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Nature’s tiny heroes: how bacteria can devour plastic pollution in our oceans

Hannah McGrath

By Hannah McGrath, MLML Biological Oceanography Lab

Plastic pollution continues to be a growing issue on our planet, especially for our oceans. The global pandemic only contributed to our growing plastic problem. During the height of the pandemic, I remember walking along Riverside Park in New York City to escape my tiny apartment; the sidewalks and shorelines were littered with KN95 masks and light blue latex gloves. As I continued my walks throughout the pandemic, the sight of personal protective equipment scattered across the city became the norm. According to lead researcher Dr. Patrício Silva at the University of Aveiro, the pandemic dramatically increased the amount of plastic medical waste that has entered our aquatic systems. These plastics can then degrade into microplastics (< 5 mm in size) through physical, chemical, and biological processes which can have adverse effects on ecological and human health.

Although microplastics are small in size, they have a disproportionate effect on the environment. For instance, zooplankton which are important players in our ocean food webs and the biological carbon pump, a process that exports carbon to the deep sea, are threatened by microplastics. Zooplankton are able to consume microplastics which can damage their intestinal tracts, alter gene expression, delay growth, and impact feeding behavior resulting in decreased reproductive abilities according to lead scientist Dr. Meiting He at the College of Marine Sciences, South China Agricultural University. Unsurprisingly, microplastics have been identified in the gut content of organisms’ at almost all trophic levels from zooplankton to humans. Microplastics are in the clothing we wear, seafood we consume, beauty products we use, and more. In fact, in a 2019 study lead author Kieran Cox, a PhD candidate at the University of Victoria, estimated that ~39,000-52,000 pieces of microplastic are ingested by humans annually!

Illustration of microplastics (MPs) entering aquatic systems and being consumed by zooplankton resulting in the trophic-transfer of MPs up the food chain (He et al 2022). 

Not only is plastic pollution increasing but so is our need to adopt effective and sustainable ways for disposing plastics at a large scale. Current methods for plastic disposal are mismanaged and unsustainable. One common way to dispose of plastic is by incineration. However, during incineration plastics release carcinogens, dioxins, furans, heavy metals and sulfides into the environment states researchers Dr. Aubrey Chigwada and Dr. Memory Tekere at the University of South Africa. Another common method is dumping plastic waste into landfills but this causes plastic overflow affecting the biodiversity of the region. In addition, landfills store not only plastic waste but all types of waste that can decompose. During decomposition processes the potent greenhouse gas, methane, is released into the atmosphere which contributes to climate change. These landfills can also leak which can contaminate nearby groundwaters. Although recycling may seem like a promising way to dispose of plastics, at large scales it is too expensive and not feasible.

A more sustainable method to dispose of plastic is using microorganisms like bacteria that can biodegrade plastics. The first study that investigated microplastic degradation by microorganisms was Dr. Cacciari and his colleagues from the University of Tuscia in 1993. The researchers used the bacteria Pseudomonas and Vibrio to degrade polypropylene. Since 1993, many researchers have studied biodegradation of various plastics using bacteria from around the globe. Bacteria naturally exist in various environments from cow dung to human eyelashes to hot springs to polar ice caps making them suitable candidates for degrading microplastics. For instance, lead author Jun Yang at Beihang University, Beijing found two bacterial strains isolated from the gut of Indian mealmoths that were able to consume the plastic polyethylene.

Image of the two bacterial strains, Enterobacter asburiae and Bacillus sp. isolated from the gut of Indian meal moths (Yang et al. 2014).

Not only can bacteria naturally degrade plastics, but they can also be geoengineered to remove plastic from our oceans. Bacteria may just be nature's tiny heroes to combat plastic pollution. Currently, Professor Song Lin Chua and his colleagues at the Hong Kong Polytechnic University (PolyU) have bioengineered the bacteria Pseudomonas aeruginosa to remove microplastics from the environment. The researchers plan to use the sticky nature of bacteria to create “tape-like microbe nets” to capture microplastics. These microbial nets filled with microplastics then sink to the bottom of the water column. The bacteria’s biofilm dispersal gene is then engineered to release these microplastics from the biofilm traps. The bulk microplastics then float to the surface and are recycled. These preliminary experiments have been successful but have not been conducted outside of a controlled setting.

