Bowdoin Science Journal

Environmental Science and EOS

Airborne Bacteria: A Hidden Regulator of Ocean Blooms

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Context

Marine phytoplankton are microscopic algae integral to oceanic ecosystems and global biogeochemical cycles. They contribute significantly to the process of carbon displacement into the deep ocean and primary production, forming the foundation of the marine food web. However, these phytoplankton populations are vulnerable to various environmental and biological stressors, including temperature changes, nutrient availability, and pathogen infections. When a phytoplankton bloom collapses, bacteria consume their organic matter, a process that requires oxygen. The decay of the bloom and oxygen levels can deplete oxygen and lead to “dead zones” that can suffocate marine life (US EPA, 2013). Researching the components of bloom dynamics enables us to better understand their interactions as a foundation of the food web and regulator of oxygen levels.

 

Fig 1. Demise of a phytoplankton bloom over the course of a handful of days (Demise of a Phytoplankton Bloom, 2014)

One of the most abundant bloom-forming phytoplankton is Gephyrocapsa Huxley, a species of coccolithophore, a type of phytoplankton covered in calcium carbonate plates known for its widespread blooms in the ocean. While viral infections have long been recognized as a primary cause of phytoplankton bloom collapse, researchers have questioned whether bacteria could be another potential source of pathogenicity. Recent research regarding G. huxleyi phytoplankton suggests so.

 

Fig 2. Calcium carbonate plating on a coccolithophore phytoplankton (Briggs, 2021)

 

This groundbreaking study by Lang-Yona et al. investigated whether airborne bacteria could infect G. huxleyi blooms and be an explanation for bloom collapses. This research aimed to analyze atmospheric bacteria as an ecological regulator of phytoplankton populations, an often disregarded consideration in the dynamics of oceanic microbial interactions and climate models. Understanding these interactions is critical for predicting changes in marine ecosystems and their impact on global carbon cycles.

Methods of the Study

To explore whether airborne bacteria play a role in controlling phytoplankton populations, researchers collected air and water samples above a bloom of G. huxleyi in the North Atlantic. They conducted this work aboard the research vessel R/V Tara, using specialized instruments to capture airborne bacteria at different heights. These included high-volume air samplers and devices called cascade impactors, which were set up at different points on the ship, including the deck and mast. This setup allowed them to collect bacteria from various altitudes and better understand how microbes travel through the air (Lang-Yona et al., 2024)

Back in the lab, the team introduced the airborne bacteria into cultures of G. huxleyi to see what would happen. They carefully watched for signs of infection, such as a drop in the algae’s natural fluorescence (a sign they were losing their ability to photosynthesize), increased debris in the water (indicating cell death), and visible damage to the algal cells. When signs of infection appeared, they filtered out the bacteria from the cultures and grew them on a nutrient-rich surface called Marine Agar 2216. This step helped them isolate specific bacterial strains. To confirm that these bacteria were truly responsible for the infection, they then reintroduced them to fresh G. huxleyi cultures and checked whether the same effects occurred.

To track how the bacteria and algae interacted over time, researchers used a technique called flow cytometry. This method shines a laser through tiny droplets of water containing cells, measuring their size, shape, and natural glow. It allows scientists to quickly count how many algae and bacteria are present and determine how the infection is progressing.

Finally, they identified the bacteria using genetic sequencing and measured their presence in air and water samples with a technique called quantitative PCR (qPCR). This method detects and counts bacterial DNA, helping researchers understand how common these airborne microbes are in different environments.

Results of the Study and Implications

The study identified the airborne bacterium Roseovarius nubinhibens as a key bacteria capable of infecting and contributing to the collapse of G. huxleyi blooms. This bacterium was found to remain viable after atmospheric transport and effectively infects phytoplankton upon reaching ocean waters. The ability of R. nubinhibens to survive and remain pathogenic after airborne dispersal suggests a more dynamic role for bacteria in ocean-atmosphere interactions than previously recognized.

The ability of bacteria to be transported via wind patterns indicates a geologically vast and major mechanism that has previously been overlooked. The findings suggest that in addition to viral infections, bacterial pathogens may serve as natural regulators of phytoplankton populations, influencing bloom duration and oceanic carbon cycling. This discovery is particularly significant because phytoplankton blooms play a critical role in the global carbon cycle by taking carbon from the atmosphere, and upon death, sinking to the deep ocean where the carbon is stored. If bacterial infections contribute to bloom collapse and can be dispersed so vastly,  they may influence carbon fluxes in ways that need to be accounted for in climate models.

Previously, viral infections were considered the primary biological driver of bloom decline, but this study introduces airborne bacteria as an additional player in phytoplankton mortality. This raises important questions about how environmental factors such as wind patterns and ocean currents influence bacterial dispersal. Additionally, climate change may impact the spread of airborne pathogens, potentially altering bloom dynamics in unforeseen ways. A warming climate and shifting atmospheric circulation patterns could enhance or suppress the spread of algicidal bacteria, with cascading effects on marine ecosystems.

Furthermore, this research highlights the complexity of microbial interactions in the ocean. Many bacterial species exhibit “Jekyll-and-Hyde” dynamics, shifting between mutualism and pathogenicity depending on environmental conditions and the physiological state of their algal hosts. In the case of R. nubinhibens, it is possible that under certain conditions, it exists in a neutral or even beneficial relationship with G. huxleyi, but when environmental factors such as nutrient depletion or increased bacterial density trigger a shift, it becomes pathogenic. The study’s infection experiments demonstrated that R. nubinhibens could rapidly induce algal demise, suggesting a transition from a benign to an algicidal state. This aligns with previous findings that some marine bacteria can switch between cooperative and harmful interactions based on chemical signaling. Understanding these complex interactions is essential for developing a more accurate picture of microbial regulation in marine environments, as such shifts can significantly alter bloom dynamics and oceanic food webs.

This study provides new insight into the role of airborne bacteria in regulating marine phytoplankton populations, demonstrating that Roseovarius nubinhibens can contribute to G. huxleyi bloom collapse. These findings expand our understanding of ocean-atmosphere microbial interactions and introduce airborne bacteria as an important but previously overlooked factor in bloom dynamics. Incorporating airborne bacterial processes into ecological and climate models will be crucial for accurately predicting future oceanic changes. Further research is necessary to determine whether other phytoplankton species are similarly affected and how environmental shifts may influence the prevalence and impact of airborne bacterial infections on marine ecosystems. Understanding these dynamics is essential for assessing ocean health and resilience in a rapidly changing climate.

 

References:

Briggs, G. M. (2021). Coccolithophores, photosynthetic unicellular algae. https://milnepublishing.geneseo.edu/botany/chapter/emiliana-huxleyi/

Demise of a Phytoplankton Bloom. (2014, November 26). [Text.Article]. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/84797/demise-of-a-phytoplankton-bloom

Lang-Yona, N., Flores, J. M., Nir-Zadock, T. S., Nussbaum, I., Koren, I., & Vardi, A. (2024). Impact of airborne algicidal bacteria on marine phytoplankton blooms. The ISME Journal, 18(1), wrae016. https://doi.org/10.1093/ismejo/wrae016

US EPA, O. (2013, March 12). The Effects: Dead Zones and Harmful Algal Blooms [Overviews and Factsheets]. https://www.epa.gov/nutrientpollution/effects-dead-zones-and-harmful-algal-blooms

 

Sunshine, Sea, and Sunscreen: How ‘Eco-Friendly’ Choices Affect Marine Life

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Since the onset of the COVID-19 pandemic in 2020, international tourism has slowly been returning to previous levels. As of July 2024, an estimated 790 million tourists have traveled internationally, marking an 11% increase from the prior year and approaching the frequency of pre-COVID travel (Global Tourism Statistics). While this rise sounds promising for economic stimulation and cultural preservation, it also reintroduces the environmental impacts associated with tourism. In the Mediterranean, for example, tourists seeking to enjoy sunny beach days may unknowingly disrupt local ecosystems through their sunscreen use. Knowing how our consumption and product use impacts environmental systems is a key factor in being able to pinpoint where environmental degradation is coming from, and being able to stop it at the source. This raises the question: do “eco-friendly” sunscreens truly provide a safer alternative?

