 percent of the human population is dependent on natural resources and thus when the wildlife fails, they fail. Because of this, they are eager to help aid in promoting conservation efforts.
Additionally, Dehgan was able to create the Wildlife Conservation Society’s Afghanistan Program which resulted in Afghanistan’s first and second national parks. Villages held local elections to set up a committee and to set up rules to govern the national parks.
Ultimately, his conservation work not only helped wildlife, but supported democracy by empowering, working with and training local communities.
Hello! My name is Anna Gotskind. I’m a first year originally from Chicago. I plan to double major in biochemistry and environmental science and policy with a certificate in innovation and entrepreneurship (I know it’s a mouthful).
I fell in love with science in seventh grade, inspired by a great teacher named Mark A. Klein. He wore a different tie every day of the year, had tarantulas as pets and frequently refused to say anything but “9” until 9:00 am. He also taught me to appreciate research and discovery, guiding me as I conducted my first independent experiment on the caffeine content in tea which helped me win my middle school science fair.
One of my other role models is Rory Gilmore from the T.V. show Gilmore Girls (yes, I am aware that she is a fictional character). Inspired by watching her write for the Yale Daily News I decided to join the Duke Chronicle when I got to campus. I quickly learned that I loved writing for a publication but more specifically that I loved writing about science. It was incredibly exciting for me to read a study, interview the researchers who conducted it and then translate the information into a story that was understandable to the public. Beyond this, it was also incredible to be exposed to groundbreaking research that had real-world impacts. Essentially, it made me feel like a “Big Girl” and when you’re only 5’0” tall, sometimes that’s necessary.
My love for science does not end in the classroom. My greatest passion is travel and I’ve been fortunate enough to travel around the world with my family exploring some of nature’s greatest wonders. We’ve hiked Bryce Canyon in Utah, Ali San in Taiwan and Masada in Israel. In December 2018 we ventured to the Galapagos, which as an aspiring environmentalist was an incredible experience. We go to see tortoises, iguanas, penguins, sharks and sea lions mere feet away. Right now I’m working with Duke Professor Stuart Pimm on a Big Cats Conservation Initiative sponsored by SavingSpecies, analyzing camera trap data of species in Sumatra, Brazil, and Ecuador. So who knows, I may be off there next. For more pictures check out my Instagram page @annagotskind (shameless plug).
I’m very excited to continue exploring and writing about the research being done on Duke’s campus!
In medical research, a professional might answer this question as you would expect: evidence can be trusted if it is the result of a randomized, controlled, double-blind experiment, meaning the evidence is only as strong as the experiment design. And in medicine, it’s possible (and important) to procure this kind of strong evidence.
But when it comes to conservation, it’s a whole different story.
Dr. David Gill (photo from The Nicholas School)
The natural world is complicated, and far beyond our control. When studying the implications of conservation, it’s not so easy to design the kind of experiment that will produce “good” evidence.
David Gill, a professor in Duke’s Nicholas School for the Environment, recently led a study featured in the journal Nature that needed to define what constitutes good evidence in the realm of marine conservation. Last Wednesday, he made a guest appearance in my Bass Connections meeting to share his work and a perspective on the importance of quality evidence.
Gill’s research has been centered around evaluating the effectiveness of Marine Protected Areas (or MPAs) as a way of protecting marine life. Seven percent of the world’s oceans are currently designated as MPAs, and by 2020, the goal is to increase this number to 10 percent. MPAs arguably have massive effects on ecosystem health and coastal community functioning, but where is the evidence for this claim?
Although past investigations have provided support for creating MPAs, Gill and his team were concerned with the quality of this evidence, and the link between how MPAs are managed and how well they work. There have historically been acute gaps in study design when researching the effects of MPAs. Few experiments have included pre-MPA conditions or an attempt to control for other factors. Most of these studies have been done in hindsight, and have looked only at the ecological effects within the boundaries of MPAs, without any useful baseline data or control sites to compare them to.
As a result of these limitations, the evidence base is weak. Generating good evidence is a massive undertaking when you are attempting to validate a claim by counting several thousand moving fish.
Gill’s measure of ecosystem health includes counting fish. (Photo from Avoini)
So is there no way to understand the impacts of MPAs? Should conservation scientists just give up? The answer is no, absolutely not.
