  We generalize Merel's work on universal Fourier expansions to Bianchi modular
forms over Euclidean imaginary quadratic fields, under the assumption of the
nondegeneracy of a pairing between Bianchi modular forms and Bianchi modular
symbols. Among the key inputs is a computation of the action of Hecke operators
on Manin symbols, and building upon the Heilbronn-Merel matrices constructed by
Mohamed.
