It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
A new study has revealed the potential for sensory deterrents to reduce marine megafauna bycatch in fisheries.
The Newcastle University research suggests that sensory deterrents can work in some circumstances and may be part of the solution to reduce bycatch.
Sensory deterrents are designed to provide sensory cues for marine megafauna (marine mammals, seabirds, sea turtles, sharks and rays) to avert their contact with fishing gear, whilst maintaining target catch quantity and quality.
There are several types of sensory technologies designed to reduce bycatch, including acoustic sound devices, using alternative bait type (for example using fish bait instead of squid), using water hose or cannon for deterrent, the use of lights and magnets, and changes to standard gear colour, such as lines and nets.
Multiple technologies were found effective at reducing bycatch in some studies, yet ineffective at reducing bycatch in others. LED lights were the only technology to date found successful in trials across all marine megafauna groups. However, they had also led to increased bycatch in some seabird and elasmobranch (shark and ray) species.
Publishing their findings in the journal Reviews in Fish Biology and Fisheries, the authors argue that sensory deterrents can help reduce bycatch in some circumstances. However, variable results, caused by environmental factors and differences in species biology, make generalisations difficult. Further problems include the cost of equipment and potential for unintended broader environmental harm.
Sol Lucas, PhD student at the School of Natural and Environmental Sciences, Newcastle University, said: “Variability in study results highlights the importance that scientists and policymakers must consider all available evidence when designing bycatch reduction plans for fisheries. This study collates evidence of the use of sensory deterrents in fisheries, contributing to these decision-making processes.”
The authors reviewed available research (116 studies) testing the sensory deterrents to reduce fisheries bycatch (incidental or accidental catch) of multiple marine megafauna species. All available literature on sensory deterrents in peer-reviewed journals were assessed and the study found that the efficacy of available technologies was variable.
Professor Per Berggren, Chair of Marine Megafauna Conservation at the School of Natural and Environmental Sciences, added: “Most of the technologies that we reviewed are immature and the potential ecological impacts are poorly understood. Further research is required to understand the long-term efficacy and impacts of sensory deterrents. Reducing bycatch of marine megafauna is critical, due to their importance for ecosystem health and for the communities that depend on fisheries for income and food security.”
The study’s authors conclude that it is likely multiple measures will be needed to address bycatch in most fisheries (including time-area closures, gear changes and catch limits). They suggest that bycatch mitigation programmes should be made on a case-by-case basis, tailored to the needs of each fishery, species and local community needs.
Reference
Lucas, S., Berggren, P. A systematic review of sensory deterrents for bycatch mitigation of marine megafauna. Rev Fish Biol Fisheries (2022). https://doi.org/10.1007/s11160-022-09736-5
IMAGE: MANY ONLINE SHOPPERS HAVE BECOME ACCUSTOMED TO FREE AND LENIENT RETURN POLICIES, BUT THAT MAY CHANGE AS RETAILERS LOOK TO OFFSET RISING COSTS. NEW RESEARCH INDICATES RETAILERS WHO ROLL OUT TARGETED POLICIES MAY HAVE BETTER SUCCESS.view more
CREDIT: PHOTO BY RACHEL CRAMER/IOWA STATE UNIVERSITY.
AMES, IA – This holiday season is expected to set another record for online sales, according to the National Retail Federation. But if consumer habits mirror previous years, 20% to 30% of the merchandise will be returned. It’s a big financial hit and logistical challenge for retailers that cover all the shipping, sorting and processing.
“Supply chain managers are really good at moving things to the customer. They’re not as good at bringing things back in because it’s a jumbled, disorganized flow back into the company for a product that they may not be able to resell,” said Robert Overstreet, assistant professor of supply chain management at Iowa State University.
To slow the backward flow and offset costs, retailers are increasingly adopting stricter return policies. Some are shortening the return window; others are adding processing fees or scrapping free shipping altogether.
