Experimental Evidence That Invasive, Crustacean Zooplankton Hemimysis Feeds on Both Microalgae and Microplastic Particles
Mentor 1
John Bergus
Start Date
28-4-2023 12:00 AM
Description
Hemimysis anomala (the ‘bloody red shrimp’) is an invasive crustacean native to the Ponto-Caspian region, first reported in the Great Lakes in 2006. Hemimysis consumes various zooplankton, but while its larvae feed on microalgae, it is not known whether adults do, or how efficiently they feed. Importantly, feeding on algae also suggest Hemimysis should be able to consume similar-sized particles, including microplastics, common in Lake Michigan. In this study we asked the questions: 1) do adult Hemimysis eat microalgae and if so at what rates? and 2) do Hemimysis ingest microplastic particles? Animals were collected from Lake Michigan and held in aquaria for up to 1 month (16 °C, 14:10 L:D cycle) until used in experiments. We exposed animals to different concentrations of either microalgae (Chlamydomonas reinhardtii, a green alga, ~25 µm in diameter) or plastic particles (fluorescent polystyrene microspheres, either 30 µm or 56 µm average diameter). Grazing rates were calculated based on removal of particles from medium (counts before and after experiments, using flow cytometry), or presence of algae or plastic microspheres in guts, measuring either gut pigment or by counting spheres under a microscope. Hemimysis grazed the microalgae at a maximum rate of ~1,000 cells per animal per hour, which was half-saturated at 9,000 cell per ml. Results based on gut pigments were similar. Hemimysis ingested both sizes of plastic particles, but only 30 µm particles were able to pass into their intestines. Grazing kinetics of the smaller particles was similar to the microalgae: maximum rate of ~750 beads per animal per h and half-saturation at 5,000 beads per ml. Our work confirmed that adult Hemimysis consumes both microalgae and microplastics, with little evidence of preference. Since fish consume Hemimysis, this has serious implications for the entry of microplastics into the food web.
Experimental Evidence That Invasive, Crustacean Zooplankton Hemimysis Feeds on Both Microalgae and Microplastic Particles
Hemimysis anomala (the ‘bloody red shrimp’) is an invasive crustacean native to the Ponto-Caspian region, first reported in the Great Lakes in 2006. Hemimysis consumes various zooplankton, but while its larvae feed on microalgae, it is not known whether adults do, or how efficiently they feed. Importantly, feeding on algae also suggest Hemimysis should be able to consume similar-sized particles, including microplastics, common in Lake Michigan. In this study we asked the questions: 1) do adult Hemimysis eat microalgae and if so at what rates? and 2) do Hemimysis ingest microplastic particles? Animals were collected from Lake Michigan and held in aquaria for up to 1 month (16 °C, 14:10 L:D cycle) until used in experiments. We exposed animals to different concentrations of either microalgae (Chlamydomonas reinhardtii, a green alga, ~25 µm in diameter) or plastic particles (fluorescent polystyrene microspheres, either 30 µm or 56 µm average diameter). Grazing rates were calculated based on removal of particles from medium (counts before and after experiments, using flow cytometry), or presence of algae or plastic microspheres in guts, measuring either gut pigment or by counting spheres under a microscope. Hemimysis grazed the microalgae at a maximum rate of ~1,000 cells per animal per hour, which was half-saturated at 9,000 cell per ml. Results based on gut pigments were similar. Hemimysis ingested both sizes of plastic particles, but only 30 µm particles were able to pass into their intestines. Grazing kinetics of the smaller particles was similar to the microalgae: maximum rate of ~750 beads per animal per h and half-saturation at 5,000 beads per ml. Our work confirmed that adult Hemimysis consumes both microalgae and microplastics, with little evidence of preference. Since fish consume Hemimysis, this has serious implications for the entry of microplastics into the food web.
