Using a low-cost autonomous surface vehicle, we will test whether nearshore microplastic concentration peaks at sites where opposing coastal currents converge — locations where the resulting vortices and convergence zones are expected to trap and accumulate buoyant particles. If our hypothesis is confirmed, we will produce a spatial map of these accumulation points to identify high-yield candidate locations for future microplastic capture stations.
Background and motivation
Microplastics, plastic fragments smaller than 5mm, are now documented in every ocean basin and have been detected in marine organisms across the food web. At the global scale, the same physical principle drives the formation of every major ocean garbage patch: large-scale current systems converge, creating zones where buoyant plastic is concentrated and retained. This is well established at the gyre scale. What is not established — and where our project comes into play — is whether the same convergence mechanism operates at the nearshore, sub-kilometer scale, producing predictable hotspots where opposing tidal currents or longshore drift meet along a local coastline. If this mechanism does operate locally, then microplastic accumulation is not random or evenly distributed; it is concentrated at a small number of physically identifiable convergence zones, and intercepting plastic at those points would be dramatically more efficient than distributed cleanup. That hypothesis is the focus of our investigation.
Research question and hypothesis
Research question: Do nearshore microplastic concentrations peak at sites where opposing local currents converge, due to the vortices and accumulation zones formed at those interfaces?
Hypothesis: We hypothesize that microplastic concentration will be significantly elevated at identified current-convergence sites along our study coastline relative to non-convergence zones, and that the strength of this concentration signal will correlate with the strength of the local convergence (as measured by current opposition and vortex persistence). If confirmed, this would establish that nearshore microplastic distribution is governed by predictable hydrodynamic features rather than being uniformly distributed or dominated solely by source-proximity effects.
Approach
The project has three integrated components. First, we plan to design and build a low-budget autonomous surface vehicle equipped with various sensors to collect data. The vehicle conducts GPS-tagged readings at 6 waypoints per deployment — structured as 3 matched pairs (3 convergence sites + 3 distance-matched control sites) — along a paired-transect layout designed to cross suspected convergence zones. Second, we will identify candidate convergence sites along the study coastline using publicly available current and tidal data, bathymetric charts, and direct observation (drifter tracking, surface debris accumulation). Third, we will deploy the vehicle across both convergence and control (non-convergence) zones across multiple tidal states, then process the resulting data into a spatial concentration map and run statistical analysis (ANOVA between convergence and non-convergence zones, regression against convergence-strength metrics) to test whether the hypothesized pattern is significant.
If the hypothesis is confirmed, the final deliverable is a spatial map identifying the highest-concentration convergence zones along the study coastline as candidate sites for future microplastic capture stations.
What this contributes
Our project contributes in three ways. First, it tests whether the same current-convergence mechanism that creates ocean garbage patches also works on a small, local scale — a question that, as far as we can tell, has not been directly studied at this resolution before. Second, it gives coastal communities a clear way to decide where to place microplastic capture stations rather than spreading cleanup efforts thin. If our hypothesis is right, a few well-placed stations could catch far more plastic than scattered cleanup. Third, it shows that this kind of mapping can be done on a low budget, which means towns and student researchers without expensive ocean equipment can run the same study on their own coastlines.
Scope and deliverables
By the conclusion of the project we will produce: (1) a publishable research paper documenting our methodology, results, and analysis; (2) an open-sourced spatial concentration map of the study coastline identifying any confirmed convergence-driven accumulation hotspots; (3) a publicly shareable build guide and parts list for the autonomous surface vehicle to support replication; and (4) an ISEF exhibition consisting of the physical vehicle, the spatial map, and a summary of statistical findings. The project falls within the Environmental Science, Earth & Ocean Sciences category.