Samuel Pruhs, “Shrimp Munch on Microplastic Lunch: Quantification of Microplastics in a Lake Michigan Invader, the Crustacean Hemimysis anomala”
Mentor: John Berges, Biological Sciences
Poster #149

The opossum shrimp, Hemimysis anomala is a Ponto-Caspian native that invaded the Great Lakes waterways in the mid 2000’s. Microplastics harm wildlife by leeching harmful chemicals, and accumulate in natural water, however, we know little about their effects in Great Lake foodwebs and nothing about their ingestion by zooplankton. We quantified microplastics in H. anomala, sampled from Lake Michigan, using the fluorescent stain Nile Red, epifluorescence microscopy and the image analysis. Animals were sampled from a Lake Michigan breakwall using lighted funnel traps. Some were immediately frozen to examine microplastic gut contents, while others were kept in aquaria for control experiments. To validate the methods, animals were allowed to graze on polyethylene microspheres (45-53 µm diameter) for three hours, while control animals were maintained in filtered water. Animals were digested to remove organic matter (which could interfere with staining) using Fenton’s Reaction (30% H₂O₂ and 7.2 mM Fe(II)SO₄), collected on filters, and stained with Nile Red (1 µg/mL in 55% DMSO). Samples were visualized under epifluorescence microscopy (40 x magnification, excitation 490 nm, emission 520 nm) and images quantified using ImageJ and custom-designed software, calculating quantity, area, and feret (largest linear length) of microplastic particles. When fed microspheres of known size, the method correctly quantified the plastic particles from the gut contents, validating the method. Microplastic particles were found in all animals, varying from 4 to 101 particles and 3 to 7240 µm in diameter. These data support the idea that Hemimysis anomala ingest microplastic particles and could serve as a model organism to examine the effects of microplastics in the Great Lake food web.