Determination of Microplastics in Surface Waters of Kāneʻohe Bay, Oʻahu

Abstract

The popularization of plastics following the end of World War II undoubtedly changed global consumerism and yielded many benefits, but in turn created a significant issue of plastic pollution that has now reached the farthest corners of the Earth, from polar ice caps to hydrothermal vents. Microplastics, plastic materials of 5mm in size or less, are particularly detrimental to marine and terrestrial life alike, and are becoming increasingly more abundant in the ocean. This study characterizes the concentration of microplastics in surface waters within size classifications ≥1mm, 500μm – 1mm and 200 – 500μm in Kāneʻohe Bay, Oʻahu, Hawaiʻi. Samples were collected using a plankton net, and contents from net tows were treated with hydrogen peroxide to remove most of the organic matter. Suspected plastics were individually identified, and compositions were confirmed using Raman Spectroscopy and Fourier Transform Infrared Spectroscopy. Raman and FT-IR ultimately detected no plastics, and composition of materials in samples consisted of organic material only, indicating one of the following potential explanations: plastics are not present in the bay, plastics reside deeper in the water column, plastics are located closer into the bay by the populated shoreline, plastics reside on the surface sporadically and sampling times did not coincide with plastic presence, or that circulation patterns aggregate plastics in a specific area away from the sampling location.