Pedro Echeveste, a researcher in marine microbial ecology and ecotoxicology at the University of the Balearic Islands, and his team have investigated this topic. Their 2024 study focused on commercial sunscreens and their chemical components’s impact on bacterial communities linked to Posidonia oceanica, or Neptune grass, a foundational species in the Mediterranean ecosystem (Echeveste et al., 2024).

Figure 1. Overview of all experimental results. The image shows all the different types of bacteria and epiphytes tested, and how their cell abundance shifted based on the type of sunscreen added to their system (Echeveste et al., 2024).

The study examined both heterotrophic bacteria (including Pseudomonas azotifigens, Marinobacterium litorale, Thiothrix nivea, Sedimentiacola thiotaurini, and Cobetia sp.) and autotrophic bacteria (Halothece sp. and Fischerella muscicola), as well as epiphytes—plants growing on the leaves of Neptune grass without being parasitic. These bacterial communities were cultured in artificial seawater at 25°C, with a 12-hour light/dark cycle and an initial concentration of 10^5 bacteria per mL. The research team added various concentrations of nanoparticles and sunscreens (0, 0.01, 0.1, 1, 10, and 100 mg/L) to each sample, exposing the bacterial communities for 72 hours.

Two commonly used inorganic UV filters, titanium dioxide (TiO₂) and zinc oxide (ZnO), were tested due to their prevalence in commercial sunscreens. The study focused on three sunscreen types: an eco-friendly SPF 50 without nanoparticles (SPF50E), an SPF 50 containing TiO₂ nanoparticles (SPF50), and an SPF 90 with both TiO₂ and ZnO nanoparticles (SPF90).

After the 72-hour exposure, the pollution concentrations that led to a 10% population decline (known as the EC10 value) were recorded. Titanium dioxide proved toxic to all heterotrophic bacteria, with Thiothrix nivea exhibiting a 10% decline at a concentration of 3.8 mg/L. Zinc oxide was comparatively less harmful, affecting only Marinobacterium litorale and Pseudomonas azotifigens at an EC10 of 1.39 mg/L for the latter.

The effects varied among the sunscreen types. The eco-friendly SPF 50 reduced phosphorus uptake by 30-50% in most bacterial species, a significant alteration that suggests interference with key nutrient cycles. The regular SPF 50, containing TiO₂, decreased alkaline phosphatase (APA) activity, an enzyme necessary for cell communication via dephosphorylation. Dephosphorylation—the removal of a phosphate group—is a critical process for signal transmission within cells. All sunscreens in the study also led to increased levels of reactive oxygen species (ROS), molecules derived from oxygen that may damage cellular proteins, DNA, and other essential structures. This data allows us to assume that any form of sunscreen, no matter the label as “eco-friendly”, or the SPF value, can impose degradational effects on our environmental systems via one mode or another.

All in all, These findings reveal that eco-friendly labels sometimes lack scientific backing, failing to account for subtle but important factors in maintaining environmental balance. Even the “eco-friendly” SPF 50 sunscreen altered bacterial populations, calling into question the validity of eco-friendly claims. 

As tourism resumes in coastal areas, the increased use of sunscreens—and thus UV filters—places greater pressure on marine ecosystems (Raffa et al., 2018). This rise in sunscreen pollution underscores the importance of studying the effects of “eco-friendly” sunscreens, as even minor shifts in bacterial populations can compound into substantial ecosystem changes when multiplied by millions of beachgoers. Achieving a truly eco-friendly sunscreen remains a challenge, but as consumers, what we can do is adopt a more informed and thoughtful approach to product choices. By balancing our personal protection needs with the planet’s health, we can work toward solutions that better align with environmental preservation.

 

References:

  1. Un tourism: Bringing the world closer. UN Tourism World Tourism Barometer | Global Tourism Statistics. Available at: https://www.unwto.org/un-tourism-world-tourism-barometer-data#:~:text=International%20tourist%20arrivals%20hit%2096,4%25%20less%20than%20in%202019 (Accessed: 28 October 2024). 
  2. Echeveste, P., Fernández-Juárez, V., Brito-Echeverría, J., Rodríguez-Romero, A., Tovar-Sánchez, A., & Agawin, N. S. (2024). Toxicity of inorganic nanoparticles and commercial sunscreens on marine bacteria. Chemosphere, 364, 143066. https://doi.org/10.1016/j.chemosphere.2024.143066
  3. Raffa, R.B. et al. (2018) Sunscreen bans: Coral reefs and skin cancer, Wiley Journal of Clinal Pharmacy and Therapeutics. Available at: https://research.ebsco.com/c/ceyvtd/viewer/pdf/db53bg7blv (Accessed: 28 October 2024).

 

Microplastic burden in marine benthic invertebrates depends on feeding strategies

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Microplastic pollution is a global issue effectively impacting all aquatic systems from the poles to tropical reefs. Current emission patterns project to around 35 – 98 metric tons of annual microplastic emission by 2030. Yet, this may only be an underestimation, as our current understanding of microplastic concentrations based on traditional sampling practices overlooks smaller debris (Lindeque et al. 2020, Borrelle et al. 2020). With this scale of rapid increase in concentrations, the implications of microplastic accumulation in marine systems have become an increasing concern. In response to this global concern, Adam Porter and his team looked towards the ocean’s floor to better understand how microplastics interact with dynamic ecosystems.

Microplastics emitted into the marine environment can adversely impact a wide range of processes from cellular metabolism to digestive functions, fertility, locomotion, and growth (Foley et al. 2018; Bour et al. 2018). Furthermore, bioaccumulation, or trophic transfer when contaminated prey is consumed by predators, magnifies microplastic burdens in organisms higher in the food chain. These above properties, in conjunction to the rapidly increasing environmental concentrations, highlight the pressing need to quantify how much microplastics marine organisms are ingesting.

Historically, our understanding of individual microplastic burdens has often assumed that levels of environmental contamination directly map onto their uptake by marine organisms. However, studies have found that this isn’t always the case. Other factors, such as feeding strategies and community composition, also impact a species’ uptake rate (Pagter et al. 2021; Bour at al. 2018). 

To bridge the mismatch of environmental concentration and individual burden, Porter et al. reviewed 412 studies on marine invertebrates from around the globe to investigate how different species traits could influence microplastic uptake. First, they gathered data from each study and assigned a geographic sector to each sampling site. Next, they evaluated each observation for a variety of variables, including feeding mode, position within the sediment, and wet weight (mass) of the individual. Then, Porter’s team used statistical tests to examine the potential influence each parameter had on plastic uptake with statistical analyses tests and visualized their findings. 

Geographically, the Pacific Northwest, Yellow Sea and Japan Trench, had the highest mean individual microplastic burden. In terms of animal class, the highest mean burden occurred in the Malacostraca class. Malacostraca encompasses common commercial species such as crabs and lobsters, which could have commercial implications on industries like lobster fishing and aquaculture. 

