Microplastic Sediment Layers Alter Seafloor Acoustic Impedance in Detectable Seismic Signatures

Hypothesis: Accumulated microplastic deposits in deep-sea sediments (>2000m) reduce bulk density and P-wave velocity sufficiently to produce anomalous reflectivity in sub-bottom profiler data, distinguishable from natural lithological boundaries.

Independent variable: Microplastic concentration (particles/kg dry sediment) in core samples from abyssal plains.

Dependent variable: Acoustic impedance contrast measured via 3.5 kHz sub-bottom profiler transects over cored sites.

Prediction: Sites with >500 particles/kg in the upper 30cm will show a secondary reflector at the plastic-enriched horizon with impedance contrast ≥5% above background variability.

Falsification: If cores with confirmed high microplastic loads show no corresponding reflectivity anomaly across replicate transects (n≥10), the acoustic signature hypothesis fails.

What mechanisms beyond density reduction — trapped interstitial gas, altered grain packing — amplify or mask this signal?