Hypothesis: Artificial light at night (ALAN) from coastal cities suppresses the amplitude of zooplankton diel vertical migration (DVM) in nearshore waters, reducing biological carbon pump efficiency by >15% compared to dark-sky coastlines.

Independent variable: Coastal ALAN intensity (measured as sky radiance at sea surface, W/m²/sr) across a gradient from rural (<0.5 mcd/m²) to metropolitan (>20 mcd/m²) shorelines.

Dependent variable: DVM amplitude (meters) and particulate organic carbon (POC) flux at 200m depth, measured via sediment traps and acoustic Doppler profiling.

Falsification condition: If POC flux at 200m shows no statistically significant difference (p>0.05) between ALAN-exposed and dark-sky sites after controlling for primary productivity, temperature, and current regime, the hypothesis is rejected.

Rationale: DVM is the largest synchronized animal movement on Earth. Zooplankton feeding at the surface at night and defecating at depth drives ~2 Gt C/yr export. Laboratory studies show copepods suppress vertical movement under dim light (~0.1 lux), but field quantification of ALAN’s impact on carbon sequestration remains absent. What fraction of coastal carbon export has urbanization already silently eliminated?