The risk with this approach, Overstreet says, is backlash from customers. He points to L.L. Bean as an example. The company ranked 16th among U.S. RepTrack’s 100 Most Reputable Companies in 2017 but fell out completely the next year after changing its return policy. L.L. Bean reduced its lifetime replacement guarantee to a year-long return window and required customers to show a receipt.
Overstreet and his co-authors say in a newly published study that consumers are more likely to shop elsewhere if they view a return policy change as unfair or breaking a promise. They’re also more likely to complain to friends and family. But retailers may be able to retain customers and protect their reputations if they specifically target “serial returners” with the policy change.
Serial returners include people who order multiple sizes, colors or models of a product to choose one and send the rest back. Last year, a Narvar study found that more than half of online shoppers in the U.S. buy more than they intend to keep. Another shopping behavior that’s contributed to the growth in returns is known as wardrobing or retail borrowing. Someone buys something for short-term use (e.g., a bassinet for a newborn, speakers for a one-time event) and sends it back before the return window closes.
"With higher costs this year and increasing volumes of excess inventory, many retail giants are considering revamping their return policies,” said Overstreet. “Change is coming. But how they implement and communicate those changes will matter.”
Targeted vs. generalized
The researchers designed a vignette experiment featuring ABCmart, a fictionalized clothing retailer with an online presence and physical stores in all medium-to-large U.S. cities. Over 460 participants were asked to imagine they were loyal customers of ABCmart and planning to return a recent online purchase.
Half of the participants were told the company was shortening its return window for all customers (i.e., a generalized policy.) The other half were told the shorter return window would affect only consumers who have abused the return policy (i.e., a targeted policy for serial returners.) Participants were told that they learned about the new policy because it was either 1.) widely covered on television, radio, and social media (i.e., high-intensity communication) or 2.) posted on ABCmart’s website and within their retail stores (i.e., low-intensity communication).
The researchers found that the participants were significantly more likely to speak negatively about ABCmart when the policy change was generalized. Further, that negative word of mouth was significantly related to customer intentions to switch to a different website.
In another survey, 100 participants were asked about their thoughts about generalized versus targeted policy changes. When the return policy change was targeted, 44% of the participants expressed positive emotions, while only 13% expressed negative emotions. The other 43% were neutral.
Those on the positive side of the spectrum often made comments about fairness. For example: “I would feel proud of the company for taking action against people who try to cheat the system.”
“Respondents largely understood that cheaters were increasing the price paid by everyone,” said Overstreet.
Thirty-five percent of the participants in the targeted policy group also indicated they would talk about the policy change with friends and family. However, they said these comments would be neutral or positive. Only one participant indicated switching to another company when the returns policy change was targeted.
However, when the return policy change was generalized, 64% of the participants expressed negative emotions, while only 2% expressed positive emotions. The other 34% were neutral. Nearly half of the participants indicated they would speak negatively about the change to family and friends (45%) and shop at another store (42%).
Retailer communication
Both showed the way the policy change was communicated to participants also mattered. Low-intensity communication for a targeted policy change led to the best outcome.
“The majority of customers are not going to be affected by a policy change that targets serial returners, so there’s no benefit to wide-scale communications. Only offenders will be upset, not the whole group,” Overstreet explained.
Pat Daugherty and Russell Laczniak, emeritus professors of supply chain management and marketing, respectively; and Tyler Morgan, assistant professor of supply chain management at Auburn University, contributed to the paper published in the Journal of Business Research. The research was funded by multiple grants from the Ivy College of Business.
Overstreet and Daugherty are working with a Ph.D. candidate at Iowa State to develop a risk framework for returns management that includes recommended mitigation strategies.
