You may remember meeting Kea Payton a few years ago when she first started going out with us to grab samples. Fast forward 2 years and now Kea has finished her thesis and is ready to share what she’s learned!
Have you ever wondered about plastics in our local waterways? Kea sure did! Her project explored 4 main questions.
Question 1: How are Microplastics Distributed in the Charleston Harbor?
No significant difference was found in microplastic concentrations between several water quality monitoring sites and Breach Inlet. This means that microplastics were well-mixed, no hot-spots were found, and there doesn’t seem to be a significant contribution of microplastics coming from the ocean.
Question 2: Are Microplastics Aggregating at Flood Tidal Fronts?
Higher levels of microplastics were found within the tidal fronts. Results suggest that microplastics are aggregating at these tidal fronts with influxes of particles coming from land-based sources.
Question 3: Do Fronts Serve as a Vector for Microplastics to Enter the Marine Food Web?
Only 1% of zooplankton examined contained these synthetic particles within their gut. This means that there are microplastics available in the tidal fronts, but zooplankton aren’t eating them. This suggests that frontal zones may not serve as a vector for entry into the food web and that our primary consumers (those at the bottom of the food web) are more selective feeders than originally thought.
Question 4: Are Microplastics Found in our Local Fish Population?
All recreational fishes examined in this study contained microplastics in their GI tracts; fishes studied include Croaker, Flounder, Mullet, Red Drum, Sea Trout, Spot, and Whiting caught in the Charleston Harbor.
On average, 3 microplastic particles per liter (43 – 100 μm) are being found in the top meter of the water column in Charleston Harbor. Physical damage (i.e suffocation, blocked and/or torn digestive tracts) from the ingestion of these small particles can contribute to various health risks for the organism and the composition of the particles have been reported to leach and sorb chemical contaminants. Such properties make these small synthetic polymers a greater ecological concern as damage and chemical uptake could expand up the food web through trophic transfer. These particles were detected in local zooplankton and fishes, but the evidence of trophic transfer remains unclear. The overall presence of microplastics in Charleston, however, does suggest a potential threat to the local marine food web.
FUN FACT: Using data collected from this study (3 particles per liter), assuming even distribution and the estimated area (36.26 km2) with the historical (3.65 m) and the maximum (15.84 m) depth of the Charleston Harbor, it is estimated that 396,937,500 to 1,722,600,000 microplastic particles (43 – 100 μm) are suspended in the water column in the Charleston Harbor; using historical and maximum depth respectfully.