 

Schematic illustration of the bioengineered bacteria, Pseudomonas aeruginosa, removing microplastics from the water column using the 'capture-and-release' method developed by researchers at Hong Kong Polytechnic University

Although scientists are developing innovative ways to remove plastics from our ocean, there have been concerns about using bacteria to do this. Engineering bacteria to break down plastics especially in hot spots like the Pacific Garbage patch may reduce plastic waste, but may also have unintended consequences. For instance, breaking down microplastics may increase microplastic ingestion by other marine organisms like zooplankton that are known to consume microplastics. Another drawback is that the bacteria aeruginosa, that was used in PolyU preliminary experiments, carries diseases for humans’ states Professor Chua. Researchers are still searching for a bacterium that could be engineered that is natural and safe to humans at a large scale. But I am hopeful that scientists will find a safe and suitable candidate since bacteria are extremely abundant in the ocean. For every 1 ml of seawater there are ~1 million bacteria!

The reality is plastic pollution in the ocean is rapidly increasing. It is imperative that we find a solution to our growing plastic pollution problem sooner than later. Bacteria may just be one solution to our global plastic problem. However, more research and experimentation are still needed to understand the true benefits and consequences of genetically engineering bacteria to remove plastic from our oceans. Will bacteria be able to solve our plastic pollution problem?

 

References

Cacciari, I., Quatrini, P., Zirletta, G., Mincione, E., Vinciguerra, V., Lupattelli, P., Giovannozzi Sermanni, G., 1993. Isotactic polypropylene biodegradation by a microbial community: physicochemical characterization of metabolites produced. Appl. Environ. Microbiol. 59, 3695–3700. https://doi.org/10.1128/aem.59.11.3695-3700.1993

Chigwada, A.D., Tekere, M., 2023. The plastic and microplastic waste menace and bacterial biodegradation for sustainable environmental clean-up a review. Environ. Res. 231, 116110. https://doi.org/10.1016/j.envres.2023.116110

Cox, K.D., Covernton, G.A., Davies, H.L., Dower, J.F., Juanes, F., Dudas, S.E., 2020. Correction to human consumption of microplastics. Environ. Sci. Technol. 54, 10974–10974. https://doi.org/10.1021/acs.est.0c04032

He, M., Yan, M., Chen, X., Wang, X., Gong, H., Wang, W., Wang, J., 2022. Bioavailability and toxicity of microplastics to zooplankton. Gondwana Res. 108, 120–126. https://doi.org/10.1016/j.gr.2021.07.021

Liu, S.Y., Leung, M.M.-L., Fang, J.K.-H., Chua, S.L., 2021. Engineering a microbial ‘trap and release’ mechanism for microplastics removal. Chem. Eng. J. 404, 127079. https://doi.org/10.1016/j.cej.2020.127079

Patrício Silva, A.L., Prata, J.C., Walker, T.R., Duarte, A.C., Ouyang, W., Barcelò, D., Rocha-Santos, T., 2021. Increased plastic pollution due to COVID-19 pandemic: Challenges and recommendations. Chem. Eng. J. 405, 126683. https://doi.org/10.1016/j.cej.2020.126683

Yang, J., Yang, Y., Wu, W.-M., Zhao, J., Jiang, L., 2014. Evidence of polyethylene biodegradation by bacterial strains from the guts of plastic-eating waxworms. Environ. Sci. Technol. 48, 13776–13784. https://doi.org/10.1021/es504038a

 

 

How long is that tail?

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By Jessica Jang

On Labor Day weekend, Moss Landing Marine Laboratories' own Pacific Shark Research Center (PSRC) had the opportunity to dissect a 14.7 feet long common thresher shark (Alopias vulpinus). The female shark was found washed up on the beach on Moss Landing already dead.

Program Director, Dave Ebert, PSRC students, and UROC students posing with the thresher shark
Program Director Dave Ebert, PSRC students, and Undergraduate Research Opportunities Center (UROC) students posing with the thresher shark

The PSRC is part of the National Shark Research Consortium for the West Coast. Currently there are 7 students enrolled in this department led by the program director, Dr. David Ebert, also a MLML alumni, and a handful of undergraduate volunteers from San Jose State University and California State University: Monterey Bay all who are ready to learn more about elasmobranchs!

The students were pretty amazed to see such small teeth on such a large shark. Thresher shark head The teeth on this animal say a lot about what it eats. Schooling fish such as sardines and anchovies, as well as cephalopods are its preferred prey. Thresher sharks are part of the mackerel shark order (Lamniformes) and excel at speed and long distances. A few examples of this order include, the white shark (Carcharodon carcharias), the makos, shorfin mako (Isurus oxyrinchus), longfin mako (Isurus paucus), the salmon shark (Lamna ditropis), and the porbeagle shark (Lamna nasus). These species in particular are endothermic, meaning that they can thermoregulate their own body temperature to several degrees warmer than the ocean water, allowing better foraging opportunities.