IMAGE: FLORIDA’S INDIAN RIVER LAGOON IS A BULL SHARK NURSERY HABITAT CRUCIAL TO SURVIVAL AND RECRUITMENT OF ATLANTIC COAST BULL SHARKS.view more
CREDIT: FLORIDA ATLANTIC UNIVERSITY/HARBOR BRANCH OCEANOGRAPHIC INSTITUTE
Stretching 251 kilometers along Florida’s East Coast, the Indian River Lagoon has experienced large-scale, frequent blooms of toxic harmful algae in recent decades. Harmful algal blooms (HABs) occur when an overgrowth of aquatic microalgae over-accumulate in a body of water, negatively affecting wildlife and humans and degrading aquatic habitats.
HAB species produce phycotoxins, potent chemicals produced by photosynthetic organisms, which can move through multiple levels of aquatic food webs as they accumulate and are transferred from prey to predator. Sentinel, or indicator, species can provide an integrated picture of contaminants in the environment.
Researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute, in collaboration with the Florida Institute of Technology and the University of Connecticut, are the first to measure multiple phycotoxin concentrations in bull sharks (Carcharhinus leucas) in the Indian River Lagoon, an estuary of national significance.
In a prior study, the FAU Harbor Branch researchers confirmed the value of the Indian River Lagoon as a bull shark nursery habitat crucial to survival and recruitment of Atlantic coast bull sharks. In recent decades, human water pollution has compromised the biological integrity of the lagoon, which may continue to degrade if environmental pollution in the area continues.
For the current study, researchers measured concentrations of phycotoxins in samples collected from 50 immature (young) bull sharks captured in the Indian River Lagoon between 2018 and 2020. They used ultra-performance liquid chromatography/tandem mass spectrometry to measure the toxins in shark gut contents, plasma (blood) and liver.
Results, published in the journal Science of the Total Environment, suggest multiple phycotoxins in the Indian River Lagoon are widespread or persistent in the environment. Analysis of 123 samples demonstrated the presence of multiple phycotoxins (microcystin, nodularin, teleocidin, cylindrospermopsin, domoic acid, okadaic acid and brevetoxin) in sampled bull sharks. The highest concentrations of most toxins were detected in gut content samples, highlighting dietary exposure as an important mechanism of toxin transfer to bull sharks in the system.
“The presence of one or more phycotoxin in 82 percent of the bull sharks sampled in our study and their prey items highlights the potential threat of toxic algae to the Indian River Lagoon ecosystem and surrounding human populations that may consume the same prey species,” said Michelle L. Edwards, corresponding author, former field technician and marine science and oceanography graduate student at FAU Harbor Branch.
Other than brevetoxin, all of the detected toxins (microcystin, nodularin, teleocidin, cylindrospermopsin, domoic acid, okadaic acid) were present in plasma samples.
“Due to their ecology within the Indian River Lagoon, including residence during early life stages and use of distinct regional areas, bull sharks in the system served as an appropriate sentinel species to survey toxins,” said Matt Ajemian, Ph.D., senior author, an assistant research professor and director of The Fish Ecology and Conservation Lab at FAU Harbor Branch. “In addition, the integrative nature of using gut contents of an upper-level predator for assessment of toxin presence, allowed us to identify toxins in several lower trophic species, including stingrays, catfishes and mullet.”
One important vector species for the transfer of phycotoxins to bull sharks in the Indian River Lagoon was the most commonly identifiable prey item in the study: mullet. In fact, 60 percent of gut contents in which microcystin was identified contained mullet.
“Mullet are distributed throughout the Indian River Lagoon and migrate to offshore areas to spawn between September and December each year, a similar pattern to seasonal offshore movements by young bull sharks that spend time in offshore areas between October and March each year,” said Edwards.
Most toxins were detected in samples collected from all three regions of the Indian River Lagoon (North, Central, South) and during both “wet” and “dry” seasons despite the tendency of resident bull sharks to spend most of their time in specific regions with varied seasonal area usage such as offshore area movements.
“Many phycotoxins can remain in the environment after a harmful algal bloom period ends,” said Ajemian. “Both microcystin and domoic acid, an acid-type neurotoxin, which was the most commonly detected toxin we found in the bull sharks in our study, can adsorb to sediments and could be ingested by benthic organisms or become resuspended in the water column. This makes tracing the timing of exposure to these toxins a tremendous challenge.”
