My story… as a plastic yogurt container
To start my yogurt containing career, I was forged from polypropylene, a type of plastic suitable for food storage. This is important to know because my degradation journey is based on my chemical structure and physical characteristics. In particular, polypropylene is a rigid and very crystalline structure, which makes it difficult for microorganisms to degrade (Maddah 2016). Also, I am a relatively low density plastic so when the tide comes in and takes me into the water I tend to float, because I am less dense than the brackish water in the Chesapeake Bay.My future
I thought I was going home to be with the other trash…there I was enjoying my trip on the dumpster truck back home to my landfill, having fulfilled my destiny as a conduit for yogurt. Anyway, the next thing I knew, we all were jostled when we went over a big bump and out I flew into the great wide world. I thought maybe I would get picked up on the side of the road and back comfortably in a trash bag, but this was not so…the next few weeks were a blur.
Welcome to the beach
When I came to, I was all alone on a beach in what I presumed to be the Chesapeake Bay, based on my knowledge of geography that all young yogurt containers learned in primary school. I seemed to be in an intertidal location because for a portion of the day the sun would beat down on me and disrupt the chemical bonds that made me a suitable and durable container for yogurt (Gewert et al. 2018; Sorasan et al. 2021). Then, the tide would come in and temporarily submerge me. The ebb and flow of the water proved damaging as well by way of mechanical abrasion and this was the start of my fragmentation.
A social magnet
I seem to be a popular meeting area for all variety of organisms including bacteria, some archaea, fungi, microscopic plants, and even some animals. And it all happened so fast! Almost instantly (Rummel et al. 2017). They all gathered on my fragments because it afforded shelter from the dangers of the open water like sunshine, predators, nutrient limitation, and even some protection from some things like antibiotics (Flemming et al. 2016). Not only did this create a whole ecosystem but it also changed the buoyancy of my fragments and led to some of them sinking, sometimes all the way to the sediment, being consumed by animals higher in the trophic chain, or simply accumulating material until the surface was altered enough to fragment and serve as a source of allochthonous carbon for heterotrophic plankton.
What it could mean
All this could then lead to what was once a yogurt container becoming a part of the microbial or biological carbon pump, where the carbon I once contained could be incorporated into biomass, enter into the cycle of labile carbon, or be sequestered as refractory carbon in the water column or stored at the bottom of the ocean or in the sediment (Galgani et al. 2022). Conversely, the biofilm consisting of microorganisms, extracellular polymeric substances, and (in)organic matter shielded my fragment from the sun and prevented further degradation from UV light (Rummel et al. 2017).
A world traveler & meeting strangers
There were also some opportunistic animal pathogens such as Vibrio that just used my fragments to travel to places they otherwise couldn’t get to, they weren’t interested in the community generated by my fragments (Kesy et al. 2020). It is my recalcitrance that makes me a suitable vessel for transporting such organisms long distances–it takes much longer for my particles to break down than other detritus such as leaves or fecal snow.
A fragmented lifestle
Some of my fragments got so small that they can even cross cell membranes and wreak havoc on tissues of higher animals, possibly causing damage to the digestive or respiratory system. Although, an amphipod consumed some of my fragments and its digestive system created even smaller nano-fragments (Mateos‑Cárdenas et al. 2020), so my interaction with animals’ digestive systems can itself lead to further fragmentation, which can be redistributed into the environment once they are egested. It is these smallest of fragments too that can directly impact biogeochemical cycles in addition to indirectly via interaction with the microorganisms responsible for elemental cycling.
My future
In total, I will likely persist as fragments at varying stages of decomposition for a very long time, possibly centuries, and may be transported via currents and turbulence to oceanic gyres where plastic debris tends to accumulate, the deep ocean, various biota, or enter into the carbon cycle. When all is said and done, the final result will be the production of carbon dioxide from my hydrocarbon backbone, as well as transformation in a yet-to-be-discovered form of the additives I contain that once made me an excellent container for yogurt. I will contribute to the geologic record of the Anthropocene by making my home in a strata that in the years to come will define the time period where humans roamed the Earth, eating yogurt.