Of all the outlined parameters, feeding strategies had the greatest impact on microplastic uptake. Omnivores were shown to have the highest rate of uptake, followed by predators, herbivores, grazers, suspension feeders, deposit feeders, and lastly scavengers. These findings support the bioaccumulation theory, one of several hypotheses concerning microplastic uptake patterns (Wang 2014). According to the bioaccumulation theory, microplastics enter the food web through primary consumers like suspension feeders, grazers, and filter feeders. The plastic they retain in their systems will then be ingested by higher trophic levels like secondary and tertiary consumers that are omnivores,predators, and scavengers. Accordingly, the microplastic burdens would be highest in predators and omnivores, which matches the study’s findings.

In addition to the quantity of microplastics retained, feeding patterns were also found to influence the size and type of microplastics consumed were also different across groups. The most reported shape was fibers. The mean sizes of these fragments ranged from 0.2 micrometers to 17 centimeters, and herbivores in general retained the largest particles, but the precise mechanisms driving these patterns remain unclear.  

These findings precisely highlight our gap in knowledge of microplastic distribution amongst marine communities. As Porter et al. highlights, a holistic consideration of subtle processes related to feeding patterns is essential in fine tuning our understanding of how our world is changing. Thus, although the study describes general trends on a global scale, future research focusing on regional subtleties is important. Subsequently, applying these findings as policy is crucial, as many marine organisms are frequently consumed commercial species. Being major consumers of seafood, the microplastic accumulation in marine animals can directly impact humans. This is particularly concerning in context of our status as the apex predator, and therefore the final stop in the chain of bioaccumulation. As the microplastic burden in marine organisms is rising at an alarming pace, the need for action is more urgent than ever.

 

Works Cited

Borrelle, S. B., Ringma, J., Law, K. L., Monnahan, C. C., Lebreton, L., McGivern, A., Murphy, E., Jambeck, J., Leonard, G. H., Hilleary, M. A., Eriksen, M., Possingham, H. P., De Frond, H., Gerber, L. R., Polidoro, B., Tahir, A., Bernard, M., Mallos, N., Barnes, M., & Rochman, C. M. (2020). Predicted growth in plastic waste exceeds efforts to mitigate plastic pollution. Science, 369(6510), 1515–1518. https://doi.org/10.1126/science.aba3656 

Bour, Agathe, Carlo Giacomo Avio, Stefania Gorbi, Francesco Regoli, and Ketil Hylland. “Presence of Microplastics in Benthic and Epibenthic Organisms: Influence of Habitat, Feeding Mode and Trophic Level.” Environmental Pollution (Barking, Essex: 1987) 243, no. Pt B (December 2018): 1217–25. https://doi.org/10.1016/j.envpol.2018.09.115.   

Foley, Carolyn J., Zachary S. Feiner, Timothy D. Malinich, and Tomas O. Höök. “A Meta-Analysis of the Effects of Exposure to Microplastics on Fish and Aquatic Invertebrates.” The Science of the Total Environment 631–632 (August 1, 2018): 550–59. https://doi.org/10.1016/j.scitotenv.2018.03.046.   

Lindeque, P. K., Cole, M., Coppock, R. L., Lewis, C. N., Miller, R. Z., Watts, A. J. R., Wilson- McNeal, A., Wright, S. L., & Galloway, T. S. (2020). Arewe underestimating microplastic abundance in the marine environment? A comparison of microplastic capture with nets of different mesh-size. Environmental Pollution, 265, 114721. https://doi.org/10.1016/j.envpol.2020.114721

Pagter, Elena, Róisín Nash, João Frias, and Fiona Kavanagh. “Assessing Microplastic Distribution within Infaunal Benthic Communities in a Coastal Embayment.” Science of The Total Environment 791 (October 15, 2021): 148278. https://doi.org/10.1016/j.scitotenv.2021.148278. 

​​Porter, A., Godbold, J. A., Lewis, C. N., Savage, G., Solan, M., & Galloway, T. S. (2023). Microplastic burden in marine benthic invertebrates depends on species traits and feeding ecology within biogeographical provinces. Nature Communications, 14(1), 8023. https://doi.org/10.1038/s41467-023-43788-w 

Wang, W. -X. “Chapter 4 – Bioaccumulation and Biomonitoring.” In Marine Ecotoxicology, edited by Julián Blasco, Peter M. Chapman, Olivia Campana, and Miriam Hampel, 99–119. Academic Press, 2016. https://doi.org/10.1016/B978-0-12-803371-5.00004-7.

Getting the Big Picture: Satellite Altimetry and the Future of Sea Level Rise Research

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Anthropogenic climate change is drastically affecting the natural processes of the Earth at unprecedented rates. Increased fossil fuel emissions coupled with global deforestation have altered Earth’s energy budget, creating the potential for positive feedback loops to further warm our planet. While some of this warming manifests through glacier melting, powerful storm systems, and rising global temperatures, it’s estimated that 93% of the total energy gained from the greenhouse effect is stored in the ocean, with the remaining 7% contributing to atmospheric warming (Cazenave et al. 2018, as cited in von Schuckmann et al. 2016). This storage of heat in the ocean is responsible for oceanic thermal expansion and in combination with glacier melt is contributing to global sea level rise. Currently, an estimated 230 million people live below 1 m of the high tide line and if we do not curb emissions, sea level rise projections range 1.1 – 2.1 m by 2100 (Kulp et al. 2019, Sweet et al. 2022). Sea level rise’s global impact has thus been a prominent area of scientific research with leading methods utilizing satellite altimetry to measure the ocean’s height globally over time. 

Originating in the 1990s, surface sea level data has been recorded using a multitude of satellites amassing information from subseasonal to multi-decadal time scales (Cazenave et al. 2018). NASA’s sea level change portal reports this data sub-annually, recording a current sea level rise of 103.8 mm since 1993 (NASA). Seeking more information on the current trend of satellite altimetry, I reached out to French geophysicist Dr. Anny Cazenave of the French space agency CNES and director of Laboratoire d’Etudes en Geophysique et Oceanographie Spatiale (LEGOS) in Toulouse, France. Dr. Cazenave is a pioneer in geodesy, has worked as one of the leading scientists on numerous altimetry missions, was lead author of the sea level rise report for two Intergovernmental Panel on Climate Change (IPCC) reports, and recently won the prestigious Vetlesen Prize in 2020 (European Space Sciences Committee). 

When asked about recent advancements in altimetry technology, Dr. Cazenave directed me towards the recent international Surface Water and Ocean Topography satellite mission (SWOT) launched in 2022. SWOT is able to detect ocean features with ten times the resolution of current technology, enabling fine-scale analysis of oceans, lakes, rivers, and much more (NASA SWOT). Specifically for measuring sea level rise, SWOT utilizes a Ka-band Radar Interferometer (KaRIn) which is capable of measuring the elevation of almost all bodies of water on Earth. KaRIn operates by measuring deflected microwave signals off of Earth’s surface using two antennas split 10 meters apart, enabling the generation of a detailed topographic image of Earth’s surface (NASA SWOT). With SWOT’s high-resolution capabilities for topographically mapping sea level change anomalies close to shore, more accurate estimations for how sea level rise can affect coastal communities will be accessible in the future.

The figure above displays the difference in resolution between Copernicus Marine Service of ESA (European Space Agency) data and SWOT surface height anomaly data (NASA SWOT).