The higher concentrations in gut contents compared to other tissues of the shark suggest that although Indian River Lagoon-resident bull sharks may be frequently exposed to phycotoxins, they may not accumulate them compared to lower trophic species.
“Research on the potential for accumulation in other shark tissues not sampled in our study may be warranted,” said Edwards.
According to Ajemian, they have just scratched the surface on what HAB exposure means for bull sharks in the Indian River Lagoon.
“This was an essential first step in developing critical baselines as we continue to monitor the responses of these animals to HABs in the future,” said Ajemian.
Study co-authors are Adam M. Schaefer, Abt Associates; Malcolm McFarland, Ph.D., an assistant research professor, FAU Harbor Branch; Spencer Fire, Ph.D., an associate professor, Florida Institute of Technology; and Christopher R. Perkins, Ph.D., environmental laboratory director, University of Connecticut.
This work was supported by the Disney Conservation Fund, SeaWorld and Busch Gardens Conservation Fund, the Harbor Branch Oceanographic Institute Foundation, and Florida Center for Coastal and Human Health. Edwards was additionally supported by the Sunrise Rotary Club of Vero Beach.
- FAU -
About Harbor Branch Oceanographic Institute: Founded in 1971, Harbor Branch Oceanographic Institute at Florida Atlantic University is a research community of marine scientists, engineers, educators and other professionals focused on Ocean Science for a Better World. The institute drives innovation in ocean engineering, at-sea operations, drug discovery and biotechnology from the oceans, coastal ecology and conservation, marine mammal research and conservation, aquaculture, ocean observing systems and marine education. For more information, visit www.fau.edu/hboi.
About Florida Atlantic University: Florida Atlantic University, established in 1961, officially opened its doors in 1964 as the fifth public university in Florida. Today, the University serves more than 30,000 undergraduate and graduate students across six campuses located along the southeast Florida coast. In recent years, the University has doubled its research expenditures and outpaced its peers in student achievement rates. Through the coexistence of access and excellence, FAU embodies an innovative model where traditional achievement gaps vanish. FAU is designated a Hispanic-serving institution, ranked as a top public university by U.S. News & World Report and a High Research Activity institution by the Carnegie Foundation for the Advancement of Teaching. For more information, visit www.fau.edu.
Detection of numerous phycotoxins in young bull sharks (Carcharhinus leucas) collected from an estuary of national significance
Climate crisis and anthropic pressure are destabilizing the Pantanal
Brazilian researchers investigated the complexity of the world’s largest wetland biome, predicting heavier rainfall and longer dry periods, and proposing six guidelines for sustainable governance of the region.
FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO
IMAGE: LANDSCAPE IN LOWER NHECOLÂNDIA, A LOBE OF THE TAQUARI RIVER MEGA-FAN IN THE PANTANALview more
CREDIT: MARIO LUIS ASSINE/UNESP
The Pantanal represents 1.8% of Brazil’s total area, occupying 150,000 square kilometers in Mato Grosso and Mato Grosso do Sul states. With a mixture of floodable and non-floodable savannas, meadows, pastures and forests, the macro-region contains the world’s largest floodplain. Together with the Chaco region, which lies further south, the Pantanal is a complex of wetlands with ample biodiversity that provides cultural and ecosystem services to Brazil, Bolivia and Paraguay.
As in the Amazon Rainforest and the Cerrado, agriculture and cattle raising are increasingly encroaching, and in recent years the Pantanal has seen an unprecedented number of fires, mostly set deliberately to clear areas for crops and pasture (read more at: revistapesquisa.fapesp.br/en/the-pantanal-pleads-for-rain/).
A new study aimed at encompassing the complexity of the natural processes that occur in the Pantanal and have become even more complex owing to the global climate crisis and anthropic activity is reported in an article published in the Journal of South American Earth Sciences. Its authors Ivan Bergier and Mario Luis Assine are veterans of scientific investigation in the region.