Large gills for breathing
Large gills for breathing

They also have big eyes to find prey and large gill slits for oxygen. Since these species are pelagic species, they require a lot of oxygen to keep moving. Lamniformes (mackeral sharks) breathe through ram ventilation, where the animal swims while opening its mouth. These species require constant motion or else they'll drown. However, some sharks have adapted to living life on the bottom, and can actively pump water pass their gills with their spiracles, which are tiny holes usually located behind the eyes on the shark. In larger oceanic species, the spiracles have lost its ability to pump water.

The dissection was a very exciting and rare opportunity, since thresher sharks are pelagic predatory fish, that spend their lives in the open ocean. There are currently only three known species of thresher sharks, the common (Alopias vulpinus), pelagic (Alopias pelagicus), and the big-eye thresher (Alopias superciliosus).

Previously it was thought that thresher sharks used to swing their tails around to catch their prey. However, a new study this summer show that they actually use their long caudal tails to stun their prey. Scientists managed to catch footage of the pelagic thresher shark (Alopias pelagicus) in action.

Students were able to take morphometric data of the shark by measuring everything from body length and fin lengths, counting the vertebrae, and noting of any visible scars or injuries.

Dave Ebert instructing PSRC students how to measure
Dave Ebert instructing PSRC students how to measure the shark

One noticeable wound was the large propeller strike that was near the end of her body.

Wound found on the shark, possibly from a propeller.
Wound found on the shark, possibly from a propeller.

They also took tissue samples of the shark's muscles, reproductive organs, and liver to detect mercury levels. Since sharks are apex predators, meaning they eat at top of the food chain, toxins and heavy metals can bioaccumulate which can cause detrimental health problems if they are in high concentrations. Stay tuned to see if we found something revealing on what may have caused her death.

Let the learning commence

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By Jackie Schwartzstein, Vertebrate Ecology Lab

When did you first become interested in science? Do you remember the first time you got excited about learning something new? In the wake of my first year of graduate school, I am practicing a little metacognition.

In the past few months I've been hearing and reading some interesting ideas about how we learn:

1. A TED talk about how to get out of the way and let students learn, unsupervised.  (Click the link and watch it!)

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Still from Mitra's TED talk

If you are reading this blog, you are already participating in a self-teaching, Internet-based learning opportunity. Sugata Mitra's talk proposes a system of teaching in communities where Internet cafes are not the norm, and undereducated youth lack the teachers they need. With his hole in the wall computer Mitra watched groups of students learn complicated scientific concepts in foreign languages, with no regular instructor or grade based incentive.  In concert with the new idea for world wide Internet distributed through weather balloons (see this site), could Mitra's inspiring concept be our future?

2. A research study popularized by my Facebook wall, about how cute baby animal pictures help you think. (Click the link to read for yourself!)

If these authors are right, you will be much more productive with your office work after reading this article. Pictures of baby animals helped study participants perform both fine motor and visual search tasks, "interpreted as the result of a narrowed attentional focus induced by the cuteness-triggered positive emotion that is associated with approach motivation and the tendency toward systematic processing".  Baby animal pictures improved task performance more than either adult animal pictures or photos of tasty food.  Remember to glance at this page again before you shut your computer in the evening and drive home - it will make you a better driver!

3. An article about how Americans are learning outside of the classroom.  (Click the link to read!)

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A learning opportunity outside of the classroom. Photo from the above article.

This article suggests a theory to explain why American students perform poorly in math and the sciences (during K-12), compared to the rest of the world.  It turns out that we might be learning more after we get out of school, bridging the gap later in life.  The authors suggest that we can continue to bridge gaps in our public science education by improving science learning outside of the classroom, during "the other 95%" of our lives.  The US has a good basis for this type of public education, with more natural history museums, aquariums, libraries, and science centers than most other developed countries.

"Insufficient data exist to conclusively demonstrate that free-choice science learning experiences currently contribute more to public understanding of science than in-school experiences, but a growing body of evidence points in this direction."

All in all, this seems to support what we are doing already at MLML. Students of marine science do a lot of their learning outside of school. Just look at our blog posts! Hands on field courses are what get us really excited here at MLML!  And we even get the chance to look at cute baby animals from time to time.

