Evaluating Suitability of Untreated Woods and Textiles for Marine Drifter Design

To better understand how anthropogenic marine debris displaces and where it accumulates, MIT Sea Grant is developing a geospatially-tracked surface marine drifter to mimic hydrodynamic properties of common debris. The drifter design aims to use biodegradable materials where possible. This study investigates the suitability of untreated wood species, natural fiber textiles, and pumice stone as components of the drifter design. Sustained buoyancy and structural integrity determine suitability, as indicated by floatation observations, mass fluctuations, and visual inspections of individual samples with prolonged seawater exposure. Samples were exposed to seawater in-situ off the shoreline of Mattapoisett, Massachusetts, USA between February to April of 2024. Cedar, sapele, white oak, and fir are recommended for more detailed study and consideration for the drifter design based on sustained floatation. Observed negative buoyancy in select wood species is hypothesized to be an effect of mineralization based on mass decreases below respective original values and potential indicators of biocorrosion. Canvas demonstrated the least visible salt damage and is thus recommended for preliminary drifter design, though a quantitative water uptake study is suggested. Pumice stone samples sustained floatation throughout the study, suggesting promising drifter performance. Unexpectedly, of all deployed components, bioaccumulation occurred most on the nylon ropes securing samples to the test frame, potentially caused by attractive surface compounds or textures.