Bergier is a researcher with EMBRAPA Pantanal – one of the decentralized units of the Brazilian Agricultural Research Corporation (EMBRAPA) – in Corumbá, Mato Grosso do Sul, and has studied the region for 15 years. Assine is a professor at São Paulo State University (UNESP) in Rio Claro, where he has worked for over 30 years.
“In this new study, we divided the Pantanal into sections, which we call functional landforms, to show how these areas behave differently in terms of hydrology – some areas dry up more quickly, some only receive water in the form of rain, some contain rivers as well as floods caused by rain – and how this natural and recurring process is being intensified by global warming and human activity, both in the vicinity and in the Pantanal itself,” Assine told Agência FAPESP.
According to the article, summer rainfall and the number of dry days in autumn and winter have consistently increased, pointing to the likelihood of increased fluvial discharge and sediment load in the rainy season, and water deficits in the dry season.
“Such a scenario indicates extreme dry cycles over all self-affine functional landforms, particularly in abandoned lobes relying exclusively on rainwater, whereas extremes of rainfall intensity at headwaters may amplify the risks of large-scale avulsions at active lobes of the fluvial mega-fans,” the authors write in the Abstract.
To help readers with the technical terms (“self-affine”, “lobes”, “megafans” and so on), let us briefly describe the geomorphological peculiarities of the Pantanal. The Pantanal is often imagined as a homogeneous structure made up of marshes and swamps (pântanos), but this is mistaken. “The Pantanal is a very large floodable area. It’s actually a series of floodplains. Its geological features make it so. It’s a morphological depression, a sedimentary basin, subject to enormous flooding in some years, with less in other years, largely as a result of variations in rainfall. It isn’t low-lying only because of erosion. It’s also low-lying because of tectonic downwarping, and earthquakes still happen in the area. I call the Pantanal a geological gift,” Assine said.
Its geological history has created a vast tract of extremely flat land, with an average height above sea level of only 100 meters. The floodplains are susceptible to whatever happens nearby, to the east on the Maracaju Plateau, associated with the savanna-type vegetation of the Cerrado, and to the north on the Parecis Plateau, in the transition to the Amazon Rainforest. The rivers that run down from the uplands and bring sediments to the plain are unusual in that they are not confined to valleys but fan out, ramify and distribute their waters via smaller rivers or creeks that form vast descending structures termed “mega-fans” by Bergier and Assine.
“Mega-fans are avulsive river systems that constantly change position. They are what make the Pantanal a mutating landscape and explain its susceptibility to anthropic interference,” Assine said.
In sedimentary geology and fluvial geomorphology, avulsion occurs when a river channel switches location along part of its course. Avulsions are characteristic of fluvial and deltaic environments, including alluvial fans and rivers with multiple channels.
“Mega-fans are self-affine, meaning similar to each other,” Bergier explained. “They’re self-similar forms that are repeated on varying scales. In our study, we set out to understand how these forms originate and are repeated. There are several mega-fans in the area. The largest is the Taquari River mega-fan, which has high fluvial discharge and spreads more sediment over the plain, occupying much of the area. There are smaller rivers with mega-fans, too. One is called the Negro. The Pantanal was formed over millions of years from this competition among rivers, which is linked to the amount of sediment created on the plateaus and responsible for the functionalities seen at present, including active lobes where the river water spreads out and abandoned lobes where water no longer flows.”
A sedimentary or depositional lobe is a formation that builds up as a river empties into other water bodies, forcing the river outwards and away from its original channel.
The Paraguay River is the Pantanal’s backbone, capturing all the water that does not evaporate or infiltrate the subsoil. The southern portion of the Pantanal is lower than the northern part, and the altitude gradient makes the Paraguay flow slowly southward toward the La Plata Basin.