To produce better evidence, Gill and his team needed to design a study that would isolate the effects of MPAs. To do this, they needed to account for location biases and other confounding variables such as the biophysical conditions of the environment, the population density of nearby human communities, and the national regulations in each place.
The solution they came up with was to compare observations of current conditions within MPAs to “counterfactual” evidence, which is defined as what would have happened had the MPA not been there. Using statistical matching of MPAs to nearby non-MPA and pre-MPA sites, they were able to obtain high-quality results.
A happy sea turtle pictured in a marine protected area (photo from English Foreign and Commonwealth Office.)
The research showed that across 16,000 sampled sites, MPAs had positive ecological impacts on fish biomass in 71 percent of sites. They also discovered that MPAs with adequate staffing had far greater ecological impacts than those without, which is a pretty interesting piece of feedback when it comes to future development. It’s probably not worth it to create MPAs before there is sufficient funding in place to maintain them.
Gill doesn’t claim that his evidence is flawless; he fully admits to the shortcomings in this study, such as the fact that there is very little data on temperate, coldwater regions — mostly because there are few MPAs in these regions.
The field is ripe for improvement, and he suggests that future research look into the social impacts of MPAs and the implications of these interventions for different species. As the evidence continues to improve, it will be increasingly possible to maximize the win-wins when designing MPAs.
Conservation science isn’t perfect, but neither is medicine. We’ll get there.
If you knew there was a grizzly bear sitting outside the door, you might wait a while before going to fill up your water bottle, or you might change the way you are communicating with their other people in the room based on your knowledge of the threat.
Ecologists call this “predation risk,” in which animals that could potentially fall prey to a carnivore know this risk is present, and alter their habits and actions accordingly.
A yellow slider turtle.
One way in which animals do this is through habitat use, such as a pod of dolphins that changes where they spend most of their time depending on the presence or absence of predators. Animals might also change their feeding habits and diving behavior because of predation risk.
Animals do this all of the time in the wild, but when predators are removed from ecosystems by hunting or over-fishing, the effect of their absence is felt all the way down the food chain.
For example, large amounts of algae growth on coral reefs can be traced back to over-fishing of large ocean predators such as sharks, who then don’t hunt smaller marine mammals like seals. As seal numbers increase, there are more of them to hunt smaller fish that feed on vegetation, which means fewer smaller fish or plankton to keep algal growth in check, and algae begins to grow unchecked.
This is a “trophic cascade” and it has large effects on ecosystems, Duke Marine Lab instructor Meagan Dunphy-Daly t0ld the Sustainable Oceans Alliance last Thursday. She has performed research both in labs and in the field to study the effects that removing large predators have on marine ecosystems.
Dunphy-Daly discussed one lab experiment where 10 yellow-bellied slider turtle hatchlings were kept in tanks where they couldn’t see people or anything else on the outside. In real life, blue herons and other large birds prey on these turtle hatchlings, so the researchers made a model skull of a blue heron that they painted and covered with feathers.
Turtles are air-breathing, so each hatchling was given the option to sit where they could be at the surface of their tank and breathe, but this spot was also where the turtle hatchlings thought the bird beak might shoot down at any time to try to “eat” them.
Their options were to get air and risk getting hit by the bird beak, or diving down to the bottom of the tank to get food. During this experiment, Dunphy-Daly found that turtle hatchlings actually decreased their dive time and spent more time at the surface. If the turtles are continuously diving, they are expending lots of energy swimming back and forth between the surface and the bottom, she said, which means if the predator were to actually attack, they would have less energy left to use for a rapid escape.
Even when there is food at the bottom, when a predator is present, these turtles alter their activity by taking deep dives less frequently so as to not max out their aerobic limit before they actually need to escape a predator.
This is one way in which animals alter their behavior due to predation risk.
But let’s say that predators were disappearing in their real habitats, so turtles didn’t feel the need to build up these emergency energy reserves to escape them. They might dive down and feed more frequently, which would then decrease the amount of the vegetation they eat.
This in turn could have an effect on oxygen levels in the water because there would be fewer plants photosynthesizing. Or another species that feeds on the same plant could be out-competed by turtles and run out of food for their own populations.
The absence of large or small predators can have large impacts on ocean ecosystems through these complicated trophic cascades.