Finally, in light of recent developments in AI and machine learning, Dr. Cazenave noted the power of these computational methods in analyzing large data sets. The high-precision data provided by SWOT requires advanced methods of analysis to physically represent sea level rise changes, posing a challenge for researchers (Stanley 2023). A few recent papers have already highlighted the use of neural networks that are trained on current altimetry and sea surface temperature data (Xiao et al. 2023, Martin et al. 2023). These neural networks are then able to decipher the high-resolution data, enabling for a greater understanding of ocean dynamics and sea surface anomalies. Dr. Cazenave explained that the key questions to answer regarding sea level rise are: (1) how will ice sheets contribute to future sea level rise, (2) how much will sea level rise in coastal regions, and (3) how will rising sea levels contribute to shoreline erosion and retreat. With novel computational analysis techniques and advanced sea surface monitoring, many of these questions are being answered with greater accuracy. As we navigate the effects of climate change, combining science and policy will allow us to design multifaceted solutions that enable a sustainable future for all.

References

  1. Anny Cazenave​. European Space Sciences Committee. (n.d.). https://www.essc.esf.org/panels-members/anny-cazenave%E2%80%8B/
  2. Cazenave, A., Palanisamy, H., & Ablain, M. (2018). Contemporary sea level changes from satellite altimetry: What have we learned? What are the new challenges? Advances in Space Research, 62(7), 1639–1653. https://doi.org/10.1016/j.asr.2018.07.017
  3. Home. (n.d.). NASA Sea Level Change Portal. Retrieved April 24, 2024, from https://sealevel.nasa.gov/
  4. Joint NASA, CNES Water-Tracking Satellite Reveals First Stunning Views. (n.d.). NASA SWOT. Retrieved April 24, 2024, from https://swot.jpl.nasa.gov/news/99/joint-nasa-cnes-water-tracking-satellite-reveals-first-stunning-views
  5. Kulp, S. A., & Strauss, B. H. (2019). New elevation data triple estimates of global vulnerability to sea-level rise and coastal flooding. Nature Communications, 10(1), 4844. https://doi.org/10.1038/s41467-019-12808-z
  6. Martin, S. A., Manucharyan, G. E., & Klein, P. (2023). Synthesizing Sea Surface Temperature and Satellite Altimetry Observations Using Deep Learning Improves the Accuracy and Resolution of Gridded Sea Surface Height Anomalies. Journal of Advances in Modeling Earth Systems, 15(5), e2022MS003589. https://doi.org/10.1029/2022MS003589
  7. Stanley, S. (2023, October 17). Machine Learning Provides a Clearer Window into Ocean Motion. Eos. http://eos.org/research-spotlights/machine-learning-provides-a-clearer-window-into-ocean-motion
  8. Xiao, Q., Balwada, D., Jones, C. S., Herrero-González, M., Smith, K. S., & Abernathey, R. (2023). Reconstruction of Surface Kinematics From Sea Surface Height Using Neural Networks. Journal of Advances in Modeling Earth Systems, 15(10), e2023MS003709. https://doi.org/10.1029/2023MS003709
  9. von Schuckmann, K., Palmer, M., Trenberth, K. et al. An imperative to monitor Earth’s energy imbalance. Nature Clim Change 6, 138–144 (2016). https://doi.org/10.1038/nclimate2876

Invasive Species: Ecological Shapeshifters?

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Watershed reeds of midcoast Maine provide a deeper look into the field of epigenetics

Forests, grasslands, and marshes are ecological battlegrounds. In the fight to hold territory, maintain access to resources, and reproduce, many organisms compete directly to occupy the same niche– the role played by a specific organism in an ecosystem. An organism’s ability to carry out these roles is dictated by its “fitness” or capacity to survive and contribute its genes to the next generation. Naturally, relative reproductive success is incredibly environmentally dependent. Most organisms are tailor-made to thrive within their native habitats via natural selection. However, this biological narrative is challenged by the proliferation of invasive species in competition with their native counterparts. In their 2016 study, Spens and Douhovnikoff argue that epigenetics may be key to understanding ecological invasiveness and that the common reed (Phragmites australis) is “an ideal model species” (Spens & Douhovnikoff, 2016) for studying this rapidly expanding subfield of genetics.

Among other things, greater phenotypic plasticity, or “the ability of individual genotypes to produce different phenotypes when exposed to different environmental conditions” (Fusco & Minelli, 2010), increases an organism’s potential to adjust to its surroundings and occupy a vast variety of niches. This becomes possible through epigenetics.  Epigenetic modifications alter gene expression without changing the underlying DNA sequence (Weinhold, 2006). Methylation, the process by which methyl groups are added to DNA, is the key turning genes “on” and “off” (Menezo et al., 2020). The addition of methyl groups prevents DNA-transcribing proteins from accessing the DNA strand, stopping the gene’s expression as a protein. This has the potential to create significant differences in structural and even cellular function among individuals that are otherwise genetically identical.

Clonal plants provide a unique opportunity to study environmental pressures on epigenetics, as these individuals can act as their own genetic control. Reeds are an excellent example of this: as facultatively clonal plants, they can utilize both sexual and asexual reproduction. Exploiting this integral feature, and the existence of multiple subspecies of reed in midcoast Maine, researchers studied the genomes of both native and invasive reeds in two separate locations, Libby and Webhannet. They addressed two questions: Do introduced subspecies exhibit greater epigenetic variation (indicating that epigenetics plays a role in the success of an invasive species)? And will the variation between subspecies genotypes be lesser than the variation within a single genotype’s epigenetic markers (suggesting that epigenetic variation can be used to adapt to an incredibly variable environment)?

Researchers sought answers by studying clusters of reeds called ramets. Since all the reeds within a ramet were genetically identical, they could selectively measure epigenetic variation. These clones were grown within heterogeneous microhabitats that contain varying combinations of nutrients and conditions. Extracted DNA fragments were compared based on the level of methylation among subspecies, genotype, and ramet.

In both sites, the invasive reed demonstrated greater epigenetic diversity than the native reed (Figure 1). Up to 71% of epigenetic variation at the Webhannet site is attributed to differences among genotypes. These results suggest that clones adjust to the demands of their environments via epigenetics, rather than genotypic adaptation. Flexibility of this kind allows for rapid specialization in response to the hyper-individualized environmental conditions of each ramet. Additionally, each site developed an epigenetic “signature” with both subspecies exhibiting distinct, location specific, morphological characteristics. The significant differences in epigenetic markers between sites hint at the potential for large scale shifts due to epigenetics, should genotype not be a factor in these differences. The distinct characteristics displayed by each species demonstrate the vast alterations necessary to survive in an environment with subtle differences.

Figure 1. Epigenetic markers clustered by species (native, introduced) and location (Libby, Webhannet). Differences within a single genotype were greater than variation between genotypes, particularly for the introduced species. Figure adapted from Spens and Douhovnikoff

While this study was small scale, it supports the position that epigenotype variation provides a strong competitive advantage in the natural world. It also suggests that further study would provide more valuable information about the relevance of epigenetics in ecology. In our rapidly changing environment, due to climate change and other human influences, these native genotypes are in danger of being displaced from their niches. Despite a species’ history with its habitat, subtle alterations can have vast impact on individuals that demonstrate low plasticity or tolerance for change. Introduced organisms who demonstrate more flexible epigenotypes have the potential to outcompete their neighbors, eroding local ecosystems beyond repair. This reality drives ecological research in the direction of epigenetics, not only for the sake of discovery, but also in hopes of protecting species who cannot adapt as quickly as we disrupt.

