The photodegradation pf plastic floating in the ocean produces changes in seawater chemistry

More than 250,000 metric tons of plastic are currently floating on the sea surface threating marine fauna from small copepods to big mammals including human beings. That floating plastic is exposed to sunlight which is its main degradation factor producing scratches and embrittlement. Commercial plastic is never pure and it contains additives and plasticizers to improve the properties required for its purpose and to make it more resistant to degradation. When in contact with water, these additives and the products from plastic degradation can leach out to the aquatic medium becoming part of the dissolved organic matter (DOM) pool naturally present in the ocean. That leaching is enhanced by sunlight irradiation. The chemical compounds leached from plastic can alter the biogeochemistry of the seawater with consequence for the marine organisms. Here, it will be shown the results of several studies in which different types of plastic (including biodegradable and aged polymers) were exposed to sunlight degradation in seawater during 1-6 days. The chemical composition of the seawater was analyzed at the end of the experiment for dissolved organic carbon (DOC), fluorescence, absorbance and pH. We found that plastic releases compounds in seawater which present a characteristic fluorescence signal. Aged plastic released a higher amount of material than virgin plastic and biodegradable plastic did not show differences regarding the petrol-based plastic. Finally, we found that the DOM and CO2 released during plastic photodegradation can alter the chemistry of seawater. These results will contribute to better understand the impact of plastic in marine ecosystems and the marine carbon cycle. Also see: https://micro2022.sciencesconf.org/426658/document