EAGER: RadPlastics-GoM

The aim of this project is to investigate how the fate of marine microplastics (MPs) could be impacting ocean tracer systems now and with future additions of plastic to the marine environment. Plastics are ubiquitous in the marine environment but estimates of their contribution to the total suspended mass present throughout the water column are sparse. Furthermore, because of their relative resistance to degradation and buoyancy compared to bulk particulates in the oceans, plastics have the potential to act as a persistent transport mechanism for adsorbed constituents and plastics-associated tracers (e.g., radioisotopes) that could be carried from areas of high concentration (e.g., coastal zones) to lower concentration regions (e.g., gyres). Key particle-reactive radioisotope tracers (e.g., isotopes of Th, Be, Pb, etc.) provide ‘rates and dates’ for chemical oceanography studies, but currently no data on how these specific chemical constituents have been and could be impacted by the abundance of suspended plastics. This project sets out to fill these gaps in our understanding and address the following hypotheses: (H0) there is little or no predicted impact of MPs on radioisotope distributions in the marine environment due to low partition coefficients (K d s) for MPs with respect to typical marine particles and/or low amounts of plastics, (H1) MPs have the potential for some impact on radioisotope distributions due to K d s ≥ those of typical marine particles, and (H2) MPs have the largest potential for impacting radioisotope distributions due to K d s ≥ those of typical marine particles and observations of cross location or depth gradients suggesting ‘inherited’ tracer signals can be transported via plastics. To achieve these scientific goals, laboratory experiments and coastal sediment sampling will be followed by two proposed cruise campaigns in the North Atlantic. The first cruise is a short, 3 station transect through the Gulf of Maine to acquire potential coastal shelf to offshore gradients in plastics and radioisotopes. The second cruise will be a two-day BATS add on to obtain open ocean gyre estimates. On both campaigns, high-volume McLane pumping will be utilized at 5 depths <1000 m to collect size-fractionated particulate radioisotope activities, plastics counts, and suspended particulate matter estimates.