 

Works Cited

Fusco, G., & Minelli, A. (2010). Phenotypic plasticity in development and evolution: Facts and concepts. Philosophical Transactions of the Royal Society B: Biological Sciences, 365(1540), 547–556. https://doi.org/10.1098/rstb.2009.0267

Menezo, Y., Clement, P., Clement, A., & Elder, K. (2020). Methylation: An Ineluctable Biochemical and Physiological Process Essential to the Transmission of Life. International Journal of Molecular Sciences, 21(23), 9311. https://doi.org/10.3390/ijms21239311

Spens, A., & Douhovnikoff, V. (2016). Epigenetic variation within Phragmites australis among lineages, genotypes, and ramets. Springer International Publishing. https://link.springer.com/article/10.1007/s10530-016-1223

Weinhold, B. (2006). Epigenetics: The Science of Change. Environmental Health Perspectives, 114(3), A160–A167.

Atlantic on the Brink: Climate Change Impacts to a Critical Ocean Circulation System

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Global warming due to anthropogenic greenhouse gas emissions poses an immense threat to Earth’s oceans, which serve as a vital climate regulation system. The influx of large quantities of freshwater from melting Arctic sea ice has the potential to critically alter ocean circulation in the North Atlantic. Changes to the physical properties of seawater in the North Atlantic could eventually lead to the collapse of the Atlantic Meridional Overturning Circulation (AMOC), an event that would result in potentially catastrophic changes to climate in the Northern Hemisphere. Predictive climate models have noted that this shift could occur in the future, developing a series of warnings that could help understand more accurately when this major climate shift could occur. Writing in Science Advances, Van Westen and colleagues report the findings of the Community Earth System Model (CESM) and their predictions regarding the impacts of the AMOC’s collapse.

Figure 1: A visualization of the Atlantic Meridional Overturning Circulation (Adapted from “The Ocean Conveyor – Woods Hole Oceanographic Institution,” n.d.).

The AMOC is a “tipping element” of Earth’s climate, meaning that it is very sensitive to changes in salinity and temperature and could have substantial, reverberating climate impacts if disrupted (Armstrong et al., 2022). Since 1950, oceanographic and climate data have displayed that AMOC strength has significantly decreased and is potentially in its weakest state over the past thousand years (Caesar et al., 2021). These changes largely result from an increased freshwater flux into the North Atlantic due to high rates of Arctic sea ice melting as a product of anthropogenic climate warming. This methodical increase in freshwater flux into the North Atlantic could eventually lead to the collapse of this critical ocean circulation system, an event that would have severe impacts on temperature and weather patterns, especially in the Northern Hemisphere. Prior predictive climate models, which fail to encapsulate Earth climate systems as accurately as the model used by Van Westen and colleagues, have not yet modeled an AMOC collapse. Van Westen et al.’s 2024 study is the first to definitively model this crucial climate tipping point.

Van Westen and colleagues performed their study in CESM version 1.0.5, a complex climate model that simulates earth systems (Danabasoglu et al., 2020). The research team set a preindustrial control simulation with corresponding earth and ocean system conditions at model year 0. To model sea ice melt, they added a methodical, yet variable freshwater flux from the Arctic into the North Atlantic which was increased linearly through model year 2200. This gradual increase in freshwater flux into the North Atlantic corresponded to a gradual decrease in AMOC strength, consistent with predictions made by the research team. AMOC strength began diminishing in model year 800 and abruptly collapsed in model year 1758. This collapse represented a five-fold decrease in AMOC strength over the course of a century from model years 1750 to 1850, a shockingly abrupt change given the slow, consistent freshwater flux into the North Atlantic. By model year 2000, northward heat transport by the AMOC in the Atlantic decreased to nearly zero.

Figure 2: AMOC strength at 1000m depth and 26° N latitude. Yellow band shows the range of previously observed AMOC strength (Adapted from Van Westen et al., 2024).

Researchers found influential and dynamic changes to physical properties in oceans across the globe with AMOC collapse. Sea surface temperatures (SST) in the Northern Hemisphere after AMOC collapse significantly cooled, with differences as large as 10℃ observed off the coast of western Europe. SSTs increased slightly in the Southern Hemisphere due to the near absence of northward heat transport by the AMOC. Dramatic shifts in salinity in the upper 100 meters of the ocean were observed in addition to the complete interruption of deep ocean convection in the North Atlantic. Sea-level also rose nearly 70 cm in some regions of the coastal Atlantic due to AMOC collapse.

Researchers also investigated potential effects of AMOC collapse on climate and sea-ice extent in both the Northern and Southern Hemispheres. Significant changes to Hadley Cell air circulation and the subtropical jet stream were observed. Sea ice coverage in the Arctic extended to 50°N in the Arctic (current sea ice rarely forms below 60°N), while Antarctic sea-ice retreated. Model outputs showed atmospheric temperature decreases by around 3℃ per decade in the Northern Hemisphere, a rate at which human adaptation efforts would be largely impossible (current rates of temperature increase due to anthropogenic climate warming are ~0.2℃). These temperature shifts were amplified by ice-albedo feedback, where increased ice coverage in the Northern Hemisphere after AMOC collapse reflects a larger amount of solar radiation back into space, reducing atmospheric temperatures further. Additionally, precipitation patterns in tropical regions shifted with a slight increase in atmospheric temperature in the Southern Hemisphere after AMOC tipping. These results explicitly demonstrate that AMOC tipping would have dramatic, cascading climate impacts across the globe.

Van Westen and colleagues’ study was also the first of its kind to develop a comprehensive warning system for AMOC collapse based on historical climate and oceanographic data and model predictions. Observation of freshwater transport at 34°S, an important proxy for AMOC strength, and the identification of a minimum value for freshwater transport at which AMOC collapse could occur are essential characteristics of AMOC tipping that Van Westen and colleagues identified. These markers of AMOC strength provide an observable set of characteristics that could help predict AMOC collapse in real life.

This research is especially unique because it provides a definitive, model-based answer to the question of whether AMOC collapse can occur in climate models. Prior researchers assumed that AMOC tipping was highly theoretical and would not be predicted in a model that accurately accounts for complicated elements of climate systems. Van Westen and colleagues’ findings clearly demonstrate that AMOC tipping is not only possible, but highly likely under sufficient freshwater influx due to melting Arctic ice.

While the simulation performed by Van Westen et al. (2024) represents an effective predictor of major changes in Atlantic circulation, more data is needed to optimize predictive climate models and apply findings to real climate systems. Van Westen’s research team was unable to provide a meaningful estimate of when an actual AMOC tipping event could occur due to uncertainties in the rate and effects of future climate change. In a paper examining crucial climate tipping points, another European research team estimated that AMOC collapse could occur anywhere from 15-300 years from now, with researchers agreeing that collapse may most likely occur 50 years from now (Armstrong et al., 2022). Another study by researchers from the University of Copenhagen predicted with 95% confidence that tipping may occur from 2025-2095 (Ditlevsen & Ditlevsen, 2023). Precise monitoring of the physical changes in the North Atlantic and stringent data collection are essential to develop more accurate predictions of when AMOC collapse could occur in real life.

This research by Van Westen and colleagues shows evidence that the AMOC could reach a tipping point due to freshwater transport, temperature changes, and salinity changes in the Atlantic, leading to catastrophic climate impacts across the globe, especially in the Northern Hemisphere. Predictive models of major climate events are instrumental in helping communicate the severity of anthropogenic climate change and should be utilized by scientists, policymakers, and advocates throughout the transition away from our reliance on high emission fossil fuel combustion.

