Megan Fitzpatrick, a final year Geography BSc(Hons) student, undertook the field research for her dissertation project.
She described the results of her work as “very shocking” and warned about the dangers facing humans who eat Sussex shellfish.
Megan carried out her investigation at Piddinghoe in the Lewes district, a site known for its poor water quality.
The student examined the mussels along with 20 litres of brackish water, finding that microplastics were regularly ingested into the digestive tract and cells of the mussels.
Each mussel was found to have absorbed 51.6 particles of plastic per day, while there were 29.45 particles per litre of water.
Megan said: “The high concentrations of microplastics observed within the Sussex mussels was very shocking.
“Studies have suggested that these particles are causing harm to the mussels, however we are unaware of the full impacts as well as the potentially severe implications for shellfish eaters – including humans.