Real-time electrochemical detection of stage-specific marine biofouling using interdigitated carbon paste electrode arrays: Barge-based field validation at Gunsan port

We report an interdigitated carbon paste electrode (IDE) sensing system for real-time, stage-specific marine biofouling detection using cyclic voltammetry (CV) and impedance spectroscopy (IS). The system exploits the distinct dielectric properties of successive fouling organisms — bacterial biofilm (ε r ≈ 81), algal cells, and barnacle shells (CaCO 3 , ε r ≈ 6–8) — to produce characteristic electrochemical signatures at each fouling stage. Electrode stability in open seawater was confirmed over four weeks (impedance: 1.82–2.93 Ω, SD ±0.3 Ω). To our knowledge, this is the first electrochemical sensing system to achieve four-stage marine biofouling discrimination — from initial biofilm to mature macrofouling — validated under open seawater conditions on a hull-representative barge platform, extending prior laboratory-scale impedance biosensor work to the full fouling spectrum encountered in maritime operations. Ten-week field validation on a moored barge at Gunsan Port (35°59′N, 126°42′E; June–September 2025) demonstrated consistent stage-specific signals across five independently deployed sensors: +150–300% at Stage 1 (biofilm), +20–70% at Stage 2 (algal attachment), −10–40% at Stage 3 (barnacle settlement), and + 30–140% at Stage 4 (mature barnacle growth). Stage 1 was detected 2–3 weeks before visual confirmation (99% accuracy; Sensitivity 100%, Specificity 98%). A 5 °C temperature rise accelerated fouling progression by approximately 40%, with the greatest effect at Stage 1. The system is milliwatt-powered and field-deployable. All performance data are specific to Korean West Sea summer conditions (21–30 °C, salinity 3.0–3.5%) and the local fouling community.