References:

Armstrong McKay, D. I., Staal, A., Abrams, J. F., Winkelmann, R., Sakschewski, B., Loriani, S., Fetzer, I., Cornell, S. E., Rockström, J., & Lenton, T. M. (2022). Exceeding 1.5°C global warming could trigger multiple climate tipping points. Science, 377(6611), eabn7950. https://doi.org/10.1126/science.abn7950

Caesar, L., McCarthy, G. D., Thornalley, D. J. R., Cahill, N., & Rahmstorf, S. (2021). Current Atlantic Meridional Overturning Circulation weakest in last millennium. Nature Geoscience, 14(3), 118–120. https://doi.org/10.1038/s41561-021-00699-z

Danabasoglu, G., Lamarque, J.-F., Bacmeister, J., Bailey, D. A., DuVivier, A. K., Edwards, J., Emmons, L. K., Fasullo, J., Garcia, R., Gettelman, A., Hannay, C., Holland, M. M., Large, G., Lauritzen, P. H., Lawrence, D. M., Lenaerts, J. T. M., Lindsay, K., Lipscomb, W. H., Mills, M. J., … Strand, W. G. (2020). The Community Earth System Model Version 2 (CESM2). Journal of Advances in Modeling Earth Systems, 12(2), e2019MS001916. https://doi.org/10.1029/2019MS001916

Ditlevsen, P., & Ditlevsen, S. (2023). Warning of a forthcoming collapse of the Atlantic meridional overturning circulation. Nature Communications, 14(1), 4254. https://doi.org/10.1038/s41467-023-39810-w

The Ocean Conveyor—Woods Hole Oceanographic Institution. (n.d.). https://www.whoi.edu/. Retrieved April 21, 2024, from https://www.whoi.edu/knowyourocean/oceantopics/how-the-ocean-works/ocean-circulation/the-ocean-conveyor/

Van Westen, R. M., Kliphuis, M., & Dijkstra, H. A. (2024). Physics-based early warning signal shows that AMOC is on tipping course. Science Advances, 10(6), eadk1189. https://doi.org/10.1126/sciadv.adk1189

S. glomerata show resistance to the negative effects of ocean acidification on marine microbes

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As more CO2 enters the ocean, the water’s pH and temperature change in processes called ocean warming and acidification. Both processes pose a risk to marine microbes, as they are unaccustomed to their new, more acidic environment. Several marine species depend on the microbes that dwell in the ocean, and if the change in pH negatively impacts the oceanic microbiome, there would be negative implications for a large number of organisms.

Microbes are essential to the development of many species in the world’s oceans. They are able to activate genes, sculpt the bodies of multicellular organisms, and provide vital life information to juvenile species (Yong 2016). But these abilities may be disrupted if the ocean’s change in pH negatively affects the microbiomes both in the water and living within ocean creatures.

Dr. Elliot Scanes and his colleagues at the University of Technology Sydney evaluated the effects of ocean acidification on the Sydney rock oysters’ (S. glomerata) ability to transfer its microbiome down to its offspring during reproduction. Oysters reproduce via broadcast spawning, a process in which sedentary organisms release all of their eggs and sperm into the surrounding water in hopes that a portion of the gonads will be fertilized (Bondar, 2018). Because these broadcasted embryos are now exposing their microbiomes to warmer, more acidic environments than the microbiomes of previous generations have been accustomed to, the microbes living within these embryos are not well adapted to the new conditions. This poorly equipped microbiome is causing fewer and fewer embryos to develop properly. An oyster’s microbiome is a necessary part of its body, and without it, a juvenile oyster may not be able to develop and function as effectively (Scanes et al. 2023).

Scanes set out to examine whether exposure to ocean warming and acidification during both broadcast spawning and early reproduction would alter an oyster’s microbiome strength.

The lab team acclimated these oysters to the lab tanks and then harvested their eggs and sperm, later fertilizing them (Figure 1.) (Scanes et al. 2023). Half of the oyster embryos were raised in tanks with a normal pH, and the other half were raised in tanks with decreased pH to mimic ocean acidification. The team conditioned both sets of S. glomerata for reproduction, then used eggs and sperm from each set to breed the next generation of oysters. The next generation was divided into four groups: first, the oyster embryos collected in tanks with a normal pH were split into two groups, with one group being raised in another tank with a normal pH and the other being raised in a tank with a low pH that mimics ocean acidification. Then, the oyster embryos collected in tanks with a low pH were also split into two groups, with one group being raised in another tank with a low pH

Figure 1. Scanes et al. depicts their experimental design. The PCO2 that appears in several of the diagram labels means partial pressure of carbon dioxide, which is a term used to describe how much carbon dioxide exists within a system (Messina 2022). Ambient PCO2 means normal pH. Elevated PCO2 means acidic water.

and the other being raised in a tank with a normal pH.

The embryos produced from these four sets of oysters informed Scanes et al. of the physiological differences that occur between oyster microbiomes that are exposed to ocean acidification at different steps in the reproductive process. The team found significant alteration of the microbiome in the parent oysters exposed to ocean acidification and concluded that when oyster parents were exposed, more oyster embryo microbiomes were prepared for the new conditions, and so the more protected oyster embryos survived (Scanes et al. 2023). This information is of much consequence because it provides a baseline for studying other microbe–sea creature relationships in the future. The marine microbiome plays a critical role in the development and wellbeing of animals like the Hawaiian bobtail squid and the Hydroides elegans, otherwise known as the “squiggly worm,” who depend on them for gene activation and information on safe places to live, respectively (Yong 2016). Now that there is evidence that the changing conditions of ocean water harms microbes, and therefore harms the creatures that depend on them, as well as evidence that exposure to these conditions protects the microbes in future generations, scientists are better informed about how to protect marine species moving forward.

Literature Cited

Bondar C. Wild Moms. 2018.

Messina Z et al. Partial Pressure of Carbon Dioxide. National Library of Medicine. 2022.

Scanes E et al. Transgenerational transfer of the microbiome is altered by ocean acidification in oyster larvae. Aquaculture. 2023.

Yong E. Body Builders. I Contain Multitudes: The Microbes Within Us and a Grander View of Life. 2016. 49-59.

SMART Conservation Software aids wildlife management teams in conservation efforts

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Those who work in the field of wildlife management aim to protect the biodiversity of ecosystems, which is critical in maintaining the health of the environment. But wildlife management workers around the world frequently experience serious challenges such as poaching, logging, illegal farming, forest fires, and insufficient resources. For example, poachers use snare loops (wire traps that tighten around the necks of animals) to catch protected species. In 2014, tiger poachers in the Sundarbans Reserved Forest of Bangladesh placed thousands of these snare loops across the entire reserve, in locations too far from guard posts to be monitored full time (Abdul Aziz et al., 2017). In most conservation groups, there are not enough funds, employees, or volunteers to efficiently manage wildlife and simultaneously prevent poachers from killing protected animals. Thus, wildlife management teams are calling for improved tools that will better protect endangered animals from further harm.

Figure 1. Snare loop around a lion’s neck. Loops can tighten around any part of the body, holding the animal in place until poachers arrive or weakening it until it dies of its injuries.