“The water intake from nearby plateaus is huge. Outflow is hindered by three bottlenecks along the Paraguay. The article shows how these bottlenecks limit the flow of water and cause flooding in the southern part of the Pantanal. The flow is so slow that in the area of the Nabileque, in the southern portion, the big floods occur only four to five months after the main rainy season. It’s a unique phenomenon,” Assine said.
All this makes the Pantanal a vast reservoir. At times of heavy rain, the amount of water entering the low-lying part of the system far exceeds the outflow via the rivers, leading to a build-up of water and flooding due to a rise in the water table. In dry period, the water level falls. Another peculiarity of the Pantanal is that it is actually located in a region with an overall water deficit. Evapotranspiration exceeds precipitation, so that water is lost to the atmosphere in dry periods, and lakes and rivers dry up as the water table falls.
This rising and falling, which is complex in itself, is made more complex by the climate crisis, which tends to produce extremes of rainfall and drought, and by human activity, whether it be deforestation of the Cerrado on adjacent plateaus or burning and clearing of land in the Pantanal, placing the entire system under massive pressure.
Accelerating changes
Bergier and Assine conducted a hydrological analysis to find out how wetter and drier periods in the Pantanal are influenced by variations in precipitation cycles, measured on the basis of the fluvial discharge from the Paraguay River, which captures all the water. They wanted to help forecasters predict which areas will suffer most from climate extremes.
The water table falls fastest in higher areas, which dry out first and are more subject to burning and other adverse events. Active lobes distribute sand across the flat area, but many lobes that were active in the past and have been abandoned by the rivers may also have areas of dry vegetation that can burn.
“The lobes distribute sand and other sediments, which fill the channels until they reach a critical state known to inhabitants of the Pantanal as ‘breaching’,” Bergier said. “The river bursts its banks and floods the surrounding land. Later the channel re-forms. With each multi-year flooding cycle, the rivers are reconstructed, reshaping the landscape. This is why there are areas of vegetation that were once gallery forests but are no longer near a river. We tried to study the Pantanal from this standpoint, focusing on its complexity and critical states that reach a threshold when the system changes suddenly. We wanted to find out how the Pantanal’s landscape resulted from these non-linearities and how it may evolve from now on.”
The Pantanal is widely considered one of Brazil’s six biomes, alongside the Amazon Rainforest, Cerrado, Caatinga (a semi-arid part of the Northeast), Pampa (grasslands in the South) and Atlantic Rainforest. However, the concept of a biome is associated with plant cover. The Pantanal is much more than that. Above all, it is a unique geological entity that divides, creates spaces and changes all the time.
For example, 30 years ago the Taquari ran down to a place called Porto da Manga. Its mouth is now dozens of kilometers farther north. “These changes are natural. In the long run, they are recurrent events, but anthropic interference accelerates all the processes involved, affecting not only the environment but also the economy, including cattle farming, which is the main economic activity in the region. Climate change is another accelerating factor,” Bergier said.
Taking all these aspects into account, the authors conclude by proposing a sustainable governance model for the Pantanal, with six pillars: recognition that self-affine functional landforms are ultimately associated with predominant types of ecosystem services; functional landforms evolve over time, and subtle environmental changes may substantially alter the nature, quality and quantity of the ecosystem services provided; changes are drastic in magnitude whenever fluvial discharge and sediment load equilibrium are far from their critical states; climate change, combined with unsustainable land-use practices, drives the system far from critical states over shorter periods of time and larger spaces; ecohydrology tools and integrated crop-livestock-forest systems can mitigate anthropic impacts on fluvial discharge and sediment load equilibrium, while positively contributing to atmospheric carbon sequestration; and external factors, such as climate change, influence the formation and evolution of the Pantanal’s large-scale self-affine functional landforms. Other external factors, such as tectonics, may also play a role and deserve to be investigated in future.
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe
A University of Maryland researcher and colleagues found that the fungus Metarhizium robertsii removes mercury from the soil around plant roots, and from fresh and saltwater. The researchers also genetically engineered the fungus to amplify its mercury detoxifying effects.
