A lot is talked about the effects on marine wildlife, formation of microplastics, toxic containments due to prolonged exposure to sea water and damaging the aesthetic value of tourist destination caused by the careless disposal of plastic waste in the oceans, but what is less known is that this same plastic serves as carrier for harmful land-based pathogens.
According to a study published in 2014, gelatinous polymers such as extracellular polymeric substances (EPSs) or other aquatic polymers bring forth their own mechanisms for carrying and transmission of pathogens into the food webs of these ecosystems (with particle aggregates and biofilms), more specifically EPS biofilms on macroalgae such as kelp capture Toxoplasma gondii, a protozoan parasite that infects animals and humans worldwide which is transported to the coastal waters through fresh water runoff. These are obtained, concentrated and retained by kelp-grazing snails which are then transmitted through consumption to California Sea otters.
As a result of this research, it is logical to be concerned whether synthetic polymers have similar capabilities of ‘trapping’ pathogens due to the ubiquitous nature of microplastic and protozoan pathogen pollution in sea water. These concerns were raised in a recent study conducted in 2022 whose main purpose was to investigate the association of zoonotic protozoa with microplastic surfaces in contaminated sea water. Cryptosporidium parvum, Giardia enterica and Toxoplasma gondii (similar protozoan parasite examined in the 2014 study) were the pathogens selected for this experiment due to their recognition by the World Health Organization (WHO) as an underestimated cause of illness due to shellfish, and due to their persistence in the marine environment, and the synthetic plastics taken into consideration for the bench experiment were two types: polyethylene microbeads and polyester microfibers.
The results demonstrated that over a 7-day period, in the case of microbeads the parasite count increased for all three of the test pathogens while in the surrounding seawater the parasite count decreased with the exception of Cryptosporidium parvum that remained relatively the same. Similar findings were found in the microfibers with parasite count associated with it, generally increasing over time but Cryptosporidium parvum remained the same till the third day, and this variation by Cryptosporidium parvum was also observed in the seawater count where it decreased significantly on the third day. Another set observations were noted in this experiment in regards to size of plastic, where it was overall observed that more protozoan oocysts tended to adhere to larger microfibers than the other microplastics.
Upon looking at available research, the implications of this readily occurring phenomenon’s severity cannot be understated. Microplastics have a pandemic ability to be consumed by a bulk of the living organisms in an ecosystem and that combined with the deadly symptoms brought about by these aforementioned pathogens create an alarming cycle that effect both aquatic organisms and the humans that consume them, that minimal effort has been done to combat