Companies such as SMART, Re:Wild, and the World Wildlife Fund developed SMART Conservation Software in 2011 to better support wildlife conservation groups. SMART is short for Spatial Monitoring and Reporting Tool, and it is a digital platform capable of collecting and evaluating data on wildlife management sites. Workers within the same management system can input data as they come across new information, allowing the platform to record what they find in real time like where animals are mating, as well as where and when poacher traps are found (https://smartconservationtools.org/). Using these inputs, SMART plots a management team’s efforts, impacts, and shortcomings over time, highlighting areas that need improvement. Once those improvements are made, management groups are better able to conserve biodiversity, enforce the law, encourage and oversee tourism, and use natural resources properly.

Figure 2. Wildlife management employees use SMART device to log important conservation information.

Companies such as SMART, Re:Wild, and the World Wildlife Fund developed SMART Conservation Software in 2011 to better support wildlife conservation groups. SMART is short for Spatial Monitoring and Reporting Tool, and it is a digital platform capable of collecting and evaluating data on wildlife management sites. Workers within the same management system can input data as they come across new information, allowing the platform to record what they find in real time like where animals are mating, as well as where and when poacher traps are found (https://smartconservationtools.org/). Using these inputs, SMART plots a management team’s efforts, impacts, and shortcomings over time, highlighting areas that need improvement. Once those improvements are made, management groups are better able to conserve biodiversity, enforce the law, encourage and oversee tourism, and use natural resources properly.

SMART is used by conservation organizations around the world, one example being the Chirripó National Park in the Talamanca Mountain Range of Costa Rica. For years, the Chirripó management team had been struggling to precisely locate and record the illegal activities taking place on protected land, making it impossible to remove offenders or convince authorities that their ongoing complaints were valid (Madrigal). But SMART software can be downloaded on personal devices, so when the park introduced SMART to their employees and surrounding members of the community, citizens who were not involved in full-time park conservation were still able to contribute (Madrigal). This added many more eyes, ears, and hands to the conservation effort, and within one year, Chirripó was able to report the exact dates and locations of 44 cases of illegal activity across the park to law enforcement (Madrigal). Once law enforcement gained access to this concrete information, they were able to operate efficiently, driving down the crime rate. More importantly to Chirripó National Park, the added coverage helped protected species such as the Baird’s tapir, the spider monkey, the puma, the agouti, and the jaguar (Madrigal). Chirripó’s experience with SMART demonstrates how useful this technology is for organizing and communicating the issues conservationists face on a daily basis.

Figure 3. SMART conservation software helps Chirripó National Park to protect animals like the Baird’s tapir pictured above.

Like most technology, SMART software is exciting, innovative, and solves modern day problems – but it also comes with some challenges. The Zimbabwe Parks and Wildlife Management Authority (ZPWMA), an organization that works to protect lions, elephants, leopards, and buffalo across all of Zimbabwe, points out that implementing SMART conservation technology can present capacity and resource issues for conservation management employees (Kavhu et al, 2021). Many workers were unfamiliar and uncomfortable with the technology, there were not enough electronic devices such as computers to collect all field data, and many of the patrol routes were without internet access (Kavhu et al, 2021). While it is possible that technological innovation is not a priority for Zimbabwe, it is also important to remember that Zimbabwe’s history is one marred by British colonialism, and the country only gained its independence in the late 1970’s (Ingham et al., 2023). These setbacks help to explain why Zimbabwe has been unable to progress as in the world of electronic technology, even if the progress is desired. These issues of technological access can be applied to other countries that do not yet have a strong electronic infrastructure, meaning that SMART works best in more electronically informed countries and falls short in countries that have not expanded their electronic bandwidth.

Figure 4. Parks in Zimbabwe aim to protect their buffalo populations.

There are some solutions to these technological problems. For example, building a strong implementation plan, motivating the discouraged workers, following the example of other institutions that have implemented SMART technology, and, most importantly, raising funds to buy more computers would make the use of SMART technology easier in Zimbabwe parks (Kavhu et al, 2021). Adding more volunteers to the conservation effort is also a great solution. If ZPWMA advertised volunteer opportunities in their communities using layperson terms, supporters of the conservation effort would be more likely to help manage the wildlife in Zimbabwe’s parks. Of course, volunteers would need to be trained so that they are able to properly identify notable occurrences in the parks, but their contributions have the potential to greatly strengthen the conservation effort.

SMART Conservation Software is off to a great start in helping to better manage parks around the world. Though SMART does find its faults in countries unaccustomed to the devices needed for software implementation, this problem will only grow smaller as the world continues to progress in the realm of personal electronic devices (given that countries like Zimbabwe want to prioritize electronic familiarity moving forward). Its ability to collect, organize, and present data across long distances and multiple devices allows wildlife management teams to care for protected species much more efficiently, making SMART a tool that revolutionizes the realm of conservation.

Works Cited

Abdul Aziz, M. et al. Investigating patterns of tiger and prey poaching in the Bangladesh Sundarbans: Implications for improved management. ScienceDirect, vol. 9, 2017, pp. 70-81.

Barrantes Madrigal, Jimmy. “Community-based SMART patrolling in one of the Great Five Forests of Mesoamerica: the Talamanca Highlands.” SMART, https://smartconservationtools.org/en-us/SMART-Community/Your-stories/Case-Study?CaseStudyID=27.

Ingham, Kenneth, et al. “History of Zimbabwe”. Encyclopedia Britannica, 12 Dec. 2023, https://www.britannica.com/topic/history-of-Zimbabwe. 

Jones, J.J.. “Snared Lioness in Kruger National Park.” Wildestofficial.com, 20 September 2019, https://wildestofficial.com/news/snare-poaching-increasing-in-kruger-national-park/.

Kavhu, Blessing, et al. Spatial Monitoring and Reporting Tool (SMART) in Mid‐Zambezi Valley, Zimbabwe: Implementation challenges and practices. ProQuest, vol. 3, 2021.

San Diego Zoo. Baby Baird’s Tapir. animals.SandiegoZoo.com, https://animals.sandiegozoo.org/animals/tapir.

Slade, James. Conservationists operating SMART device. Smartconservationtools.com, https://smartconservationtools.org/en-us/SMART-in-Practice/How-we-use-SMART. 

SMART. “About Us.” SMART, https://smartconservationtools.org/en-us/About/About-us. The Great Projects. Buffalo in Zimbabwe. thegreatprojects.com, https://www.thegreatprojects.com/volunteer-in-zimbabwe.

Chernobyl Wolves Living with Cancer

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A peculiar phenomenon is occurring in Chernobyl, Ukraine. It has been a ghost town since the nuclear accident in 1986, and radiation levels are too high for humans to live safely. When the accident occurred, it released over 100,000 lbs of radioactive material into the atmosphere which was dispersed across Europe and the USSR. Over 100,000 people were evacuated from over 200 villages. An exclusion zone with a 30 km radius was created to protect humans from the radiation that still remains (NPR, 2024). The level of radiation varies within the CEZ because wind and rain spread the radiation when the accident occurred. Wolves are in a unique position as the apex predators– they encounter radiation exposure at every level of the food chain. From a contaminated deer eating contaminated grass, wolves are one of the most radiation-exposed animals in the CEZ. The wolves in the CEZ are exposed to much higher levels of radiation than are considered safe for humans. For humans, the annual limit is 1 mGy, but for wolves, they are exposed to 2.6-35.7 mGy on a daily basis (MIT News, 1994). Despite this high level of radiation, the wildlife is thriving, filled with elk, deer, boar, and wolves. While radiation is typically thought of as a risk for developing cancer, the Chernobyl grey wolf population is thriving in tandem with this disease, developing a population that is nearly seven times as dense as surrounding wolf populations. Puzzled by their strange ability to survive in these harsh conditions, researchers set out to determine what was going on. Scientists measured nine wolves’ movement and radiation levels within the CEZ through a GPS containment-monitor for six months. They found that the level of radiation varied depending on where the wolves were within the CEZ (Hinton et al., 2019). Although the level of contamination varies, these high levels of radiation may be enough to drive natural selection, helping wolves thrive in these harsh conditions (Love et. al, 2020). 