BabyPufferFish
Baby Puffer Fish. Photo from http://www.thecutereport.com/index.php/2007/09/06/baby-puffer-fish/

Hope your summer is full of exciting things to learn!

A Point Sur Adventure

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Marine Ecology students on the Point Sur cruise sort and record organisms from the Monterey Bay.

By Kristin Walovich

The Marine Ecology class embarked on a seafaring adventure last Monday on the Moss Landing research vessel the Point Sur to observe the biota of the Monterey Bay. The class was joined by members from the Monterey Bay Aquarium, MBARI and even Professor Emeritus Greg Cailliet who arrived bright and early for a 7am departure time.

After braving choppy water and a bit of rain we began our day with a beam trawl, designed to sample creatures from the ocean floor at 600 meters depth. Unfortunately we were left empty handed when the net returned to the surface with a hole caused from large rocks lodged in the net.

Despite our first strikeout, our second mid-water trawl yielded a wide array of fish, crustaceans, jellyfish, and a plethora of other gelatinous creatures. Once on board the Point Sur, each animal was classified into separate glass dishes and recorded, giving the students a chance to practice their species identification and exercise their Latin nomenclature.

The highlight of the trawl (quite literally) was a group of fish called the Myctophids, or Lanternfish. These fish have light emitting cells called photophores that help camouflage them in the deep ocean waters in which they live. Lanternfish regulate the photophores on their flanks and underside to match the ambient light levels from the surface, rendering them nearly invisible from predators below.

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Lanternfish emit light from cells called photophores that help camouflage them from predators.

The last tow of the day was called an otter trawl; but don’t worry, we didn’t catch any sea otters.  This net is name for the ‘otter’ boards positioned at the mouth of the net designed to keep it open as it travels thought the water. The animals are funneled to the back or ‘cod’ end of the net and are brought to the surface for the class to observe.  We saw several species of flatfish including the Sand Dab, Dover and English Sole, several dozen octopuses (or octopodes depending on your dictionary) and even a pacific electric ray.

After a long day of sunshine, high seas and amazing sea creatures the Marine Ecology students were excited with their discoveries, but also ready to be back on solid ground.

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6 am: Not Just For Sleeping Anymore

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By Alex Neu, CSUMB/UROC research assistant

Sunrise at Sunset Cliffs
Sunrise at Sunset Cliffs, San Diego

Like most kids growing up, I envisioned a scientist as someone sitting behind a microscope or  pouring colorful liquids into a flask to make some kind of potion. During my internship I have seen a variety of work researchers do every day and that stereotype certainly does not do them justice. An average day might include sitting behind a computer doing a literature review, taking water samples in the lab, extracting enzymes from specimens and going to a meeting based entirely on statistical analyses. These tasks have all been incredible learning experiences, but recently I got a taste of my new favorite activity in research: going into the field.

Seagull and coffee mug
We weren't the only ones in need of a pick-me-up for a 6 am collection

Our first day of collecting crustose coralline algae (CCA) began promptly at 6 am at Sunset Cliffs in San Diego. Since CCA are common in the intertidal pools at Sunset Cliffs, we had to be sure to collect on a lower low tide, and it just so happens that this week those low tides were much earlier than would have been preferred. Caffeinated beverages in hand, our small team trekked to the shore and discussed distinctive features of the species we were looking for. Many species of CCA look similar and multiple species can inhabit the same small cobble. We split up and waded through the low tide, searching beds of sea grass and small rock crevices for any stones with a distinctive layer of calcified red algae. After about an hour we had found enough samples to run our experiment and we headed back to the lab to take a closer look at the CCA.

The following day found us out in the brisk morning air of Sunset Cliffs once again, this time searching for an articulated species of coralline algae .We found ourselves once again searching the warm water of the seagrass beds to collect healthy samples with a delicate touch. As the sun rose over the cliffs we started on our way back to the lab with the treasures of the day to begin our experiment. Being a part of an experiment from the very beginning and knowing exactly where each of your samples comes from makes a project just a little more special and is something you can be a little more proud of when it’s run its course.

Dozens of Diatoms

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By Catherine Drake, Invertebrate Zoology Lab

The last field trip of the fall semester for the Geological Oceanography class was to the Monterey Formation on Toro Road in the Salinas Basin. As we drove up through the hills on the winding road, we came across a grayish cliff that must have spanned about a mile down the road. The students got out of the car, and as we walked along the road, we noted the striations and laminations within the sedimentary layers. What’s especially interesting about these layers is that they are biogenic sediments: they consist of organic particles, usually in the form of skeletal fragments of marine organisms.