Mercury pollution of soil and water is a worldwide threat to public health. This new work suggests Metarhizium could provide an inexpensive and efficient way to protect crops grown in polluted areas and remediate mercury-laden waterways.
Thestudy, which was conducted by UMD professor of entomology Raymond St. Leger and researchers in the laboratory of his former post-doctoral fellow, Weiguo Fang (now at Zhejiang University in Hangzhou, China),was published in Proceedings of the National Academy of Sciences (PNAS) on November 14, 2022.
“This project, led by Dr. Fang, found that Metarhizium stops plants from taking up mercury,” said St. Leger. “Despite being planted in polluted soil, the plant grows normally and is edible. What’s more, the fungus alone can quickly clear mercury from both fresh and saltwater.”
Metarhizium is a nearly ubiquitous fungi, and previous work by the St. Leger laboratory had shown that it colonizes plant roots and protects them from herbivorous insects. Scientists have known that Metarhizium is often one of the only living things found in soils from toxic sites like mercury mines. But no one had previously determined how the fungus survived in mercury polluted soils, or if that had implications for the plants the fungus normally lives with.
St. Leger and other colleagues had previously sequenced the genome of Metarhizium, and Fangnoticed that it contains two genes that are very similar to genes present in a bacterium known to detoxify, or bioremediate, mercury.
For the current study, the researchers ran a variety of laboratory experiments and found that corn infected with Metarhizium grew just as well whether it was planted in clean soil or mercury-laden soil. What’s more, no mercury was found in the plant tissues of corn grown in polluted soil.
The researchers then genetically modified the fungi, removing the two genes that were similar to those in mercury remediating bacteria. When they replicated their experiments, modified Metarhizium no longer protected corn plants from mercury-laden soil, and the corn died.
To verify that the genes were providing the detoxifying qualities, the researchers inserted them into another fungus that does not normally protect corn from mercury. The newly modified fungus performed like the Metarhizium, protecting the plants from mercury-laden soil.
Microbiological analyses revealed that the genes in question expressed enzymes that break down highly toxic organic forms of mercury into less toxic, inorganic mercury molecules. Lastly, the researchers genetically engineered Metarhizium to express more of the detoxifying genes and increase its production of the detoxifying enzymes.
In their final experiment, the researchers found they could clear mercury from both fresh and salt water in 48 hours by mixing in Metarhizium.
The next step will be to conduct experiments in the field in China to see if Metarhizium can turn toxic environments into productive fields for growing corn and other crops. Current methods of remediating polluted soils require toxins to be removed or neutralized from entire fields before anything can be planted. That can be very expensive and take a long time. But Metarhizium simply detoxifies the soil immediately surrounding the plant roots and prevents the plants from taking up the toxin.
“Allowing plants to grow in mercury-rich environments is one of the ways this fungus protects its plant home,” St. Leger explained. “It’s the only microbe we know of with the potential to be used like this, because the bacteria with the same genetic capabilities to detoxify mercury don’t grow on plants. But you can imagine simply dipping seeds in Metarhizium, and planting crops that are now protected from mercury-rich soils.”
In addition to its potential as a cost-effective tool for reclaiming polluted lands for agriculture, Metarhizium may help clear mercury from wetlands and polluted waterways that are increasingly threatened by mercury pollution as climate change and melting permafrost accelerates the release of the toxic metal into soils and oceans.
This research was supported by a National Natural Science Foundation of China Grant (Award No. 32172470) This story does not necessarily reflect the views of the funding organization.
