Mussels, Microplastic, and Multistress

Riley Frisk, Colby Klaiman, Cole Hennigan, and Dr. Geoffrey Dilly


In the rocky intertidal zones of California, mussels are a keystone species that serve as a basal food source. Mussels are often used as a model organism in marine bioindicator studies; they are easy to handle in a lab, filter feed, and naturally experience wide temperature fluctuations. Exposure to higher temperatures, microplastics, and persistent organic pollutants can all lead to organismal stress in marine ecosystems. We explore the effects of thermal, microplastic, and pollutant stress on mussels using custom built aquaria and feeding tanks. Six total mussel treatments were studied – varying temperature, plastic, and pollutant quantity – over three time points. Our experiment aims to determine the combined effects of each stressor by analyzing the organism’s genetic expression of stress response.
144 mussels were collected from Ventura Harbor pier on May 15th, 2021, and size sorted to 5-7cm long. They were then cleaned of epifauna and acclimated to their tanks for three weeks, acclimating them to temperature by max 1℃ per day to a final temperature of 16℃ or 24℃. Each mussel was fed 4000 algae cells/mL twice per week for 1 hour. The experiment exposed sets of 24 mussels to 6 different conditions. Each temperature group were either fed only a control 4000 cells/mL of algae, or received an additional 10μg/mL of low density polyethylene (LDPE), or a combination of LDPE and Benzo-ɑ-Pyrene (BaP), a known carcinogen, at 15μg/g. Eight mussels were sacrificed from each condition after 1 week, 2 weeks, and 4 weeks. For each mussel, gill, digestive, and foot tissue were dissected and flash frozen with liquid nitrogen, then kept at -80℃. Subsequently, total RNA has been isolated from the gill tissue using Trizol extractions and clean/concentrate kits. This RNA will next be sent out for illumina sequencing to compare differential gene expression between the treatments. Following this analysis, we will use qPCR to quantify the expression of specific genes.

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