The Monterey Formation consists of an incalculable amount of diatoms, which are a type of phytoplankton and are primary producers, meaning they take up carbon dioxide while. Diatoms have siliceous tests, meaning that their cell walls are silica based; so, when diatoms die, they become part of a siliceous ooze and get deposited on the seafloor. Considering that diatoms usually range from 2 to 200 μm and the Monterey Formation spanned almost a mile, which means that there were hundreds of millions of diatoms at the time! Primary production must have been incredibly high during that time period, which was approximately between 11 and 3 million years ago.

Diatoms are phytoplankton that produce oxygen through primary production.

Invertebrate Spotlight: Christmas Tree Worms

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By Catherine Drake, Invertebrate Zoology Lab

For those of you vertebrates who still have their holiday decorations up, here is an invertebrate you might enjoy learning about: the Christmas tree worm.  These polychaetes, Spirobranchus giganteus, are tube-building worms that have two “crowns” in the shape of Christmas trees, hence their name.

Many Christmas tree worms assembled together.

These appendages are an extension of their mouth and catch prey that swims by and then transport it by cilia to the worm’s mouth.  Additionally, the appendages act as part of the worm’s respiratory system, and are thus commonly referred to as gills.  Christmas tree worms are generally found in tropical waters and live within corals in calcareous tubes formed by the worms.

The appendages on these polycheates aid in the catching of prey.

Capture the King Tides!

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An opportunity is quickly approaching for you to get involved in marine science.  All you have to do is pull out your camera and snap some pictures.

On January 20, 21 and 22, and February 6, 7, and 8 king tides will take place along our coast.  What’s a king tide?  A king tide is the one of the highest seasonal tides.  For example, on January 21st the high will be 6.3 feet and on February 7 it will be 5.8 feet.  The California King Tides Initiative is asking members of the public to help document these big tides, because they can help us visualize what rising waters along our California coasts might do in the future.

Blog creator and MLML alumna Erin Loury contemplates the future of Capitola's beaches during a 2011 king tide. (photo: Center for Ocean Solutions, Mike Fox)

When king tides coincide with big swell, they can have some impressive and damaging results.  You can see pictures from past king tides and learn more on the California King Tide Initiative home page.  So charge those camera batteries, and get ready to see science in action.  And remember, have fun and stay safe!

Pitching Oranges in the Name of Science

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by Diane Wyse, Physical Oceanography Lab

One sunny afternoon at the beach in Moss Landing, beachgoers were treated to a tangy surprise. Dr. Erika McPhee-Shaw’s Physical Oceanography class made the most of the beautiful weather and nearby beach to observe the effects of alongshore transport in the surf zone.

Physical oceanography students observing wave action on the Monterey Bay. Photo: Jason Adelaars

From the shore, students observed the waves breaking and made predictions about the direction of alongshore transport and where convergent rip currents would occur.

Feeding surfers? Not exactly. Vertebrate Ecology Lab student Emily Golson pitches an orange to observe it move in the surf zone. Photo: Jason Adelaars

How did they test these predictions?  Why, launching citrus into the surf zone, of course!  Members of the class warmed up their pitching arms and threw oranges into the water from the beach.  They observed and discussed where the oranges traveled as a means of visualizing transport of sediment and plankton with the movement of water in the near-shore environment.

Students discuss the movement of the oranges in the surf zone. Photo: Jason Adelaars
Dr. Erika McPhee-Shaw launches an orange in the name of science. Photo: Jason Adelaars
Physical Oceanography Teaching Assistant Shandy Buckley (L) discusses alongshore transport with students. Photo: Jason Adelaars

Removing Algal Bullies from Monterey Bay Aquarium!

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Diana Steller speaks to the algae underwater, "No no no little brown algae, no bullying."

Have you ever needed help from your friends when confronted with a brown algae bully?  The Monterey Bay Aquarium has, they needed divers to help rescue algae in one of their tanks.  Moss Landing Marine Labs MS 105 Marine Science Diving class had the opportunity to dive in the Monterey Bay Aquarium’s kelp forest habitat tank (their kelp tank site is here).  This tank receives water from just offshore of the aquarium and gets all kinds of baby critters from the water that normally settle and grow just outside the aquarium.  Some of these baby drifters are the spores of an alga (singular of algae) named Dictyopteris undulata.  This alga has been bullying the other algae in the tank and outcompeting them for space.  The dive class was tasked with helping remove the algae and you can see from the photo above we were not happy with this little brown bully!

Student Will Fennie aids in collection of the bully.