IMAGE: LARGER CIRCLE SIZE REPRESENTS AREAS WITH GREATER TICK ABUNDANCES. CIRCLE COLOURATION DEMONSTRATES THE PROPORTIONAL RESULTS OF PATHOGEN TESTING FOR TICK POOLS. LIGHT BLUE REPRESENTS TICK POOLS THAT WERE NEGATIVE FOR PATHOGEN TESTING. PROPORTIONS OF TICK POOLS THAT WERE POSITIVE AND HARBOURING BABESIA ODOCOILEI (TURQUOISE), BORRELIA BURGDORFERI (LIGHT PURPLE), OR RICKETTSIA RICKETTSII (DARK PURPLE) ARE NOTED ON THE MAP.view more
CREDIT: MCGILL UNIVERSITY / UNIVERSITY OF OTTAWA
Tick-borne pathogens, known for causing illnesses such as Lyme disease, are on the rise in Central Canada – presenting new risks in areas where they were never previously detected.
The findings from researchers at McGill University and the University of Ottawa demonstrate the need for more comprehensive testing and tracking to detect the spread and potential risk of tick-borne pathogens to human and wildlife populations throughout Canada.
“Most people know that diseases can be transmitted to humans through the bite of infected ticks. Ticks can carry and spread several disease agents, called pathogens, that can make people and animals sick,” explains Kirsten Crandall, a PhD candidate under the joint supervision of McGill University Professor Virginie Millien and University of Ottawa Professor Jeremy Kerr.
“While the bacteria that causes Lyme disease is the most common tick-borne pathogen in Canada, other tick-borne pathogens are moving in,” she adds.
To investigate the presence and prevalence of several emerging tick-borne pathogens, Crandall and her team analyzed small mammals and ticks collected in Ontario and Quebec. The researchers found that five emerging pathogens were present across their study sites in Central Canada, including the pathogens causing Lyme disease and babesiosis, a malaria-like parasitic disease.
They discovered that two pathogens, Babesia odocoilei and Rickettsia rickettsii, were detected outside of their historic geographic range in Quebec. These pathogens spread both babesiosis and Rocky Mountain spotted fever. “The presence of these pathogens changes the risk of disease for Canadians and animals in some densely populated areas of Canada,” says Crandall.
Transmission spread in different ways
Typically, pathogens are transmitted to a tick after feeding from the blood of an infected host, like a small mammal. However, the researchers found evidence of pathogens that could spread in other ways. Babesia odocoilei and Rickettsia rickettsii can also be directly transmitted from adult female ticks to larval ticks. Additionally, small mammals like mice can transmit the parasite Hepatozoon after ingesting an infected insect, spider, or tick.
“It’s challenging to assess the spread of certain emerging or re-emerging tick-borne pathogens, as many of them are not reported to public health agencies in Canada,” says Crandall. “Only two tick-borne pathogens are listed as nationally notifiable diseases in Canada: Lyme disease (Borrelia burgdorferi) and tularemia (Francisella tularensis). However, we are seeing increased cases of diseases like anaplasmosis and babesiosis in humans in Canada.”
Detecting the spread and potential risk
According to the researchers, the spread of emerging tick-borne pathogens has steadily increased in Canada because of climate change, habitat fragmentation, and changes in the abundance of tick populations and their hosts.
“If we don’t know that pathogens are present, we can’t equip Canadians with the information they need to protect themselves. COVID has diverted public health resources away from challenges like this one, and we need to remember that these tick-borne diseases are on the move too,” adds Jeremy Kerr, a Professor and Research Chair in University of Ottawa’s Department of Biology.
“It’s an immense endeavour to track in real time the emergence of these pathogens across Canada, and this is when field research like ours can contribute significantly. The work of our student is a beautiful reminder that fundamental research matters, and in this case, can play a role in public health,” says Virginie Millien, an Associate Professor at the Redpath Museum at McGill University.
Pathogens detected in small mammals in Ontario and Quebec, Canada
UNIVERSITY OF OTTAWA
Larger circle size represents areas with greater small mammal abundances. Circle colouration demonstrates the proportional results of pathogen testing for individual small mammals. Light blue represents small mammals that were negative for pathogen testing. Individual small mammals that were positive and harbouring Babesia odocoilei (turquoise), Babesia microti (pink), and a Hepatozoon species (teal) are noted on the map.