Scientists set out to uncover if the radiation from Chernobyl was enough to drive natural selection, allowing the population to evolve in such a way to protect it from radiation. Researchers analyzed the wolves’ fecal samples for parasites, took blood samples to sequence the full blood transcriptomes, a collection of mRNA transcripts, and muscle tissue samples. The study also looked at the blood cell composition of these wolves, to take a closer look at the immune cells, which are indicative of different types of stress or disease (Love et. al, 2020). The study compared CEZ wolves to those in Belarus, outside of the CEZ, and to wolves in Yellowstone National Park (NPR, 2024). They found that some of the fastest-evolving genes “have some role in cancer immune response or the anti-tumor response in mammals” (NPR, 2024). These genes are called Endogenous Retroviruses, or ERVs, which are associated with neurological, autoimmune, and oncogenic diseases in humans. Not much is known about these cells, including what exactly triggers their activation and what regulates them. What scientists do know is that not all ERVs are bad– helpful ERVs can help stimulate a retroviral immune response which helps spur tumor cell death. Scientists believe that environmental stimuli, like radiation exposure, likely influences ERV activation; however, more research still needs to be done. Wolves in the CEZ have higher levels of ERV expression, indicating that there are divergent ERV regulatory patterns between wolves that are exposed and unexposed to radiation. While scientists must learn more about ERVs and their effect in wolves, more research is needed on the effects of radiation contamination in the environment and what is driving cancer development in radiation-contaminated habitats (Love et. al, 2020).

Although there is evidence of a genetic component of wolves being resistant to cancer, there is another important factor to keep in mind– human presence. Humans have largely been absent from the CEZ for nearly forty years, so wolves are free from the pressures humans bring. For instance, perhaps for wolves the pressure from hunting is so that it may be better than having to deal with cancer. Essentially, hunting may pose a bigger threat to wolves than cancer. Other human-related pressures these wolves do not face are land, pollution, human disease, and more. However, more research must be done to fully understand all the pressures these wolves are under. While research in the CEZ has been halted because of the war in Ukraine, the wolf population is likely thriving because of a genetic component and from no human pressures (NPR, 2024). 

Researchers hope to return to the region to find and identify these cancer-resilient genes which could inform human cancer treatments. Although their research is paused, the Chernobyl wolf population is a remarkable feat of perseverance and resilience. 

Figure 1. A gray wolf in the Chernobyl Exclusion Zone. (Chernobyl’s Mutant Wolves Have Evolved Anti-Cancer Abilities | IFLScience, n.d.)

Literature Cited

Chernobyl’s Mutant Wolves Have Evolved Anti-Cancer Abilities | IFLScience. (n.d.). Retrieved April 21, 2024, from https://www.iflscience.com/chernobyls-mutant-wolves-have-evolved-anti-cancer-abilities-72831

Hinton, T. G., Byrne, M. E., Webster, S. C., Love, C. N., Broggio, D., Trompier, F., Shamovich, D., Horloogin, S., Lance, S. L., Brown, J., Dowdall, M., & Beasley, J. C. (2019). GPS-coupled contaminant monitors on free-ranging Chernobyl wolves challenge a fundamental assumption in exposure assessments. Environment International, 133, 105152. https://doi.org/10.1016/j.envint.2019.105152

Love et. al (2020). Long-term Implications of Chronic Radiation Exposure: A Genomics Study of Two Canids Reveals Evolutionary and Ecological Impacts of a Nuclear Disaster – ProQuest. (n.d.). Retrieved April 21, 2024, from https://www.proquest.com/openview/f5f17943e75ddda6f147cd66201a344b/1?cbl=18750&diss=y&pq-origsite=gscholar&parentSessionId=Rfd%2FKuzxeAQaOHLv1Bl3gFx7bPxf1AU%2BWGySS9I3SGg%3D

MIT News (1994, January 5). MIT News | Massachusetts Institute of Technology. https://news.mit.edu/1994/safe-0105

NPR: Short Wave. (2024, February 5). NPR. https://www.npr.org/2024/02/05/1198909263/cancer-wolves-ukraine-chernobyl-radiation

The Melting Arctic’s Impact on the Gulf of Maine

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Recent observation and nutrient analysis in the Gulf of Maine has found that within the past 50 years nutrient sources have become more limited, impacting the entire ecosystem. The Gulf of Maine receives nutrient-rich waters from the continental slope that enters through the Northeast Channel, north of Georges Bank (figure 1). These continental slope waters originate off southern Newfoundland and travel into the Gulf of Maine passing by Labrador and the Scotian Shelf, all the while accumulating and retaining its high concentration of nutrients. Nutrients from this water source, such as nitrate and silicate that exist in excess within continental slope water, make the Gulf of Maine a highly productive area. Nitrate is of particular interest as it is often the limiting nutrient. In other words, nitrate is often scarce in an ecosystem and therefore is the nutrient that puts a cap on the accumulation of biomass such as phytoplankton. However, recent observation and nutrient analysis in the Gulf of Maine has found that within the past 50 years nutrient sources have become more limited, impacting the entire ecosystem.  

              Figure 1. Map of Gulf of Maine

Since the 1970s, studies have shown a notable decrease in the abundance of nitrate in the Gulf of Maine. Along with this change, the deep waters in the Gulf of Maine have become cooler and less salty. In 2010, Townsend et al suggested  that these changes all originate from the accelerating melting of ice in the Arctic. Since salt does not freeze, when water freezes in the Arctic, the ice it forms is made of freshwater. As this freshwater melts at a faster rate than the Earth has previously seen, it changes the salinity of the water, making it fresher and therefore less dense. Deep ocean circulation is based on density and so with this change in density, comes a change in the way water circulates the planet. 

Given the changes in densities of water in the Arctic, a new source of water from the bottom of the Atlantic ocean carrying far less nutrients now supplies the Gulf of Maine.  With the changes in deep ocean circulation patterns, now water entering the Gulf of Maine passes closer to the bottom of the ocean. As this water passes the ocean floor, microbes in the sediment remove nitrogen from the water (for use as a nutrient), a process called denitrification. While this benefits ecosystems at the bottom of the deep ocean, by the time the water reaches the Gulf of Maine, much of the nitrate in the water has already been used. 

The Gulf of Maine will become less productive as ecosystems are supplied with low concentrations of nitrate for long periods of time. Phytoplankton, the first step of the food web, absorb these nutrients and use them for growth. Once phytoplankton are less abundant, animals that rely on them for food will begin to struggle. As nitrogen deficiency continues up the food chain, it will eventually reach the larger fish upon which we in Maine rely on for our food. The gradual loss of nitrogen rich waters to the Gulf of Maine is not only a sad reminder of climate change’s far reaching consequences, but also presents a growing issue for the fishing industry in Maine which relies on the productivity of the water. 

 

 

Work Cited

Townsend, D. W., Pettigrew, N. R., Thomas, M. A., Neary, M. G., McGillicuddy, D. J., & O’Donnell, J. (2015). Water masses and nutrient sources to the Gulf of Maine. Journal of Marine Research, 73(3), 93–122. doi:10.1357/002224015815848811